I am looking into a v-8 conversion with a 5-speed, but I want to get good gas mileage. Is it possible for the isuzu tranny or the getrag to be regeared? What gears world work best? where di I get them?

Thanks for all of your help in advance

Hey Hym!
I also remember seeing a limited slip differential available too...
Nice for your conversion...
crash...

I was simultaneously wondering the same thing! I talked to Archie, who is working on the LS1 motor (98 and up Camaro motor) kit for Fieros, but recommends the LT1 motor (93-97). I have never riden in any car with an LS1, but I own a 94 Camaro LT1, 6speed. That thing can drive at 1500 rpm and still pull fine. In fact, at 100mph it turns at 2400rpm. There is no need to run that thing over 3000 rpm except for an instant when racing. It goes beyond gas mileage with our application; how about top speed or lastability. I don't think you would get much more than 50,000 miles out of an LT1 or LS1 with stock gearing if you're in the habit of going 90mph all the time. That's not scientific, just speculation. When I cruise, I never exceed 2000rpm in any gear. If you look at the torque band, it runs out somewhat early (check out http://www.tcnet.net/~dstorer/jf/). That tells me runing the engine at 3-4000rpm would ruin it before its time. That engine will generate some heat when running at higher rpm's. With the Isuzu or Getrag, 90mph is 3 about 3000rpm, so that ratio is undesireable for a sweet swap like the LT1 or LS1. So I would like to reitterate your question......Thx, Ed.

You know, that brings up a good point for
discussion.Our little cars were built in an
era of 55mph speed limits,so really the entire car was engineered to hardly ever
exceed about 75mph!todays cars are built for
70 plus mph and occasionally going 90mph!.
Try this-jump in your fiero and drive 95mph,
then jump in a 2001 grandam gt and do the
same thing-see the difference?I did it and
was suprized at how much better todays cars
are engineerd,designed and built!.I am just
pointing this out because if you rebuild your
car to go 100mph,you are doing somthing that
car was never intended to do!(I have a 87GT
with a SBC w/5spd so I should'nt talk!)This
was just somthing I was pondering the other
day.........

No manual transmission available for the Fiero is geared tall enough to let a V8 stretch its legs.

Hym,
Build the v8 to fit the gears you have. Change the cam profile to fit the rpm range for your gears. If your looking for the best fuel mileage go with a fuel injected engine. When I put the v8 in my 84 I did not even worry with fuel mileage. I wanted that G pull.

I've heard a number of V8 owners mention on here that 1st gear in a 5-speed V8 Fiero is almost useless. They usually start off in 2nd gear. That tells me it's way too steep a gear for the V8. I'm thinking a low 3 series (3.08-3.23) would be good for a typical SBC swap, whereas I believe most Fiero manual tranny's are between 3.60 and 4.10. That must be why the econo-coupe 4 speeds are so valued for the V8 swaps. Any thoughts? Most of the hi-perf gearsets I've seen for the Getrag are either stock ratio or steeper. Anyone make numerically lower differential gear ratios for them?

A final gear change can be done. Especially on the Isuzu. However, it won't gain much less RPM anyway. The stock 5 speed has a very well balanced ratio for the typical V8 with a mild cam and carb.

With a standard trans you really can't put much more than 250 to 300 hsp on the clutch anyway (using a Dual Friction Centerforce). It will have major slippage and failure problems when you increase the hsp.

Therefore, you are back to the drawing board anyway. Either drop down to a mild cam, carb (fuel injection) unit, or find a way to get a larger diameter clutch and heavier duty trans.

Otherwise, if you want a V8 that will cruise at 1,500 RPM and have 300 or more hsp, just get a late model six speed F-Body and leave the engine in the F-Body.

I got this off the Fiero racing list which I moderate:

Hi guys. I know this sounds self-serving, but I joined the list today because I wanted to let you know about a tranny I have for sale on ebay. It is a 4-speed manual with Webster straight cut gears. I got it with a Citation X-11 that used to be an SCCA IT racer. The former owner of the car got the tranny from another racer and never installed it. I have no idea what the gear ratios are, but they are certainly suitable for track use. The tranny looks to be freshly rebuilt. I do not plan to trace the car anymore (except for autocrosses) so I have no need for the tranny. It is yours for the taking, but THE AUCTION ENDS TOMORROW MORNING! Search on ebay under "fiero race transmission". Last I checked, the high bid was only $167.50. Shipping will be $75 or less, depending on location.

Jerry Brownell, Driver
Team Yo! Rallysport
#553 Group 5 Chevy Citation http://ourworld.compuserve.com/homepages/teamyo

I know it's a 4spd , but if the gearing is for a track , it's likley a nice setup , close ratio..

