Chevy duromax 3500 won’t come out of first gear!!!

[Aquaribus]

Hey, any advice on this would be very appreciated. We’ve been dealing with issue after issue in the last month. Lastest thing is it won’t shift up, just stays in first. Yesterday we got a new spark plug and then it worked for the rest of the day, went to head out of town this morning and the problem was back. We just dropped the transmission pan and replaced the 1-2shift solenoid. Didn’t fix it so we’re feeling a bit defeated.

We’re trying to take the fuse box out to clean it since it’s been oily and making things go haywire. Hard to believe it could be that since a brand new fuse went in yesterday but so far that’s the only thing that’s seems to have made a difference.

Anyway, she’s a 2006 Chevy Duramax 3500 diesel

Ideas??

 

[Aquaribus]

Oh and the speed sensor for the transmission seems fine? In that it is securely connected, I saw on some other forums that that was sometimes the solution

 

[Albatross]

I would replace the speed sensor, they're generally fairly cheap, and often solve the safe/limp mode problem you seem to be having.

Some trannies have multiple speed sensors, input & output, but I'm not 100% about the newer ones.

The other problem that I know is common (or used to be) is actually the main tranny connection to the computer used to be a bit of a problem for some Chevys.