8.1L Allsion puking transmission fluid

[nremtp143]

My 8.1L Allison started puking tranny fluid while running down the interstate yesterday. The truck was unloaded and not towing. I've done lots of reading and seems there is a couple of problems with some of the Allisons. I've known that you have to watch the fluid levels in the older Allisons and keep it in the center of the hash marks while hot or else you can risk a hot transmission, but I didn't know about the problems with the torque converters not locking up and generating LOTS of heat while not towing. To be fair, there are hundreds of reports of this on many of the GM truck forums, but with the millions they've sold, it doesn't seem like all that many. I am just in the beginning stages of trying to figure out what went wrong and how much damage has been done. I will be pulling the codes(if any) later today to see if it shows a TC malfunction. From what I've read, the problem is not with these trucks towing, it's from them NOT towing! Very interesting. The transmission has had a couple of times in the last month or so that it didn't down shift while at a stop like it should, but had no other warnings whatsoever. The spin on filter has been changed 3 times by me in the last 15K miles(I bought it used) and it has been functioning fine otherwise up until this week. Have any of you had troubles similar to this out of your Allison and if so, what damage was done if any.
Thanks

[nremtp143]

sc3283 wrote:
are brake lights stuck on? Do you drive with your foot resting on the brake pedal?

I know pre-allison GM trucks would kick out the lockup clutch in the converter when brake lights come on.

Ive never tried nor noticed if this occurs in my 04 1 ton Chevy(with allison)

No I don't. I am a one foot driver. I even thought about this as a possible problem since my Suburban did that exact thing years ago. Thanks for trying to help solve this guys. Talked with a tranny guy yesterday and he said it was either the TC or the internal electronics that have gone bad. Said most TCs of the Allison do not go bad, however he has done some that have. Not sure. Guess after vacation, I'll pull the pan and see what she looks like as well as the magnet on the spin on filter.

[nremtp143]

#40Fan wrote:
Does the shift indicator on the dash light up and show correctly?

Yes. Everything else seems fine. Cranked the truck yesterday and drove it around town and it ran and shifted fine.

[sc3283]

are brake lights stuck on? Do you drive with your foot resting on the brake pedal?

I know pre-allison GM trucks would kick out the lockup clutch in the converter when brake lights come on.

Ive never tried nor noticed if this occurs in my 04 1 ton Chevy(with allison)

[_40Fan]

Does the shift indicator on the dash light up and show correctly?

[nremtp143]

From the overflow on top. It got that hot! After vacation I guess it will be time to really investigate and see what happened. The Dmax forums says it's not that uncommon for them NOT to throw codes when slipping. If it ever stops raining so I can examine it thoroughly, I'll see what else I can tell you guys.

[othertonka]

Just curious, where is it puking fluid from? the dip stick or somewhere else?

[Turtle_n_Peeps]

Tiger4x4RV wrote:
How many miles on the truck? My 2006 8.1L 4x4 maintenance schedule says change both filters at 50K miles. I did it a bit before then. 55K now, no problems. Of course, since the Tiger is a Class C, it is always towing.

Allison says never to change the internal filter on the 1000 unless you rebuild.

They also say never to flush.

[nremtp143]

OK..curiosity got the best of me. Went out and tried to retrieve codes. None were found. Makes me wonder is it a filter issue, or did it just not slip bad enough to catch the TC slippage code? When it happened, it even gave the "transmission hot" warning on the dash. Not sure what to do now.

[nremtp143]

It has 144k on the clock. I've only owned it since 128k. It was supposed to have had it done when I bought it so it has not been done by me(I know, hence the problem i guess:(). Had receipt for it, but no way to really tell. It is storming so bad here, just haven't felt like trying to get the codes(if any). May try IF it ever slows up!

[Tiger4x4RV]

How many miles on the truck? My 2006 8.1L 4x4 maintenance schedule says change both filters at 50K miles. I did it a bit before then. 55K now, no problems. Of course, since the Tiger is a Class C, it is always towing.

[nremtp143]

The internal one has not been changed. The coolers are clean and both lines we're replaced last summer due to leaks. Not sure which way to go first.

[transamz9]

Have you changed the internal filter yet? What about any transmission coolers? Have you checked to see if they are clean and flowing air?