Around town my transmission worked fine. On trips, I noticed shifting was a bit unusual and checked the fluid level. Nothing registered. I added fluid, lots of it. Went to a Jiffy lube type of place and had them check for leaks. Nothing. No signs of where it went. Back at home, went to dealership and they said "sure, no problem, had a lot of this type of thing" and replaced something that had burned out. I can't find the receipt yet to find what the part was, but apparently this is common. Ever heard of anything like this? Truck runs like new again BTW.

 

You did not give many specs. on your truck. if it is a 4x4 check your transfer case.

 

Had to have been the vacuum modulator.

When the internal diaphram leaks, ATF is sucked into the intake and is burned.

Diagnosis is easy, just remove the vacuum line to the intake and inspect for ATF inside the line.

Steve

 

Yep, That was it. Took me awhile to find the bill (which was under warranty). Until this started I never realized how much fluid the trans can hold. I'd drop in 4 quarts just to get the dipstick wet on the end. Had to do this daily on our trip.
Thanks for the response. I was just wondering if this was common, and I guess i now know it's not so Un common.