Howdy folks, thanks for having me on your forum!

as a preface here to my question, I'm a former 3rd gen TA guy that's finally decided to come to the Fiero side (still looking for a car, want an 88 Formula). I sold my Trans Am last year to pay for my truck (needed something better for PA Winters), but a year without a fun car has killed me. I decided I wanted something with some cornering capabilities, and being a Pontiac fan, decided the Fiero was my best bet!

I've always had hard, fast shifting, whiplash inducing automatic transmissions. While I don't expect the same thing from the Fiero, I want the best I can get.

So, onto my question: What is the best automatic transmission I can build for a Fiero, that is easy to swap in (even with the stock 2.8L V6)? What are my best options for rebuild and hard hitting shift kits for these transmissions? Does anyone know any secret hop-up techniques for an applicable transmission? For example, my Uncle Doyle plugs a fluid passage in the TH-350 and TH-400 valve bodies to REALLY make them slam into gear fast and hard.

We are fully capable of doing a rebuild on our own.

Thanks in advance folks!

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- Darryl

[This message has been edited by Reborn756 (edited 03-17-2020).]

With a stock 2.8L or 3.4L I would use a 4T60 transmission with the axles that can fit your car. . Its has four speeds, easily bolts right up and only requires minor wiring changes to the TCC . Performance shift kits are available and not difficult to install.

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Thanks for the quick reply Dennis! Where can I find information regarding the TCC wiring?

happy to hear about it being a direct bolt in, that's what I was looking for!

Do you have any information on the best rebuild kits and shift kits are for this transmission? We normally using Transtar and No-Yo-Yo kits. What vehicles and years are suitable donors for the transmission?

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- Darryl

I second the 4T60.

I think the Georgia Fiero Club website has a page on the swap that would help.

quote Originally posted by olejoedad: I second the 4T60. I think the Georgia Fiero Club website has a page on the swap that would help.

I used this info when I installed a 4T60 in my Indy.
http://web.archive.org/web/...s.com/tech/440-4T60/

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[This message has been edited by fierosound (edited 03-18-2020).]

Thanks for all the information so far fellas, I'll check that Georgia club site and that link there!

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- Darryl

If you're using a stock Fiero engine, or something from the same era, then the 4T60 (aka TH440) is probably your best bet. For engines with more advanced electronics, the 4T65-E would be a better choice.

Thanks BlackTree! Anyone have recommendations on the best shift kits and modifications, and rebuild kits?

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- Darryl

Go to: Fiero th440-4t60 automatic transmission conversion.
I can't figure out how to post it here. I'm BC.
Good Luck

Anyone got a recommendation on where one would find/buy one of these transmissions? This is all a first for me so I am not sure where to look outside of googling it.

quote Originally posted by Cunnive: Anyone got a recommendation on where one would find/buy one of these transmissions? This is all a first for me so I am not sure where to look outside of googling it.

More on the trans at Ogre's Cave
http://home.comcast.net/~fierocave/aodproj.htm

I came across this information.
(not sure if complete or accurate)

Cars to check: 1983-1992
Century 1984-1993 TH440 - T4/4T60
Electra 1985-1990 TH440-T4/4T60
Park Avenue 1985-1990 TH440-T4/4T60
Reatta 1989-1990 440-T4/4T60
LeSabre 1986-1991 TH440-T4/4T60
Regal 1988-1992 TH440-T4/4T60
Riviera 1986-1990 TH440-T4/4T60
Allante 1991-1992 4T60
Eldorado 1986-1990 TH440-T4/4T60
Fleetwood - 4 speed FWD 1984-1990 TH440-T4/4T60
Celebrity 1984-1990 TH440-T4/4T60
Lumina 1990-1992 TH440-T4/4T60
Ciera 1984-1989 TH440-T4
Cutlass 1988-1989 TH440-T4
Olds 98 1985-1989 TH440-T4
6000 1990-1991 4T60
Bonneville 1987-1989 TH440-T4
Bonneville 1990-1991 4T60
Grand Prix 1988-1989 TH440-T4
Grand Prix 1990-1992 4T60

Handy reference to codes on RPO sticker.

ME9 : TRANSMISSION, AUTO 4 SPD, THM 440 T4 (4T60)

