I've come to realize that a turbo car is only fun when its a manual... so I need to know the decreased amount of HP that I can to push out of my engine swap in order to get one. So does anyone know the power limits of the getrag and muncie?

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Your ability is your only speed limit.

Archie has some information on that...

http://www.v8archie.com/faq.htm

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RickN
White 88GT 5spd
White 85GT Auto

Yeah but Archie is speaking from a sales persons point of view, if he told everyone that if you treat your car with abuse, then your transmission is going to have problems. Then how many people would be purchasing one of his V8 kits if they think thier transmission is going to be trashed before an oil change. Not everyone that gets a V8 treats treats it like a baby. If they wanted a car they can treat with little or no abuse then why have a V8? Not to seem immature but the reason why I'm building a a 400-500 HP Ecotec is for fun. Yeah I'm young and dumb, but there's no reason why I shouldn't enjoy life. Who knows when it ends.

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Your ability is your only speed limit.

Horsepower isn't what transaxles are rated for. They're rated for the amount of torque they can handle; not quite the same thing.

Since horsepower is equal to (torque in ft.lb. X RPM) / 7272 it's possible to have a high revving engine with low torque that produces high horsepower; this is the "magic" way to run high horspower with a Fiero tranaxle and have things stay stuck together.

Many (including myself) believe that the V6 Muncie 4-speed is the strongest of the Fiero manual transaxles but the ratings for it and the Getrag / Muncie 5-speed are identical: 250 ft.lbs. max. That's the factory "last for 100,000 miles, no warranty claims" rating so you can probably go up to 300 ft.lbs. without any ill effect other than a shortened transaxle lifespan.

So if your Ecotec produces 300 ft.lbs. at 10,000 RPM that'd be 412 horsepower. That'd be a nice exciting ride and should go for many, many miles without spitting out transaxle parts.

There are no problems with the transmissions if they are driven as the factory intended. When you add extra horsepower and or torque way over the original design they will fail. Even a stock 2.8 engine has enough horse power and torque to break the transmission. Now if you have a slippery clutch or cookie cutter tires with a ware factor of 300 or higher this can help to keep the transmission from premature failure. If you load the transmission as in a throttle roll on the transmission will take large amounts of torque from any engine combination you might want. All three transmission’s can take about 350 to 400 ft, lbs of torque with no problem if you load the trans first (no shock load).
What fails in the transmission over time is the differential gears (spiders). These gears are too small to absorb the power and the gears will start to loose their case hardening over time and fail. Now if you try to launch the car (drag racing) that’s a different story. Their are other problems with the transmission that also come into play. At high rpm’s above 7500 you can’t shift the transmission do to the key’s in the synchronizer will lock the synchronizer keeping you from shifting. Until the rpm’s drop. The first gear synchronizer can also be twist off the shaft with repeated hard launches. The axles can brake if the axles are not straight from the outer CV joint to the inner tripod (horizontal). We have seen the tripods on the axles brake also twisted shafts and just about any way the transmission can be broken.
The Isuzu, Muncie and Getrag transmission also has their problems besides what we have talked about.
The Isuzu 5speed has gear ratios that are not well suted for higher output engines. 1st gear is way short and the 5th gear shift fork is made of aluminum, so shifting into 5th and reverse needs to be done with ease or you can break the fork. Also the shift cables on this transmission are in your face when you open your deck lid you might not like this. The transmission is also inexpensive and easily obtainable.
The getrag 5 speed transmission is also a good choice. The problem with this trans is the high price and is difficult to obtain. This transmission also has a 1st gear that is to low for the higher output engines thus rendering 1st almost useless. We have seen a lot of differential carrier bearings fail in this transmission and also the support for the throw out bearing fail.
The 4 speed 1985 to 1986 seams to be the best transmission for strength. The 1984 transmission cases don’t have he ribbing on the case for reinforcement. The drawback for this transmission is the four speed.
The top gear is a little short and 1st gear is not as low as in the other transmission’s but still too low. With this transmission the final gear ratios can be ether 410 362 or 323. This can be changed by using the ring and pinion out of the 1984 standard 4 speed and performance 4 speed. Some transmissions came with 323 gears and some with 410 but not as many with 323. If you use the 323 gears this puts 1st about half way between 1st and 2nd in ratio and 4th just a click below the 5th gear ratio as in the Getrag. With this combination you can run about 110mph in 3rd. Unfortunately you can’t change the ratio’s with the Isuzu or the Getrag as the pinion gears and ring gears are not the same as the Muncie.
The 125 auto is not good for anything but the stock 4 cyl. If you put it behind a high out engine and drive it like a 4 cylinder the 125 will work just fine. Even with a highly modified 125 it will fail in a relatively short time. If you want an automatic, put a 460 or a 465 transmission behind the high output engine, its not that difficult. With this trans you will have a 4speed overdrive and a trans that can handle the horse power and torque.

