Hi!
I was on the strip for the first time 3 weeks ago, and run my first run ever, but I thought it was boring. And I really love turning and want to go on both road racing tracks and autoX.
While I where at the track, 200 miles away one way, I broke both the clutch and the pinion bearing.

The question I have for you is, do the stock 10bolt, with modifications of course, hold for 500rwhp at a road course?

What type of differential should I go with? I want to be able to “drift” some as well.
And what gears should I go with? 3,73?


Thanks, Anton, in the cold rainy Sweden

 

I ran a 94 Z28 530rwhp car for about 2 hours at Road Atlanta on road racing slicks, car had 4.10 gears in the stock 10 bolt (with t/a girdle). I've always thought the greatest stress on the 10 bolts was through hard launches on slicks.

Not sure about drifting, but if the tires are spinning I'd think that would relieve some of the stress from the rear.

 

Most people agree that the 10 bolt is just fine for rr/auto-x.
But most of those people are NOT running that much power either.
Then some (like roy on here) run a 9" axle even though they are not running that much power through it.
At least part of the reason the 10 bolts are preferred is because you have the greatest choice of rr type diffs for them, along with the lowest weight/power losses of anything available for our cars.

Most people stick with a 3.42 ratio, but that DOES depend on the courses you're running, engine power/range/powerband, etc.

The two most popular diffs are the Torsen T2R (but there have been some defects/malfunctions in the cases of the latter, most recent ones sold), and the Auburn Pro "Racer's Diff" which has a lot of bias AND still is covered under the Auburn D-REX warranty program despite being labeled a 'racing' part!!

There are others which are good (the Easton/Detroit True Trac for example), but usually they do not have enough/as much bias as the two mentioned above.

You will probably get a lot more and quicker responses/feedback if you join www.frrax.com and ask this over there, even though there are members on BOTH sites.

 

if you dont launch or shift very hard and violent, the rear should be alright. but, to be safe, id build the 10 bolt before buying a 9in or 12 bolt. weld the tubes, c-clip elims, high strength axles, maybe stronger (not just deeper) gears, and TA cover, along with a high perf. synthetic gear oil, changed often. 3.42s arent bad for road racing. 3.73 are alright, but personally i wouldnt go deeper, unless youre mostly on very tight, short autoxs.

 

3.73's are a great all around gear ratio for the automatic, but alot of people like the 4.11's with the 6 speed.

As far as the 10 bolt goes they can be quite durable, but there main weakness is the bearing caps and the C-clips. The bearing caps can be supported by a TA gridle, but if you eliminate the C-clips with a eliminator kit they have a tendancy to leak alot. So any good hardend axles are a good fix, but also upgrading to a 8.5 inch 10 bolt from the 8.2 inch 10 bolt is a cost effective way to get more strength. I ran a stock 8.5 10 bolt with a gridle with a 500 horse small block all over hell and back, and its still in great shape.

But a ford 9 inch is a great upgrade but it can cost your about 2500 "new" plus dollars or roughly 1500 "used" where as a built 8.5 inch 10 bolt can be sourced for about 1200 "used" but where you save the real money is that the 10 bolt uses the same brakes as your 8.2 inch 10 bolt. So if you have to add brakes to a 9 inch ford your talking another 1000 plus dollars in the mix.

 

Thanks for al the replys! I apriciate it!

Dailydriver: What do you with bias? how mutch the diferential "locks"?
Witch one do you drive? The Torsen T2R?

EchoMirage: Yes thats true of course! The problem is that I always do those fast shifts and not heavy launches but i do launches on the street since I tend to race all japanese tuners i see.. Always fun to se them go down.

L7 Sierra: Okay, I have a TA Gridle laying around in the garage. Where do you find a 8.5 inch instead of the 8.2?
The problem where i live is the cost for transports of parts. I do't even want to think about the shipping price for a rear axle from usa to sweden..

Right now I think I have to go the economy road... I have not had the time to disamble the axle totaly, but i have opened the cover and i cant se any damage to the differential or the gear, but i think the front pinjong bearing is damaged. I will probobly by a new set of gears, with 3,73 ratio. just to get the car going and get to the track once this season. And during winter i ripp it apart and build it with a new diferential and axels.

 

dont forget to weld the tubes

 

Hey Swede
I used to run a 10 blot , then switched to Ford nine inch . The paranoia of grenading the 10 bolt differential and a axle walking out racing speeds was a little un nerving .
Problems I had with the 10bolt were minor, but caused problems.
LSD DIFF became a 1wheel power wonder when hot.
Had a long brake pedal from from the play in the c-clips.
Pinion seal leaked always.

If you decide to go with a Ford nine inch, specify the A10 roller bearing option if available. The standard ball bearing axle bearings are not up to the task of road courses if using R compound tires. I change my axle bearings yearly.
For the differential try to get the Detroit Trutrac race version . This version comes with a higher bias plus has a spring preload like the T2R, but is quite a bit cheaper then a T2R.

 

EchoMirage: thanks i will do that!

Roy: Thanks for your input!

What about a Corvette C4 IRS axle? Dana 40/60 am i correct?
How are they for road racing and how do they hold up to heavy abuse?

 

Don't know much about that , but the Owner of Movit Brakes had a BB 600hp Chevy in a ZR1 before he stepped up to the C6 Z06. It never had a problem.

 

Where can i order those differentials online?

Thanks for al the help!
By the way, is it beter with LCA's with pollybusings or P-rods?

 

C4's came with 2 diffs: auto's got D36, manuals 1985 and later got D44. The D36 is OK for road racing, but it is marginal for drag racing on sticky tires above about 450 rwhp.

The D44 is pretty stout. It lives to about 600 hp on the strip and it is very strong for a road course car. It is significantly stronger than the C5 setup.

 

You might try the one of the sponsors here . The company that sent mine to Germany is out of business. The company that built my third member is in Washington and Tennesee . If you google Randy's ring and pinion you will get te company that built my dropout.