Transfercase Leak

alz · October 8, 2007

I've got a 99 Suburban with the auto 4x4 option, think it's a NP246. Recently noticed it was leaking and I cannot determine where. It seems wet on the backside, lower half. It gets all over the crossmember right below the tailshaft. I'd like to say it was the tailshaft seal, but it is getting wet forward of it. Does this sound like something others have had happen? What was the cause and the fix?

Thanks Al.

5Alive · October 8, 2007

Look for a small 1/8" square hole in the magnesium case tail shaft housing about half way up the back side. The symptoms you describe are indicators of a very common problem with the NVG 246, 261, and 263 transfercases. It's called "pump rub", where the wear clip to the pump actually wears a HOLE into the transfer case. This is a poorly designed retaining wear clip, and I'm not even sure that the updated design from NVG/GM is any better.

Visit thedieselplace.com for a thorough discussion of this problem, and some various solutions. This problem is so common there are not one, but two competing kits in the aftermarket to resolve it. Search "pump rub" and "hole" + "transfer case", and "merchant automotive" on google and on thedieselplace.com , and you will have more reading than you can fit in the rest of this year. The pictures that members have posted will assist you in locating the exact spot of the leak.

Some people have JB welded the hole, but the real fix involves removing the transfer case, splitting it apart, getting a new part(s) from the after market to keep it from happening again, getting a new case half housing from GM, and rebuilding your transfer case.

Since the pump rotates all the time, even in 2WD (causing the clip to beat a hole into the case), it isn't a question of IF this will happen. It's just a question of WHEN. It usually occurs around 80K miles. It has appeared as early as 40K miles.

I'm thinking of taking out my transfer case and having the the aftermarket parts installed NOW, before mine starts leaking. I'm just waiting until the bumper to bumper warranty expires. IMO, GM should be ashamed to expect customers to continue to pay for such poor engineering.

alz · October 9, 2007

Thanks, I check that out better tomorrow. Mileage is at 82k. If I JB weld, will the hole continue to get bigger and then possibly crack?

warscout2 · October 9, 2007

what year did they fix this I have a 2001 that i just bought that has 107000 onb it i just changed the rear main seal do i need to worry about this and might it have been changed and what should i look for if it has

alz · October 9, 2007

After doing a lot of reading, it doesn't look as if they did fix this problem. Some people with 06 and 07 models having problems too.

Is the rear half of the tcase a dealer only item?

The upgraded parts look to cost about $250 plus the cost of the new case half.

alz · October 9, 2007

I was under there today. I could not find where it is leaking. I'll have to clean it up good first. Looks as though it's been leaking for a while. Pretty dirty under there. Where is it common for the hole to be?

5Alive · October 21, 2007

I'm not sure if the problem that we are describing applies to the 1999 model year or not. If you have the NVG / NP 246, I don't see why it wouldn't apply, but maybe in later years GM made some type of cost cutting manuever that made this problem appear. If that is the case, then maybe the leak to your 99 is due to another cause?

As to where the 1/8" x 1/8" worn window is located, there are some great pictures with arrows floating around the net. I changed computers and don't have them in my favorites anymore, so I can't link you. But do a search on the internet, and in particular do a search on thedieselplace.com , and you will find the pics.

I was under there today. I could not find where it is leaking. I'll have to clean it up good first. Looks as though it's been leaking for a while. Pretty dirty under there. Where is it common for the hole to be?

alz · October 23, 2007

Thanks, the truck is at the trans shop now. It was the pump rub problem and there was a hole in the case. I know the owner of the shop pretty well, he rebuilt the trans in my F150 and is friends of the family. He is having the case welded up by someone he knows that welds magnesium. Then he will clean up the welds to make a tighter fit so the pump has virtually no movement. He says he has never had anyone come back after doing this repair. It's only going to cost me $350 including new seals, pump rebuild, and remove and install.

Thanks for heading me in the right direction.

Al

alz · October 26, 2007

Got the truck back today. $350 to fix the leak, new seals, pump rebuild, and change trans filter and fluid. Glad to be leak free again.

alz · August 14, 2008

After putting 12k miles on this fix, it's leaking again. Looks as though I'm going to replace the rear case half and install one of two fixes that I found. Anyone have any experience with using this fix:

http://www.riversidegear.com/categories/tr...roduct-630.html

If I do replace the rear case half, it looks as if there is just a bushing and the tailshaft seal. Can the bushing and or seal swap over? Does anything else need to go into the new case?

alz · September 23, 2008

Check this of my "to do" list. I got the case half, pump plate, gasket and seal from Riverside Gear. Very fast to door service. Got it done about 3 1/2 hours. That t-case is heavy. If anyone has any questions, I'd be glad to answer.