jheis

We had our first rain of the season on Sunday

I was making a (normal) left turn from a stop when the rear end on my '89 tried to come around on me. Took me totally by surprise. Fortunately, there was no one in the next lane & some quick counter-steer caught it, but it certainly got my attention!

Is this normal behavior for a limited slip? I think the PO made some comment about the car being a bit tricky in the rain, but I didn't think too much about it....

James

heinrich

What do you drive James? auto or 5-speed? GT or S4?

jheis

Heinrich, this was in my newly acquired '89 S4 5 speed.

heinrich

Then there should not be a problem at all. I drove an '87 5spd with LSD for years and later installed an 89S4 2.64 and it was solid on both LSD boxes.

Where I HAVE seen LSD cause issues, is where tyre pressure was way over on an auto with LSD I bought years ago (as in 44 front, 72 rear on the left only). No idea why the PO did that or how it happened.

jheis

Tire pressure was 36 all around. I have no experience with limited slips, but it seems (to me) that I'm getting quite a bit of chatter - especially in turns from a stop. Probably the first thing to do is get some new Redline oil in the trany - no idea what's in there now.

James

ubercooper

Do you have standard suspension and sway bars? If not, the increases stiffness in the rear mixed with the fact that you are not having that extra power spun away on the inner wheel can make the rear end come around.

If you are getting chatter than definitely change the transaxle oil and dont forget to inspect the drain plug/use a clean drain pan to check if any metal shavings are swimming around.

Lizard928

pretty standard.

I run my tires around 32PSI and get perfectly even wear.

just be gentle around corners and you will be fine.

heinrich

I never had any chatter with either of my 2 LSD's.

AO

A rear wheel driven car is going to naturally have a tendency for the rear end to want to come around on you. Add a slippery road and the behavior is accentuated. Think of pushing a piece of uncooked spaghetti along your counter. It eventually wants to spin around.

The LSD helps when there is poor traction on just one of the rear wheels by providing positive traction to the one that has grip. It sounds like you had equally crappy traction for both wheels. I don't think the outcome would have been any different if you had had an open diff.

If this happens again on a dry road, then you might look at your suspension setup. Too stiff of a rear end will cause over-steer (what you experiences). You can either loosen the rear end up a bit (if you have adjustable droplinks) or you can try stiffening the front end to neutralize the rear.

mark kibort

i remember a friend that had a huge oversteer problem..... it wasnt the car's problem!

jheis

The car has the sport suspension (474) with red Boges - swaybars and droplinks are stock.

Since it was the first rain of the season, all the accumulated oil would have come to the surface, but I've been driving my '82 with an open diff for 17 years & I've never had the rear end come around on me like that - not without provocation anyway

James

anonymousagain

James, fundamentally the tires lost traction for speed/water/oil on the road. FORTUNATELY, you had LSD to even out the slide during correction and allow power feed to control it.

In a non-LSD car, you may have encountered less "swing" of the *** end, since the inside tire would have spun while the outside just slid. However, upon correction a non-LSD car has far more pendulum effect as tires begin to bite and power transfers back to the "lightest" wheel spinning.

Go practice in an open area, to find what left/right feels like when it breaks loose, as well as how easing the power will bring it back into shape smoothly. Then you'll be prepared.

FWIW, an open diff is fine for most everything and likely most won't need an LSD (maybe trying to keep higher hp to the ground). Nevertheless, the slide in an open diff car is more difficult to control/correct since you cannot rely on the balance of both wheels spinning, as a predictable occurrence during correction.

Be glad you have LSD...just take a little practice to understand how it reacts.

Gary Knox

James,

Are you sure the car has a limited slip? The '89 GT's had a LSD standard, but neither the S4 automatics nor the S4 5 speeds had it standard. There are quite a few '89 S4 5 speeds (including mine) that did not come equipped with the LSD.

Gary

jheis

I've autocrossed the car once so far and didn't notice anything untoward - except that I was no longer one-legging it out of tight turns.

The HUGE oversteer in a normal left hand turn in a light rain certainly got my attention - it was like I was driving on ice!

Anyone know the current thinking on which Redline to use? I read an email from a Redline rep back in 2007 where he recommends straight 75W90NS rather than a blend because "the current 75W90NS contains a slight amount of friction modifier so the basis for the mixture isn't there." I stopped by our local distributor, however, and the Redline display information says exactly the opposite, i.e., use the straight 75W90 and add friction modifier because 75W90NS doesn't contain a friction modifier. Unfortunately, the counter was manned by Sgt. Schultz (I know nothsing), so I walked out empty handed.

James

jheis

Hi Gary

Yes, it has option code 220 and it definitely has chatter.

James