ok yall i have a 4 speed manual tranny from an 84 se . is this the good tranny wiith the sought after fd? this tranny is attached to a iron duke. i wanna put it on a 3.4 will the bell housing from a 2.8 4 spd fit a 2.5 4spd? do i even need to change the bell housing? lookin forward to yalls help thanx skoon

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84 gt project
84 daily driver
84 donor for hmmmmm

Hi there,
From what I have read on this forum, the '84 Muncie housing is considered weaker than the '85-86 housing. Do you know which final drive ratio you have? Mine is the 4.10 "performance" fd (considered more common due to number produced), there is also the 3.65 "economy" fd. I also read here that the '84 housing is still pretty strong, just not as strong as the 85-86. For more info, you might try PMing V8Archie, he's pretty knowledgable about these trannys.

quote Originally posted by ktthecarguy: Hi there, From what I have read on this forum, the '84 Muncie housing is considered weaker than the '85-86 housing. Do you know which final drive ratio you have? Mine is the 4.10 "performance" fd (considered more common due to number produced), there is also the 3.65 "economy" fd. I also read here that the '84 housing is still pretty strong, just not as strong as the 85-86. For more info, you might try PMing V8Archie, he's pretty knowledgable about these trannys.

IIRC the '84 Muncie 4-speeds came with either a 4.10 FD or a 3.32. Sport or economy. The V6 4-speeds came with a 3.65 FD.

Yeah that 4.10 is good for acceleration, if that's the transmission you have. But, the 4-cylinder 4-speed transmissions lacked ribbing on the case of the transmission, so it can't take as much power. The 85-86 V6 4-speeds had a much stronger case.

If you do have the 4.10 you could possibly swap the gears into a V6 transmission? I think I've heard of this being done before.

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1988 Pontiac Fiero GT 5-speed
1986 Pontiac Fiero SE 4-speed

[This message has been edited by Tinton (edited 04-06-2008).]

I've been running the 84 case with the 4.10 FD for 4 yrs with a drive like you stole it behind a modded 3.4 DOHC and have never encountered a case failure. With that said, I would still recommend a 85 V6 4 speed with the 3.65 FD as a great choice for an all around ( economy, performance , toughness perspective ) trans

quote Originally posted by skoon: ok yall i have a 4 speed manual tranny from an 84 se . is this the good tranny with the sought after fd? this tranny is attached to a iron duke. i wanna put it on a 3.4 will the bell housing from a 2.8 4 spd fit a 2.5 4spd? do i even need to change the bell housing? lookin forward to yalls help thanx skoon

If the trans still has the sticker on it, you can identify the final drive. Some say that there is a set of numbers cast into the bellhousing, also that identifies it. The bellhousings for all the Fiero transmissions have the same bolt pattern and will bolt to the 3.4, 2.8, or 2.5. I believe there has to be a little grinding done to mount the Th125 to a 3.4, though. One of the axel shafts has a different spline, on the 84 trans and you'll need to purchase an 84 axel for that, if you're installing it into a later year. Looks like all yours are 84 though, by your signature.

I currently have the 4:10 behind a 2.8. In a recent event, I filmed from my car. Upon reviewing the film, I noticed that in changing gears, you could see the front of the car lift, even in 4th gear. It does offer quick acceleration. Since I was told that this was a 3:32, and it wasn't, this trans will be up for sale soon. I've only run it for about a month. All new seals, and the requisite New drive axel with CV joints comes with it.

thanx guys its out of the car right now ill look for a sticker how do i tell the fd without splitting the case or is this the only way. as always yall come thru appreciate it and yup all 84s

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84 gt project
84 daily driver
84 donor for hmmmmm

The sticker with the barcode has 614DW_M on it if it's a 4:10. In absence of the decal, you can put it in 4th, turn the drive axel 1 turn and count the revolutions of the input shaft. Should equate to 3:32 or 4:10 to 1. I don't have my 3:65 here, so I can't help you with the casting numbers, or where they're located on the bellhousing.