12V92 ZF Gear Temperatures

It varies and I see one gear different from the other as much as 20F, but I would say under 150F (not certain on your gear because you didn't provide the model number). Generally with gears, the cooler they run the better and I usually see them run somewhere between 100F-130F on the Detroits. The gears seem to run hotter on the newer electronic diesels and even over 150F.

I agree with CaptJ regarding the Detroit Gear Temp.

I have capitol gears behind a pair of DDs and they run right around 100-110 degrees.

I have one gear that sometimes likes to foam the oil (it is very strange, sometimes it foams it and sometimes it does not)

When the gear oil gets too foamy it cant transfer the heat efficiently and the gear starts to heat up.

gauge vigilance and an IR Temp gun with ER visits is a good thing....

Foam is caused by air getting into the fluid. If you have a remote mounted filter I'd check the lines carefully and any external lines to see if there's a place it's sucking air. It can also be caused by low fluid levels......

If you can't keep you hand on it it's too hot.

Bamboo,
I agree, you should be able to touch the gears.

I really like to use an IR temp gun and compare and monitor temps. Its a great way to detect an issue and monitor the engines. I also use it to ck the hvac, electric motors, and anything else

CaptJ,
I agree there must be a leak somewhere on the suction side. (if it were on the pressure side there would be oil everywhere)
The strange thing is that sometimes it is fine for weeks or months and then it will foam. Pressure in the gear is fine.
there is a 1 inch hose on the suction side from filter to gear that could be the issue. That hose will be changed on the next gear oil change.
I do know that the gears that I have are very sensitive to oil levels:
too much and it will foam, too little and it will foam. And foam is bad!
I use SAE 30 in the gears and some have recommended switching to SAE 40 is the problem continues after the hose change.
For now I just monitor the temp and oil and it seems to be operating WNL.

I recently rebuilt the other gear because it was developing a shift delay and had low pressure. BTW, The bill was an emotional experience.....Im not looking to repeat that experience on the other side..........

RC thanks for info,

I have 671 TIBs, my gears coolers are cooled by raw water, which then goes to the inter cooler, and then to the heat exchanger and then out the exhaust.

(im pretty sure the only coolant is in the block and main heat exchanger where the coolant is cooled by raw water, I don't think my coolant is used to cool anything else besides the block, oh yea I forgot, and the oil cooler)

do you recommend 40 in the gears?

I currently run straight 30 in the gears and 40 in the mains.
Im pretty sure that all the oil is anti-foam.