4t60e drive and driven sprocket change?

[Jbrogan]

i have a 4t60e 6wfw i want to swap the drive and driven gears so that i can get a 3.69 fdr. my diff is 3.29. so i was wondering how hard it is and how much stuff i will have to remove to get to them? i am hoping to just lower the engine out throught the bottom of the engine bay and remove the side plate on the trani and work on it leaving it attached to the engine. is that possible??

[torq455]

i believe it is on that one. assuming you are doing this on the retta? once that side cover comes off i think there is a valve body with check balls, then the sprockets and chain. if you pull the valve body off the ball fall everywhere. check this out first! if you DIY and think you have the check balls in the right places, you could gernade your tanny!

[IsaacHayes]

Stock FDR on L body is 2.97 IIRC. You'll need a DHP to reprogram the shiftpoints /speedometer as OBDII isn't as forgiving at the older IIRC on gear changes... Have to ask 3400-modified to be sure as he knows about all of this.

[Jbrogan]

are you sure that i have to reprogram the pcm because the speed sensor is the diff and it calculates speed by how fast the axels spin, its after the gears so it should just say however fast my axels are going witch would be Whatever. now the shifting points. i thought that it would shift when the engine rpms reach a certain point or something. im not sure of that one. I do knowe that people have taken 3.33s out of monte carlos and put them in grand ams and it made em way faster and everything worked fine. does anyone know for sure answers, i dont want to dig myself into a hole, but i really want those damn gears shorter.

[91parkave]

shift points might be off but the FDR will need to be programed in obd2 cars, The PCM has a written value as to how both the axle speed and how fast the govenor is moving if either is out of spec it might cause the trann to go in limp mode

[torq455]

the PCM will shift the tranny at a given mph vs. tps, not rpm vs. tps. it will shift late or at a higher rpm. Grand Am's? what years? obd I should be cable controlled from the throttle. the governor will handle when to shift at what speed.

[3400-95-Modified]

you need to fix your ECM, in a 95 setup it shifts from RPM, with a 96 the MPH is set to be more of the trigger so when your RPM per MPH raises it tries to shift at the same MPH but cant because your hitting your RPM limiter already.

I swapped to a 3.33 trans in my OBD1.5 95 setup a long time ago and NEVER had a shift issue... I put in the OBDII 96 wiring and ECM left stock shift tables and was bouncing the limiter on the first test run. I don't think the 95 ECM takes into consideration the MPH when shifting, I'm not sure since I can see their shift table logic.