KAAZ lsd

[Driven97]

Out with the old:



In with the new:



After much hemming and hawing, I decided to go with the KAAZ LSD for my autocross car. Ray over at KAAZ USA was amazing, and set my unit up to my specs (reverse 1.5way, 1 pair of plates disabled) at no charge. He suggested full locking for track use or autocross on R-comps, as their 915 units aren't as aggressive as their ones for imports. I'm on street tires, so we elected to disable a pair for 60% locking.

I did the swap myself without removing the trans from the car. I precision measured the old & new diffs and used those measurements to order the correct shims to get everything back to within <0.05mm from how the old one came out. The KAAZ was slightly different dimensions - ~0.80mm narrower, with the ring gear 0.67mm offset. For reference, 0.10mm is about the thickness of a sheet of paper.



915 shims are hard to find and expensive, 996 ones are the same thing, readily available, and 1/3 the price. Check them though, as mine were slightly off nominal. I got lucky and the stackup errors cancelled out.

My 140k mile carrier bearings measured out 0.02mm (passive side) & 0.03mm (load side) thinner than new ones.

I verified preload via the gap method:


And double checked I didn't make a math error with gear mesh paint:



Coast side is beautiful. Drive side is a little towards the toe, but apparently this happens as gears wear, and getting the vertical mesh position is the important part. That looks great, and is a dead nuts match for the visible wear on the ring gear.

Overall, about ten hours of work since I'm slow with a wrench, plus several days waiting for parts. Only did a quick pair of test drives, but car drives nice and quiet (well, no louder than it was before) and the diff seems to do what I expected it to do. If all seems well after a more extended test drive, I'll have the car in competition this Sunday for a full review on the diff.

Disclaimer: This thread provided for entertainment only. I am an idiot. My method is not the official shop method. I wanted to do it myself and learn something. Get this done by a professional. When Pete Z or Matt Monson read this their hearts will explode. Brush twice daily. Please recycle.

[KTL]

Nice job!

I'd be interested to see what others say about your original open diff. The "windows" in the housing look different that what i've seen before. I'm certainly no expert as i've only played with a handful of diffs. Just curious if anybody mentions anything about the original diff.

[Elombard]

What is the ~ cost on the Kaaz?

[Driven97]

Probably not cool to link, but I bought direct from the kaaz website. Prices are listed.

[Driven97]

Autocross last Sunday went well.
video

This is my first car with a Salisbury (clutch) style diff, and I'm pleasantly surprised at it's action. It's quiet and smooth. It's imperceptible when it locks / unlocks. The only time I've noticed it is reversing out of the driveway, you can slightly feel the plates trying to grab.

In competition, however, car handled massively different. It's going to take some driving style changes, and perhaps some setup changes, to exploit it.

Inside wheelspin has been eliminated, and I now have the newfound capability of power oversteer. Did my first ever power induced spin in the car. Lift throttle stability is massively improved. Low speed / light throttle maneuverability hasn't suffered noticeably, but I do have a bit more corner exit push at full throttle than I had with the open diff.

We'll see how this guy holds up once in breaks-in & in the long term, but as of right now I am one happy customer.

[Tippy]

You did what you're supposed to do - measured and checked tooth contact.

Steve W and Matt Monson should congratulate you for not simply tossing in the new unit without any verification.