My 99 Expy 5.4L does a fabulous job towing our 26' travel trailer. My question is about going down the hills. I slip her down into a lower gear to allow the engine to do most of the braking, but I soon start smelling a slight scent of trans fluid. It doesn't smell like it's heated and I noticed this same thing on our last tow vehicle which was a 95 E-150 5.8L I had the tranny serviced and inspected at the dealer and they reported no problems. Why do I get this scent?

Ken

 

On downgrades I will use the manual control on the brake controller to give short pulses to the trailer brakes to help limit speed. Always lock out O.D. on downgrades. Start down at slow speeds. Use limited braking to take load off transmission, some medium braking than off completely to cool brakes. Don't overrev the motor. Turn on air cond. to increase drag. You may be doing these already, good luck...... I have never noticed this odor using 89' 302 or my 99' 5.4 while on many mountain miles.. pulling 6500lbs.

 

You'd be really surprised how hot an auto trans gets while 'coasting' down hill and letting the engine act as a 'brake'..... I've got a trans temp gauge on the output line and when going downhill in third or even OD, and my foot is off the gas, the temp will always RISE...

Add just a little bit of gas, and the temp drops again. This is because the TC is unlocked when you are coasting down hill, so it's heating up, just as it would if it was unlocked and you were pulling the hill. When you add a little gas to it, the TC locks up and that's when the temp starts going down.

Now, you don't want to be going down hill in OD and having to press the gas all the time, that's for sure, but I'll sometimes put it in third and then press the gas a little. It really depends on the downhill grade.... On the hills around here, I find that I rarely have to hit the brakes at all... And pressing the gas pedal is needed to actually maintain speed!

I also play around with hitting just the trailer brakes when I do need to slow down. Also, when I do use the truck brakes, I hit them hard and slow down fast, then let off. They will stay "cooler" doing it this way, then one long steady brake application. Basically, the longer you have your foot on the brake pedal, the hotter the brakes are going to get, even if it's really light pressure. It don't take long at all to heat 'em up!

Of course, every situation is going to be different, but it sounds like to me that you did heat up that fluid some on those downhill braking runs... Probably nothing to worry about, but you should be servicing the trans once a year anyway, right??

Good luck!

Mitch

 

Remember brake pads are cheaper than transmissions. Just use them as MitchF150 says. I smoked my brakes years ago on my very first trip. Of course it was downhill from summit in Smoky mountain NP.

 

The problem isn't the price of the pads. The problem is the brakes can fade. Putting you in a world of hurt

 

I've pulled tons of stuff with my truck and never noticed that scent. My differential does make a smell on really hot days when I'm pulling something hard. It smells like diff dope though. You gotta remember that your tranny and diff are working just as hard going down against a steep grad as they are going up it.