Ok I have a 89 RS with the 5.0tbi. I plan on putting a 355 that will be around 400hp in the car. From what I researched I believe my car has the 7.625 10bolt with 2.73 gears. I don't mind having it all rebuilt with 373 gears and a limited slip but my question is can I put 373 in the car with a limited slip. Should I go with something else. Didn't really want to go through all the trouble of another rearend. This is gonna be a sunday driving toy. It will have street tires no slicks.

 

Should be fine if it's setup properly with a Torsen, 28 spline axles, and a girdle cover. The 98 to 02 fourth gen rear ends are setup this way and the LS1's put out 350 HP. With street tires you will be fine.

GD

 

You can use a 3.73 gear with limited slip it will work fine, you could always use a locker instead as it wont wear like the limited slip

 

Who makes a locker for the 10-bolt rear end ?

 

https://www.powertrax.com/traction-s...er-9207762805/

 

X2 thats what I did! your 89 should be 28 spline axles already I like GM used gears there were lots of 4x4 blazers with 3.73s
this will hold up fine but beware when you put sticky tires on it it will implode

 

89 may have 26-spline axles, may have 28. Most had 26. In that year, and even some of 90, ya gotta look. Can't "assume" anything.

 

26 splines stopped in 87- 88 and up 10 bolts are 28 spline
I believe all 9 bolts were 28? But don't quote me on that

 

The beginning of the changeover from 26 to 28 was toward the end of 89 model-year production. In these cars as well as S trucks. Certain gear/brake/whatever combos changed over sooner, as though they continued to deplete existing stock before replenishing. None AFAIK changed over before that. Some gear/brake/whatever combos did not exhaust stock and get the new version until after 90 production began. Some 90s still have 26 splines.

9-bolts don't matter. It's irrelevant how many splines they had, ever. I couldn't even tell you because it's a non-issue.

Wishful thinking about 87-88 won't wish it into reality.

 

When I asked about a "locker" for 10-bolts, I was thinking about the Detroit Locker type . . .

I suspect that unit you posted might fail, if used with 400-450 RHWP and sticky tires.

Dave

 

I've been running a 10-bolt with thick 3.73 gear and a detroit tru-trac for years. No issues yet, (fingers crossed). Been behind a 350, small supercharger, small nitrous shot, 396 SBC, and now a BBC. Some guys blow them with a 305. Roll of the dice i guess?

 

Is that on slicks / drag radials or on "street tires" ?

Dave

 

I'm on 325/50/15 nitto drag radials. Even narrowed the rear about 3 1/2" per side and put s-10 axles in it, lol.

 

I can confirm my 89 Trans Am with a Dec 88 build date has 26 spline axles.

 

When I did my rear rebuild I got new 28 spline axles to go with the new posi

 

Same here.

My 83's rear now has "features from the future": 28-spline axles & carrier (Superior axles and Eaton - not Gov-Bomb - carrier), PBR brakes, C5 wheels, ... still has the weenie stock gear ratio though, which I kinda regret; 3.73. The T-56 BEGS for more gear.

 

Its driveline shock that kills them. Whether due to slamming gears, or wheel hop, that's the kind of stuff that's most stressful.

Kind of surprised I haven't killed it yet with the LT1 and the T56 slamming gears. But the tires tend to let go before that. Plus I've to all tubular stuff back there, so the suspension stay pretty solid and parts don't flex which would contribute to wheel hop.

 

im putting close to 400 on the 7.5 its auto i did upgrade to eaton posi had the tru trac but that thing made noise while cruising light throttle read they do that b/c of the amount of lash the gears have. stock 28 spline axles and upgraded cover never put a slick on and try my best not to launch hard the stock unit held up to a few passes but it would go to one leg when power was put to it, you also need to keep the car light like under 3000 and the rear will last you

 

I was running 13.5s quarters on street tires with a bone stock rear end. She held up fine. This is about where I'd expect you to be. Sticky tires will kill it fast, so I think that's your biggest factor.

Axle swap was more of a PTA and cash than I thought when I made the choice to run sticky tires so avoid it if you don't need it. It was the little things that grew hair, like brakes...