Differential Change Question

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10-09-2016
Pector55

Differential Change Question

I just swapped my Getrag 3.06 out in favor of a Getrag 3.91 differential. I used the HP Tuner wheel change to modify the diff setting to 3.91 and entered the stock 28.01" tire size. I also did the Init and the gear change did take. Is there anything else that I should be changing in the TCM or ECM?

I am experiencing an issue when turning hard left, it feels like the clutches to not allow the inside wheel to spin freely so it clunks a little. It does not do this when turning right. My abs lights come on when this happens. I have no codes. I swapped out axles on the left side and I confirmed the tone ring looks good and the abs sensor is connected.
10-13-2016
06300CSRT8

try to disable TCS in the scanner and get it to clunk again. You might actually be hearing the brakes getting applied from the TCS system from seeing different wheel speeds on the inside vs outside wheel.

This a new Getrag or used? Upgraded clutches? Does it drive fine otherwise, like any DTCs getting thrown from the TCM?
10-14-2016
Pector55

Quote:

Originally Posted by 06300CSRT8

try to disable TCS in the scanner and get it to clunk again. You might actually be hearing the brakes getting applied from the TCS system from seeing different wheel speeds on the inside vs outside wheel.

This a new Getrag or used? Upgraded clutches? Does it drive fine otherwise, like any DTCs getting thrown from the TCM?

Thanks for the feedback. I will give that a shot.

This is a used Getrag and I suspect the issue is clutch related. When I put it in, I used Mobil1 that states it includes the additive for an LSD. I then suspected the clutches and heard from others that the Mobil1 additive is not sufficient. I added the Mopar additive. That seemed to help initially but it then became problematic again. I planned on draining the oil, replacing it with mopar diff 70-90w plus the additive, assuring the torque specs are still correct on the 3 diff bolts and then verifying the axle bolts are still torqued properly. I will also disable the TCS in the scanner and testing.

When the car is driving straight there are no issues at all and I have no DTCs.
10-14-2016
06300CSRT8

Additive doesn't do much for the actual friction of the clutches, it is more designed to quiet down gear chatter in some of the FWD cars with a LSD, which use ATF4 and need the additive.

If you can bear the pain of pulling it back out, I would swap in a HHP upgrade set of clutches. Doesn't take very long once its out.

Another fun test is completely disable TCS and do a burnout, check the darkness of the two strips. One will be clearly darker than the other if clutches are your prob. Did the previous owner mention if clutches were upgraded already? Have heard some that were upgraded have issues releasing when in a tight turn.
10-25-2016
Monzsta

Those axles have a magnetic ferro-elastic band that the ABS uses as a tone ring. It is extremely fragile and real easy to damage given the difficulty of removing the axles from the suspension. After messing up a few I found it easier to pull the diff out leaving the axles in place, then replacing an axle, or seal with the diff on the bench becomes very easy.

If you have a scan tool that will read each ABS wheel speed handy a damaged tone ring or sensor will quickly be apparent. They don't always throw codes.
10-26-2016
Pector55

Quote:

Originally Posted by Monzsta

Those axles have a magnetic ferro-elastic band that the ABS uses as a tone ring. It is extremely fragile and real easy to damage given the difficulty of removing the axles from the suspension. After messing up a few I found it easier to pull the diff out leaving the axles in place, then replacing an axle, or seal with the diff on the bench becomes very easy.

If you have a scan tool that will read each ABS wheel speed handy a damaged tone ring or sensor will quickly be apparent. They don't always throw codes.

So my original issue with cornering was solved when I swapped out the fluid again and found chunks of metal. The spider gears were damaged so I yanked that diff and put in another. This one is quiet and corners properly. I do still have the ABS light and I noticed that it goes off and then comes back on after a couple min of driving. I suspect a little damage to the tone ring on the passenger side. While troubleshooting the diff, I had swapped axles on the driver's side and that tone ring was good and there was no change to the ABS light. I'll pick one up from ModernMuscle ($40) and swap it out.

I pulled my buddy's 215mm axles and 2.65 open diff and put in my old 3.06 Getrag and used axles. I was able to tap his old tone rings off and swap them with no problem. I'm not sure what caused my problems but I suspect it was from me trying to install the diff the first time by myself, laying under the car, with the axle attached to the diff. lol Last night it took me 1 hour to put in the replacement and that included torquing it all down and putting my exhaust back in. Install the axles first and also support the control arms up parallel with the ground and use a transmission jack to support the diff. Night and day difference on the install.