Transfer Case Teardown NP261
#1
Transfer Case Teardown NP261
So I heard some weird noise coming back from the track last night and since I was taking the torque converter out anyway I figured I may as well see what kind of damage the tcase is taking. I am probably the hardest person on a transfer on this site besides maybe stock48, but my truck is heavier (5000 with me) than his so I was curious.
I have put about 3500 miles on it in the last year and a half. Probably have an honest 150 4wd-hi launches with 4 drag radials on this tcase with at least 600+hp. Its a stock unit, 250,000 original miles. Only thing that has been changed is the fluid, 80e input gear, and added one of those pump saver things when I did the input gear. It is the manual floor-shifter version.
Just slight wear on the pump saver thing. Back case half still looks perfect.
Magnet is pretty gross...I am guessing most of the material is from the chain.
And the only actual damage I could find was the bushing for the mode fork.
The reason there is so much play in the front dshaft typically is because the ONLY thing transfering power to the front is the middle row of teeth. Notice the big spaces in between them.
When you shift into 4wd, the shift fork pushes that outer sleeve down onto that row so it looks like this:
Here is a view of the input planet assembly...this is pretty cool. The gear on top fits inside the assembly. When in 2wd it fits all the down on the furtherest row of teeth. When you move it to neutral the mode fork pushes it up slightly so it is between the two rows. And in 4lo it moves it to the top most row of teeth, which is how you get the gear reduction of 4lo.
And here is the whole assembly stood on the input shaft. Notice the shift and mode forks.
I plan to replace the chain and that mode fork, as well as the input and output seals, but otherwise everything looked perfect, especially considering the hell I give this thing.
I have put about 3500 miles on it in the last year and a half. Probably have an honest 150 4wd-hi launches with 4 drag radials on this tcase with at least 600+hp. Its a stock unit, 250,000 original miles. Only thing that has been changed is the fluid, 80e input gear, and added one of those pump saver things when I did the input gear. It is the manual floor-shifter version.
Just slight wear on the pump saver thing. Back case half still looks perfect.
Magnet is pretty gross...I am guessing most of the material is from the chain.
And the only actual damage I could find was the bushing for the mode fork.
The reason there is so much play in the front dshaft typically is because the ONLY thing transfering power to the front is the middle row of teeth. Notice the big spaces in between them.
When you shift into 4wd, the shift fork pushes that outer sleeve down onto that row so it looks like this:
Here is a view of the input planet assembly...this is pretty cool. The gear on top fits inside the assembly. When in 2wd it fits all the down on the furtherest row of teeth. When you move it to neutral the mode fork pushes it up slightly so it is between the two rows. And in 4lo it moves it to the top most row of teeth, which is how you get the gear reduction of 4lo.
And here is the whole assembly stood on the input shaft. Notice the shift and mode forks.
I plan to replace the chain and that mode fork, as well as the input and output seals, but otherwise everything looked perfect, especially considering the hell I give this thing.
#2
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Join Date: Apr 2010
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Ah those links and pins of that chain brings back memories working at borg warner. I dont know how many damn studies i did for surface roughness, tolerances, and such on them damn things lol.
#3
These transfer cases are tough. I've put 50k+ miles on mine since the turbo went on(600+whp) and before that it was a heads/cam 6.0L. I did the 80e input, a new chain, and the wear clip about 55k mile ago, but the transfer case has 178k total. I have done hundreds of 4wd launches(every time I get the chance), and in the winter I use 4wd a good bit, because it's fun, but a little hairy driving in snow and ice with that much power.
Last edited by brent1976; 06-14-2013 at 11:25 PM.