Has anyone replaced the eLSD with a mechanical diff?

The concern is that when the eLSD doesn't engage the car has a "rear axle" message and that prohibits disabling the driving aides.

I'm curious if its been done and to what effect? is there a way to trick the ECU into thinking the eLSD is still there and functional?

 

I am not sure what the concern is. The eLSD provides many advantages over a mechanical limited-slip and it rarely fails. Rear-axle error messages are most often caused by other issues in the car that affects how the eLSD operates.

Bill

 

The concern is wanting to know if anyone has replaced the eLSD with a mechanical one and if so, to what effect.

the eLSD unit is heavier than many aftermarket LSDs
my eLSD is failing (indicated by individual wheel speed data, inside rear tire spinning a LOT faster on exiting from a left hand corner)
the electrical sensitivity of the eLSD control is something i'd like to eliminate. I get the rear axle message every single time on first start after turning off the kill switch and the car has to be restarted, this is a mild inconvenience i'd like to not have at all.
I've heard reports of the eLSD turning off and creating the rear axle message randomly while using a lithium battery. (which is curious because i have one coming)

 

Maybe the resolution would be to fix the eLSD. There are only a few failure items that can cause the inside rear wheel to spin and those items are outside of the diff. All service messages are generated by codes. When you get the Service Rear Axle message have you hooked up a scanner and see what code is generating the message? Have you checked the differential clutch fluid level or used a GM MDI Scan Tool to bleed the system to make sure it is filled properly? The eLSD Clutch System takes about a quarter of a quart of Dexron VI. If you add fluid you have to do the bleed.

Bill

 

Bill, I think Lobster's car is getting pretty darn close to (or already is) a "full-blown" race car. At this point a more traditional route probably means less headaches in the long run.

Lobster....all I can think to offer is to call LG or your shop of choice to see what they say. With what you have invested in the car, seems like they'd share some knowledge with you.

 

if i have to replace the eLSD I will, im not really looking for advice on troubleshooting or ways to fix the current eLSD I know how to do that already.

I'm curious if anyone has straight up replaced it with a wavetrac or something and if the eLSD can be tuned out of the ecu?

 

well a shop says that the eLSD can't be deleted via tuning at all. so i guess that's my answer. that sucks.

oh whale.

 

So if the eLSD isn't functioning, you can't turn off stability control or something?

 

yah if the eLSD doesn't turn on you wont be ale to disable TC/AH at all Mechanically it would just operate as an open diff.

I'm not at that point in my case the diff itself may be fine, it could just be the diff controller or whatever i was just looking at it as an opportunity to replace it with a mechanical unit.

 

Gotcha. I was just curious. You might be able to substitute programming from a base model that didn't have eLSD, but I don't know which specific modules would be needed and how that might affect other systems in the car. It could be a pretty big undertaking.

 

Don't non Z51's have a conventional LSD? May be that might be a solution??? Just a thought... Good Luck...

 

Z51 without MRC would also have a mechanical diff. The problem is reprogramming everything else in the car to match that configuration.

 

C7s also come with non electronic LSDs. What do you have to replace, a control module perhaps, from that car?

 

I'd keep looking, that tuner doesn't speak for everyone. It is software, it can be defeated with hardware or software. You just need to find someone with the skills.

 

yah ive made phone calls and sent emails to a ton of shops.. so far i've gotten it cant be done... or we have no idea... or no response at all.
at a certain point ill just give up it will probably end up costing more than its worth anyway.

 

If you don't mind, PM me your VIN. I won't promise anything, but I'd like to do a little research on this.

 

Threw this together over lunch today. I pulled the calibrations for Lobster's car, and a similar 2015 1LT base I pulled off AutoTrader. I was mistaken about part of this. I thought the Z51s without MRC didn't get the eLSD. eLSD is standard on Z51. It's only PTM that's bundled with MRC. The base cars also have different transmission and diff ratios, so some of this stuff may be related to that rather than the rear diff type. Same with the different brakes, and dry sump vs wet sump.

I wouldn't recommend swapping or cross-programming modules unless you have someone you really trust who can work on this stuff. This is all for informational purposes only. It's just a semi-educated guess from a hobbyist, and trying to implement any of this could leave you with a bricked car or worse.

I didn't check every module in the car, or highlight all the calibrations. I really doubt the door modules for instance have anything to do with this. Same with the window calibrations in the BCM. I just ignored all of that.

I'm pretty sure you'd need to change all of the orange calibrations. The ECM you could probably do with HP Tuners and someone who really knows the E92 ECM inside and out. You might be able to just swap the chassis control module with one from a base model. It would be missing the 2nd plug, so you'd need to jumper the chassis expansion GMLAN wires in that plug to avoid interrupting the bus. You might be able to program a Z51 CHCM with the base calibrations...or you might brick it. I have no idea.

The body control module would be the tough one. That controls the keys and the security system. DO NOT screw around with the BCM. It does not have a sense of humor. I don't even know for sure if it would need to be programmed. I would guess it does though. The BCM seems to send out the messages to the rest of the car that tells the other modules what features it's equipped with. If it sends out a signal that says it's supposed to have eLSD, then that could cause a bunch of errors on the cluster and elsewhere.

Speaking of the cluster, I was really surprised it didn't have any changes. But if it's just passively listening for fault messages from other modules, then that would make sense.

 

Just wondering: what if you just change the diff to a traditional OS Giken or perhaps a Torsen one, and then also remove some of the stability control sensors (like steering wheel position sensor) so stability control would just error out without disabling ABS?

You could easily try this out without any permanent change by unplugging ediff controller (or removing fuse), and then also unplugging one such sensor to see if stability control is still alive.

 

because I am not that smart and never thought about it until a few seconds ago when i read those words.

 

Only if someone's figured out the right resistors to wire into the electronics to fool the 'puter.'