Rearend Questions.

[seawolf18]

I am doing a 5.3 LS swap for my 85 cutlass. I will also be using a 200-4r transmission(built up of course). It will be used as a street car. I am putting in a little bit larger cam(nothing wild), and home porting the heads on the 5.3. My question is with the rearend. Right now it has a non-posi with 2.14 gears in it. I want to go with 3.73's and a posi. This is a budget build, so no moser 9" for me. I can get a brand new 26 spline auburn style posi for $370.00 bucks, or I can use the 28 spline used auburn I have out of camaro, and buy new moser axle shafts that fit. I figure the cost would be about the same, but I would have a brand new posi unit, instead of a used one. Would using the 28 spline axles and posi be any stronger than the 26 spline unit and axles? I've been told the week point of these rearends is the ring gears, since its so small. Ideas?

 

[DRIVEN]

I'd go the 28 spline route. Maybe spend a few extra bucks for a cast rear cover with cap supports. The 7.5" is tougher than most people think if not blatantly abused.

 

[jrm81bu]

I'd go with the 28 spline carrier as well. To me the weak point isn't the ring gear it's the spider gears and that carrier will get rid of that.

 

[307 Regal]

I'd go the 28 spline route. Maybe spend a few extra bucks for a cast rear cover with cap supports. The 7.5" is tougher than most people think if not blatantly abused.

x2

I'll be building up a 7.5 this summer with a 28 spline '96 Camaro LSD and a girdle cover. Have you considered rebuilding the Camaro diff?
Whenever someone asks about 7.5 rear strength, I always refer to LS1GN. He's running a 6.0 LQ9. All he has behind that is a 7.5 rear with an Auburn posi from an '83 T/A and a girdle cover and he's been in the 12s with that setup.

 

[jrm81bu]

I'd go the 28 spline route. Maybe spend a few extra bucks for a cast rear cover with cap supports. The 7.5" is tougher than most people think if not blatantly abused.

x2

I'll be building up a 7.5 this summer with a 28 spline '96 Camaro LSD and a girdle cover. Have you considered rebuilding the Camaro diff?
Whenever someone asks about 7.5 rear strength, I always refer to LS1GN. He's running a 6.0 LQ9. All he has behind that is a 7.5 rear with an Auburn posi from an '83 T/A and a girdle cover and he's been in the 12s with that setup.

Ya, but i'm thinking he broke that. Regardless, after having my rear tires pass me on more than one occasion, I can't say i'm too fond of the 7.5.

 

[78sik ick]

Not sure if I have a 7.5 or 8.5 but its just 4.10 with posi and the guy i bought it from has slips in the 11's i haven't made a pass with it and not sure how built it is but hasnt let go yet in the last 2 years

 

[seawolf18]

I know the 7.5 would not survive if I tried to put slicks or drag radials on it. I used to have a 02 camaro LS1 6-speed. I had it putting out 420 horses to the wheels with the stock 7.5 in it. I was running street tires, and had a girdle on it. The rear survived the whole time I had it. I am going to put the 28 spline axles and posi unit in it.

 

[Gbody]

Will this kit work??
http://www.summitracing.com/parts/sag-ev10-6

 

[434MONTE]

Howdy,

By the time you spend the money on the GM rear end, break it a couple times and have to fix it.....save your money and get a 9". You can (eventually) have a couple of rear pumpkins to swap for various events and you'll never break it. Make sure to have the axles/lug studs set up for the bolt pattern of the wheels you're using, and upgrading to 1/2" studs and nuts would be a good idea a the same time (since you don't like being passed up by your wheels).

I'm running a 3.50 gear with the 200-4R and with the .67 overdrive, that makes a 2.35 in OD. it is a freeway flier. The gearing in the trans launches it pretty well. My next move will be to a 4.11 or 4.30 which with the OD would be 2.75 or 2.88. Either of those gears would be ok for all around driving.

Build your car from the back to the front, you'll save a lot of money and be a lot safer. Take it from a guy who broke a lot of parts back in my high school days. If I had all the money I spent trying to save money, I could have built another car.

By the way, if you go to a 9", there are inexpensive adapter brackets you can get to hang a couple of the caiipers that are readily available from boneyards that normally come on the front end you your car. With a couple of inexpensive rotors, you now have a 4-wheel disc car. Later, find an old Caprice or Buick wagon that has the tall spindles and 12" rotors and you'll have a budget set up that works great! That spindle swap is a bolt in. All you have to do is that is even remotely tricky is the brake lines. If you find the stuff for the front first, use the old calipers from the front on the rear.

Later,

Pat

 

[JBreu]

I say scrap the ford 9" idea , keep your GM car all GM Grab a 12 bolt rear from a '66-'72 "A" Body car and you will be happy you did, all ya gotta do is get the 12 bolt swap kit from UMI Performance...I went this route and have a bulletproof rear end