12 Bolt Gear Swap
10-16-2015, 09:29 PM
#1
12 Bolt Gear Swap Hello!
I currently have a strange 12 bolt in my 2000 Trans AM w/ 4.11's. I am running out 3rd with 50 feet left in the 1/4 and want to go to 3.73's to give myself some more room. I have it set up to shift at 6500rpm and don't want to push my stock bottom end any higher.
I have never done a ring and pinion swap before and have a few questions.
The rear has about 13k miles on it, do I need to put all new bearings in it with such low mileage? Rear end is very quiet as it sits now.
With going from 4.11 to 3.73 on a series 4 carrier will the shim thickness on the pinion be fairly close? I am going to have to take the pinion somewhere to have the bearing pushed on and don't want to have to make several trips due to adjusting shim thickness.
Thanks for any advice!
I currently have a strange 12 bolt in my 2000 Trans AM w/ 4.11's. I am running out 3rd with 50 feet left in the 1/4 and want to go to 3.73's to give myself some more room. I have it set up to shift at 6500rpm and don't want to push my stock bottom end any higher.
I have never done a ring and pinion swap before and have a few questions.
The rear has about 13k miles on it, do I need to put all new bearings in it with such low mileage? Rear end is very quiet as it sits now.
With going from 4.11 to 3.73 on a series 4 carrier will the shim thickness on the pinion be fairly close? I am going to have to take the pinion somewhere to have the bearing pushed on and don't want to have to make several trips due to adjusting shim thickness.
Thanks for any advice!
10-17-2015, 09:25 AM
#2
How tall are your tires? F-body.org/gears shows 114mph @ 6100 rpm. If you're using a 26" tire have you thought about a taller tire to extend your top end? Plus I understand a taller tire will hook better.
http://www.f-body.org/gears/
http://www.f-body.org/gears/
10-21-2015, 07:45 PM
#4
I'm also looking at a 12 bolt gear change but from 4.10's to a 3.55 gear set. I read about the 3 and 4 series carriers so does that mean I have to buy a different posi unit? I've done plenty of 8.5 10 bolts but never a 12 bolt. Any help is most welcome. Cheers.
The ring and pinion swap is pretty easy too Nicely, just take your time and don't get in a rush. Buy new bearings because they're cheap and take the old pinion bearing off and sand down the inside with a hone or what ever you can come up with until it slides off and on the pinion easily then setting up the rear is cake. You'll need some marking compound to, if the kit doesn't come with it your local Chevrolet dealer will have it.
The ring and pinion swap is pretty easy too Nicely, just take your time and don't get in a rush. Buy new bearings because they're cheap and take the old pinion bearing off and sand down the inside with a hone or what ever you can come up with until it slides off and on the pinion easily then setting up the rear is cake. You'll need some marking compound to, if the kit doesn't come with it your local Chevrolet dealer will have it.
10-22-2015, 08:32 AM
#6
So that is the case then that you would have to replace the carrier to go from 4.10's to 3.55's. That's a bummer, perhaps I'll just go with some 3.73's.
To answer your questions about the shims too Nicely you always put the shims that are currently in it back in for your starting point. I can only think of once or twice where I really had to move some shims around to get my pattern and tolerances right. The pinion shim is usually really close with shims it's set up with but that's why the test bearing is handy. See if a buddy has a backlash gauge, and go with a crush sleeve delete kit for drag race applications. Also the ring gear bolts are reverse thread so don't forget about that when you hit it with your impact gun to get those off lol. Hit the back of the ring gear with a non-aggressive file to remove and check for any high spots too. The first one always seems scary but after you'll be like "that was easy" and you'll be helping your buddies with theirs. Good luck!
To answer your questions about the shims too Nicely you always put the shims that are currently in it back in for your starting point. I can only think of once or twice where I really had to move some shims around to get my pattern and tolerances right. The pinion shim is usually really close with shims it's set up with but that's why the test bearing is handy. See if a buddy has a backlash gauge, and go with a crush sleeve delete kit for drag race applications. Also the ring gear bolts are reverse thread so don't forget about that when you hit it with your impact gun to get those off lol. Hit the back of the ring gear with a non-aggressive file to remove and check for any high spots too. The first one always seems scary but after you'll be like "that was easy" and you'll be helping your buddies with theirs. Good luck!