F16 : RATIO, transaxle final drive 2.53
F17 : RATIO, transaxle final drive 2.84
F25 : RATIO, transaxle final drive 3.32
F29 : RATIO, transaxle final drive 2.82
F62 : RATIO, transaxle final drive 2.39
F67 : RATIO, transaxle final drive 3.19
F68 : RATIO, transaxle final drive 3.45
F75 : RATIO, transaxle final drive 3.18
F77 : RATIO, transaxle final drive 3.73
F79 : RATIO, transaxle final drive 2.97
FP0 : RATIO, transaxle final drive 2.55
FP1 : RATIO, transaxle final drive 2.72
FP2 : RATIO, transaxle final drive 3.58
FP3 : RATIO, transaxle final drive 2.73
FP5 : RATIO, transaxle final drive 2.95
FP6 : RATIO, transaxle final drive 3.54
FP7 : RATIO, transaxle final drive 3.73
FP8 : RATIO, transaxle final drive 3.54
FQ2 : RATIO, transaxle final drive 3.48
FQ6 : RATIO, transaxle final drive 4.12
FQ8 : RATIO, transaxle final drive 2.96
FQ9 : RATIO, transaxle final drive 3.21
FV0 : RATIO, transaxle final drive 3.67
FV1 : RATIO, transaxle final drive 3.72
FV3 : RATIO, transaxle final drive 3.11
FV4 : RATIO, transaxle final drive 3.71
FW2 : RATIO, transaxle final drive 3.06
FW3 : RATIO, transaxle final drive 4.02
FW4 : RATIO, transaxle final drive 3.89
FW5 : RATIO, transaxle final drive 4.10
FW6 : RATIO, transaxle final drive 3.42
FW7 : RATIO, transaxle final drive 3.83
FW8 : RATIO, transaxle final drive 4.28
FW9 : RATIO, transaxle final drive 3.43
FWS : RATIO, transaxle final drive 4.10
FX1 : RATIO, transaxle final drive 3.94
FX2 : RATIO, transaxle final drive 2.66
FX8 : RATIO, transaxle final drive 3.61
FY1 : RATIO, transaxle final drive 2.36
FY3 : RATIO, transaxle final drive 3.79
FY5 : RATIO, transaxle final drive 3 52
G11 : RATIO, transaxle final drive 2.56

[This message has been edited by fierosound (edited 03-21-2020).]

I am sorry for resurrecting this thread but i've been following it closely and will be doing the TH440/4T60 upgrade and wanted to check if this tag is what I should be looking at when determining the correct drive ratio for my current transmission.

I am guessing from the tag my transmission falls in the 2.8L/173 | 1985/86 | 3.06 | 5CD, 6CD area for my 86.

Anyone able to confirm for me if I am correct or should I be looking for something else?

Thank you!


Edit: I also forgot to ask -- when this upgrade is done, the guide says you need to use a set of axels for a Manual Transmission Fiero. My question is - do I buy 2 of the short CV Axles for the manual transmissions and use them for both rear wheels? From what i'm looking at on RockAuto, it looks like the rear right axle is much longer than the rear left.

[This message has been edited by Cunnive (edited 04-14-2020).]

The three letter codes are on the RPO sticker, which is on the front left wheel well (near the master cylinder). I don't think the transmission tag has any useful information.
most likely your code will be one of these......

FW2 Transaxle, final drive, 3.06 ratio
FW5 Transaxle, final drive, 4.10 ratio
FX8 Transaxle, final drive, 3.61 ratio
F75 Transaxle, final drive, 3.18 ratio
GX3 Transaxle, final drive, 3.33 ratio
GY5 Transaxle, final drive, 3.65 ratio

[This message has been edited by Gall757 (edited 04-14-2020).]

quote Originally posted by Gall757: The three letter codes are on the RPO sticker, which is on the front left wheel well (near the master cylinder). I don't think the transmission tag has any useful information. most likely your code will be one of these...... FW2 Transaxle, final drive, 3.06 ratio FW5 Transaxle, final drive, 4.10 ratio FX8 Transaxle, final drive, 3.61 ratio F75 Transaxle, final drive, 3.18 ratio GX3 Transaxle, final drive, 3.33 ratio GY5 Transaxle, final drive, 3.65 ratio

Thanks Gall! I was able to locate the sticker you were referring to and found that FW2 code in there. So 3.06 it is!

My next question is, do I need to look for a TH440/4T60 transmission with a final drive ratio of 3.06 too? Or can I get one that has a 3.33 final drive ratio? Will that cause any problems?

I also just wanted to reiterate my last question too

quote Originally posted by Cunnive: Edit: I also forgot to ask -- when this upgrade is done, the guide says you need to use a set of axels for a Manual Transmission Fiero. My question is - do I buy 2 of the short CV Axles for the manual transmissions and use them for both rear wheels? From what i'm looking at on RockAuto, it looks like the rear right axle is much longer than the rear left.

Thanks!

[This message has been edited by Cunnive (edited 04-16-2020).]

The 3.33 final will work well two. (87-88 had 3.33 in the TH-125C)

Your speedo will be off a bit.

quote Originally posted by olejoedad: The 3.33 final will work well two. (87-88 had 3.33 in the TH-125C) Your speedo will be off a bit.

3.33 is a good choice. Speedo is driven off the differential carrier, so tire size is the thing that changes it. Use the gears from the 125 for the speedo. I would avoid anything older than 1986. They were under clutched, had weaker sprags, ect. The early ones cost us a bunch in R&Rs and R&D back in the day. 88 and newer had most of the best updated stuff from the factory.

quote Originally posted by OldsFiero: 3.33 is a good choice. Speedo is driven off the differential carrier, so tire size is the thing that changes it. Use the gears from the 125 for the speedo. I would avoid anything older than 1986. They were under clutched, had weaker sprags, ect. The early ones cost us a bunch in R&Rs and R&D back in the day. 88 and newer had most of the best updated stuff from the factory.

Which gears do I need to save from my current 125C transmission to help correct the speedometer issue? Is there a reference or guide I can follow?

[This message has been edited by Cunnive (edited 04-17-2020).]

Remove the drive gear off the top of the 125 governor and the 125 driven gear. I'm not aware of a chart, but there's probably one out there somewhere. If your tire diameter is the same as the stock Fiero, the 125 stuff should be right. As a rule of thumb, one tooth on the driven gear = about 3 MPH change. More teeth = slower speedo. Less teeth = faster speedo.
Marc