Actually the muncie 4 speed's came with 4.10, 3.65, and 3.32 final drive ratios.

Getrag differential problems?

https://www.fiero.nl/forum/Forum2/HTML/064025.html

quote Originally posted by Fast Red: The 125 auto is not good for anything but the stock 4 cyl. If you put it behind a high out engine and drive it like a 4 cylinder the 125 will work just fine. Even with a highly modified 125 it will fail in a relatively short time. If you want an automatic, put a 460 or a 465 transmission behind the high output engine, its not that difficult. With this trans you will have a 4speed overdrive and a trans that can handle the horse power and torque.

That's a strange comment. Are you aware that there have been runs using a modified TH-125H transmisson in Fieros that have run 10's and 11 second 1/4 mile times!!! You can enlarge the clutch packs on these trannnys, add a shift kit, a high stall speed torque converter and make other mods that will make this tranny much stronger than stock. I run a worked TH-125H behind a highly modified /turbocharged 3.4L and I've come off the line with boost many times at 2500RPM and have beat the crap out of it for three years. The tranny still works as good as the day we put it in. Good for a 4 cyl only- I don't think so!!
In contrast there is little that can be done to modify the stick. In speaking with an original member of the GM design team a while back; he told me that the GETRAG was designed to take a maxium of 250 ft lbs of torque. It may last a while with higher torque but you are pushing the limits.
If you want something that will last for drag racing the automatic will. Your engine will labor more on the highway with the auto and it's not as much fun as driving a stick but for the 1/4 mile; I maintain that it's the way to go for consistancy -no human can shift faster than a carefully prepped automatic can..

What axles do you use on the 4t60 and 4t65 - and has anyone ever used the 4t40?

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Your ability is your only speed limit.

[This message has been edited by IEatRice (edited 06-14-2005).]

That's a strange comment. Are you aware that there have been runs using a modified TH-125H transmisson in Fieros that have run 10's and 11 second 1/4 mile times!!!

Dennis

Think about what you are saying! If the 125 is as strong as you say the GTP guys would be all over it. 10 sec pass maybe one time.
The transmission is smaller, lighter and you don’t have to deal with an ECU to operate the transmission.
I did not say the transmission will brake immediately with high torque engines but it won’t last long. A 3.4 turbo is not a high torque engine. A 350-383 or a hotrod 3800 SC or Turbo can be. Even the 465 hot rod transmission has problems handling high output engines.

[This message has been edited by Fast Red (edited 06-14-2005).]

quote Originally posted by Dennis LaGrua: That's a strange comment. Are you aware that there have been runs using a modified TH-125H transmisson in Fieros that have run 10's and 11 second 1/4 mile times!!!...

Pls show me ten...and then show me how long!!...Can someone pls Call fieroX in here...or lets get clubgp.com in here...NO when talking performance tranny it will be a good thing not to mention a 125C...you are indisriminantly saying ppl are running almost 400-500 ft/lb Tq in this trannies and living to tell about it...or just one quarter mile pass!?!?
Anywayz like already pointed out...longevity is directly correlated with how the said drivetrain is treated...all the so-called bulletproff trannies can be shredded given the right circumstance...and the more well built the tranny is, then the longer it can potentially hold up...

quote Originally posted by Whuffo: Horsepower isn't what transaxles are rated for. They're rated for the amount of torque they can handle; not quite the same thing. Since horsepower is equal to (torque in ft.lb. X RPM) / 7272 it's possible to have a high revving engine with low torque that produces high horsepower; this is the "magic" way to run high horspower with a Fiero tranaxle and have things stay stuck together. Many (including myself) believe that the V6 Muncie 4-speed is the strongest of the Fiero manual transaxles but the ratings for it and the Getrag / Muncie 5-speed are identical: 250 ft.lbs. max. That's the factory "last for 100,000 miles, no warranty claims" rating so you can probably go up to 300 ft.lbs. without any ill effect other than a shortened transaxle lifespan. So if your Ecotec produces 300 ft.lbs. at 10,000 RPM that'd be 412 horsepower. That'd be a nice exciting ride and should go for many, many miles without spitting out transaxle parts.

