Allison wont shift out of 1st gear

[Fishnfool]

My brother just called me from near Parker,AZ. and says his Allison wont shift out of 1st gear. He has a 2001 D-Max and is pulling a big King of the Road 5th wheel on vacation. Has anyone heard of or experienced this happening and if so what was the fix?
They are calling Bradley Chevrolet in Parker and will probably be having them look at it, Anyone have anything to say good or bad about them or can you recommend a better dealer within 100 miles of Parker?

[Fishnfool]

Well - His truck is on a flatbed being transported to Lake Havasu Chevrolet right now. He did say that they did some minor 4-wheeling yesterday and this morning when they started up the SES or Check Engine light was on and the tranny made a noticeable clunk when he shifted it and would not shift out of 1st. Will post more when I hear from them again.

[mdrag]

Fishnfool,

Too late now, but I would have checked the (2) connectors on the Neutral Start Back Up switch (NSBU), or Park Neutral Position (PNP) switch as GM refers to it - to ensure that they were not knocked loose while 4 wheeling.

I'm transferring this topic to the 2500HD/3500 HD Trucks & Drivetrain forum.

ON EDIT: Let us know what the dealer finds out - codes etc.

[ 02-11-2003: Message edited by: mdrag ]</p>

[MountainMax]

This is a problem w the 01s. The NSBU switch has been upgraded in the 02s & 03s. I recently had mine changed. It was doing the same thing.

[Fishnfool]

MountainMax

Can you provide any more info on your fix for the problem? Is there a TSB (Technical Service Bulletin) or can you scan and e-mail me a copy of the dealer repair order? I am trying to help get them back on the road sooner.

Thanks-Dave

dwbany@sonic.net

[Fishnfool]

Sorry for the late update but the dealer replaced a valve body and that fixed problem. They are headed back home and have had no more trouble.