Rearend swap

[81qcmonte]

Hey Guys,

I want to change my rearend from my Monte 81, cose it is 7.5 with 2.29 gear...

What type of rearend and from which car do you think it can fit without any modifications..?

Do you think I should go with an 8.5 posi ?

Do you know if a rearend from a Camaro Iroc Z 89 will fit ??

What do you have under...??

Thanks

Ben

[85t5mcss]

The only thing that is going to fit with no mods is another G Body rear end that is also the 7 5/8" (more commonly called the 7.5) A Monte SS will have a more desireable gear ratio like 3.42 or 3.73 depending on what year u get and will bolt right in.

IF u manage to find a 8.g it will bolt right in with the exception of your driveshaft will need shortened 1". If u find one, I will gladly trade my 7.5 for the 8.5!

Camaro rears will NOT work since there r no upper control arm mounts. F Bodies only use lower control arms with a panhard and torque arm.

8.5 is stronger than the 7.5 but even a 7.5 will hold decent torque as long as u don't run slicks. I'm still on factory rear and I have been beating on this car for a while. Especially since the 5 speed went in. Woo Hoo!

BTW, welcome to the site.

[81qcmonte]

Do you think this carrier it's a good start to make it posi or it's look like cheap part ??

cgi.ebay.ca/New-GM-Chevy-Mini-Spool-7-5-10-Bolt-Rear-End-26-Spline_W0QQitemZ170465590499QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item27b08a7ce3

[81qcmonte]

This one looks better : cgi.ebay.ca/Powertrax-1932-LR-Differential-Lock-Right-Locker-26-Spl_W0QQitemZ390189971622QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item5ad92278a6

[81qcmonte]

or that one : cgi.ebay.ca/GM-7-5-10-BOLT-AUBURN-POSI-GM-CHEVY-7-5-26-SPL-3-23-UP_W0QQitemZ370224331602QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item563316fb52

[85t5mcss]

Auburn and Powertrax are both good units. Stay away from spools unless this is drag only. Spools lock the rears together and seriously cause turning issues. Popping and 1 wheel trying to hop because they want to turn at same speed.

I like the Powertrax unit more just because they seem to hold up to more abuse.

[81qcmonte]

Normally, am I suppose to have an 26 splines in my 7.5 ?

THANKS

[twomanymontes]

I agree with Keith, No Spools!!! Very hard on the axles, plus the mini spool is for Dirt tracks only, they won't hold up to drag stip use. The powertrax system is nicer and easier to install. That Auburn set up is a complete carrier and you willneed to install new bearings, set up the ring gear so it will mesh with the pinion properly. I'm going to go with the Powertrax when I finally get around to rebuilding the rear in my car.

As for the spline count, I believe it is 26

[85t5mcss]

Yep, 26 for Montes but always a good idea to check first.

[81qcmonte]

How this powertrax working when you hit the pedal to the floor ? is it locking, avoiding burnout for more traction.... cause they put those on Jeep, truck to get more traction. I wanna good traction but I wanna make some white smoke too !!!

[twomanymontes]

The powertrax set up is very simular to that of a posi, it will allow slipage when the axles turn at differant rates like on turns, But will lock them together when the torque is applied

[81qcmonte]

ok thank you, I will probably goes with a 3.73 gear and a powertrax unit ! I'm going with a th350 transmission and I heard it will be better to have a 3.42 gear and higher than a lower gear cause of the 3 speed transmission !! Is this true or not?? I'm not an expert in transmission, drivetrain ... axles..

THank you guys

Ben

[85t5mcss]

I dont have the calculator in front of me right now, but 3.42 will gv good acceleration and keep RPMs down on the highway. 3.73s r good with overdrive. 4.10s on a TH350c were not highway friendly. I would hit 3rd gear while crossing a 4 lane highway. Rear tire diameter will affect RPMs also. All depends on what u plan on doing with the car. If u go with a TH350c, it will only drop RPMs about 200 when it hits lockup. Not an advantage really. Converters are cheaper for the regular TH350 that are 81 and earlier.

[81qcmonte]

My th350 come from a 76 or 78 camaro.
Your talking about a calculator, is it possible to have this free on the web or...
So it will be better for me to have something like a 3.42 with the th350 and what do you think about the torque converter... My monte is not my daily driving, I'm doing like 1500 miles a years with cause my monte is in a storage in the winter. For sure, I want something powerfull,fast, going in highway too, some smokey tire and the gaz is not really an issue ( for 1500 miles a years ). I'm not planning to go on drag strip every week-end.

I just want a good fealing when I'm driving it, some kick back in the bench....

If you have any ideas, just feel free ...

Thanks

Ben

[81qcmonte]

oups, sorry

[81qcmonte]

I can have the posi unit with gear ( 3.23 ) from a camaro 84. It is suppose to be a 7.5. I know the complete rear end does not fit, cause of the control arm, but do you think the inside of the cage will fit ?? Is this something really complicated to swap ??

thanks

Ben

[85t5mcss]

As long as the axles have the same spline count, then yes. Easy swap, but will require special tools to set up backlash. U can eyeball it, but not worth the risk. Usually a trans shop can set backlash. Do yourself a favor and get an extra crushsleeve.

[twomanymontes]

Swapping the rear end internals is a big task if you have never done it before. Like Keith said, setting the proper back lash and torquing the pinion are the major stepping stones. the rest is pretty easy. There are plenty books as well as places on the net to get the info on how to do it, So my first point of advice would be, read the procedure thouroghly before attempting. I've done aquite a few rear ends, But I still don't always feel comfortable setting them up and have another tech take a look to be sure I'm set properly

[81qcmonte]

If it's an 7 5/8 rear is this a big problem?? It looks like it is the same size as the monte ss.

[81qcmonte]

Sorry guys you've already gave me the answer in the first reply.

I've heard the powertrax unit make an ratcheting sound when you turn, lock and unlock, and some people said that is very frustrating sound...

I think finally I will go with an auburn posi unit and I don't know which gear right now. I will probably go to a mec. shop for the swap.

Thanks guys

Ben

[85t5mcss]

Sound won't mstter as long as the exhaust is loud enough or the stereo is loud enough. I never noticed any noise out of mine, but the car was very loud. Too loud. Either way u can't go wrong. I would say that rebuilding a stock posi is an option but the parts r pretty pricey anyways. Go aftermarket for the added strength. Take a look at the aluminum covers that have preload adjusters on them also. It will help keep everything in line and last longer.