[chris32]

It looks like the 1981 GMC Caballero 7.5 axle can be 26 or 28 spline. Is that correct?

Thanks

 

[87next2last1]

Factory is 26

 

[87ls5.3]

Factory is 26

Yes, the factory 7.5 is 26 spline. If you are looking at replacement posi units there is a 28 spline option and you can use the Grand National axles. The 28 spline carrier is an F-Body unit that's actually 7.65 but will bolt into the 7.5 housing as a direct replacement with no modification. I went this route and have been very happy!

Joe

 

[chris32]

Yes, the factory 7.5 is 26 spline. If you are looking at replacement posi units there is a 28 spline option and you can use the Grand National axles. The 28 spline carrier is an F-Body unit that's actually 7.65 but will bolt into the 7.5 housing as a direct replacement with no modification. I went this route and have been very happy!

Joe

To clarify, I would just need to order new a set of 28 spline axles from an aftermarket for an 5th gen El Camino but the axle bearings and ring and pinion as well as pinion/carrier bearings for 7.5 will work on the 28 spline carrier?

Also, any feedback on the strength on the 7.5? For example, is the ring and pinion, carrier and/or axles the weak link compared to say 8.5?

Thank you

 

[87ls5.3]

To clarify, I would just need to order new a set of 28 spline axles from an aftermarket for an 5th gen El Camino but the axle bearings and ring and pinion as well as pinion/carrier bearings for 7.5 will work on the 28 spline carrier?

Also, any feedback on the strength on the 7.5? For example, is the ring and pinion, carrier and/or axles the weak link compared to say 8.5?

Thank you

No, the 7.65 carrier is larger and the ring and pinion are different but fit perfectly in the 7.5 housing. The larger F-Body carrier is made for the 28 spline axles. Quick Performance sells a complete kit for around $550 shipped and they have the axles but I bought direct from Moser for about $330.

A 7.5 built like mine should take 400hp with traction and hold up just fine and I can tell you I have hit mine with 330hp/340tq with full on drag radials and it's been taking the punishment pretty good. I only wish I had welded the tubes for a bit more strength but hasn't been an issue yet. If you want it to take any more just find a Fox Body Mustang 8.8 and get an install kit from Trick Chassis, the 8.8 can be built to handle 1000hp if set up right. Quick has a kit for that one too around $575 and I'm buying one of those for my Mustang as soon as I get it running.

Good luck and hope I cleared up the confusion, let me know if you have any more questions.

Joe

 

[chris32]

Thank you for all the detials.

 

[chris32]

OK, I bought a used 7.5 28 spline posi carrier out of a mid 90s Camaro with 3.08 gears. Plan to tear into this weekend and will let you know how it goes.

Thanks again

 

[SmallBlock850]

@87ls5.3 -- would you mind posting links to the rear-end components you utilized please?

 

[87ls5.3]

@87ls5.3 -- would you mind posting links to the rear-end components you utilized please?

GM 7.5" & 7.625" 10 Bolt / Posi / Gears / Bearing Kit (quickperformance.com)

This is what I used.

I also ordered Moser axles in 28 spline #A102810, can't believe I actually remembered the number.......
A102810 - 10 Bolt 28 spline C-Clip Axles - Fits 1982-87 Cutlass, El Camino, Grand Prix, Monte Carlo - Moser Engineering

Keep in mind there is a year change for 81 and older and 82-99 7.5" rearends. You'll need to know the year of your housing. And will make a difference. The Quick posi kit covers everything at the center of your housing, the only extras I got were outer bearings and seals at the brake end. If you order from Summit make sure you order 2 since they are sold separately! Don't ask me how I know......... The gears do have a slight whine on coastdown but otherwise really quiet, from everything I've heard it's the cut on the gears not an adjustment problem. My lash and pattern came out dead center of spec.

I also added the TA performance girdle just because it looked really cool and for the extra support. Probably not necessary but what the hell, it looks awesome from behind!
Chevy 7.5" 10 Bolt / Aluminum Girdle Cover / TA Performance / TA_1809 (quickperformance.com)

I have beat the hell out of this rearend with a 400hp LS motor and it has taken it all with the Nitto TQ drag radials. I haven't had it on an actual drag strip so can't promise it will take that that but I've been happy so far!

Have fun and good luck!

Joe

 

[SmallBlock850]

@87ls5.3 Thank you Joe! I'm prepping the car for the new humdinger 383 I'm about to plop in it. I honestly doubt the car will ever see the drag strip but, I'm taking into consideration the 44 year old rear end (stock 125k miles) and predict it's going to implode sooner than later with this new stump puller of a powerplant. I was looking at that exact same kit and am now weighing the options of simply upgrading the 26 spline or going full send on a 31. Again, I really appreciate the links and info. Great thread!

 

[chris32]

I started taking the rear end apart two weeks ago and ended up busting my knuckle on the ring gear and having to get 4 stiches. Got in there today and finished taking it apart and ordering parts so hopefully next week put it all back together. Just wanted to send a quick update and also a reminder to stay safe.

 

[chris32]

Today I replaced the lower control arm bushings and ran it on the jack stands. The rear end sounded good so I just need to put the rear brakes back on and bleed the rears. Hopefully get it done in the next couple of weeks. Just wanted to send a quick update.

 

[chris32]

I was able to finish up today and take it for a victory lap. Seems to be working ok and has a little more giddy up with the 3.08 vs. 2.56. Big project, glad its done.

 

[SmallBlock850]

Very nice, can't wait to get my piece of junk running!