M37 Overdrive

[Charles Talbert]

We are designing an auxiliary oil tank to double the case oil capacity, pump, and oil cooler to be used in conjunction with a NP200 case. It will be going into an M37 project with a new all electronic Cummins. Pictures will be on our website when the project is completed in the next few months.

We have used NP200 cases in Cummins trucks capable of a 75 MPH red line. Never a single issue. We typically run a 50 weight synthetic oil designed for gear box use that lowers temperature and provides way better lube than mineral based petroleum oils. I'm thinking of running 40 weight Royal Purple in this new setup, my feeling is that may be even better as it flows so well at lower temps. Royal Purple pumps much easier than any conventional oil, easier on the pump motor and will flow through the cooler core easier.

My thoughts on the issue being discussed previously in this thread, I can't imagine any truck powered by a 230 engine would be in danger of transfer case issues if a good lubricating oil is used and the case is in good condition. Cabell Garbee runs one in his Cummins M37 frequently on interstates at 70+ MPH while towing a loaded M101 trailer. Never have heard of any issues he has had.

[MasterYota]

That is good to hear Charles - perhaps the overheating issues refered to the NP200 have been exagerated?

Am I understanding your post correctly Charles - You're in development of an externaly mounted resevoir and oil pump system to assist in lubricating the NP200? Or is this system designed for the new electronic diesel your installing?

Either way, it sounds like an interesting setup.

[Charles Talbert]

That is good to hear Charles - perhaps the overheating issues refered to the NP200 have been exagerated?

Am I understanding your post correctly Charles - You're in development of an externaly mounted resevoir and oil pump system to assist in lubricating the NP200? Or is this system designed for the new electronic diesel your installing?

Either way, it sounds like an interesting setup.

You have understood correctly, a huge reason that NP200 T/cases usually run at elevated temps is because there is only 5 pints of oil in it when full. I'm satisfied just being able to increase the oil capacity would make a noticable difference in top temp even without the cooler in play. We are fabricating a separate tank for it so as to increase the oil capacity in the system while not raising the oil level above the full mark within the case itself.

We are going to do some testing with it to see how the temp is affected doing the hook up different ways, with, without cooler, etc. I'll let you know how it all goes when we get there. I plan to put a t/case oil temp gauge in the instrument panel so monitoring will be easy.

[lebowski]

I was reading the 1950's Volvo TP21 transfer case is basically an NP200 with cooling fins cast into the housing. It was an attempt to keep the tc temp lower. The drivetrain is supposedly somewhat modelled after WW2 Dodges.