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.

 

[Matthew Jeschke]

Ah thanks, yeah I just double checked that. Might have been lighting. There's no gap on outer diameter of seal anywhere. I'm ordering a new one, especially since my friend's seal in the same kit just failed in same way.

Are you pretty careful about using a tool? I think I'll build a tool out of some wood with hole cut for shaft, and a section of PVC pipe to drive it on this time. Last time I don't believe shaft was in, I put a piece of 2x4 plywood over the seal and gently tapped it in with a rubber malot. Pretty sure I couldn't' have damaged anything. I also lubed seal with transmission assembly goo (Vaseline / petroleum jelly)

 

[Matthew Jeschke]

I called USA Standard Gear tech support. The guy was nice but not too knowledgeable. I parted ways as he really didn't know what I was talking about. My question was this...

When installing the front output shaft seal (a two way seal), should the outer seal be supported, inner, or do both have to be supported. I wondered if I shouldered wrong part of the seal and caused the inner seal to walk out / prematurely fail.

I didn't use the recommended tool in factory service manual. Rather a block of wood and tapped it in till fully seated. My process mainly supported the outer radius / seal.

I had wondered if I messed up the seal doing that. He really didn't understand. Does anybody know? I'm honestly being cheap and trying not to buy a one time use $100+ tool

 

[randeez]

pretty sure in the vid you made, the seal isnt in far enough.
ive rebuilt a couple NPs and BWs that front output seal is a pita if its the same one.
it is two piece and needs to be pressed out on the female output and also into the housing - at the same time. ive tried to set it in the housing first and then put the output shaft in - doesnt work, and also pressed down the shaft and tried to set it in the housing- also not worth a shit. which you dont know its going to leak until you install it, fill, and drive it. so both times i think ive ended up pulling front driveshaft, pulling the seal out and "lubing" a new seal up with some trans fluid safe rtv and beating it in with tranfercase installed with the appropriate seal installer or with 1-1/2" sch80 pvc i think is real close

 

[Matthew Jeschke]

@randeez thanks dude! So you made a tool out of PVC? My buddy said he thought the runout on the seal he installed was bad too. He revised his tool and gave it another shot, he made it out of PVC as well. Was going to go to ACE and see about buying some PVC to rig a driver up.

Otherwise I see they sell this one on ebay but is $100 HERE

On another note, I probably efd up the input seal too as is the same style but I cannot see that as is in the transfer case adapter / mount.

 

[Donal]

Is this the seal? Is the drain hole at bottom? Is the case mating surface hole clean and free of burrs? Is the seal surface well lubricated with oil before installation? The wiper inside the seal needs clean oil for installation. The shaft seal lip needs lubrication before installation. The shaft surface should be clean and free of burrs, maybe polish before oiling and installation. Filling the cavity between the seal lip and the wiper with petrolem jelly is good. inspect the lip spring and lube it as well. No sealant or rtv or permatex is needed and can cause leaks between the case housing hole and seal mating surface.

 

[Matthew Jeschke]

@Donal not that one...

There are two separate two way seals. One is on the outside of the case, this is the front output shaft seal. It's leaking. I ended up buying the tool and will just install it with the tool. I'd tried otherwise and it failed.

My question left is, I assume the input shaft seal just as fickle since it's the same design as the front output seal? I probably installed it wrong that be the case

 

[randeez]

I don't remember any of the ones I've done having a problem with the seal on the input shaft and I don't remember it being a two piece - but I haven't specifically done a 246.

To state the obvious...the transmission fluid does have a path into the tail housing where the adapter to the transfer case is. Are you sure that's not the fluid you're seeing?

 

[Matthew Jeschke]

WOW @randeez & @rockola1971 DANG I just coughed up the dough and bought the tool. It's immediately apparent, visually, the original seal was not seated correctly.

First I could see the inner seal WAS raised on one side / runout was quite a bit. I pulled it and used the tool to install the new one... After seeing one correctly installed it was IMMEDIATELY apparent I'd not installed the original one correctly. The recessed radius for the driveshaft boot on the shaft likes to catch the inner seal and pull it out. The tool helped support it so that wouldn't happen. Somebody could possibly make a tool out of PVC... but the tool made installation a no brainer.

My next concern, is if I did it on the input shaft as well, however, there's not much for the seal to get caught up on there so I assume it's not as vulnerable to that issue?

I'm going to monitor fluid level none the less to ensure it's not getting into the transfer case adapter...

 

[rockola1971]

WOW @randeez & @rockola1971 DANG I just coughed up the dough and bought the tool. It's immediately apparent, visually, the original seal was not seated correctly.

First I could see the inner seal WAS raised on one side / runout was quite a bit. I pulled it and used the tool to install the new one... After seeing one correctly installed it was IMMEDIATELY apparent I'd not installed the original one correctly. The recessed radius for the driveshaft boot on the shaft likes to catch the inner seal and pull it out. The tool helped support it so that wouldn't happen. Somebody could possibly make a tool out of PVC... but the tool made installation a no brainer.

My next concern, is if I did it on the input shaft as well, however, there's not much for the seal to get caught up on there so I assume it's not as vulnerable to that issue?

I'm going to monitor fluid level none the less to ensure it's not getting into the transfer case adapter...

Id monitor the fluid level in the Tcase and the Tranny for the next year.

 

[Matthew Jeschke]

I've been staring at my core. The tcase I bought to use while I was rebuilding mine. It's been sitting completely disassembled on my bench since I finished this project. I think it's time to clean up my garage and get parted out, or rebuilt and sold. The one thing that held me back from before...

The original clutch pack spacer was all chewed up. I think somebody maybe tore it down before and didn't spec spacer correctly. I'm not sure how to spec one w/o measuring the old one or that stupid expensive factory tool. Any tips would be appreciated.