Limited Slip Recommendations

[Sidney]

For Sale:

Eaton/Detroit Locker Truetrac posi.

Part Number 911A319.

For GM 7 1/2 rear diff.

Brand new in box.

Sold car before getting it installed.

Summit price is $409.95.

Make offer.

Sidney Franklin
Bloomington, IL

SFrank944@aol.com

[HoustonNW]

Me too...but only in Little Bend and Buzzard's Neck. Where was your wheel spin happening?

I noticed it in the uphill Wagon Wheel and Horseshoe corners, which seemed to overheat the rear tires more than usual and the car got very loose everywhere. However, now that I think about it, it was spinning at the uphill #5 at ECR and in the slow corners at MSRH along with the standing starts.

Did you make suspension changes for Cresson? I went up ~25% in spring rates and think that was more of a factor than the diff "going bad".

No changes other than going to poly bushings in the rear sway bar.

I went with the Auburn Racer's diff (clutch style diff w/ 800lb preload springs) before Hallett last year and it's been flawless up to now. I still can't say anything bad about it. The slippage I got at Cresson was pretty easy to drive around with just a line change - braking later w/ more trail-braking to slide the rear, turning in 1/2 car length earlier, then hard on the gas to stop the slide and straighten the car completely fixed it. No 1 wheel peel at all. Dunno if it was any faster but it sure was fun With a smoother radius sort of line, it would spin the inside tire from apex to track out. Just a data point for you to play with...may or may not help.

What diff is in your car now and how old is it? Was last weekend the first time you noticed the problem?

I don't know the history on the diff in the car now but I do think that a lot of my wheelspin in the last three races have been from one wheel so it definitely seems to be getting worse.

I think the powertrax can be installed without removing the ring gear since you are reusing the carrier. Tho I *think* it MUST use an open diff carrier. If you have the T2 that was stock in the LS1 cars, I believe you'll have to replace the carrier (from a V6?) and that may be why it's not listed in that link. Pretty sure you'd use the 10-bolt 7.625" 28 spline one, 92-0776-2805 or 92-0776-2885

Not sure I can figure out what is needed to use the Powertrax, I've never even opened up a diff before. However I just got a $625 labor quote from Late Model Racecraft (where we had the dyno day) and so I think I will learn!

With any diff swap, I don't see why you'd have to remove the pinion gear. I've done it by just swapping over the ring gear to the new carrier (LEFT HAND THREADS!) and checking the backlash/pattern. Have never needed to shim anything so far since I've always reused the gears in the rearend, YMMV. If you're installing new gears, it's a whole 'nuther story.

No new gears, I guess I'll buy a magnetic base dial indicator to make sure that I don't need to re-shim. New tools are always good.

Trutrac, Eaton, Auburn - maybe I'll just flip a coin.

[HoustonNW]

OK, I've decided on the Trutrac. It seems that the torque-distributing diffs (Torsen) have the best performance under braking and that is where I need the most improvement.

Eaton recommends dino oil only, no synthetic. The factory weight is 75W-90. Any recommendations on brands? Is the weight OK for race use?

I am planning on replacing the ring gear bolts and probably the diff carrier bearings. Can I get the bearings off the old diff carrier and reuse them? Any tricks to getting the bearing races out of the housing?

[Alien]

If it's a new carrier without bearings already on it, buy new bearings and get those pressed on. I wouldn't try to remove the ones on your current carrier to try reuse them, not worth it. The races fall out when you remove the diff bearing caps off the housing.

[mitchntx]

OK, I've decided on the Trutrac.

Now is not the time to skimp. Do it once and forgetaboutit ...

It's easy to take $1000 worth of nice parts and turn them into metal dust in very short order.

Also make sure you order model specific. Not all 10 bolts are the same.

Redline diff fluid. I use 80W120 because the 75W90 was puking out the vent, especially in August.