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Gapper_ca
11-29-2008, 09:12
Ok here goes. first part of sep i replaced all the seals and installed a transfercase pump saver. i checked everything out at that time. bushing looked fine, some wear but expected at 180,000 kms. bearings all great, chain etc... new oil and back together. yoke was tight after install. checked it all after a few days, no visible problems. fasat forward 2 months, time for oil change, up on the hoist, what is this black oil dripping from back seal of case, figure damn seal has gone again... grab yoke and moves up and down a 1/4" figure that the bushing has gone. take it to the local mechanic as i have no time to do fix and also he has correct tools and a better lift. up on the lift and 15 minutes later case is off and on the bench. (took me over one hour fist time, center lift tho.) can see that the bushing has let go and walked forward into the case. pull it apart and black sludge everywhere. figure out after that the bushing let lose and spins on the case, metal filings then fill the oil and plug the oil passages and screw pump.... so after getting all the parts cost over $1400 to rebuild it. if i went to GM cost was $$$$$$$$ had to replace rearoutput shaft, fork and gear and clutch for 4wd, pump and reaoutput bearing, rear half and new seal and rear yoke. Bearing kit rom rebuilder was $175 with new seal kit. rear bearing from GM $185 . truck had no vibration at the time of discovery. talked with rebuilder and says that is very common for this case NVG 263 with Dmax/Allison. usually he sees them totaly exploded. i fugure that the previous owners did not change oil at all as when i first got truck at 143,00 i changed it and was black then. so probably been going from day one. so now i have a rebuilt transfercase at 185,000 kms. hmmm same one in my 96 gmc had 365,000kms and never had a seal changed..... regular oil changes was all i did.

DmaxMaverick
11-29-2008, 09:23
Unusual. What oil did you use in the TC?

Gapper_ca
11-29-2008, 12:45
dextron III ATF as per GM Manual and dealership. it is a electronic shift manual transfer case.

DmaxMaverick
11-29-2008, 16:34
That's the right stuff. Curious about the cause, though. The TC's are normally very durable (except for the pump wear thing).

Gapper_ca
11-30-2008, 16:56
yes that is what i thought as well. figure that once the bushing let lose that it wars the case and fills the oil with fillings and such, eventually plugging the oil passages . wonder if this then causes the pump wear thru's as pump is working harder to move oil, mine was worn out lots of play on the shaft and such, if i had the clip i could see that wearing out quickly with all that movement.