Another NP200 heat thread!

[Mikel]

Right now my M715's NP200 is in my '63 J300. I'm getting ready to fire it up, so I went to fill up the TC with gear oil. The old gear oil came out brownish, but very clean. I put my finger inside the drain hole and I noticed about 1/8" of a muddish substance.

I have filled the 200 with gasoline to hopefully dissolve the residue and plan on flushing it numerous times before I put gear oil in it.

I wonder if this may be a factor in the overheating issues these things suffer.

Mikel

[chicklin]

I am certainly no expert, but I wouldn't think it would contribute to the heat issues. If the entire inside was coated that way, maybe it would act as a sort of insulation, trapping the heat. But since it's just the bottom of the case...

The build-up probably causes the gear oil to break down faster, which I suppose could amount to more heat in the long run, but I think people have said the NP200 overheats with brand new gear oil, anyway.

[randyscycle]

My NP200 has been thoroughly cleaned, overhauled with new bearings and seals, and correct preload, and it still makes noise at anything over 40 MPH and gets hot at any extended running over 50 MPH.

It takes about 30-40 minutes of steady highway speed and it will get up to around 190 degrees (read on a temp guage installed in my transfer case) on a warm day. Driving further on for another 20 minutes or so it will climb to 220 degrees. After that, it doesn't take long for it to shoot up to the end of the scale if you keep pushing it.

Running synthetic or conventional gear oil makes no difference in temperature either. They are just an antiquated design, plainly put.

[Barrman]

90% or so of the NP200's in M715's will not handle more than 30-45 minutes at 2500 drive shaft rpm or more. That is just a fact of life for these trucks.

Replace it, drive slower, change axle ratios or get bigger tires

[Mikel]

Well, I have 3.08's in my truck, so the NP200 will be seeing almost half of the RPM's compared to an M715.

[Barrman]

The funny thing about the NP200 is non M715 peopel want them. The guy I bought my NP205 from really wanted to do a flat trade for the 200. He drag races SD Ford's and goes through a lot of parts. He thought at the time that a 200 would be the best he could get.

MR.Positive expressed some interest in a M715 200 compared to a "lighter and weaker" M37 version of a 200.

Then you have the monter truck guys that want a 200 because you can clock it almost 90 degrees down for more lift with less drive shaft angle.

Yet, we all want to get rid of them and feel good to get $5.00 from one that is good. Go figure?