djnice

Go around a corner and only the inside tire spins. Has anyone had this issue?

For what its worth (I UNDERSTAND THE SCREEN IS NOT ACCURATE THAT IS WHY I SAID "FOR WHAT ITS WORTH". I AM NOT USING THE SCREEN AS AN INDICATOR THAT THE INSIDE WHEEL IS SLIPPING! I MENTIONED THE SCREEN AS A POINT OF COMPARISON TO WHAT OTHER SEE TO FIND OUT IF I COULD RELY ON IT AS AN INDICATOR OF A BAD WHEEL SPEED SENSOR, ETC.), driving straight the eLSD screen is all over the place with bottom bar graph bouncing to red when starting from stop or coming to stop. The picture of the axle changes to yellowish color occasionally. Car is 18 Z06 M7.

When it gets hot it throws codes for various controllers getting taken off line. No wheel speed sensor codes. Will see what the dealer figures out tomorrow.

djnice

Per GM, dealer messed with the connector on top of the rear diff. That's probably the one to the eLSD clutch control module. The tech said he didn't think it was the problem. I was getting all kinds of lost communication to control module codes. I go test the car and its okay for 5 minutes then the diff stops locking so it stays open and shows 0% lock on the eLSD screen. This only happens when the car is hot. Go back to the dealer, but its too late for the tech to test it.

So yesterday I get the car hot give it the tech to test drive. The car will not repeat the issue and no more codes, no more 0% diff, etc. Then the tech and I drove the car for awhile. Still no issue. So maybe the connector fixed the connectivity issue. However, the tech agreed with me that the diff is not locking like it should. When the car is cold, in first gear, TC and STB off, I can take a corner and step the rear out as much as I want using throttle. When it is hot it won't step out because one tire spins. Any one have ideas what is going on or what to test? My next step is to change diff fluid.

Another thing I have noted that I am not sure if it is normal or not. When I watch the eLSD screen and the sweeping bar at the bottom. It sweeps to 30% and turns red when starting and coming to a stop. And it occasionally sweeps to red when just letting the car slowly roll forward or backward when in neutral. Does anyone know if this is normal? I don't think my GS did this.

spearfish25

It was told a long while ago that a GM engineer said that diff screen is garbage and should be ignored.

As for the ediff not working when hot, something is amiss if that's true. It may be worth trying some of the PTM submodes to see if that wakes up the ediff. Put it in Sport 1 and give it a go.

djnice

Yes, trying PTM submodes is on my to do list.

I disagree that the screen is garbage, but even if it is it should be consistent from your car to mine. So I still am curious to know if others are seeing the sweeping bottom bar indicate 30% wheel slip when the car is rolling slowly?

The reason I don't think the screen is garbage is it clearly shows slip between the wheels and % of clutch lockup. This is useful for trouble shooting if nothing else.

spearfish25

If the screen is legit, why does it show any percent of wheel slip when driving in a straight line? Makes no sense.

lobsterroboto

The diff screen is absolute garbage disagree all you want but it's still wildly inaccurate

djnice

Understood about the screen and my problem has nothing to do with the screen. When hot the car spins one tire in a corner and leaves one tire black mark on the asphalt. It doesn't do this when the car is cooler.

Also, the service axle, parking brake, and rear axle off messages came back last night. So it will go back to the dealer next week.

SnowyATX

Don't recall the number but my car shows 2 digit slip going in a perfectly straight line. It's garbage.

SnowyATX

That sucks man. Sorry for the issues!

djnice

Mine does not show slip on the highway, but shows some on slower roads. And the glitches at low speed in the video below.

This video from a ZL1 represents the glitch with the eLSD screen. The ZL1 guys are saying it is making launch control not work correctly. My 17 GS w/A8 didn't do this, but my 18 Z06 w/M7 does it. By the way, when the axle goes to 100% as you see in the video it is actually locking. I can hear the pump and actuator engaging the clutches. It only happens during the first 2 minutes of driving.

djnice

Its nearly impossible for the dealer to troubleshoot because it goes away when I take in to the shop, and GM is saying it could be a number of things so they don't know where to start. We will keep trying, but I am starting to think this will end up a buy back.

lobsterroboto

I would start by replacing the diff.


what you describe seems like the diff just isn't locking up at all when it starts getting warmer.


