Have a 1999 F550 7.3 with an automattic. Contacted local dealership and service recommended an exhaust brake/Converter lock combo to prevent brake ware. Truck hauls heavy water loads max GVW on steep off-road grades. Total transmission failure due to overheating occured within 120 miles. How can the two not be related? I have read that there is a problem with this tranny not maintaining high enough pressures. Is this true? Any info would be appreciated.

Thanks

 

...Welcome to Ford Truck Enthusiasts!
Stick around someone will be by shortly to answer your question.
We are happy you have chosen the best source for Fords!

Enjoy FTE....and
JOIN CLUB FTE -SUPPORT THE FORUMS!
…..See you on the boards.

 

Exhaust brake on an automatic needs to be coupled with a torque converter lockup when the brake is activated (actually slowing the truck, not just turned on). If yours was not set up that way I would suspect the heat generated by the torque converter "slipping" is what did your transmission in. Maybe look to the installer?

Dave / Believer45

 

Some brands of the converter lockup circuits are designed to UNLOCK the converter below a pre-set speed so that it doesn't stall the engine when you slow below idle speed. That pre-set speed might be as high as 25 mph. So if you have been on off-roads at a low speed, and depending on the exhaust brake, you might have been in the unlocked mode of the converter lockup circuit. If you were slowing a very heavy load down a steep grade that way, with the T/C unlocked, a lot of energy was being put into the tranny fluid by the unlocked slippage of the torque converter. You could have really overheated the fluid. To get an idea of the kind of energy involved, take your loaded truck and use the truck brakes to quickly stop it from 50 mph or so. Hop out and feel the brake drums. Be careful; they'll be hotter than hell. You put all the energy of the 50 mph truck into the brakes to stop it. Thats the kind of energy you put into the tranny fluid with the T/C unlocked and slipping.
If the T/C was truly locked up, at least one of the suppliers of the lockup circuit claims that there has never been a case of tranny damage using his product. I'd suggest you contact the manufacturer of the product you installed and discuss your problem with them.
Good luck. My final suggestion is to swap your truck for one with a manual transmission. That will guanantee that the slowing down energy using compression is dissipated in the engine, which has a great big radiator and fan to keep it cool.
Warren