Pulling off the Perfect NP246 Transfer Case Rebuild

[rockola1971]

And your help! Everybody wants to use that dumb tool for a gazillion dollars to spec the clutch stack spacer. I'd have been sunk if you'd not have pointed out to just measure them by hand. Maybe the only time your really need that tool is if you have a new clutch drum?

Yup a new clutch drum or to verify that you have warped drum. Even then a caliper when used to measure in the right places on a drum/basket will tell you everything you need to know.

 

[Matthew Jeschke]

So I tore down my core NP246 that I pulled off. It had a clunk. It would clunk on transmission shift from 1st to second when I accelerated very lightly in 2HI. I had suspected the transmission was doing it, but when I installed the rebuilt transfer case it went away. I didn't find anything in the case to lead me to believe parts were defective. Only issue I found was the selective spacers were probably too big, they were scored. Everything else looked just fine.

I assume too much endplay on ring gear / input could cause a clunk as planets drive the input forward. How much endplay is acceptable with that ring gear / input? Anybody know? How might I verify that theory? Or maybe I should look elsewhere?

I'm curious as I may rebuild this case too and sell it or sell off the parts.

 

[Ferrera12]

I've got all the parts ordered minus few incidentals; encoder, clutches, vent, etc. Actually not sure where to order factory clutches from... Rock auto didn't have them, ebay does but I never fully trust eBay.


You have convinced me What you mention is how I did it in my 4L60E build (more or less). I'm really perplexed as to why they do it differently for the drum on the NP246 with that stupid complex tool. For the 4L60E build I put a feeler gauge between the pressure plate an the top clutch and checked the gap met spec in my book.

The only question, and I'm sure you're accounting for this... They don't give me a spec for gap, only for using that stupid tool. So if I spec off the old clutch pack height, won't there be wear to account for? I've 250,000 miles on that transfer case. Do clutches wear much? idk...

Practically fell apart, really easy to work on except for those double seals. Came with 6 pinion planet already.
View attachment 381882View attachment 381883

Has anyone gotten their hands on a Manual for this ?

 

[Matthew Jeschke]

Okay so I'm dumb. I only looked at pictures in factory service manual when I rebuilt my case. I didn't read the instructions. Somebody pointed out to me that the chain should be oriented in the same way it was taken out. Is that a big deal? I know I oriented the gears in same way I just didn't mark the chain at all for which direction it had been installed. I also reused the old chain and gears. Would that make any difference at all?

 

[Matthew Jeschke]

FNA Front output shaft seal has went out already I don't know if it's a defective seal or I installed it wrong. I don't think I installed wrong but it leaks between the two parts of the seal (two way seal). It leaks quite profusely once I get moving so I think it suddenly failed. Almost looks like inner most seal is pulling out but hard to tell.

Curious are there better brand seals that one could expect to last a bit longer... if it was truly defective?

When installed I carefully tapped in with a block of pine wood.

Thanks!

 

[Donal]

FNA Front output shaft seal has went out already I don't know if it's a defective seal or I installed it wrong. I don't think I installed wrong but it leaks between the two parts of the seal (two way seal). It leaks quite profusely once I get moving so I think it suddenly failed. Almost looks like inner most seal is pulling out but hard to tell.

Curious are there better brand seals that one could expect to last a bit longer... if it was truly defective?

When installed I carefully tapped in with a block of pine wood.

Thanks!

Post picts and number off the old seal and the new one that is failing now.

 

[Matthew Jeschke]

I have a little video here

I really think the seal is defective. Damn thing leaks between the inner and outer part. I wrote USA standard gear to ask if they'll send me a new one. I don't know the part number for the specific seal, it was a bundle kit, kit is ZTBK351

In video, I mean brake parts cleaner, not brake fluid. Damn stuff took the engine paint RIGHT off my transfer case. I would have assumed engine paint would stand up to solvent. I guess not.

 

[rockola1971]

I have a little video here

I really think the seal is defective. Damn thing leaks between the inner and outer part. I wrote USA standard gear to ask if they'll send me a new one. I don't know the part number for the specific seal, it was a bundle kit, kit is ZTBK351

In video, I mean brake parts cleaner, not brake fluid. Damn stuff took the engine paint RIGHT off my transfer case. I would have assumed engine paint would stand up to solvent. I guess not.

Brake parts cleaner will dissolve most paints. It appears in the video that the seal was not driven in fully to its seat.

 

[Matthew Jeschke]

Brake parts cleaner will dissolve most paints. It appears in the video that the seal was not driven in fully to its seat.

What made you think it wasn't driven in all the way? I know I mentioned that but you saw something too in the video?

That said, a friend bought the exact same kit and had that exact same seal fail in the same way now I'm starting to think USA Standard Gear got in an order of defective seals for their kits. I left them a message but is the holiday.

 

[rockola1971]

What made you think it wasn't driven in all the way? I know I mentioned that but you saw something too in the video?

That said, a friend bought the exact same kit and had that exact same seal fail in the same way now I'm starting to think USA Standard Gear got in an order of defective seals for their kits. I left them a message but is the holiday.

From what it looks like to me in the video it appears the seal is not driven fully at the 2oclock to the 5oclock position of the seal outer diameter. It looks like the face of the seal in the video is not almost or at flush with the bore but it does on the other areas of the seal especially the 6oclock to 12oclock area. In the video it appears the 2-5oclock areas of the seal are around a 1/16" or possibly more out of the bore. This all of course could be just the lighting and reflections or even the brightness level on my monitor.