stock 8.5 rear-how much will it take?

[rfwave]

As stated. I know many people will say this or that but who has actually pushed the envelope with their stock 8.5 GN or T rear? How much power have you run through it in stock form and had it survive?

 

[WSLN 6]

Not sure what it will take.....mine is still stock, stock axels,driveshaft etc. I don't have a transbrake though.

 

[Cheeseburger]

Once you start getting 1.5 60 foot times consistantly you will run into problems.
In my experience the teeth on the ring gear broke.

 

[UNGN]

Once you start getting 1.5 60 foot times consistantly you will run into problems.

+1

I have personally seen 3 times guys totally psyched about "finally running 1.5" 60 ft times, only to have a axle break a couple runs, or a couple trips to the track later.

 

[rfwave]

Once you start getting 1.5 60 foot times consistantly you will run into problems.

How much hp/tq does that equate to roughly?

 

[Slow91z]

I know a few guys running low 1.5's and 1.4's with stock 8.5's just aftermarket axles...If your breaking ring gears I suggest trying a aftermarket rear end cover with the pre-load bolts, it may help.

 

[rfwave]

How much hp/tq does that equate to roughly?

Tough crowd here. Your 60 foot time info is appreciated but all I'm looking for is a ballpark on how much hp/tq these stock 8.5s will take?

 

[ngnowner]

estimate

Tough crowd here. Your 60 foot time info is appreciated but all I'm looking for is a ballpark on how much hp/tq these stock 8.5s will take?

I would say reliabilty will drop quickly above 400ft/lbs RWTQ. But the stock trans will probably give up before that.

 

[rfwave]

Thanks ngnowner. Its interesting between the 7.5 and 8.5 10 bolts. I know a fellow who ran a completely stock 7.5 rear in a g-body that was a low 12 second car. He ran this rear untouched for almost 3 full summers of drag racing twice a month plus driving on the street before it gave out. I thought the 8.5 was built really heavy duty in stock form but it sounds like a minimal upgrade in stock form vs the 7.5 rear. Obviously the 7.5 isn't even considered a performance rear and wasn't even available on GNs or turbo T-types but the comparison is noteworthy. Thank you for the info, its much appreciated!

 

[UNGN]

An 8.5" is way stronger than a 7.5". It's when you start pulling the front wheels you need forged axles, then you are good for 600 HP or so with an automatic.

 

["Turbo-T"]

The 8.5 is said to be almost as strong as a GM 12 bolt.

How much hp/tq does that equate to roughly?

I think that has more to do with how well the car can hook as opposed to the power rating. Once you start getting the power to the ground the weakest link is the next thing to go, be it a ring gear, a transmission or something as simple as a u joint.

 

[GSTOY]

My old 70 GS w/stage 1 motor had a 8.5 posi rear in it, and took every bit of hp/torque that I threw at it with slicks. Wish I could say the same about all the torque converters that I blewup

Steve

 

[turbows6]

From what I've seen when you start making 500 rwhp the stock axles are at their limit, but with good axles you can safely run at that power level with a turbo buick. A heavier car with a stick would probably trash an 8.5 with that kind of power though.

 

[SPOT MY 6]

My 100% stock rear end broke an axle on my second 1.5 60' off the footbrake. Ive now got several low 1.3's on my built 8.5" 10 bolt. Moser spool, moser 33 spline axles, factory original GM 3.42 gear from 1986, welded axle tubes, TA cover, and the housing/tubes are triangulated. Check the vid in my sig to see how well it holds up. I can post a pic of the whole rear end so you can see how the triangulated bars are welded if you are interested.

 

[HP Man]

A lot of info is required to determine just what it will endure. In my opinion it is a far cry from the BB Buick rear. It is a GM Corporate design and was used in other G Bodies as well as a TR. Currie doesn't recommend welding the axel tubes because of two unlike metals, their advice not mine. Weakness of the 8.5; pressed in axel tubes, small diameter pinion shaft, flimsy backing plates, tin clips holding the wheel cylinders that bends under braking, c-clip retainers, gov lock posi. The new 12 bolt complete would be better choice, or Dana 60, or 9". I agree with the tranny comment though but compared to what some 109 blocks, 2004R trannys, and the 8.5 rears are enduring, is amazing. Speed,breaks parts for sure but what a ride! My 02 cents. Gene

 

[rfwave]

SPOT MY 6, that is an amazing video! Very nice car! And who says you need a Ford 9 inch to go fast:biggrin:

 

[coach]

These 8.5's must be better than the early 10 bolts. I blew up 6 of the front loader style in my 62' Chevy before going 9" Ford. This is good news, but I am suprised. My 62 is lighter than a GN by about 200#'s. I am glad to hear just axles and gears down the road. Just wondering , do most stay with the 3.42's since we go taller tire?

 

[rfwave]

Just found this link. Is this gentleman a board member here? Anyway hes throwing decent power at a mostly stock 8.5 sans axles, c clip elims and a diff. cover!

1987 Buick Regal Street Sleeper - Features - GM High-Tech Performance

 

[Grumpy]

Just found this link. Is this gentleman a board member here? Anyway hes throwing decent power at a mostly stock 8.5 sans axles, c clip elims and a diff. cover!

my daughters GN went 9.94 @ 138+ in street trim with a stock rear that had axles, c c lips and a rear cover Car weighs 3661 if I remember right :wink:

 

[Turbo1dr]

I actually broke this axle where you see the car sitting.....on dirt. Foot braking the car up to 19psi on cold brakes with the e-brake on.....SNAP! The car was getting upper 1.4 to 1.60 sixty foot times at the track.