88 Monte Carlo LS differential

[LT1 Monte]

I now realise the car has 7.5" and have been read about changing etc.

My question is how many splines are the axles in our differentials? How many are in LS Camaros? Seems the 7.5 holds up in LS Camaros etc so wondering.

Also besides a GN is there a GM 8.5" that will fit our cars? From what I have read seems the Ford 8.8 from a Fo body might be the best differential for us.

Thanks
JAck

 

[megaladon6]

the 7.5 is a 26 spline, the 7.625 (available on the monte SS) is a 28 spline.
GN, olds 442 (year specific) and IIRC the 84-85 hurst olds had the 8.5.
94-96 impala/caprice axles are a close fit. the UCA's need to be shortened about 3in and the lower arms can be forced into place, but should have the axle side ends canted in about 8-10*(and or get a heim style end). the axle is wider and will require a deeper backspace and the bolt pattern is 5x5 instead of the normal 5x4.75. you can have the axles drilled for a second pattern or use 5x5 wheels. the caprice axle (specifically the 9C1 package) has 12?in disc brakes, a 30 splines and a good posi.
there's also the earlier a-bodys that had a 12 bolt, mods are necessary to the CA's also.
honestly, every axle needs some sort of mods to it or the control arms.
the LS camaro may have an 8.5, all 7.5s are the same and all break with serious power.

 

[LT1 Monte]

So the differential from a 94 - 96 Caprice (8.5) will work? If so that is great news since I saw one in the boneyard today..

 

[megaladon6]

well it's not a direct bolt in, but it's close. i have one that's going in when i have time to work on it. but i did have it mocked up on the car with the LCAs bolted in. the UCAs angle is good, just the mounting points on the axle are farther forward, by about 3in, you'll need to modify a set of adjustables. the LCA's may work fine with stock arms since they twist, but i did get them bolted in with tubular arms. i wouldn't recommend it without heim style ends (del-a-sphere, johnny joints etc) plus they are about 1.5in wider on each side so stock backspaced rims won't work. i'll be using C5 rims so it helps me.
but i think they're a closer fit than any other axle.

 

[LT1 Monte]

Thanks for the word on the B Body rearend. I received this reply in another thread in the new user section, and want to include the information here to aid others searching:

Before i put much cash in any of the factory rearends i'd go with something like this, wish i had instead of the 12 bolt.

http://www.quickperformance.com/ads.htm

I may pay the extra money upfront and go with this setup.

Thanks
Jack

 

[megaladon6]

nothing wrong with the ford 9", but i'll ask, do you NEED it? they tend to be expensive when you price out the total build, admitedly not by too much more if you're replacing everything on a 12bolt or 8.5in. but they're also heavy and take a bit more power to turn, so outside of the dragstrip they aren't the best choice (at least IMO)
(BTW for anyone looking at getting the explorer rear disc brakes w/drum p-brake on a ford 9---every and i mean EVERY time you pull the rotors you will be replacing the p-brake springs for the shoes. the rotors seem to instantly build up a ridge of rust in the drum section and there's no way to back off the shoes enough to clear it.) yes, chevys have had this problem also, but not as bad

 

[85GPLef41]

the 7.5 is a 26 spline, the 7.625 (available on the monte SS) is a 28 spline.
GN, olds 442 (year specific) and IIRC the 84-85 hurst olds had the 8.5.
94-96 impala/caprice axles are a close fit. the UCA's need to be shortened about 3in and the lower arms can be forced into place, but should have the axle side ends canted in about 8-10*(and or get a heim style end). the axle is wider and will require a deeper backspace and the bolt pattern is 5x5 instead of the normal 5x4.75. you can have the axles drilled for a second pattern or use 5x5 wheels. the caprice axle (specifically the 9C1 package) has 12?in disc brakes, a 30 splines and a good posi.
there's also the earlier a-bodys that had a 12 bolt, mods are necessary to the CA's also.
honestly, every axle needs some sort of mods to it or the control arms.
the LS camaro may have an 8.5, all 7.5s are the same and all break with serious power.

I thought the 7.625 had 26 splines? What years of Monte SS had the 28 splines?

 

[LT1 Monte]

nothing wrong with the ford 9", but i'll ask, do you NEED it? they tend to be expensive when you price out the total build, admitedly not by too much more if you're replacing everything on a 12bolt or 8.5in. but they're also heavy and take a bit more power to turn, so outside of the dragstrip they aren't the best choice (at least IMO)
(BTW for anyone looking at getting the explorer rear disc brakes w/drum p-brake on a ford 9---every and i mean EVERY time you pull the rotors you will be replacing the p-brake springs for the shoes. the rotors seem to instantly build up a ridge of rust in the drum section and there's no way to back off the shoes enough to clear it.) yes, chevys have had this problem also, but not as bad

I am putting in a 4L80E in the Monte to ensure I can DD the car. Also my definition of a DD is diferent than most, I have two houses one in TN one where I work in AL I often drive between them on weekends. I want to set it and forget it!

I would much rather pay alittle more and not worry a 9" in my setup should be indestructable! I expect the 9" to match or exceed the 4L80E, could I build a 4L60E to hold? Maybe, I have a 4L60E in my Turbo Roadmaster and after 2 years it is still fine... Do I need more?

Yes the 1 2 shift has never been 'firm' and I promised myself I would not make that mistake again. I plan to have a DD that I will drive to and from the track and go low 11 and eventually into the 10's...

So IMO yes I need it, or feel the 9" is worth the expense. It is all about how much you are willing to buy as insurance. We haven't even mentioned that since it is turbo'd I will have the ability to turn a dial to increase the boost so...

 

[megaladon6]

i just wasn't sure if it was a DD or a track car. i agree, if you're shooting for 10's go with the 9 and the 4l80e. you could even look into the 6l95e it's a heavy duty (like the 4l80) auto trans but with 6fwd speeds! there's also a 5spd version thats easier to find.

 

[LT1 Monte]

i just wasn't sure if it was a DD or a track car. i agree, if you're shooting for 10's go with the 9 and the 4l80e. you could even look into the 6l95e it's a heavy duty (like the 4l80) auto trans but with 6fwd speeds! there's also a 5spd version thats easier to find.

Well the budget isn't unlimited I have found a reasonable priced 4L80E and it can be controlled from the stock Vortec so that helps. I hope to get the entire 4L80E and yank torque for ~1850

The 10's isn't where I expect the first vrsion to get but say a year or two from now make some modifications and it could be there. The turbo's will be sized for 10's so it will go there someday.

I think I estimaed the setup to be 10 - 12K so I know it won't be cheap. The car is definately not a fast looking car which is the attraction o me. I want more of a sleeper. I hope to take some pictures this weekend.

Also I want to try and avoid a roll cage. I will probably add a roll bar but don't want the halo on a street car...what will help the budget is a friend has a machine shop so that shold substantially reduce the cost of the build