Ins & Outs of Transfer Case Rebuilds

[ashyers]

Thanks to everyone for their for their help! I spend some time today doing my "homework" today so things go smoothly with the students tomorrow.

I'm thinking I can make a spacer for setting the idler bearing preload outside the case by measuring the thickness of the case and duplicating it with short spacer. I'll try and find a piece of hex stock and then I can put a wrench on it to torque the assembly.

As far as an arbor, it looks like I just need to be a few thousandths under the diameter of the idler shaft and a bit shorter than the idler gear so I can remove it from the case with the arbor holding the inner bits.

Curious to see what we find this week. It looks like the case has a date code from '54 and the truck's a '51, so it's been replaced somewhere along the way.

Andy

[06boblee]

Sure would be nice if someone (hint-hint) would take a LOT of pics of the process of rebuilding one of these! I have to replace my shift rods (rust) and figure I'll find other bad stuff. I want to install an oil cooler (external, pump driven), has anyone done this?

[ashyers]

I'll try and take some photos, of course I guess they won't be of much use if we screw things up !

Ran the T-case through the jet wash today, I love that thing! Clean in 15 minutes. So far it looks like there was a bit of shifting going on between the mounts and the case, which I understand is typical. One bolt on each side was a bit loose and I hope that was the "clunk" I've been chasing. Fortunately the holes in the brackets were not all wallowed out. Once the box was clean I spent some time turning flanges and shifting levers. My concern at the moment is the backlash in the "input" shaft, it has the most play by far and I'm very curious to see what we find tomorrow. It does not have the play of a dog ring gearbox, but it's close...

[Elwood]

Sure would be nice if someone (hint-hint) would take a LOT of pics of the process of rebuilding one of these! I have to replace my shift rods (rust) and figure I'll find other bad stuff. I want to install an oil cooler (external, pump driven), has anyone done this?

I just finished rebuilding an NP200 for my truck. If you need photos, I took some during the process. Just let me know if you need anything specific, and I'll check my image file.

Charles at M Series Rebuild has done the external oil pump and cooler on the NP200 transfer case. He's posted here about it in the past, or you could call him.

He also has stainless shift rods for the NP200. Well worth the expense to prevent future leaks.

[06boblee]

Which manual shows the disassembly and repair of the transfer case?

[Elwood]

Which manual shows the disassembly and repair of the transfer case?

TM 9-8031-2 Power Train, Body and Frame for 3/4-Ton 4x4 Cargo Truck M37

[06boblee]

Well, I'm ready to get into it. The tag on the bottom says it was rebuilt in '75. Almost no play at any of the yokes- all turns smoothly, so I hope to get it done with new seals and shift rods. Got my fingers crossed!

[CSCameron]

SUBSCRIBED!

I'm getting ready to do mine too. Please post pics of your progress. I'm waiting on parts before I pull mine.

Clark

[ashyers]

Here's the flange for the rear driveshaft. The area where the seal's lip made contact is well worn. The area where the felt ran is not too bad. I guess it stayed oil saturated over the years!

RearOutputFlangeSmall.gif (97.33 KiB) Viewed 1764 times

Worn but OK...

RearOutputBrgSurfSmall.jpg (203.73 KiB) Viewed 1764 times

Not good... (edit: mating outupt gear killed too)

BrakeOutputBrgSurfSmall.jpg (205.89 KiB) Viewed 1764 times

[ashyers]

Tired! Looks like 1954 may be the last time this thing saw any TLC.

RearOutputOuterBrgSurfSmall.jpg (199.78 KiB) Viewed 1764 times

Now this is a weird one. The shims were destroyed! The preload on the bearing was OK, but when we pulled the flange the shims just fell apart. Guess we are not doing this too soon.

RearOutputShimsSmall.jpg (233.53 KiB) Viewed 1764 times

[ashyers]

Ouch! I think I can run this with a bit of dress up. It's probably been like this for many decades, possibly since new. (edit: It ate something, the mating gear has some damage too. Hope to find a better one.)

RearOutputGearSmall.jpg (239.74 KiB) Viewed 1764 times

Another shot of the missing chunk.

RearOutputGear2Small.jpg (189.78 KiB) Viewed 1764 times

[Elwood]

Andy, I'd guess that there's a small piece of shim unaccounted for, and it went through those gears, breaking out a chunk of that one tooth?

One of the NP420 transmissions that I disassembled had the same failures of the shims, and the PTO was missing an entire tooth on one of the gears. The broken tooth and the remains of the shims were in the bottom of the case. Oddly enough, until I tore it apart, there was no indication of anything wrong internally, other than the usual sloppy shifting.

[ashyers]

Light reading:

https://www.scribd.com/doc/87972233/Gea ... s-SEBF8193

Thought some of you may appreciate this.

Andy

[Elwood]

Light reading:

https://www.scribd.com/doc/87972233/Gea ... s-SEBF8193

Thought some of you may appreciate this.

Andy

Good stuff. Thanks for posting that link.

[just me]

I have some random NOS gears in my pile from buying grab bags from ABLinn. Shoot me some good pics and some dimensions of that gear and I'll see if I have a match.