• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Allison 6 speed issues.

T

Timothy_james07

New Member
Messages
2
Reaction score
5
2007 classic gmc sierra duramax. Truck has reverse as normal. As soon as it’s shifted into drive it goes into shift range inhibited. I’ve tried a different tcm. Replaced the internal harness due to leaking into the plug. Gone through the entire harness. The truck will move forward if the harness is unplugged at the transmission. So far what I’ve noticed is that the turbine sensor won’t go to zero when put in drive. It stays at engine rpm so it won’t allow it to complete the shift. It’s not throwing any codes. Hoping someone that knows these transmission can offer some insight. Starting to think whatever in the valve body that applies pressure to the c1/c2 clutch packs is to blame. Thanks in advance.
 
Thank You Timothy for coming to thetruckstop.us
I know not one thing about transmission problems but its possible there might be someone in here that does.
There is one member of the forum that has been going through a lot of health problems and He is mighty sharp on transmission problems so maybe by using the @ sign I can call Him up and see if he is doing good enough to respond.
@THEFERMANATOR
YOU doing okay ?
 
I just got the same thing yesterday on my 2006 Duramax. A little over 200k on the meter. I drove truck to do some tree work. used the truck all day. I shifted into 4L and gently pulled a tree down. Put truck in reverse and backed up to where I started. Finished up my job, loaded up the truck and started to drive away. Drove about 2 to 3 miles an hour, put truck in N, pushed button from 4L into 4H, Tcase then showed N. I put truck into D and nothing, Allison does nothing when you shift from P to R to N to D. Whole truck stays in N. I get shift range inhibited on DIC.
1ST Time I ever had to get truck towed home...
What gives here? Where should I start?
 
Yes. I tried everything I could. I was cutting wood, so I had no tools. Had to get flat bedded home. The Transfer case seems stuck in neutral, and the Allison when going from Park to Reverse to Neutral to Drive does not respond. Seems like the Allison is stuck in neutral too. The DIC displays SHIFT RANGE INHIBITED...
 
RI Chevy Silveradoman said:
Yes. I tried everything I could. I was cutting wood, so I had no tools. Had to get flat bedded home. The Transfer case seems stuck in neutral, and the Allison when going from Park to Reverse to Neutral to Drive does not respond. Seems like the Allison is stuck in neutral too. The DIC displays SHIFT RANGE INHIBITED...
Click to expand...

Let us know what the outcome is, just in case my 2006 Chevy 2500HD ever does the same thing.
 
Just need to figure out how to get these plugs seperated. Hopefully one of the things mentioned here fixes it.

I tried the 1st suggestion. No help. Still not working. No change in situation.
On to NSBU Switch.
 
I'm not getting good vibes here. I have a feeling that this will be like a dog chasing his tail.
No codes thrown at all. Truck starts up in P and N, so I think I can rule out the NSBU. When going from P to N to D, nothing. When trying to shift back into P, I get a loud grinding clicking noise from front. I might try changing speed sensor seeing it is a cheap try.
 
RI Chevy Silveradoman said:
I'm not getting good vibes here. I have a feeling that this will be like a dog chasing his tail.
No codes thrown at all. Truck starts up in P and N, so I think I can rule out the NSBU. When going from P to N to D, nothing. When trying to shift back into P, I get a loud grinding clicking noise from front. I might try changing speed sensor seeing it is a cheap try.
Click to expand...
Pretty sure the noise you're hearing is the park pawl grinding, because the transmission is still spinning. It sounds like your transfer case is still stuck in neutral. That might also cause the Range Shift Inhibited message, not sure about that.

You should be able to remove the transfer case encoder motor and manually shift the transfer case back to 2 high. I would start there. You might not have a transmission problem at all.
 
Well. @Lennydmaxguy hit the nail on the head. I dropped the front drive shaft, took the encoder motor off, manually shifted the transfer case (counterclockwise) 2 clicks until it didn't go any further, took the encoder motor apart, lifted out the big gear and rotated it clockwise about an inch so it would line back up with the transfercase shaft that I manually rotated, buttoned it back up and everything works as it should.
I am shocked. I shifted from 2wd to 4wdH and back. I didn't try 4wdL. I'll do that another time as I need the truck.
No codes, I think I was the one who caused it from not placing truck in N when going from 4wdL to 4wdH.
In any event, this has been a learning process. Hope this helps anyone else if you ever encounter this issue.
 
You must log in or register to reply here.
Back
Top