Pulling off the Perfect NP246 Transfer Case Rebuild

[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.