Transfer case bearing adjustment

[John S]

I have assembled new bearings in my NP200 transfer case on my 55 PW. The 15 to 30 inch pound torque called in the manual for the driven gears assemblies seems a bit tight to me . Is this best held on the low end of the spec?

[Charles Talbert]

I have assembled new bearings in my NP200 transfer case on my 55 PW. The 15 to 30 inch pound torque called in the manual for the driven gears assemblies seems a bit tight to me . Is this best held on the low end of the spec?

No, anywhere between 15 & 30 or all the way up to 30 inch lbs. is just fine if you are using all new bearing cones & cups. A good bearing preload is a must. I assume you are checking this spec before the oil seals are installed? The preload will loosen as the new set up wears in a bit, you don't want end play occuring after wear in takes place, this is why the heavy preload is necessary. If end play occurs, bearings will be destroyed in a short time.

[John S]

Thanks Charles,. That is the info I was looking for.

[Desoto61]

I'm dredging up threads from way in the past here, but I was setting up the bearings in my t-case last night and couldn't get the pre-load within the 15-30 in. lb. spec.

Closest I could get was about 35 in. lbs. or so. I assume this should be OK, but wanted to make sure before I bolt it all together for the last time.

[John S]

I got mine into spec as i recall. Are you setting it dry or with lube? Some specs call out specific methods for lube. I do not recall this one. Dry could raise the torque a bit.

[Desoto61]

I've tried setting it up about a dozen times now and just can't seem to get within the 15~30 range. I'm either a little below 15 or a little above 30.

The older instructions in my WDX manual say dry but both the M37 and later PW manuals say with lube.

My original tries were dry, I just tried adding lube but that didn't seem to change it much if at all that I could tell.

[Charles Talbert]

I've tried setting it up about a dozen times now and just can't seem to get within the 15~30 range. I'm either a little below 15 or a little above 30.

The older instructions in my WDX manual say dry but both the M37 and later PW manuals say with lube.


My original tries were dry, I just tried adding lube but that didn't seem to change it much if at all that I could tell.

The only reason you can't get a correct set up is that you aren't doing it correctly or you aren't using the correct thickness shims in the right combination. It should be done with wet bearings, doing it dry is fruitless. Are you reaching correct torque? Are you spinning the assembly several revolutions to allow the bearings to seat after torquing before checking pre-load? Are you checking pre-load before installing the oil seals? How are you adjusting the shim pacs? What I'm saying is this; if I got a 15 in. lb. reading, I would remove a thin (.004") shim and recheck. If this adjustment sends it over 30 in. lbs., then you need to remove a thicker shim and add a thinner one to get the pac thickness somewhere in between. Continue to change the combination as many times as it takes until you get a suitable set up. With new bearings, a 15 in. lb. set up is too loose, this would be for previously run bearings that are good and suitable for re-use. With new bearings and a fresh set up, it should be in the 25 range. As new bearings wear in, the set up will loosen, a higher torque set up is used with new bearings so when they settle in, things aren't too loose. The lesser in. lb. values needed with bearings that are previously "run in" is because they will not loosen as much since they have already been worn in.

[Desoto61]

I'll have to see if I can get some thinner shims then, because none of my combinations would let me get there, the thinnest shim I have though is .008 in. But .043 is too tight and 0.047 is just a little too loose, and I can't seem to get a value in between with the shims I have.

I initially set them up dry per the WDX manual but after looking at the military manual (and the later PW manual here) I lubed the bearings and re-checked the values, they didn't seem to change much that I could tell, at least not enough to make the difference I needed.

The rear axle bearing support is right at about 25 in. lbs. so that's good.

I imagine the idler shaft should be set up to the same spec, though there's not real way to measure the torque other than a calibrated hand. The manual says a "slight drag".

[Desoto61]

Ok, I ordered a shim kit (McMaster-Carr PN 3088A939) that has shims as thin as .001, so I should be able to get it dialed in as soon as that arrives.

Thanks for the help.

[Charles Talbert]

I'll have to see if I can get some thinner shims then, because none of my combinations would let me get there, the thinnest shim I have though is .008 in. But .043 is too tight and 0.047 is just a little too loose, and I can't seem to get a value in between with the shims I have.

I initially set them up dry per the WDX manual but after looking at the military manual (and the later PW manual here) I lubed the bearings and re-checked the values, they didn't seem to change much that I could tell, at least not enough to make the difference I needed.

The rear axle bearing support is right at about 25 in. lbs. so that's good.

I imagine the idler shaft should be set up to the same spec, though there's not real way to measure the torque other than a calibrated hand. The manual says a "slight drag".

The idler gear setting is "free rolling, but with absolutely no end play". It gets no pre-load.

[Charles Talbert]

Ok, I ordered a shim kit (McMaster-Carr PN 3088A939) that has shims as thin as .001, so I should be able to get it dialed in as soon as that arrives.

Thanks for the help.

The shims originally are .004", .005", .0125", .015". Start with a pack, one of each thickness, have plenty of each thickness on hand to build a proper pack. We custom cut ours from bulk shim stock with our own custom built die and punch cutter. No wonder you couldn't make it work with nothing thinner than.008". Are the ones you ordered of the correct inner and outer diameter? They must fit properly in every respect in order to produce and hold a correct set up.

[Desoto61]

They have the same ID as the bearings with a slight positive tolerance which is close to the ID of the OE shims I measured, the OD is a little bigger than the OE shims but not by much, and thickness runs from .001" to .125". I ordered multiple sets so I should have enough for both the bearing support and the idler gear setup.

[Desoto61]

That did the trick. Shims came today (McMaster-Carr is really fast). I set up the bearings at 0.043" and checked the torque. It was too high, so I added a 0.002" shim put the assembly back together and ended up with about 24 in. lbs. running torque. Thanks for the help.