Your equation is wrong. hp = torque*rpm/5252 . not 7272.

As far as transaxles... go ask Fiero X what they CAN'T handle...

bump for later

T-125 for 4 cyl only?
I'm running low 14s with a Turbo 2.8 and a stock (no rebuild) T-125 and 114K miles.
Seems to be holding up fine. Could use a shiftkit.

My son put over 200K on his.....beating the crap out of it.

Pls...14's and 10's are like this:

14s................................................................................................................................................................................. .................................................................................................................................................................................... .................................................................................................................................................................................... .................................................................................................................................................................................... 10's!
TH125...lol!! somebody pls show me how many 125Cs in the 10's...

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the ORIGINAL 3800 II v6 intercooled turbo...

Laugh all you want, the fact is, the 125C is the only transverse transmission ever to see a 10 second pass in a Fiero... that is if my memory serves me right.

The 125C's strength is in its simplicity. it takes only a few hours to rebuild the transmission. Almost all failures with this transmission are "soft" part (clutch) failures, or jamming valves. Mechanically the hardware the engine comes with is pretty dam tough. But when you put some more thaught into it, the same applies to the 4T60(-E) and the 4T65-E. Brute hardware, and usually has clutch failutes. What it all comes down to is the shift kit, the clutch materials and tolerances and proper operating pressures to ensure full grip of the clutches, you will have a strong transmission if the correct modifications are performed.
Unfortunatly for manual transmissions, there is very little that you can do to prevent failure, except modify driving habbits. FWD manual transmissions are the simplest, lightest and cheepet drive lines that can be built, I dont understand why they haven't got it right yet. I'm hoping this 6 speed that they started making is all it promises to be.

quote Originally posted by Fierobsessed: Laugh all you want, the fact is, the 125C is the only transverse transmission ever to see a 10 second pass in a Fiero... that is if my memory serves me right. ...

How many cars?
Your memory has indeed failed you Apparently if it doesn't exist on the board then it doesn't exist? but the 125C IS NOT the only transverse to have gone into the 10's...believe it or not!
Believe it or not, if the 125C were all that then a lot more ppl would have flocked over it...period!! The 4t60-HD is what the 125c wishes it could be...I digress...the point is it every tranny has its limits, disregarding abuse... parts have design limits, so to say with 'a few clutches here or bigger bands there' does not put the real issue down...because whatever you can do to the 125C can be done to the 5 or 6 other GM transverse tranny to make them even stronger!!
A 125C IS NOT A tranny you want when it is time to put power to the ground...if it were then in the performance realm we would all have been bamboozooled...

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the ORIGINAL 3800 II v6 intercooled turbo...

quote Originally posted by Fierobsessed: the 125C is the only transverse transmission ever to see a 10 second pass in a Fiero.

Like I said, In a Fiero...

The whole point of my post was to point out that the 125C is actually a good competant transmission for the drags. Its so simple inside, its pretty hard to mess the little thing up. Kinda like a 2 speed powerglide... They were so simple with there single planetary reduction, that as long as the clutches held, the transmission was dam near bulletproof. Strength in simplicity. Just because its small, light, and cheep and old... doesn't always mean it's a weak piece of junk.

Granted, I've seen a Turbo 3800 GP run a 10.998 with a built 4T65-E. But that's not a Fiero transmission.

Looking back at the origional question, and title realizing there is no mension of an automatic anyway.

Let me provide the details.
Archie has a customer that built a drag race only Fiero which used his kit coupling a SBC w a 400 HP nitrous kit to a modified TH-125H. His name is Pat Caircia and he runs C & C automotive in Mt. Pocono, PA. Pat tried running he GETRAG and blew up a few after one run or two. He then switched to a modified TH-125H and drag raced the car over three seasons with not a single failure. This car was featured on Archies website for a long while. I spoke to Pat prior to building the TH-125H that I currently run before I decided on my tranny choice.. BUILT CORRECTLY the TH-125 is bulletproof!
The other guy that ran 11's in a V8 Fiero using the TH-125H was a Canadian fellow. I believe that he ran a transmisson shop and I'll have to ask our Canadian friends to post his name. His low 11 runs were shown on an mpeg video a year or two ago right here on the forum.

