I am looking to swap my stock auto for a 4t60. What car would be the best places to get one from? I would think that the later the year the better but I really dont have any idea. Were there any major differences besides final drive ratios like pump designs or anything that would make one year more desirable?

Also when having a 700r4 built I remember getting extra disks for one of the clutchpacks, a shift kit, corvette servo and different boost valve. Are there similar upgrades that should be done when rebuilding the 4t60 and where would the best source for info and performance parts for this trans?

Thanks

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86 GT

I imagine the strongest would have been behind the cadillac V8s and GM 3.8s and of course the latest design before electric would have the most improvements.

I kinda figured that later would be better. Sometimes companies try to reinvent stuff or cut costs in materials and casting processes in mid production. Just wondering if there were any specific ones to watch out for.

I believe the best one was the Cadillac Allante F7. With proper adjustment for firm shifts, a standard stall converter, and a large stacked plate cooler, any of the 1988 or newer should be durable. Try to find one with the 3.33 final. I'm collecting parts for this also, going from a 4spd. I have the P6000 HD brakes and big cv's so I'm hoping I can just use the P6000 HD axles as is.

http://spacecoastfieros.com/tech/440-4T60/index.html
http://fp.enter.net/~rockcrawl/4T60a.html
http://www.bulkpart.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=2&Category_Code=4T60-440-T4

Got mine out of a '90 Chevy Lumina Euro Sport. It had the right final gear ratio, torque converter and everything. Works great. A lot of misinformation about the axels in the links above though.

One way to make sure the axles wont bottom out in the tripods if the rear bottoms out is to temporarily remove the clip from the outer cv so it wont lock the axle in, remove the spring from the strut, then with a floor jack lift the suspension through it's full range of motion or atleast with the axle straight out and with the suspension full compressed. Without the snap ring you will be able to slide the axle back and forth to check how much extra travel you will have at the tripod for things like the engine/trans torqueing in their mounts.

Badger, did you check for endplay or did you just snap the axles into the outers and go? If not, have you bottomed out the car since the swap? I guess you used the manual fiero outer cv's? Did you offset the trans to the driverside at all or just line it up?

(I put a ford tbird IRS rear in my miata and ordered custom length axle shafts from Moser, so I have been down this road before.)

quote Originally posted by badger: Got mine out of a '90 Chevy Lumina Euro Sport. It had the right final gear ratio, torque converter and everything. Works great. A lot of misinformation about the axels in the links above though.

I'd be curious what the misinformation is. I might be doing this swap someday
thanks
Dave

quote Originally posted by ditch: I'd be curious what the misinformation is. I might be doing this swap someday thanks Dave

As I understand it, the donor vehicles listed aren't right. What I suspect happened is that I had the 4T60 put on a stock 2.8. I think the axle information is about OTHER engines. It's only a guess as to why the info was wrong.

Also, if I recall correctly, the Space Coast article says you have to cut the cradle on an '88. Not true.

<see response below also>

quote Originally posted by fiero4.3L: Badger, did you check for endplay or did you just snap the axles into the outers and go? If not, have you bottomed out the car since the swap? I guess you used the manual fiero outer cv's? Did you offset the trans to the driverside at all or just line it up?

Not a single clue. I had this done for me by a particularly skilled Fiero mechanic. (I might be able to replace a headlight, if you give me the whole day.) His comment was "I was surprised at how much in these build threads didn't agree with what I actually found." Particularly, some (most? all?) of the axels listed weren't what was needed. He told me what he did, but it sounded like Charlie Brown's teacher. <imitates muted coronet>

As a mechanically clueless customer, all I can say is that it was WAY worth the time, effort and expense. For the first time since 1985, I can hold a conversation in a normal tone of voice in a Fiero at 70 mph! It practically idles down the highway. Best upgrade I've ever made.

[This message has been edited by badger (edited 10-27-2005).]

thanks for all of the info. I have also encountered about a million different answers on the axle question. I like the idea of taking the suspension thru its travel without the spring. I am sick of getting the same gas milage out of a leaky 2.8 as I did with a built small block in a 3300 lb car.

Dan, the best 4T60 (non-electronic) transmissions are those produced in the last years before GM started using the "E" version in all of their cars. That would be 1992 w-body with the 3.1 V6 engine. To my knowledge, all 4T60's that came mounted to 3.1's had the 3.33 final drive ratio which would be a great match for the Fiero 2.8. If you are looking for lower rev's on the highway, you might opt for one with the 3.06, 2.97, or 2.84 gear ratio. The 3.06's and 2.84's were most commonly found in GM H and C body cars (Bonneville, Park Ave, etc). But be careful here because in 1992 gm switched to the "E" versions in these cars. The most common car you can find the 2.97 version in was the Buick Reatta.

