7.5 rear suggestions

[SoFloG]

After getting my 359 sbc running right in my 88 cutlass finally I decided to powerbrake it. Well, it has posi. I find this unusual being that it was an all original 1 owner car with a 7.5 10 bolt. Did a few more burnouts, and every time both wheels lit up. I've been searching high and low for an 8.5 or 12 bolt to mo avail. What do you guys think about putting 3.73s in the 7.5 since it already is posi? And what do you recommend for gear oil for the rear now that I actually want to take the cover off and change oil and gasket and inspect it? Thanks

 

[SoFloG]

My motor is about 350hp being conservative, and th350 trans with 2800 stall.

 

[lilbowtie]

It may or may not be a posi - Did it have the tag? If it is chances are it's a gov lock posi(not desirable) and it may not have the right series carrier for 3.73. To answer your question a well built 7.5 will handle 350 hp but that's about the max and will take $$ to get there. I personally wouldn't put any money in the 7.5 cause the money would be better spent else where. If your rear is a posi you can get a few $$ selling it.

 

[theoldsone]

I know people who have respectable running small blocks in their g body's with 7.5's. I put the 3.73's on mine. The point is if you want to hook and launch hard then no don't do it.

 

[pontiacgp]

If you do want to change the rear end don't overlook an 8.2 rear end, it has 28 spline axles and will hold up to 500 hp

 

[jlcustomz]

I've had performance gear 3.73's & an eaton posi with posi additive & standard gear oil behind an ls1 with t-56 trans for over 14 years now. I do boil over the tires here & there, but I always try to be conscious not to rev too high & hit the clutch too hard, particularly from a dead stop & on hot pavement. I have to agree with ok if you don't hook too hard.

Call it careful or call it lucky. looked into the ford mustang 8'8 swap before, seemed to be a lot of bs to go through to make it work, hard to keep it low budget. The new ford 9" premade housings have made things drop in price for them , but still not a low budget thing & I've always heard there is more power loss with a 9". G-body 8.5's are a lot harder to come by these days & most would have the gears you want in them & probably a lot of wear;;;; more money. New premade 12 bolts are even more money.
So I'm still trying to refrain myself from breaking the 7'5 for now.

 

[SoFloG]

Thanks. What tag should i be looking for? What is a gov lock posi? And, I just want to preserve this for the time being. I refuse to put anything other than gm parts in my car.

 

[lilbowtie]

The tag would be on one of the cover bolts telling you to use posi diff-lube. Google (GM gov lock posi)

 

[Robert Ciminieri]

After getting my 359 sbc running right in my 88 cutlass finally I decided to powerbrake it. Well, it has posi. I find this unusual being that it was an all original 1 owner car with a 7.5 10 bolt. Did a few more burnouts, and every time both wheels lit up. I've been searching high and low for an 8.5 or 12 bolt to mo avail. What do you guys think about putting 3.73s in the 7.5 since it already is posi? And what do you recommend for gear oil for the rear now that I actually want to take the cover off and change oil and gasket and inspect it? Thanks

Do what you can to get away from that rear. The 3 series gear is better than the 4....a little larger pinion, but any hp and a little pushing it is bound to blow. Look into Currie or strange.

 

[olds307 and 403]

Why you already changed engine brands, the Ford 9" is very durable and parts galore. That 7.5" doesn't stand a chance as is. I broke a no slip and then blew up open spider gears and they are bigger than the posi spider gears. I would put the Tru Trac worm gear posi, eliminating spider gears and 3.73 gears with 28 spline axles to have a hope in hell.