How to install final drive?

**darkhorizon** · 08-08-2011

Remove passenger side tire, upper strut mount bolts (the 3 in the engine bay), remove the lower ball joint (brake caliper and swaybar link removal are probalby a good idea somewhere in there).

After you have the axle somewhat free from the car (it will still be attatched to the chunk of suspension), you can HOPEFULLY just yank the axle out of the transmission... in the case you can not pull it out, you need to get the removal tool from somewhere...

After the axle is removed, unbolt the 4 diff cover bolts, remove diff, install new diff.... It is probably just easier for you to just see how it is assembled when you remove it for information on how to reinstall the new one.

You may want to pop the inner axle out of the trans on the other side, so the output shaft slides out with the diff. You can do the driver side axle pop without removing anything.

**BillBoost37** · 08-08-2011

Technically you aren't supposed to take the output shaft out of the passenger end of the trans. This is because the lube dam is brittle plastic and the output shaft ramps up slightly.

DH covered it, here's the way I do it. Nearly the same, with pics and not taking the strut.

http://www.grandprixforums.net/how-r...xle-39805.html

Installation. (I need to get some pics, maybe tonight)
There is one key thing you need to ensure. NEVER EVER force the diff cover. If it's not fully and I mean 100% seated before you put a bolt in...then you have a bearing that slid out of place.

See page 365 (aka 3rd page of pdf)
http://www.automaticchoice.com/Catalogue/4t65e.pdf

Look at the section labeled J on the left side. In that section there is an unlabeled bearing between parts 565 and 863. That bearing sits in a groove on the back of 863. If 863 shifts while you are working on the diff (very common) that bearing can fall to the output shaft and keep 863 and the rest of the final drive from sitting all the way into the trans. You can be preemptive and pull 863 and the bearing. Keep the bearing orientation the same, then use a bit of grease to hold the bearing to 863 and put them back in. The rest should them go 100% and your cover shoudl bottom out fully w/o any force.

**chapmanrandall** · 08-08-2011

Thanks for the responses but will I be able to get to the final drive gear as well?

**OH4CompG** · 08-08-2011

Originally Posted by chapmanrandall

Thanks for the responses but will I be able to get to the final drive gear as well?

To what are you referring as the final drive gear? All grand prix's have 3.29 ratio differentials, but between the GT and GTP there is differences in the drive sprockets on the other end of the trans that will determine whether it's 3.29 or 2.93.

**BillBoost37** · 08-08-2011

All GP's didn't end up with the same 3.29 diff's.
There are two drive/driven gear combos that came from the factory. 1:1 aka 35/35 and 1.121:1 aka 33/37. The first 35/35 is used in all non SC'd transmissions. The 33/37 was used in all SC transmissions with a ending ratio of 2.93.

For example a NA car with 3.05 gear ratio had the 35/35 sprockets and a 3.05 diff. A GT with 3.29's would have had 35/35 sprockets and a 3.29 diff.

The diff ratio is referred to in the manuals as the final drive ratio. Therefore if we look at the ATSG book, it can be quite confusing at first. Because the final drive of an SC car is listed as 3.29, couple that to a gearset 33/37 that's where the 2.93 overall ratio comes from.

Yes..the diff and it's 4 planetaries are your final drive.

**chapmanrandall** · 08-08-2011

I'm not even sure if I have the name right sorry. But its the gear inside the trans that the differential slips in to. The 3 lil gears on the diff actually are moved by this in the trans.

**BillBoost37** · 08-08-2011

Ahhh follow that link I posted. Give us the part number. 862 right?

It's called a pinion. That does not need to change in the 4T65E transmision to change the gear ratio or the diff.

In the 4T60 prior version transmissions they kept changing the tooth count and pitch on the pinion which made swapping things around much tougher.