Also, I do have CV axle building info on my website if you need it.

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power corrupts. absolute power corrupts absolutely.

Custom Computer Tuning | Engine Conversions | Turbocharging | www.gmtuners.com

By comparing part numbers of cars that came with both the 125c and the 440T4/4T60, I have come up with the following list of vehicles whose axles should be a bolt in. Other cars may have parts that will fit but I could not verify. Also, I don't know any cars that recieved both 125c and a 4t60E to compare part numbers on.

440T4/4T60 axle assemblies that fit fiero for length and stock rear hubs:
1984-89 Chevy Celebrity with 4spd auto and LD brake (smaller fiero sized wheel bolt pattern)
1984-1987 Pontiac 6000 with 4spd auto/LD brakes
1987-1989 Buick Century with 4spd auto/LD brakes
1984-1987 Cutlass Ciera with 4spd auto/LD brakes

Also, the pass axle on 125c can be reused if using driverside LD P6000 or cutlass ciera axle.

Source:
http://www.cvaxles.com/retail.htm#Catalog
I did find a couple mistakes in the catalog which is why I'm not making claims about outer cv size and spline. Otherwise I think it is accurate.

For those like me who have already converted to the big bolt pattern on the rear from using century/p6000 hubs, big brakes, and outer cv's, or if you are reusing your fiero manual outer cv's and just need the axle shafts and inner cv's/tripod's, use the following axles for the 440t4/4t60;
84-89 Pontiac 6000 HD brake
84-93 Buick Century HD
84-93 Oldsmobile Cutlass Ciera HD
84-90 Chevy Celebrity HD

[This message has been edited by fiero4.3L (edited 10-28-2005).]

quote Originally posted by fiero4.3L: By comparing part numbers of cars that came with both the 125c and the 440T4/4T60, I have come up with the following list of vehicles whose axles should be a bolt in. Other cars may have parts that will fit but I could not verify. Also, I don't know any cars that recieved both 125c and a 4t60E to compare part numbers on.

Hold on, fiero4.3L. My apologies if I'm wrong, but isn't there a flaw in this reasoning? I'm completely mechanically inept, but doesn't the axel go between the wheel and the transaxel? The length of the axel would be determined by the body of the car and the position of the engine. The fact that a particular model of car had both the TH125C and the 4T60 as an option shouldn't suggest that those axels will work in a Fiero. It does say that the diameter is right, but not the length.

So here's where my ignorance shows: does the length matter? Is there a lot of room for play in the length, but the diameter is critical?

I should know more about it, having just done this swap, but writing a check to the qualified mechanic who actually did the work makes you less of an expert than you would think.

One thing I can say with certainty is that the end result of a 4T60 and a 2.8L is magnificent. I HIGHLY recommend the 3.33 final gear though. It leaves you with almost the exact same first gear, and by the time you hit 4th and the TCC locks up, you're practically idling at 70mph. Any lower, and I'd be afraid of lugging in highway trafic. No danger of that here. This is simply the best Fiero I've ever driven, and only a hair off of stock.

btw, There are TWO ways to adjust the shifting. An adjustable vacuum valve to adjust the "shift hardness", and the detent cable to adjust the RPM. It's a great deal all around.

The idea is to find a car that has the same distance between the outer cv's as the fiero. Such a car would use the same axles as the fiero for a given transaxle if the outer cv's have the same center spline. If the part number is the same, the length is the same and the transmission is in the same position. Armed with that info, if such a car was available with a 440T4, the axles will be the correct length. In addition, those cars that I listed have suspension and outer joints that are interchangeable with the fiero's based on the brake option. You will also note that the outer cv joint is also listed separately from the axle assy's.

FYI, auto fieros have small hub splines and 20mm axles. Manual fieros have small hubs and 24mm axles. The LD brake cars have small hub splines and 20mm axles for the 3spd auto. HD brake cars have large hub splines and 24mm axles for the 4spd auto. There are also "adapter" axles that we're used with odd combinations of LD brakes and a 4spdauto or HD brakes and a 3spdauto.

