Grand Sport Service Rear Axle.

[korvettekarl]

So about a week after the warranty ends I get this message in the DIC. 2017 Grand Sport 7 speed. Didn't seem to affect anything until I went on my favorite exit with the off camber dog leg. I usually hit this one at around 95 or better. Now I can feel the rear end fighting itself. Anyone have any idea what sensor is failing/failed? It was an intermittent warning on the DIC until this week. Now it shows up on every start. Any help is always appreciated. PS, all fluids have been changed in the transmission and the axle. And yes I used the GM gear lube with the limited slip additive in it.

 

[Bob Chadwick]

Take it in and see if they will help you out. I had a door panel go bad one month outside the warranty and Chevy paid for 75% of the replacement.

 

[korvettekarl]

Well you must have a great dealer. I don't think they exist here in Vegas. I have purchased control module for the rear end. I will install this weekend if I can get my 72 Nova off the lift. I will let everyone know how it turns out.

 

[korvettekarl]

Well I bought the module. I have my car on the lift. Does anyone know where this module is located? I can't find it from underneath.

 

[korvettekarl]

Finally found the part under the right rear fascia. A bear to reach it. Glad I have a lift. Nice to not have the different sides fight each other. Handles like it supposed to again.

 

[Hib Halverson]

So about a week after the warranty ends I get this message in the DIC. 2017 Grand Sport 7 speed. Didn't seem to affect anything until I went on my favorite exit with the off camber dog leg. I usually hit this one at around 95 or better. Now I can feel the rear end fighting itself. Anyone have any idea what sensor is failing/failed? It was an intermittent warning on the DIC until this week. Now it shows up on every start. Any help is always appreciated. PS, all fluids have been changed in the transmission and the axle. And yes I used the GM gear lube with the limited slip additive in it.

I'm going to guess there's a problem with the eLSD, Note that the hydraulic actuator uses ATF, but the clutches, which are inside the rear drive unit, are lubricated with the axle lube. The drive axle lubricant is Dexron LS 75W90. It has additive already in it so you should not have added additional friction modifier. The first thing I'd do is change the drive axle lube, again, using Dexron LS 75W90, but do not add any extra friction modifier, then road test.

If the problem goes away, it was too much friction modifier that was causing the issue.

If the problem persists either the controller or the hydraulics that control the clutches inside the axle are problematic. If you get to that point, your choices are three 1) throw parts at the problem starting with the controller, 2) have the dealer read the fault codes and repair as necessary or 3) if you are a DIY with the proper scan tester, read the codes then buy a three-day or one month subscription to GMSI, the web-based GM service information and repair per those instructions.

 

[korvettekarl]

Thanks Hib. This is the car I replaced with that Grey 2017 with the automatic that kept throwing the torque tube on. You came by my house to check it out. Once again you come up with the most informed answers. I will throw it on the lift and have another look. I replaced the controller but it started throwing codes after a month or so. Now that I am retired I have a lot more time on my hands. Once again, THANKS.

 

[korvettekarl]

Hib, I have reread your email. When I replaced the rear axle gear lube I used GM LS Gear Lube 75-w-90. I have replaced the rear axle sensor, part number available when I get home. I am going to change the gear lube again today or tomorrow. In the transmission itself I used a synthetic ATF. You think I should replace the tranny fluid using the GM recommended? Really getting tired of the "SERVICE REAR AXLE" display every time I fire this thing up.

 

[korvettekarl]

Finally ended up taking it to the dealer(yuck). They did replace the same module I had replaced twice. They say they guarantee it for 2 years so we will see. Thanks to everybody's replies.