allison transmission suddenly quits

[amos68]

GMC 2005 Duramax Allison transmission. 109k miles

I pulled a trailer home and parked.
Next day I start engine and transmission light is on. Put in drive and clunk. Truck barely moved. In reverse, nothing.

Never had a problem in the 3 years I owned it. Run great.
Fluid level ok.

Anyone have an idea whats happened?

My kids expect to go camping Thursday.:(

[Kennedy]

I would start with a scan tool to determine why the light is on. The light comes on to tell you that the system has some information for you to help diagnose the issue.

How long since you've changed the spin on oil filter?

What are you running for fluid?

What if any power adders are you running


It could be as simple as the NSBU switch on the side of the shift lever, but this was more of an early model thing and the later switches have been very good.

[amos68]

Thanks for responding.
Don't have a scanner. I'm not that technical minded.

I switched to a AMS double oil filter and oil. about 1k miles ago

In the transmission, I use Mobile 1 synthetic. about 1k ago

No power adders. I find it odd the way it occurred. It's run fine for 3 years.

[More Power]

Thanks for responding.
Don't have a scanner. I'm not that technical minded.

I switched to a AMS double oil filter and oil. about 1k miles ago

In the transmission, I use Mobile 1 synthetic. about 1k ago

No power adders. I find it odd the way it occurred. It's run fine for 3 years.

Got to get the codes.... even if you need to pay someone to come to you.

However, what's new in 3 years is the recent switch to synthetic ATF. Not that synthetic is the problem, but some aspect of that service may be the cause.