If the axle is too long and the tripod bottoms out in the cup it can break the tripod, transmission, etc. When the suspension is compressed the axle plunges deepest into the cup (I.E. on a hard drag strip type launch with a big motor and soft springs). If you never bottom out the car for whatever reason and they are slightly too long, you'll never have a problem. It's like driving toward a wall and stopping just in time.

I would not say it would work if it didn't. I expect to buy my parts this weekend.

quote Originally posted by fiero4.3L: I would not say it would work if it didn't. I expect to buy my parts this weekend.

Why not? Everyone else has. At least when it comes to axels for the 4T60 it seems.

You are WAAAAYYYYY over my head with the explanation. I just thought I saw a flaw in the reasoning and was hoping I could save you a trip to the boneyard or parts store. Sorry.

Nothing wrong with a little debate. I have a couple yards I'm checking out this morning. How hard can it be to find a 90ish 3.1L Lumina? Otherwise I'll look for the 4 digit codes on any loose trannys, maybe pickup a couple $25 cores just to see if they have the 33/37 sprocket set. I don't expect to find axles with good outer cvs but maybe I'll get lucky.

I think if I we're wanting a drag racer, the 3.1L converter would stall high enough bolted to a 4.3L. For everyday commuting I'd rather have a caddy unit with a low K factor. Much easier on the trans.

I would think with all of that 4.3 torque the lower stall would feel better in everyday driving. Probably better on gas in the city too.

Looking at the 4 digit codes would be nice but it seems that a lot of the yards have gone all high tech and wont let people just browse.

As far as the axles are concerned are the auto parts store ones any good? The 1994 baretta drivers side axle complete was only 69.99 I thought someone said that parts store axles were not good for swaps. Different diameter so not as strong as factory? Perhaps they were just talking about high hp swaps. Or maybe they were wrong.

I talked to a salvage yard yesterday that said they dont even sell axles to the public any more because the remanufacturing companies were selling them so cheap. easier for them to just sell all of their cores to those reman guys.

[This message has been edited by DanGT (edited 10-29-2005).]

Did'nt see any luminas at the small yard I went to. I had many 440t4's to choose from. The trans codes are impossible to read with out serious yoga or getting under the car. I picked up a trans with code 8FCH. If it said 8CFH it would be 3.33. At this point I don't know what I bought, except that it was in a heavy olds wagon with a 3.8 so it should be geared 3.33 and have the best parts for an '88. I still need a 125c speed sensor since the olds used a cable, a neutral flexplate to bolt to my crank adapter on the 4.3L, a cooler, and a auto shifter. The fluid did smell a little burnt but I'm going through it anyway with new clutches and seals. If I don't find metal in the pan I'll reuse the converter. I got every nut, bolt, and all the wiring. Not bad for $100. I did have to pull it myself. It took about 2 hours.

I'm getting my axles from a parts store. I think the cv's don't last as long as oem's because they are repaired by welding then remachining. The axle shafts are just cleaned and reused if they are reman. New oem joints can be bought later individually as necessary. FYI, Moser can make custom length axles for around $150 each. I just bought a set for something else.

So who can tell me what final I have? Anybody have Karl Hamilton's email? He came up with the 3.33 code chart.

You want the latest year you can get for all GM tramsmissions.

Transmissions get even more rolling changes than engines. Most people are familliar with Mid Year vehicle changes but GM changed production of the automatics a bunch of times to address various problems they were seeing as warranty claims etc. These changes could did and do occure any time GM sees a problem they want fixed.

If you have to go with an early year, and you really want it to last, get someone that knows what they are doing and has access to the TSBs from GM and/or the trans parts houses. That way you can purge out all the common defects/weaknesses. You can also use aftermarket parts to build them up into the 65 and maybe the 80 strength classes. These parts will include better clutch packs along with other things depending just what version of trans you have. (You can also get better clutch packs etc for 3T40/TH125c)

The current GM numbering works as GOSS(E) Gears forward, Orientation, S(S)trength class, and E when present means Electricaly controled by the PCM. (Most GM transmissions are E now.)

4T60 means 4 forward gears Transverse mount 60 strength class.
4L60 would be the same except it's an inline unit for a front engine RWD/4WD vehicle.

E units can't be dropped into cars that don't have PCM systems. I'm told you can change teh valve body with a non E unit but I wouldn't recomend trying that unless you know what you are doing. GM made allot of valve body changes and many are not interchangeable.

