How hot ?

[Kaiser2boy]

Just how hot should the transfer box get? I had Lady M. out for a nice go today , all on nice roads and did not push it. I did not use 4WD at all or LOW .
I got home after about a twenty mile ride and was checking for leaks and put my hand on the transfer box.
It was hot. Not enough to burn me and I could keep my hand on it but boy it was hot. The oil in there is a synthetic 90/120 wt gear oil and it is full.
Will that heat level off or just keep geting hotter as I drive farther?
I drove one of these things back in the 60s while in the Army and we drove 100s of miles only stopping for gas. I never had one blow a box from over heating , blew and engine or two but no gear boxes.

[Charles Talbert]

If you could hold your hand on it, you are good to go as far as heat. You could be better though if you would put lighter weight oil in it. The heavier the oil, the hotter it will run.

Straight 40 weight Royal Purple synthetic does extremely well. All our rebuilt cases get an initial fill of that. I know folks running Cummins powered trucks on the interstate at 75 MPH; at times also pulling a fully loaded truck bed and a trailer. No issues. We have done a thermostat controlled cooling system for the t/case that greatly reduces this issue; but I wouldn't say it is a necessary accessory just for knock about driving.

[Kaiser2boy]

Thanks , Figured I would just check and be sure about it.

[MoparFreak69]

I personally would be concerned with that much heat from only running 20 miles in 2wd. When running in 2wd everything in the transfer case is sitting stagnant and not moving, only the input and output shafts are connected and spinning. This means there should just be a couple bearings rotating, which shouldnt produce much heat at all.

The heavy lube you have in there could be contributing to the temps a bit. I would try a lighter lube, something along the lines of what Charles recommended should work perfectly and reduce those temps, providing there isnt other problems within the case itself.

[Charles Talbert]

I personally would be concerned with that much heat from only running 20 miles in 2wd. When running in 2wd everything in the transfer case is sitting stagnant and not moving, only the input and output shafts are connected and spinning. This means there should just be a couple bearings rotating, which shouldnt produce much heat at all.

The heavy lube you have in there could be contributing to the temps a bit. I would try a lighter lube, something along the lines of what Charles recommended should work perfectly and reduce those temps, providing there isnt other problems within the case itself.

This info is NOT CORRECT for the NP200 transfer case.

The input / ebrake output shaft is turning, the intermmediate gear is turning, the rear output gear is turning, and also the front axle output is turning unless you have front wheel lock-out hubs. The reason for higher than normal heat production is because of the design of the t/case that I just described. Long story short almost nothing is dormant in this case if the truck is in motion; and nothing at all is dormant without lock-out hubs.

[MoparFreak69]

I appologize for thinking we were talking about the 205 t-case instead of the 200.

Since he had started a thread a while ago mentioning problems when shifting OUT of 4wd (meaning disengaging the front output shaft with a shifter lever) that he was not utilizing a t-case that was full time 4wd like the one you describe, rather a shiftable one like the 205.

Either way, with proper preload any rotating bearing will not produce a large amount of heat, certainly not enough to make the case almost too hot to touch after only 20 miles, unless that 20 miles was done in 20 seconds, but we know an M37 isnt going to do that.

[Charles Talbert]

I appologize for thinking we were talking about the 205 t-case instead of the 200.

Since he had started a thread a while ago mentioning problems when shifting OUT of 4wd (meaning disengaging the front output shaft with a shifter lever) that he was not utilizing a t-case that was full time 4wd like the one you describe, rather a shiftable one like the 205.

Either way, with proper preload any rotating bearing will not produce a large amount of heat, certainly not enough to make the case almost too hot to touch after only 20 miles, unless that 20 miles was done in 20 seconds, but we know an M37 isnt going to do that.

I'm not describing a case that is full time 4WD. The NP200 front axle drive output can be shifted into a neutral position via the control lever. The stock M37 has axle flange hub caps instead of front wheel lock-out hubs as original, and will still drive the front drive section via the wheels rotating even when the t/case front axle section is in neutral.

There is 1 ball bearing on the front axle drive shaft output that will be dormant if front wheel lock-out hubs are installed and the free wheeling position is selected at the hub. Everything else in the case will be in motion 100% of the time the truck is moving. These cases have a natural tendancy to run on the warm side within as little as 4-5 miles. Driving farther than that doesn't get it much hotter, it's just the nature of the beast unless an oil cooling system is put in place.

