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Old 04-13-2016, 07:30 PM   #1
nvestysly's Avatar

1992 29' Excella
Van By The River , Georgia
Join Date: Feb 2002
Posts: 1,304
4 X 4 Transfer Case "Pump Rub" NP246, NP261 and NP263

There are probably many Air Forums members who tow with late 1990's to mid 2000's GM trucks with New Process / New Venture transfer cases.

If you have a 1/2 ton or 3/4 ton 4 X 4 vehicles in you should be aware of "pump rub." I recently experienced this problem and I think I corrected the issue before any long-term damage was done.

Here are two links to solutions to the "pump rub" problem.

And a link to a PDF file describing the fix as well as a links to a YouTube videos showing installation of the two common fixes

So here are the details for my recent situation.

I was at the local dealer for periodic service (aka oil change). I go to the dealer because they charge less for an oil change than I can do it for myself and they notice potential issues that I might miss.

On this particular visit the service technician mentioned he saw evidence of an oil leak. He was not very specific and I didn't ask any questions because I thought the leak(s) were from the usual rear main seal and the transmission pan. I knew both areas leaked but neither of them were serious IMO.

A week later we towed the Airstream about 500 miles from home and immediately noticed a light spray of oil on the front of the trailer. The oil slick worsened as we traveled and by the time we were home the residue on the trailer was all the way to the rear bumper of the trailer. I had checked the engine oil and transmission oil but neither needed to be topped off. I didn't check the transfer case and ultimately that was the location of the problem.

The dealer didn't mention pump rub but GM is definitely aware of the issue and has distributed a technical service bulletin but has stopped short of a recall because the problem doesn't typically exhibit itself until 80 - 100 k miles and many years. Our K2500 Suburban is 11 years old and has just shy of 100k miles.

So be forewarned. You may not catch your problem in time. If the transfer case loses all it's oil you'll be looking at many $$ for the repair.

I did the repair myself using the Merchant Automotive kit. All the parts were under $500 and it took me about 7 hours in the driveway with a little help from a "car" buddy.
Lucius and Danielle
1992 29' Excella Classic
1996 GMC Suburban C2500 7.4L
2005 Chevrolet Suburban K2500 8.1L
Got a cooped-up feeling, gotta get out of town, got those Airstream campin' blues...
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