Either way this does sound pretty crappy, i would like to know the outcome.

djnice

I changed the diff oil at 3,644 miles. It didn't look as bad as others I have changed. Makes me wonder if the hydraulic pump or axle control module are not correctly activating the clutches. I wonder if the hydraulic system just needs to be bled?

wagoetzmann

I though the eLDS % number displayed was the % clutch engagement called for....not the amount of differential slip.....???

NSC5

Since the eLSD control depends upon steering input could this be the sensor or communications error causing the problem. When cornering the eLSD has to act somewhat like a normal open differential allowing the outer wheel (assuming it is following the longer path) to revolve at a faster rate but with eLSD it is also considering the line you want to take so that the torque vectoring of the driven rear wheels becomes a steering/handling assist.

How hard do you have to be coming out of a turn to have the inside wheel spin/slip? I would expect the steering to be really squirrelly at that point if you have one rear tire solidly gripping and driving while the inner wheel is losing traction because either the differential has locked when it shouldn't trying to force both rear tires to rotate at the same speed through a turn or the inner wheel is receiving the lion's share of the power which is the controller's method of trying to help straighten the car by rotating the inner wheel faster than it normally should given the radius it is following.

davepl

I think the display is fully accurate, and have not seen any conclusive information or data to the contrary.

It makes perfect sense to me when I look at it (clutch pressure or PWM duty cycle on one axis, wheel slip on the other).

Inaccurate compared to what though? How or why does anyone think it's wrong, other than "Someone said that Spring Mountain said that a guy at GM said it didn't make sense".

A lot of legends get started that way, like the Track Mode & Wheel Damage thing.

All that said, I don't think the display is really related to the problem, which is wheel slip when hot. One thing you could do is try a launch and watch/record the wheel slip and clutch pressure displays. You'd -expect the wheel slip to register and the clutch pressure to go up in response to the spinning. Curious what actually -does- happen! If the display were accurate then if you see no slip, it's not detecting the wheel spin. If you see slip and high clutch pressure but it still spins, the clutches are shot (or something like that).

djnice

That is correct. The top number is clutch engagement. It can go to 100%.

The bottom is a sweeping bar that shows speed difference between the two rear wheels. As the bar sweeps further to the right there is greater speed difference and typically resulting in increased clutch engagement.

I agree, but didn't want to get into that argument. I am looking for knowledge about my problem and not arguments. LOL. I have read, that earlier versions (early 2015) were giving bogus info and GM acknowledged they were fixing it.

It does appear to have glitches at low speed as you can see from the video. Does yours do this too? The ZL1 guys say it affects launch control.

davepl

Could it be noise/error/defect in a wheel speed sensor? It reads erroneous movement and declares that it's transient wheel slip... just a wild guess.

If that were the case though I'd expect the clutch application to shoot up in response, but you don't see that in the video. Sorry I can't be more helpful, just thinking out loud...

Warp Factor

Tire slippage on the inside tire during a curve is normal, even with a completely locked differential.

Are you saying that the inside tire is spinning ape-chit or something, like engine rpms going crazy?

I hope I'm not driving anywhere near you while you are focused on things like the differential gauge, or the "horsepower" gauge. I consider these things to be more for entertainment, than sources of useful information.

Bill Dearborn

I agree. The inside tire has to turn slower than the outside tire when in a turn because it is going a shorter distance. The problem is in a tight turn under high power the inside wheel will break loose and receive all of the engine torque. An LSD or eLSD will apply a brake to the inside wheel to limit wheel spin and transfer torque to the outside wheel so power can still be delivered to the ground. That doesn't mean the inside wheel won't spin it just means it will spin less since a certain percentage of torque is transferred to the outside wheel that is also why the term limited slip is applied Vs no slip. If you had a truly locked diff the inside wheel would hop and skid because it would be trying to turn at the same rate as the outside wheel.

Bill