Designed by the Getrag Co. of Germany for GM as the high output 5 speed transaxle, built by Detroit Diesel Allison in Muncie, Indiana. (usually referred to as the Getrag to cut down on confusion)
Each of these transaxles are used on many different GM front wheel drive cars as well as on the Fiero. There are a range of different final drive axle ratios available depending on the car and the year etc. but they are all basically the same internally and have the same bell housing bolt pattern.
This means that any of them can bolt up to either the 2.5 litre 4 cyl. engine or the 2.8 litre 6 cyl. or for that matter the Quad-4 or the 3.8 litre monster-motor. The difference is in their capacity for torque and in the arrangements of the external shifting mechanism which is a bit unique on the Fiero.
Thus, you should be able to adapt a 5 speed Getrag from a Cavalier (J-car) for use in a Fiero with only a couple of minor modifications on the OUTSIDE of the transmission. This is an important and useful fact now that Fiero Getrags are getting rare. The modified parts look very simple and should not pose a big problem for anone who is capable of an engne swap.
As for the torque capacity - the Isuzu will fit the V6 cars but is said to not be heavily enough built to take the torque - so this is not a good swap. Zsolt in Toronto had an Isuzu in a V6 car and it only lasted a year or so before melting down on a fast trip down a freeway (ouch).
[Note: This seems to depend on who you ask. V8 Archie, and others, say the Isuzu's work fine with the V6's and V8's without problems.]
The [V6's] 4 speed Muncie is very heavily built and can be used with any engine including a V8 (within reason) and the 5 speed Getrag is also a heavy duty unit.
The post 1989 Getrags have a different speedometer drive arrangement which uses a magnetic Hall effect sensor instead of that idiotic goddamn gear driven VSS unit. (I have had a problem with the VSS gear falling off - can you tell that I am still a little tense about it)?
This means that if you buy a post 1989 transaxle out of another type of car - you will have a lot of extra hassle getting the Fiero speedometer to work with it.
From: Peter Frise (edited with corrections from Scott Backer)
"Does anyone make a kit to adapt a 5-speed Getrag from another GM car?"
Rodney Dickman (1-414-762-9244) makes a kit which does this conversion. I got his name off the list about 2-3 months ago (I am planning a 3800/5 spd swap) . The kit (cheap like $50) basically consists of some bracketry to convert from a Cavalier type shifter linkage to a Fiero linkage - internally and in the actual details of the trans case itself, there is apparently no difference. The axles also are supposed to hook up without modification.
From: Peter Frise (with help from Paul Herder)
"I would like a 5-speed Getrag for its higher power rating, but I prefer the ratios of the weaker Isuzu 5-speed. Any suggestions?"
The muncie getrag is a quick-change transmission. Buy one (cost about $1200 brand spanking new) and just get a new set of gears for it. Hell, you can even put smaller gears in for racing and then swap in taller ones in about an hour for freeway use :-)
I just happen to have one of my bills in front of me when I had mine replaced, and they bought a brand-new one from Detroit - came in a crate hot off theg assembly line - $1075 !! Not bad. A junk-yard rebuilt one is close to $800. It shifts very smoothly, and will handle lots of power.
From: Evan Langlois
"I heard that the Lumina Z34 with the 200 hp 3.4L Twin Dual Cam engine has the Getrag 283 5-speed transaxle (RPO M27), which has a greater torque capacity than the MG2 unit used in the regular 3.1-equipped Lumina."
I have seen this tranny from a Grand Prix w/ 3.4 TDC engine. It is the next generation Getrag 5 spd. It has strengthing webs inside the bell housing and a much better slave/throw-out bearing system. One weird point, it uses a special clutch with is PULLed to release.
Tranny is $2500 rebuilt. Clutch is $300. I won't be buying one any time soon.
From: Dave Cole