tranny help

[smokin150]

Ok, after a bit of searching and digging, i have installed a temp gauge on my zf tranny. I pull about 12-14k in trailer weight a day plus have my camper on the back of the truck. Ive noticed my temps for the tranny running anywhere between 250 and 300+ deg. From what im to understand this isnt normal. Temps are good till i get on the hwy then it skyrockets. Ive changed the fluid and started running synthecic amsoil, but im concerned that ima blow the trans apart with these high temps. Now that being said, im on a rathe tight budget atm and cant really afford to put hundreds of dollars into the truck so im looking for somewhat inexpensive ideas to help cool this trans down. Ive seen the bolt on coolers for the pto cover but they are a little out of my price range. Any ideas?

 

[SparkandFire]

Suffice as to say, I am not sure what "normal" is for the ZF transmission.

I do know that Ford/ZF starting installing external pressurized loop cooling on the ZF6 transmissions.

The ZF5 is also a "constant mesh" type gearbox, in which all of the main shaft and counter shaft gears are running together all of the time, and the loading and unloading of the gears is accomplished by engaging them on the shaft side. The nature of this arrangement is that there is constant heat being generated.

All that being said, I have no idea what temp mine runs at. I've wanted for some time now to get a gauge on it. The ZF5 is NOT as susceptible to high temperature failure as a slushbox, since there is no clutch/friction dependency like there is on an E4OD or C6. The ZF5 bearings are preloaded to account for thermal expansion of the case and internals, though. Since the case is aluminum I can imagine there is a great deal of tolerance shift inside when they are hot, but that really is the extent of the risk, the tolerances shift at some known amount. I would think if there really was something wrong with operating the transmission at 250+ degrees, you would hear it... gears whine a great deal when they are out of mesh tolerance.