I'm also told you could take the gear/clutch pack from an E series and put it into non E unit to gain the bulk of what makes the strength class number. IE you could make a 4T60 into a 4T80/85 that way. (80/85 were not available at all as a non E unit far as I know.)

Exactly what gearing you want depends on some things.... low gearing will give you performance. slightly higher gearing will help fuel economy. (This is also affected by tire size. see the various articles in my cave.)

Here's the interesting twist in all this... If you have 3.33:1 now and stay with 3.33 gears in the 4T60 you actually go down in gearing in first gear because 4T60 has a lower 1st gear along with the overdriven 4th. (Again see in my cave.) What this means is that if you move from a 3.33 in a 3 speed up to 3.06 you won't lose as much performance as you'd think in the bottom end.

3T40: 2.84 1st x 3.33 "final" = 9.4572
4T60: 2.92 1st x 3.06 "final" = 8.9352

Remember that final ratio in an automatic isn't as simple as the final gear set. There are more ratios available depending on what chain is combined with the final drive.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurasic Park)

The Ogre's Fiero Cave (It's also at the top of every forum page...)

Thanks for the cave info. About the trans running too cool, the bypass in the front pump was eliminated once GM went to locking converters out of concern for pressure changes. The older trannys would bypass the cooler and lines if the fluid was too cold/thick. External thermostats are available to do the same thing. I'll be going back to the yard monday to get the 3 digit code off the jamb for the trans.

Of the many 440t4's I had to choose from, everyone I looked at was an '88 or older. A heavy duty option like a wagon should have better parts than a light duty option versus just getting the last trans made a particular year. Except for someone who rebuilds 440t4's everyday, I dont know anyone who would be more qualified than me. Sure, it will take me longer to do, with a few more trips to the store, but the end result will be the same, if not better than somebody trying to finish before lunch. All the TSB's that are going to be put out for a 440t4 have been out for a long time. The basic manual is $16 and the update is another $16. I also have All Data Pro access. I have rebuilt many manual trannys and had the valve body out on a few autos but never a complete auto overhaul.

Now I am really confused! I am planning to do this swap with a 3.4L engine. I bought an 87 Fiero GT with a bad knock in the engine. Were there different automatic transmission, gear ratios in Fieros or were they all the same? I would like to know, what car and year to go look for.

Don Z.

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WWW.CLEVELANDFIEROS.COM

https://www.fiero.nl/forum/Forum1/HTML/052322.html#lastpost
My rear defuser
It will be painted at the end of summer!

Click "Ogre's Cave" above red fiero on banner. Then click powertrain/axle & tranny/gear ratio.

I just ordered my rebuild kit including steels, filter, adjustable modulator, new TCC noid, a Derale 22,000 lb plate cooler, the manuals, and a bushing kit for $248 shipped. The axles I got off the wagon have good inner joints and appear to be correct length but I won't know for sure until its mounted. If they are all I will need are the inner boots. My outers are practically new.

Are the trans dimensions the same on 'E' and non-'E' trannys?

quote Originally posted by USFiero: Are the trans dimensions the same on 'E' and non-'E' trannys?

NO. The non-E 4T60 trans (which is identical to the 440-T4) is shorter than the 4T60-E and 4T65-E transmissions. Depending on how you mount the trans on the Fiero cradle, you can get away with using the OEM Fiero right side auto trans CV axle on the right side of the 4T60 when installed in the Fiero. However, this axle is smaller and lighter duty than the Fiero manual trans axles and are only good for a low 13 sec 1/4 mile Fiero (depending on weight). For the left side you are still going to need to use the 94 Beretta 3100 4T60-E left axle.

The Mark Williams company in Colorado can make axles from 300M which is the strongest stuff around. Moser has their own alloy which I think is 4000 series. MW quoted me around $550 a pair for 300M. You can match up virtually any transaxle to work in a fiero with custom axles. The axles don't wear so they are a one time purchase. When the joints wear out, just buy them individually.

Cut the outer fiero axle end off inboard of the boot groove. Cut your transaxles axle outboard of the groove. Once the transaxle and engine are permanently mounted, lay the axle ends in a short piece of angle iron with heater hose clamps lightly holding the axles in the groove. Swing the suspension, making the axle as long as possible then shorten it 3/8".Make sure the tripod end of the axle doesnt contact the raised inside edge of the cup when rotating with the suspension hanging as far down as the strut will let it. If it is contacting, shorten the axle a little more which will raise the axle away from the cup. Too much and the top of the tripod will come out of the cup. Tighten the clamps, remove the axle's, measure overall length, Write a letter with exactly what you want done, make a copy for yourself, and ship the axles to Moser/MW. These are custom "racing" parts and there won't be any warranty so make sure you get it right and check them when you get them back with your copy of the letter. It's that simple.

