2012 GMC C2500



January, 8, 2007 AT 6:34 PM

My '97 Sub is giving me what feels like a rear driveline shudder at initial take-off in 2wd fwd or reverse. I took it to a trans shop and the test drive confirmed the shudder. I had them lube the driveline after checking the U-joints and do a trans service with filter r& r. I still have the shudder and it's beginning to intensify. Could I be having some type of problem with the rear posi-traction device? Does it require any special lube additives? I can't find any forum problems with the Corp 14 bolt diff. But that doesn't mean something hasn't been found on other Sub 3/4 ton 4x4's. Thanx in advance, Mac in Spokane WA

2 Answers



January, 9, 2007 AT 11:43 AM

Hey mac,
If your positive its a posi rear end than it needs the recommended fluid (possibly synthetic) and a limited slip additive. I would also recommend a complete service on the rear diff (cleaning!) And not just a fill! You may be able to get some info from your local gm shop for the specs! Let us know!




January, 10, 2007 AT 6:09 PM

I feel stupid !

Yesterday my shudder turned into a rig that had trouble getting out of its own way. It began to run very ruff in traffic coming home from work. It became obvious that it was a new problem and it was indeed electrical.

Only under power at roll away did the shake increase and at idle stopped in gear it was shaking about every 15 seconds like a MISS. Parked and idling it DIDN'T miss or give any indication of a problem.

I got it home and set the E-brake and got the hood open only to hear the snap of a leaking plug wire. With a mirror and a little darkness I could see the #4 shooting an arc to the boot shield about every 15 seconds but it ran smoothly in between.

A little RTV shot into the split in the boot and an overnite setup and today it runs like a new truck.

I don't quite understand why every 15 seconds but I'll live with being stupid now that I fixed it.

Thank you for coming back to me about the rearend tho, I'll get it cleaned and re-lubed as preventive maintenance.

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