------------------

Jonathan McCreery
86 GT 4spd
Koni's , Coilovers, Big Bars , 17" Trmotorsports Typhoons , 11.25" vented discs, Wilwood 4 Piston Calipers , Pirelli P Zero's, Short Shift, No cat , Cold air induction , Geni Stainless tips, White face gauges , Momo shift , momo pedals..Autocrossed , Tracked , abused.

The stock Isuzu 5 speeds (85-88 2.5 L4's transaxle) has a FDR of 3.35:1

Quaife sells a LSD for ~$1000

GM has the following FDRs available (no, I don't have any part numbers)

3.35:1
3.578:1
3.833:1
4.117:1

The stock Getrag 5 speed (86-88 2.8 V6) has a 3.61:1 FDR.

The only other "stock GM" ratio available is a 3.94:1

The Quad 4 Getrags have a closer spacing to the gear sets than the V6 Getrags but they too only have the 3.61:1 or 3.94:1 FDR (actually the 3.94:1 was ONLY available in the Quad 4 Getrags!)

So the best FDR transaxle is the 2.5 L4's Isuzu 5 speed. I have one of the 3.35:1 FDR Isuzus in my 88 Coupe with a HO Quad 4. It will run 60 mph @ 2000 rpm. (with a 7200 rpm red line that means I would be doing 210+ mph @ red line in 5th! )

Unless you want to spend $$$$$$, the stock Isuzu gear set is the best available 5 speed transaxle for the V8 AND gas mileage.

Paul

[This message has been edited by pherder (edited 06-19-2001).]

I don't think the Isuzu is up to the job. It is a low torque rated tranny if I remember correctly.

The Getrag/Muncie is rated to 200hp but I've seen them take a lot more without breaking. I think it will be up to the job. I am only aware of one replacement gear (3.94 -1) which can be used in place of the 1st gear. It is not a good swap.

I would love to see a new final gear come on the market.

[QUOTE]Originally posted by Chris McDonald:
[B]A final gear change can be done. Especially on the Isuzu. However, it won't gain much less RPM anyway. The stock 5 speed has a very well balanced ratio for the typical V8 with a mild cam and carb.

With a standard trans you really can't put much more than 250 to 300 hsp on the clutch anyway (using a Dual Friction Centerforce). It will have major slippage and failure problems when you increase the hsp.

The Isuzu 5 speed has a well balanced ratio for a V-8 for Saturday night cruising, not to allow it to stretch out, as Will said. Actually, not even for medium to long trips. There is no need to turn that LT-1 at more than 2,000 rpm when going down the road to work, even if it's 10 miles away. Ride in a car with an LT-1, see what I mean. It will gladly tach out, but prefers to cruise along at 2-2,200 rpm. I think it would be uncomfortable to zip along on a long trip at 3,000rpm with an LT-1. With the 2.8, it's about right. I love the concept of the LS-1 swap, but the transmission is a problem for anything but racing around on Saturday night.

Has anyone ever thought about swapping in a Mitsu 3000gt/stealth tranny? It would be stronger and it has a 6-speed.

quote Originally posted by Rashaam: Has anyone ever thought about swapping in a Mitsu 3000gt/stealth tranny? It would be stronger and it has a 6-speed.

I've never seen one. Is it transverse mounted? I would have thought it was a longitudial tranny.

It is transverse mounted with an output shaft in the rear to the transfer case(that would be easy enough to remove). Those trannies can hold upwards of 320hp stock and I have seen some hold 600hp engines, mind you the engine is turbocharged so the power comes on more gradually.

[This message has been edited by Rashaam (edited 06-19-2001).]

Great idea on the Mitsu tranny, but I want to talk options that are feasible with a limited budget. Has any one switched gears for a v-8. to get better mileage. Gas prices are killing me and I want this to work. I know allot of other people are interested in this to, so lets work together.

I'm not sure about this, but I think I read another post where someone wanted to transplant an entire 3000gt engine and transmission into a Fiero. The problem was the rotation of the transmission output. I don't know if the engine rotates the opposite direction and the tranny is the same, or if the tranny reverses the output, or if this is all bullsh!t. And even if the tranny can be installed and run the correct direction, will the gears be turning the way they were cut? Someone with access please clear this up for everyone, because I agree that the 3000gt tranny would be good, depending upon the final drive ratio.

That opens up another can of worms; what is the final ratio of the 3000gt tranny. Mitsubishi's, like most jap cars like to rev up, so we might not be gaining anything up top. I drove a Stealth a while ago and remember something like 3,000 at 85 mph, so if I remembered correctly, we're right back to square one. Just because a tranny has 6 speeds doesn't mean it has a sweet final ratio.

