4T60 conversion for a 3.4 (Page 1/2)
fierobear OCT 22, 01:46 PM
My pushrod/iron head 3.4 has been mated up with a TH-125 and it is failing. I've been wanting to change to a 4 speed auto, especially because the RPM at freeway speed is 3,800. I'm told a 3.33 final drive ratio is the best for this application. I also need to know how you adapt the shifter to the 4 speed. Opinions, advice?
olejoedad OCT 22, 03:41 PM
No adaptation of the Fiero auto shifter is needed.
The detents for transmission range are built in to the transmission select shaft.
You will need to modify the length of the transmission select shaft arm, off the top of my head I don't remember the length needed.
hercimer01 OCT 22, 05:40 PM
I did that swap in my eighty eight formula.Look at my link.

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Project Genisis Lo Budget 3800SC swap SOLD

88 Coupe under construction SOLD

88 formula 3.4L 4t60 swap SOLD

1988 Fiero GT Medium Red Metallic Paint Job Maybe HOK Brandy Brandywine SOLD

88GT resurrection in progress.

richard in nc OCT 22, 07:19 PM
https://web.archive.org/web...s.com/tech/440-4T60/
fierobear OCT 22, 09:29 PM

quote
Originally posted by hercimer01:

I did that swap in my eighty eight formula.Look at my link.




That was for an "E" transmission?
olejoedad OCT 23, 07:01 AM
All of the respondents in this thread have used the 4T60.
Not the E version, which does not use a throttle valve cable.
82-T/A [At Work] OCT 23, 07:44 AM
This is an old website that I used to maintain, but I have gearing information for the 4T60 here: https://www.pontiacperforma...icles/4T60_Info.html

And instructions and pictures how to adapt it to an 84-87 and 88 here: https://www.pontiacperforma...es/4_Speed_Swap.html

88 requires slight modification to the subframe, but for the 84-87, you just drill a hole to move a bolt.
fierobear OCT 23, 11:52 AM

quote
Originally posted by 82-T/A [At Work]:

This is an old website that I used to maintain, but I have gearing information for the 4T60 here: https://www.pontiacperforma...icles/4T60_Info.html

And instructions and pictures how to adapt it to an 84-87 and 88 here: https://www.pontiacperforma...es/4_Speed_Swap.html

88 requires slight modification to the subframe, but for the 84-87, you just drill a hole to move a bolt.



Excellent information, VERY helpful. Thanks!

hercimer01 OCT 23, 10:17 PM

quote
Originally posted by fierobear:


That was for an "E" transmission?



No. Where do you see "E"?
fierobear OCT 25, 03:57 PM

quote
Originally posted by hercimer01:


No. Where do you see "E"?



Some of the write up in the other thread seemed like there were issues that would come with an E transaxle.