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?
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.
Some of the write up in the other thread seemed like there were issues that would come with an E transaxle.
The Fiero ECU will not be able to control the 'E' version, as it is electronically controlled by a drivetrain computer such as an OBD1.5 ECU or and OBD2 PCM.
We did the 4T60 swap way back when and don't recall much except that it was an easy bolt in with a change of trans mounts, a new torque converter a couple of small wiring changes. Don't recall if the shift lever on the trans needed to be reversed so let me look at my old notes and post more info here later. My suggestion would be to use a rebuilt unit not a junkyard unit.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
[This message has been edited by Dennis LaGrua (edited 10-29-2025).]
We did the 4T60 swap way back when and don't recall much except that it was an easy bolt in with a change of trans mounts, a new torque converter a couple of small wiring changes. Don't recall if the shift lever on the trans needed to be reversed so let me look at my old notes and post more info here later. My suggestion would be to use a rebuilt unit not a junkyard unit.
82 TA has it right, You will need the transmission, new transmission mounts, the 4T60 torque converter w bolts, new std GM 4T60 transmission mounts, a new bracket for the shifter cable, a simple mod for the trans shifter arm and a rewire of the TC lock up solenoid. New trans cooler hoses are recommended. Allow about a day to pull the powertrain to get it all installed.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
