Strange transmission problem

[Stelth]

I have a 2001 GMC 1500 van. 4.3 V-6, I forget what transmission, but automatic.

I've been driving back and forth to a job that's about 45 miles away for a week or so. No problems. Today, after I get off the freeway, I'm thinking I smell transmission fluid. Stop at a light, and realize there's smoke coming out from under my truck, and it's obviously transmission fluid on a hot exhaust component. Not a good place to park, so I drive another mile and pull into a parking lot. I look under the van, and transmission fluid is running off the back of the pan and the crossmember, and not in little drips. Lots of big drips coming fast. I can see that I left a trail through the parking lot.

I get the van towed to my mechanic, who puts about 2.5 qts. of fluid into the transmission, and puts it on the lift. Nothing. Runs the engine in gear on the lift for a while. Nothing. So then I drive around the neighborhood for 15-20 minutes at speeds of up to 45 mph or so, up and down hills, stopping, starting, etc., and nothing. Not a drop of transmission fluid anywhere. So I drive home, and now my van is sitting in my driveway, not leaking.

What could have happened?

 

[Trav]

Could be a line fitting. IIRC these use push in line with an o ring retained by a modified C clip, if it does it again look at where the lines go into the transmission.
Just a wild guess but i suspect the line may be moving in the fitting with drive train movement.
I have seen something similar on a Chevy Venture.

 

[gomes512]

Had this happen to my truck. Noticed a trail when I was driving to the store. Couldn't get it to repeat the next day. Blew the quick connect line fitting that goes to the radiator day after that, lost all 14 qts going down the block without realizing. Luckily I shut it down immediately after I lost forward power. The clip Trav mentioned lost it's tension.

I'd get it on a lift again in drive and start yanking/wiggling all the lines. Bet you'll find a nice surprise that way.

 

[Stelth]

I took it back and put it on the lift, and wiggled the cooler lines. Not even a drip. I'm mystified.

 

[ltslimjim]

^any from the transmission casing or pan? Does it have a replaceable in pan filter?

 

[Stelth]

Originally Posted By: ltslimjim
^any from the transmission casing or pan? Does it have a replaceable in pan filter?


It's not leaking at all. Both before and after this experience, it's been completely dry.

 

[morepwr]

There is a vent tube on top of the trans. Maybe it somehow got warm enough to blow some out of there? Was it recently serviced and possibly overfilled? I have seen the cooler lines break the little fittings like other have but they never just quit leaking after they start. Very weird it wont repeat the problem.

 

[TooManyWheels]

Very likely it overheated and blew fluid out the vent or the dipstick tube. If you have a check engine light soon, and a corresponding code related to trans slippage, you will know what happened. Not that you will care all that much at that point.

 

[yonyon]

If the manual valve were in 2 the trans might get pretty hot. The radio or even an open window could mask the noise, but not the sluggishness. Maybe a page of newspaper got stuck to the radiator and fell off when you stopped? Weird things happen sometimes, and they usually only happen once. It can be frustrating.

 

[Stelth]

Update - took it to a trans shop, and the codes were slippage and overheat. Fluid was a nice dark reddish brown, with a fair amount of [censored] in the pan. I am now (hopefully) getting a soft part rebuild, new converter, and new solenoids for about $1500. Supposed to be ready Friday.