New Member
Have a 2003 GMC Durmax with allison trans 47,000 miles. This has happened 3 times in last 20,000 miles. I park truck, Trans working ok. Start truck put in reverse to back up, trans makes a clunk, put in drive and trans will not shift out of low gear, engine motor light comes on. I shut off truck for approx half hour and restart everything works okay. Engine light off and trans. works okay. Had to dealer, they can't find anything wrong. Would appreciate your help, Bill



They have a gentleman, that hangs around the forum who is very knowledgeable about the Allison Tranny. If you look up his profile, you may find his E-mail address.