[iranch]

How hot is hot

If you could hold your hand on it, it isn't hot, it's only a little warm. Put your hand on the head of the engine when it's warmed up to 160 and you will find it's a lot warmer than the trans or transfer case. You are well within the acceptable operating range, don't worry about it.

Dennis

[gusbratz]

navy always said the threshold for pain was 140 degres farenheight. i find that is about right.

[Kaiser2boy]

My truck does have hub lock outs and I leave them in 2WD unless playing.
I will try lighter oil. I tried finding nutral with the lever and it can be done but I am not sure it will stay in nutral while bouncing along the road.
The hub locks left in the 2wd should do about the same thing , yes?

[Charles Talbert]

My truck does have hub lock outs and I leave them in 2WD unless playing.
I will try lighter oil. I tried finding nutral with the lever and it can be done but I am not sure it will stay in nutral while bouncing along the road.
The hub locks left in the 2wd should do about the same thing , yes?

I'm not sure I understand you completely. If you have the front axle engaged at the transfer case and are expecting the lock-out hubs to do the whole job of disengagement; the hubs will be short lived. You should have a defined neutral detent that you can feel at the front axle lever. If not you have a problem that needs to be addressed right away.

[Kaiser2boy]

Sorry.
My brain was in nutral. I was thinking of the high low lever .
The 2WD/4WD clicks nicly into 2WD or 4WD. I normally drive with the lever in 2WD and have the hubs open.

I was having a flash back to another post about being able to select a nutral with the High / Low lever.

I guess I will have to go back to taking my Ginko pills on a more regular time table.

[MoparFreak69]

If you have the front axle engaged at the transfer case and are expecting the lock-out hubs to do the whole job of disengagement; the hubs will be short lived.

While I see what you are trying to say with your statement here I have to offer a disagreement with reasoning.
It is common practice for the budget minded (read: no budget) enthusiast to add manual hubs to a full time 4wd truck to increase fuel mileage, without having to spend the time or money putting a part time t-case in the rig. This can be done with ill effects to any part of the drivetrain. Yes, doing this will not give you the benefit of reducing front axle component wear nearly as much, which is a big reason for going with manual hubs, but it will not cause anything to wear out prematurely. Everything will still rotate just the same as it would if the hubs were engaged. The only difference would be the splines connecting the hub to the axle shaft will not be in place.

[Charles Talbert]

While I see what you are trying to say with your statement here I have to offer a disagreement with reasoning.
It is common practice for the budget minded (read: no budget) enthusiast to add manual hubs to a full time 4wd truck to increase fuel mileage, without having to spend the time or money putting a part time t-case in the rig. This can be done with ill effects to any part of the drivetrain. Yes, doing this will not give you the benefit of reducing front axle component wear nearly as much, which is a big reason for going with manual hubs, but it will not cause anything to wear out prematurely. Everything will still rotate just the same as it would if the hubs were engaged. The only difference would be the splines connecting the hub to the axle shaft will not be in place.

It is also common practice for budget minded fixes to sometimes cause undesirable results.

Mopar, I just really don't have the time to sit around an argue with you, so I'll just finish off with this and you can think however you wish.

If you read the fine print info that comes with better quality hubs, you will realize right up front that hub manufacturer's do not recommend using lock-out hubs in this manner. The deal with this practice has an ill effect on the lock-out hubs themselves, I was not suggesting issues anywhere else in the drive system. Yes this is another thing that I've also seen through experience over the years. If you will go back and re-read my post that you are desputing here, you should understand that I said the HUBS would be short lived, not any other system components. Of course you don't believe it, and that's fine as frog hair; try it yourself and learn the hard lesson as many have already done before you. This would only prematurely destroy your hubs that you paid for, and nobody else's.

[MoparFreak69]

Wow, sure are receptive to counter points arent you?

I was not trying to make a personal attack, but that seems the way you took it. I'm not the least bit sorry.

I was simply sharing some of my personal experiences and some that I have seen others do, whether 'kosher' to manufacturer's fine print or not. I dont feel running in this manner will severely harm a hub but you seem to so, to each his own. I dont run that way because I have a part time transfer case so no need to put any wear on parts that can stay still until needed.

I already appologized for my misinformation due to wrong t-case model, I wont keep beating that dead horse, although you seem to enjoy it so.

*edit* I should have added this to the other post. *When the hub has proper lubrication*