For a manual I'd have to say either the 4 spd in the v6 case or the Getrag.
Tina has exploded many 5 speed muncie, and recently switched to a getrag with cryo treat, no failures, and she has previously ran 11's on the 5 speed muncie with her 383.
California Kid was running 12.2 with his vet engine with the getrag, also cryo treated the case, again no failures except axel shafts.
The problem is that most people running 3.8 or larger with big torque is they put in a 20 year old transmission that has never been overhauled. I believe the getrag with a cryo treated case has already passed the test for big torque engines with the two mentioned above. The four speed 3.65 final drive is probably just as strong, but if you have to modify them to handle the power in the first place why not get the extra overdrive?
P.S. I remember the car featured on archies site, that car was badass. I have an auto with a 3.33 final drive, but again if it also has to be modified to take the abuse, why not do a 4t60 or better to have the extra gears.
I think that if you had a 4spd and 5spd getrag modified, which they would have to be any way you would find very little difference between them in strength.

The guy from Canada that ran the 11 was using a modified 4T60, his name is Troy Ritchie of TR transmissions. Pretty badass that car.

quote Originally posted by hoola47: For a manual I'd have to say either the 4 spd in the v6 case or the Getrag. Tina has exploded many 5 speed muncie, and recently switched to a getrag with cryo treat, no failures, and she has previously ran 11's on the 5 speed muncie with her 383. California Kid was running 12.2 with his vet engine with the getrag, also cryo treated the case, again no failures except axel shafts. The problem is that most people running 3.8 or larger with big torque is they put in a 20 year old transmission that has never been overhauled. I believe the getrag with a cryo treated case has already passed the test for big torque engines with the two mentioned above. The four speed 3.65 final drive is probably just as strong, but if you have to modify them to handle the power in the first place why not get the extra overdrive? P.S. I remember the car featured on archies site, that car was badass. I have an auto with a 3.33 final drive, but again if it also has to be modified to take the abuse, why not do a 4t60 or better to have the extra gears. I think that if you had a 4spd and 5spd getrag modified, which they would have to be any way you would find very little difference between them in strength.

you mean a 5speed isuzu is what she had before the 4speed is the muncie \
why would you need to modify the 4speed? from what I understand the metal used ont he 4speed gears isn't very affected by cryo treating - the only thing to do is replace the synchros, blocker rings, and bearings to make it a nice fresh tranny

quote Originally posted by Fierobsessed: The guy from Canada that ran the 11 was using a modified 4T60, his name is Troy Ritchie of TR transmissions. Pretty badass that car.

I stand corrected. I knew Troy was running an auto for his 11 second runs but I thought that it was a TH125H . It's good to know that the 4T60 when built can also take that type of power. However, I'm sure that Pat Ciarcia was running a TH-125H in his Fiero and ran mid 10's. Pat told me so and also has time slips to proove.
In theory the 4 speed should be the strongest manual. Look at the Muncie case examine the width of the gears and compare these to the GETRAG. The muncie has a reinforced case and wider gears.
However, I would not trust any Fiero manual behind a "bonzai" high torque engine as I've seen reports of many burned clutches and blown gearboxes. The Fiero linkage and shifter also makes for a sloppy shift.
On the highway the 5 speed is more pleasant to drive and it can be argued that the stick is more fun to drive, but for drag racing applications and street/strip, the auto is the box to win with.

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87GT 3.4 Turbo- 0-60 5.2 seconds -Best
Engine Controls, ECM goodies, Chip
re-programming & odd electronics stuff

quote Originally posted by Kohburn: you mean a 5speed isuzu is what she had before the 4speed is the muncie \ why would you need to modify the 4speed? from what I understand the metal used ont he 4speed gears isn't very affected by cryo treating - the only thing to do is replace the synchros, blocker rings, and bearings to make it a nice fresh tranny

Cryo treating affects any heat-treatable metal... They'd better be using something heat-treable for gears.

quote Originally posted by Will: Cryo treating affects any heat-treatable metal... They'd better be using something heat-treable for gears.

it affects some more than others - some gears have been shown to gain very little from cryotreating

built Getrags with Webster racing gearing can be found here: https://www.fiero.nl/forum/Forum1/HTML/052661.html

quote Originally posted by Kohburn: it affects some more than others - some gears have been shown to gain very little from cryotreating

Also depends to some extent on the initial heat treatment. Cryo treatment is a continuation of the heat treatment quench that usuall stops at room temperature. If the initial heat-treat was not very aggressive, then cryo treatment won't be very effective.