I believe that 35s and 5.89s will be a good combo because that puts me at 2904 rpm@ 65mph according to the calculator and that calculator is assuming that I will have a true 35" tire which most are not so hopefully that can make up the difference I need.

 

Which thermostat are you running. I could only find a 180 and I could use a 195 up here in the winter.

 

These engines are truly well engineered. Don't mess with the thermostat. The thermostat on these engines are bypass type not the opened/closed type we are used to.
Read this for the details; http://mb.bolinko.org/15/warsztat-mainmenu-32/silnik-om617-mainmenu-75/69-engine-cooling/388-coolant-circuit-and-engine-cooling.html

I'm always of the mindset "leave well enough alone".

 

Another thing you guy's that want to wheel with this motor is it has a FRONT sump, so when you are wheeling up that steep hill you're oil pump is going to suck air causing no oil pressure and engine damage. Changing to a rear oil pick-up/sump will be a big modification.

 

I have accented and descended some very steep hills and stopped on some with engine running, I have not experienced this. And hopefully won't.... I think this is moot point. Nobody complains about the countless vehicles with rear sumps loosing pressure going down steep hills. Nor do you hear of the problem in the very capable om617 Unimog.

 

Wait a minute they put this motor in a mog!? This I must see

 

That was inaccurate information, it was the G-Wagon I was thinking of. Early 80's I think?

 

Still a bad *** ride! I was like dang if it powered a mog I should totally be able to run 37s

 

You might like this.
https://www.google.com/url?sa=t&source=web&rct=j&ei=-JoMVaPIIKHIsQTbm4BI&url=http://m.youtube.com/watch%3Fv%3DbhHnADr70w8&ved=0CBwQtwIwAA&usg=AFQjCN EKU67gPrn8LNLSwIGVwsOq3ezs3Q

 

I could be wrong, but I doubt the G-wagon has the same oil pan as the passenger cars do.