Thanks EdsB52. I know that the new 3000gt vr4 has a 6-speed but the older ones had a 5-speed and I was only talking about the twin-turbo model. I can't find the gear ratios for the 6-speed, but I know that 6th gear is 0.59:1.
Here is the ratios for the 5-speed.
1st 3.07
2nd 1.74
3rd 1.10
4th 0.82
5th 0.66
final drive ratio 3.97:1

Good work Rashaam, I think we can eliminate the regular 3000GT from possibility. However, as we all know the VR4 has gobs more power and could be geared lower on the final drive. I wonder what we would be shooting for on the final drive in order to be in contention, 2.70? Did you check into that situation about the output turning backwards to the needs of the Fiero? I believe the engine goes in the 3000Gt backwards to the conventional. Honda civics are the same; transaxle on the right side. I think 3000GT's are the same.....check it out.

I believe the 284 Getrag had a 3.42 final drive and taller ratios for all the gears.

A little better, but not close to where we need to be.

Yeah does anyone know anyone that works for a tranny shop, or machine shop, Maybe we can have gears cut to change th ratio. Just a thought

Hym,

If your looking for economy, think about using an automatic with OD from a 88-92(?) Caddy. The car had a 4.5-4.9 CI V-8 and got decent economy. I don't know the final ratio but, since they were low RPM torque motors I doubt that you'd see them turning much more than 2400 RPM at 70 MPH.

Shifting is fun but for highway economy, a higher geared automatic may be better.

------------------
Roy :D
87 GT

The final drive pinion is mad onto the end of the output shaft. To change it you'd have to turn it down, girnd it to size, then have the shaft anealed and re-heat treated.
Then you'd have to get custom gears made to replace the stock units. If you have that kind of money, be my guest...

Would that hose your first three gears though Will? Maybe not, the LT-1 would probably have enough torque to pull 800lbs less, even with a steep ratio. Actaully, the work described, along with changing the usual synchros might cost what, 700-1000? Not bad considering the wear reduction to the engine, fuel savings, and overall driveability. The problem is though, that I fear, I think in order to obtain the desired top gear, you would lose the first couple. Meaning they would become too steep. Would it be possible to change the top 2 or 3 gears without affecting the first 2 or 3?

To get ~1500 at ~75 mph, you'd need an FD in the low 2's (I guesstimated 2.1). This would push 1st from ~5 mph/1000RPM to ~8.3mph/1000RPM. With a 6K redline, first would top out at ~50 mph, making it just shorter than second would be in a stock trans. This is a little steep for a first gear. I think a reasonable compromise could be achieved between highway gearing and acceleration gearing.

[This message has been edited by Will (edited 06-20-2001).]

Actually Will, my Z-28 goes 9-10 mph in first gear at 1,000 rpm. I don't think people fully appreciate the torque properties with the LT-1 motor. The problem is the weight. It weighs 80lbs more than the 2.8 per Archie. So your figures are about what we're looking for in a transmission, if the numbers are correct which I don't doubt.

Good call EdsB52 I checked out my brothers Stealth and the transaxle is on the right side. Is it still possible to swap it over or am I going down the wrong road? I want a stronger, better geared tranny for my V8 Fiero. Any ideas? I even checked out the Skyline tranny but the engine would have to be to far forward.

Just wanted to interject here and say that the LT1 with a 5sp Getrag will sit steady at 2000 rpms on 5th gear @ 70-75MPH.
Also, I would not call that first gear useless. It has a good pull up to the redline before you are forced to shift. That, however, might come sooner than most people would like. As far as I know, there is nothing you can do the the Getrag to aleviate this. And it does get kind of anoying after running 2K for a few hundred miles. But, rest assured tho', that even in 5th gear @ 2000 rpms, a drop of the hammer will take you into the 120's land before you can realize it. This is when you forget all about gear ratios and start enjoying your Fiero.

------------------
Winston Ojeda
88 Formula LT1
Milwaukee, Wisconsin, USA
http://www.FieroLT1.com
Home of the Fiero LT1
wojeda@FieroLT1.com

quote Originally posted by FieroLT1: Just wanted to interject here and say that the LT1 with a 5sp Getrag will sit steady at 2000 rpms on 5th gear @ 70-75MPH. Also, I would not call that first gear useless. It has a good pull up to the redline before you are forced to shift. That, however, might come sooner than most people would like. As far as I know, there is nothing you can do the the Getrag to aleviate this. And it does get kind of anoying after running 2K for a few hundred miles. But, rest assured tho', that even in 5th gear @ 2000 rpms, a drop of the hammer will take you into the 120's land before you can realize it. This is when you forget all about gear ratios and start enjoying your Fiero.

