Leaking Trans Fluid

[Whitelm]

Has anyone else had this happen to them? I have a '71 k10 with a th400. When I drive it around just joyriding everything is fine. But when I have to use it for what it was intended, as a truck, and put it through the ringer, it leaks transmission fluid. Not just a little bit either. It does not leak when it is sitting, or when I take it for a casual drive. Only when I really have to make it work.
I have cleaned the outside several times trying to find out where it is coming from but I can't pin point it. The other day I could smell fluid so I stopped to take a look and found the front drive shaft soaked with fluid. Why does it only leak after hard use? Any ideas??

[LockDoc]

Originally Posted by Whitelm

Has anyone else had this happen to them? I have a '71 k10 with a th400. When I drive it around just joyriding everything is fine. But when I have to use it for what it was intended, as a truck, and put it through the ringer, it leaks transmission fluid. Not just a little bit either. It does not leak when it is sitting, or when I take it for a casual drive. Only when I really have to make it work.
I have cleaned the outside several times trying to find out where it is coming from but I can't pin point it. The other day I could smell fluid so I stopped to take a look and found the front drive shaft soaked with fluid. Why does it only leak after hard use? Any ideas??

I'm not a transmission guy but I wonder if the cooler tube in the radiator is partially plugged and the trans is overheating when used hard. Has the truck ever had a transmission failure? If it overheats, I think it can blow fluid past the front seal. Hopefully others will chime in with other ideas..... or correct me if I'm wrong.

LockDoc

[extd56]

There is a overflow tube I believe at the top of the transmission if it is over heating could be coming from there

[GRADYS Performance]

Try lowering your transmission fluid level a small amount on your dipstick. If it is run clear to full on the stick when checked at low temp it will expand when heated up with heavy duty use and come out the vent tube. Most likely that is why you are only having the problem during high load usage.

[Whitelm]

The transmission was rebuilt a year ago. While I was at it I had the Radiator taken through a complete R&R. I don't think that the trans lines are plugged. I have not noticed any fluid coming from the breather tube. Every time I have noticed a heavy leak the fluid has been running down the front drive shaft, and the front of the transmission has been wet.

[special-K]

The front driveshaft is on the right and so are the dipstick tube, module, and kick-down cable. I suspect one of those is not seated/sealer properly and higher pressure gets past it. I don't know automatics that well at all, but isn't their, or aren't there, pressure relief valves. Might could be something to do with that not working properly as well.

My front seal leaks and has been leaking since I've owned the truck. The only real issue with it is leaking while parked a long time, like over winter. That is about the only time I need to top it off, and maybe needs some once by summer. I tow, haul loads in bed, and get on it and it doesn't lose fluid. I hope to get it on a lift this winter and reseal everything from crank seals to pinion.