Dont expect them to tell you how much it will cost without seeing the parts. They should call you once their engineers review the parts. If you dont want to pay, they ship them back. Only takes a couple weeks.

quote Originally posted by DanGT: where would the best source for info and performance parts for this trans?

http://www.bulkpart.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=2&Category_Code=4T60-440-T4manuals
There are 3 ATSG books for this trans. All three are full of info on problems they had and what to do to fix it. Mostly, they are bandaid fixes for problems that some of the transmissions might have depending on the tolerances of the parts installed, driver abuse, what they are installed in. They also have build codes you cant get anywhere else for specifics about the chain drive ratio and the final. For example, I noticed the W-body 3.1L also had the highest stall speed at 2025rpm for getting out of the hole out of the 3.33 equiped transmissions.

I also found that pull-a-part is the best place for a rebuildable core. Complete transmissions for only $50. Most of the cars they are getting are late '80's, early '90's and the trunks are all open for you to inspect the "Service Parts Indentification" label on the card board tire cover or stuck to the trunk lid. Of course, those could be from another vehicle which is why you must check the tag on the trans too. This is pretty easy to do since all the cars sit so high and are on gravel.

I've torn down the '88 trans I bought previously for $100. If I'd checked the trunk tag I would have known it was 2.84, 1:1 chain. The fluid was a little dark, pulled the pan and found nothing, cut the filter open and found a shaving. There is damage to the reverse band($8) but otherwise the trans is in good shape and very clean inside. It took most of the day to pressure wash the outside and tear it down completely, keeping everything in subassemblies. No special tools YET other than two long skinny #1 flat blade screwdrivers to remove the C-clip from the diff. A normal length screwdrivers handle will prevent you from getting the right angle to push the snap clip off. Once its popped out, the shaft will slide out, allowing access to the big snap ring holding the diff in. The diff is right behind the passengerside axle seal. On a 4t60e, the case is two pieces so you can unbolt that end, pop the clip and pull it out easily. On a 440t4, the diff is the last thing to come out.

The rebuild kits are slightly different for 89-92 440t4's so go with atleast a 89, preferrably a 92 like Ogre said. I already bought my kit and except for the damage to the side of the reverse band which I need to analyze, looks good so I'm just changing the final and probably buying new aftermarket sprockets from Aceomatic.

For those considering doing this, I'd like to emphasize that this isnt shade tree work. You need a pressure washer, large clean work table(floor vinyl covered plywood is nice), small clean parts washer, clean tools, air compressor preferably with water filter, a mount fabricated up where the case can be rotated during assembly, manuals(have photos of mount), a few specialty tools, clean lint free rags, clean hands, and patience. It's not that complicated but it is delicate and must be perfectly clean inside or the valves will stick in the bores.

As an update to my 440t4 rebuild, I had bought a 2.84 final, 35/35 trans for $100 before I fully realized how the identification system worked. I went to pull-a-part and removed a 3.33 final from a 4t60e in about 30minutes. Quick and easy with a 2-piece trans case. They sold the diff to me for $13 as a #415 or 451 gear, trans. Having no luck finding 3.4L DOHC luminas, I called Aceomatic trans today and ordered a used 33T/37T set for $41 plus shipping(U84705A and U84706A). That set is rare and hard to find since it only came on certain quad 4 cars and the 3.4 DOHC's but if they have it, it's cheap. I've gone from the garden variety 2.84 to 3.73 for $71. A few selective thrust washers and I should be in good shape.

I hope you have some sticky tires. 3.73 sounds like it will be fun. I Found a salvage yard in town that has a huge selection of engines and transmissions. They have them all in a climate controlled warehouse and the engine size make and model and milage of all of the transmissions are documented. I figure with their info and the codes from the id tags on them I should be able to get what I am looking for. They want about $100 for the 4t60s from running cars under 100k miles. Seems fair I think. This would be my first trans rebuild so I would rather start with one that ran rather than a big case of gear soup.

Turns out my boss used to work at this salvage yard and his uncle still does so I might get a discount. He said they were an honest place to deal with. The only problem now is if they give me a good deal on stuff I might come home with a 3800sc engine and trans by accident.

