I rebuilt my NP200 this weekend

[rpgdeity]

So I just wanted to share some of my observations while rebuilding the NP200 thats going in my 725. First off, the main reason I did the rebuild (replaced every bearing, race, and seal) was that the bearings in there were burnt bad. All black and brown and nasty looking. My 725 shows around 28K on the odometer, but the guy who owned it before must have drove it hard, because so much is wore out on this truck, anyways...

So my first observation after completely disassembling the case and cleaning everything was that ALL of the oil holes in the shafts and gears to move oil around to kinda important things like the bearings, were completely clogged shut. Some of them I had to take a small drift and punch out the baked hard gunky stuff in the holes. I can only guess that it is heated and dryed oil. It was just hard black and brown stuff.

Other thing I noticed was that the bearing preload was WAY off on both rear outputs. It is supposed to be between 15-30 inch pounds, one was waaaay loose, and the other was horribly tight. So after adjusting the shim packs I got both preloads within specs.

I am interested to run this case and see how both noise and temperature will be affected. I just wanted to share some of my observations with everyone, might want to consider at least doing a tear down and cleaning of your 200 if you plan on keeping it in there and want good use out of it. The darn thing is so close to resembling an NP205, I don't see why I can't make this case work just as well too. Just my 2 cents.

[george walker]

How did you measure the preload in your rebuild? Sounds like it might have been run dry at one point an/or never gotten an oil change. I have done several of these and the main weakness is the use of tapered brgs in the output assy's, they wont keep their preload very long(by 30k on avg)and that brings the noise. Later designs went with straight roller brgs.or ball brgs. im sure because of this. In a stock application, either m-37 or 715, I had never had a overheating issue with one. But I can see where a modified powerplant or higher gears could bring it on. Mine has 40k an its whining, it actually doesnt leak much at all so im hoping to just replace the seals and pull the output assy's out and reset preload but leave the case in. as long as the brgs look ok...

[rpgdeity]

I followed the directions in the military manual. After replacing bearings and races I went with the 0.0365 shim recommendation per military manual. Lubing the bearings with gear oil I then used an inch-pound torque wrench to check the rotational torque required to turn the shaft without the oil seal, the manual says it needs to be within 15 to 30 inch-pounds. I added or removed shims in order to acheive the rotational torque required. Did I do it right? Anything else I need to consider while rebuilding the 200?

[brute4c]

I, for one, really appreciate the info!!

[k8icu]

Can a 200 be turned into a 205? Is it just a matter of changing some bearings? In other words we all want the 205 because of it's perfomance, yet the 200 is just like the 205 so can the 200 be modified into a 205 or get the perfomance of the 205?

[BubbaWilkins]

My NP200 has NP205 output shafts. Beyond that, I'm not sure what other components have been swapped since I didn't actually do the work. I'll make an inquiry with someone who would know and post back.

[randyscycle]

I found similar things when I did my transfer case as well. It still sings above 40 MPH though, but it does seem to take a lot longer before the temp climbs up to a dangerous level. That is with all new bearings, seals and synthetic gear oil.

[george walker]

RP what type of tourque wrench did u use? To be able to correctly read the rolling preload it needs to be the old fashioned bar type wrench, or a dial indicator type, an audible click type wont work for this type or measurement.If so you did it correctly. It isnt a measurement you can guess at, the chances of getting it right arent very good.

[rpgdeity]

Yeah, used the beam type. Randyscycle, what type of synthetic did you use? Now that the case is squeaky clean, I'm thinking about going with synthetic gear oil.

[randyscycle]

I just used Mobil 1 Synthetic 90W. I did it mostly because these things tend to run hot, and figured it would stand up a bit better. So far, so good.

T-case runs as hot as 220 on a really hot day on the road at speed. I have a trans temp guage installed in mine right in the bottom of the sump.