Transmission leak at Drive Shaft

[JackRH]

This week I spotted a leak under my 02dmax and it looks like it is coming from the area where the drive shaft attaches. I drove the truck for about 10 miles and parked it for a couple of days and no leak. Then after setting for a day or two the leak appeared again.
I can't see where it might be coming from when I get under the truck.
The fluid level is full according to the dip stick.
I'm not mechanical minded so I have no idea what this may mean.
Any insight would be appreciated and about what I should expect when I take this to our local chevy dealer.

Find time to happen as we are in the shopping process for a 2011 chevy or GMC.
Jack

[More Power]

Is this a 2WD or 4?

Jim

[JackRH]

It's a 2WD

[cowboywildbill]

Is it slinging it around the drive shaft tunel/ floor of the cab that's over top of the rear of the tranny? If it is it could be the trans tail shaft seal. If it is, it's an easy fix and a seal doesn't cost that much. Sometime's it can be the yoke also. That's a lot more expensive.
Check the bearing also in the tail shaft to make sure that didn't cause the seal to go.
But I'm betting it's just a seal.

[Kennedy]

This one can be a bit tricky. It may be the seal, but it may well also be the yoke itself leaking at the internal welch plug behind the splines. More often than not this has been the case.

[More Power]

Is there excessive play at the spline - where the yoke slides into the trans tailshaft? If so, this excessive play could be allowing the yoke to wear out the seal sooner than normal.

Jim

[JackRH]

I power washed the greasy area and the leak appeared to be where the dip tube enters the transmission pan.
Since then I have taken a 900 mile trip to Oklahoma and the leak has never shown up again. Don't know if the washing seal it off or what the heck happened.
The fluid level shows full but that does leave me with a question since the level always shows full at the "Hot" level on the dip stick even when the truck hasn't been driven. The ambient temps are 80+ in my shop where the truck is parked so could it be that the liquid is simply not cold enough to show at the cold level on the dip stick. The oil appears to be very clean.
Is it possible for some other fluid to be getting into the trans to cause it to show full at the hot level all the time. Seems like I would be able to tell if the fluid was contaminated.
Jack

[More Power]

A somewhat commonly reported problem (if you prefer to call it one) for the early Allison transmissions is the result of torque converter drainback, which causes fluid level to rise over time to a point above the rubber dipstick seal. Initially, GM instructed its technicians to run the trans 1-qt low. There's likely lots more reading about this here, by using the search function. Driving the truck once or twice a week will usually lessen the effects of TC drainback. When these sort of leaks are reported - usually after the truck has been parked for a week or more - the engine needs to run for 30 seconds to a minute before the truck will move in gear. It's all due to TC drainback.

Jim

[JackRH]

Thanks Jim that makes me feel better. I'll do a search and see what others have said regarding that.

Jack