I see you've never driven an LT-1 w/a 6 speed. 2000rpm at 75 mph sounds a little low for the getrag tranny, because I don't care if you strap a frickin turbojet engine to the getrag, the ratios are the same from the input to the output in given gears. My Fiero's been down for a while, but as I recall, 75mph is more like 2,500rpm. That's patriotic and all to say that we should forget about gear ratios and just enjoy, but the net amount of enjoyment is correlated with the gear ratios. That's why the 84 Fiero sucks so bad. I had an 84 with that bullshit ratio, I totalled it and bought an86 w/a 5 speed. The same exact car was night and day because of the transmission. I loved the thing. Ya sure, it was a little slow on acceleration, but once you wound it up to 90, it performed as well as any v-6 and some v-8's, better in way of handling due to the reduced weight. So if your stuck with the stock ratio of the getrag (which is perfect for the 2.8), then you've never realized the awesome potential of top sped and overall driveability that you could with a more suitable ratio.

Oh ya, I know that at 2,000rpm you just drop the hammer and it goes, you're right before the meat of the torque band. The idea is to cruise at an rpm below the HP and Torque band.

It would be cool for someone to invest the time and money into R&D'ing a more suitable tranny ratio.

get taller tires. =Þ hehe

i have a getrag in my car. 2000rpm is about 55-60mph. even with my six it pulls good enough that i usually dont have to downshift to pass. my feeble mind cant imagine what 330ft lbs of torque would be like. wanna take me for a ride anyone?

------------------
JOEJOE Aol:SSFiero

88FORMULA
SSFiero@Aol.com

"Kids in the backseat cause accidents, accidents in the backseat caused me!!"

quote Originally posted by KissMySSFiero: get taller tires. =Þ hehe i have a getrag in my car. 2000rpm is about 55-60mph. even with my six it pulls good enough that i usually dont have to downshift to pass. my feeble mind cant imagine what 330ft lbs of torque would be like. wanna take me for a ride anyone?

That's about what I thought, so if 2,000 is 55-60, then 75 is about 2,500rpm. The getrag is a good tranny for the 2.8 or I imagine the 3.4 pushrod or TDC, since the TDC likes to rev out. But for a motor that loves to produce gobs of torque at as low as 2,500 rpm, the Getrag is insufficient. To me, putting an LT-1 in front of a Fiero getrag is like putting a Harley in front of a Suzuki GSXR transmission. Wish I had a Fiero w/an LT-1, I would gladly give you a ride! I'm not a Camaro guy, but when I drove my 94 Z-28 for the first time, it was the low RPM torque that sold me. Now I'd like to have that feeling w/my Fiero!

Well, I am not making that up. That is what I get. I see it every morning on my way to work. Unless the tach is all out of wack, and it has been converted to V8 mind you, 70MPH is EXACTLY 2000rpm and 80MPH is EXACTLY 2600rpm. The LT1 idles at exactly 850. I used the ECM real timed output to calibrate the tach so I doubt is off at all.

quote Originally posted by EdsB52: I see you've never driven an LT-1 w/a 6 speed. 2000rpm at 75 mph sounds a little low for the getrag tranny...

------------------
Winston Ojeda
88 Formula LT1
Milwaukee, Wisconsin, USA
http://www.FieroLT1.com
Home of the Fiero LT1
wojeda@FieroLT1.com

My car: 245/60-15 has diameter of 26.57" and turns 759 turns per mile

at 1 mile per minute (60 mph), the wheel is turning 759 RPM. With a 0.74 OD, and 3.61 FD, that works out to 2027 engine RPM at 60 mphl, and 2534 at 75.

Let's do a sanity check on the numbers you posted:
2000 RPM at 70 MPH is 35 mph per 1K RPM

2600 RPM at 80 MPH is 30.8 mph per 1K RPM

You're running a manual, right?
Your tach is hosed up.
You can not do both of these in the same gear.

Good math Will. I have never been able to mathematically translate RxT=D very well, but those numbers reinforce my contention that the Getrag works better w/an engine that likes to rev a little. That's why I like the TDC motor/Getrag combination, especially for someone that wanted to road race. However, overall driveability/reliability can't be beat by a pushrod motor, so the LT-1/LS-1 with the right transmission would be my favorite swap.

Just thinking last night about trannies. How about the NSX tranny? Could that work?

Come on Rasham, good to keep the options coming, but 3 things prohibit the use of that tranny.

1. It's probably geared like the Getrag, maybe worse. I believe the NSX motor likes to rev.

2. Even if the gearing worked, he cost would be so enormous it would be cheaper to go just about any other route.

3. Actually, this should have been first. Isn't the NSX a true mid-engine car? Not a rear engine car that was advertised as a mid-engine, like the Fiero? I think the engine in the NSX is linear (crank running fwd-aft). An awesome application, but would require stretching the frame and making a true mid-engine out of the Fiero.

I think it would be possible to modify the Getrag to work for the LT-1/LS-1, and wouldn't cost more than $1,000. That sounds like a lot, but really isn't compared to the wear, gas, and driveability gained.