Allison trouble

[duramaxdrvr01]

The strangest thing happened yesterday. I started my 01 2500hd to take it on a drive since I hadn't driven it in a week or so. Upon pulling out of the garage I noticed the check engine light was on and the truck had no reverse,first or second gear, even when i manually put it in those gears. I called the local dealer and made an appt. to bring it in to have the fault code read and hopefully solved. After about a half hour, I started the truck again, and this time everything worked perfect. No problems at all, except the check engine light was still on. Well, hopefully the dealer can figure it out tomorrow, but has anything happened like this to anyone else and does anyone have any ideas what happened? Thank You, Jim , by the way, the fluid level was perfect and regular maintanence has been performed on the tranny.

[BobND]

I have no experience with the Allisons, however, once in a while my 4L80E will throw a similar fit if the batteries are a bit weak after sitting unused for a while, and voltage gets too low during cranking. Letting the batteries charge a bit, shutting it down and restarting it makes the PCM reboot, and it works just fine. (1994 K-10, 6.5 turbodiesel.) A friend of mine with a '95 had the same problem a time or two over the years. I hope your problem is similar, and it only needs the computer trouble code cleared.

[DmaxMaverick]

Welcome to the forums, duramaxdrvr01!

Sounds like torque converter drain back. This can happen when your truck sits for a long period of time, like a week or more, and the torque converter drains out into the pan. There are no known adverse effects from it, other than the inconvenience of having to shut down and restart. The no reverse, and 3rd gear only is "limp mode", and is invoked anytime the TCM suspects a failure, like a lost fluid coupling (TC).

If you can live with this happening only after it's sat for a while, don't worry about it. There is a TSB on the issue, and a fix that replaces a check spring in the tranny, but it may not be worth having it done. You have already experienced the worst it will ever be. If you are out of warranty, the dealer will charge you for whatever they do, including diagnostic and clearing of the code. I suggest finding a method of reading/clearing the code that won't cost anything, like Autozone (many still offer free code reading). Another option would be to ignore the SES lamp for a little while, it will go off and clear itself after a few driving cycles.

[madmatt]

the fix for this is just a couple of new pressure reg springs and pistons that go in the pump hsg. the parts cost is minimal , the kicker is the labor I think CP time is about 8 hrs. Also we're instructed to install a vented level indicator. This fix doesn't eliminate drain back, just the DTCs and their resulting actions. the bulletin # for this is:03-07-30-011c

[DURASAM]

After 2 or 3 restarts the SES light will go out and the code will reset itself. My 01 does this all the time,because like you, I don't drive it often enough.