Thats good. If I didnt already have the practically new 4.3 in the fiero I would just go with the 3800 4T60E combo. The only thing I dont like about 3800's is the aluminum oil pump housing built into the timing cover which really isnt an issue as long as replacement covers are affordable. I think even a 3800 with sc weighs less than the 4.3L with its adapters. The only aluminum heads for a 4.3L were for Bush Grand National cars in the late '80's by Brodix. I just want a reliable trans at this point.

Before I put the 4.3L in my miata, I considered a 3800 but the oil sump is in the wrong place for rack clearance. Those cars are tight everywhere and custom headers are required. I also have a complete 4.9L in storage and my wife's former turbo miata chassis to put something in. Decisions, decisions...

quote Originally posted by theogre: I'm also told you could take the gear/clutch pack from an E series and put it into non E unit to gain the bulk of what makes the strength class number. IE you could make a 4T60 into a 4T80/85 that way. (80/85 were not available at all as a non E unit far as I know.)

Can anyone confirm this statement? if this is true then TONS of people could be doing this. I am alos going to call a couple tranny shops around town and ask about this.

I'd like to know the answer to that as well. I was under the impression that there were some dirrerences in the clutch packs etc in addition to other changes as the transaxles "evolved".

so from what I understand the manual axles cv joint will allow me to use axles from HDbrake 4speed cars which seem easier to find. Basically making adapter axles. I found a manual fiero at the junkyard and Im wondering if I need to grab the axles for my swap.

I used a 1990 Cadillac Seville STS 4T60 and had it rebuilt with hardened parts, 3.33 final drive installed (it had 2.84) and ordered the 37/32 chain and sprockets to get 3.73

The torque converter was replaced with a 1675rpm stall (but mated to a V8 it will act like a 2200rpm stall)

Also added was a Trans-Go shift kit.

I will take pics of it installed once I get the LT1 back from rebuild.

Ryan

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1986 Fiero2m8 (LT1 NOS / 4T60 Auto)

This is the best 4t60 thread I have seen in a long time. Just when I am looking for one. Thaks to all for great info

I had a friend of mine who works at the a chevy dealer try to get me one at cost. I was trying to get a 1992 lumina one cause it was the latest non E model that I could find. I dont know if the 92 is the reason it was so high but it was 1300 at cost. Apparently the GM remanufactured ones are discontinued So junk yard it is. Has anyone used a 4t60E and piggybacked an ECM from the donor car? Seems like it would work with just a few sensor inputs to tap into. Would having 2 ecms hooked up to one sensor screw with the computer that was controlling all of the other functions?

i just called chenny trans- up in hamlake MN. and jeff (the owner) said that internally there is not much different in the 4t60 and 4t60e. The only differences are are how htey are controlled. The electronics themselvs to do make the 60e stronger but the improvment of the same exact parts that are used in the NON-e are used in the "e" so that is what makes it stronger. and as far as he can tell one could transfer the parts from the to the "e" to the non-e. Also he said that the 4t80e was actually physically larger than the 4t60e so with that he thinks that the parts from the 80e will now work at all with a 60 series. Then i asked him what about the 65e/65e hd. Then he said they may be close but without actually looking at the parts for the 65 in comaprison to the 60 he cannot trully say if they will interchang seeing that he has had no experience in doing the thing i was asking.

I just talked to Jeff at Engineered Performance about this and he said that they will build 4t60/4t65e hybrids with true clutch type posi diffs for $2500. So it can be done. This is basically a 60 with 65e internals but not the electronics. He also informed me that the 60 has a weak second gear, a single clutch overdrive and soft internals. This hybrid deal is what they recomended for a 350hp V8 fiero. They also sell the posi diffs for $550. The Fieros get the race version since they are RWD and most of there posi diffs are for FWD apps. This could be a great solution for the auto v8 swap guys.
Here is the contact info I got.

Jeff Ianitello
Engineered Performance
1129 Cobb Parkway SE
Marietta, Georgia 30060
770-528-3882
www.engineered.net

Thanks Dan.
Good contact.

My axles should be the weakest link now after having the trans rebuilt with the best parts that would fit.
I'll have to cross that bridge if/when the axles break.
I like the idea of upgrading to thicker axles - if only I can find a manual Fiero at the wreckers to get the outer CV's etc.

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1986 Fiero2m8 (LT1 NX / 4T60 Roadster Build)
https://www.fiero.nl/forum/Forum2/HTML/071642.html

http://fp.enter.net/~rockcrawl/4T60a.html