Transfer Case upgrade

JDC2500HD · January 6, 2012

Purchased the Merchant Automotive upgrade kit for my NP1 263 tranfer case that fell victim to the "pump rub" issue. Today I installed the upgrade kit and everything was fine until I drove about 2-3 miles down the road to go home. After I stopped at my mail box to grab my mail, when I accelerated to go up the drive to the house I heard a growling noise. Went for a short drive and from time to time after accelerating I would hear the growling. It did not seem to be consistent. Sometimes it would last a short few seconds and other times it it would growl till I stopped.

Can anyone give me some ideas? Did I do something wrong or not do something?

p.s. There were no noises, grinding or growling prior to the upgrade.

dodge123 · January 6, 2012

Did you notice what condition the driveshaft in-put slip yoke was in when you re-installed it? If there were any imperfections such as scoring or it was worn in any way you probably destroyed the aluminum bushing in the transfer case tailhousing, I DID! Wait for a few more responses but you may want to pull the driveshaft again and inspect with a flashlight.

To test, grab the yoke where it comes out of the transfer case and try to move it up, down side to side. It should not wiggle. You will feel play if you push it in and out that is normal.

I made the mistake of installing the original driveshaft into the new case and withing a few miles realized i screwed up bad. I had to order the new bushing, rear seal, drop the transfer case and take the rear half to a tranny shop where they installed the parts. You can get a new slip yoke from a dealer, however you need to have the driveshaft re-balanced as well as replace the u-joints. My local autopart international sent the whole driveshaft to their rebuilder/balancer. There they installed a new yoke, replaced u-joints and balanced the thing. The GM factory balances the driveshafts when they are installed in the truck. When anything is replaced the shaft will be out of balance and cause vibrations. Hope it helps.

If this is indeed the case, when you separate the case halfs, use a magnet and check the fluid for metal shavings, if there are it is a possibility the bearings could be in jeopardy. There will definitely be aluminum shavings but since it is soft metal the bearings should crush it up into powder anyway. Make sure you flush the case very well. I was lucky and the bushing was not worn down to the steel backing yet.

gmtech4 · January 7, 2012

Did you notice what condition the driveshaft in-put slip yoke was in when you re-installed it? If there were any imperfections such as scoring or it was worn in any way you probably destroyed the aluminum bushing in the transfer case tailhousing, I DID! Wait for a few more responses but you may want to pull the driveshaft again and inspect with a flashlight.

To test, grab the yoke where it comes out of the transfer case and try to move it up, down side to side. It should not wiggle. You will feel play if you push it in and out that is normal.

I made the mistake of installing the original driveshaft into the new case and withing a few miles realized i screwed up bad. I had to order the new bushing, rear seal, drop the transfer case and take the rear half to a tranny shop where they installed the parts. You can get a new slip yoke from a dealer, however you need to have the driveshaft re-balanced as well as replace the u-joints. My local autopart international sent the whole driveshaft to their rebuilder/balancer. There they installed a new yoke, replaced u-joints and balanced the thing. The GM factory balances the driveshafts when they are installed in the truck. When anything is replaced the shaft will be out of balance and cause vibrations. Hope it helps.

If this is indeed the case, when you separate the case halfs, use a magnet and check the fluid for metal shavings, if there are it is a possibility the bearings could be in jeopardy. There will definitely be aluminum shavings but since it is soft metal the bearings should crush it up into powder anyway. Make sure you flush the case very well. I was lucky and the bushing was not worn down to the steel backing yet.

how do they balance in the truck? just asking