Range shift inhibited on new trans build

Jdherron

New member
Aug 12, 2023
4
3
3
Tennessee
Hey y’all, so i just installed a built transmission and it simply won’t go into gear. When I put it in drive it shows range shift inhibited on the dash, and throws 35 codes (incorrect ratios for all the gears, shift solenoid stuck off, pressure switch low control circuit, etc). I installed a stage 4 kit from dmax store. My truck is an 03 but the transmission I built is an 05, however I reused my existing 03 valve body and all my existing electrical harnesses. Any ideas what could be causing this?
 

Jdherron

New member
Aug 12, 2023
4
3
3
Tennessee
List the codes here

NSBU switch indexed wrong?

Here are the codes I’m getting—
P0748, p0763, p0768, p0773, p0778, p0841, p0847, p0872, p0873, p0875, p0701, p0880, p0711, p0717, p0721, p0722, p0731, p0732, p0733, p0734, p0735, p0736, p0741, p0742, p0763, p0768, p0773, p0846, p0848, p0871, p0873, p0747, p0777, p0746, p0 776, u1096, p0743, p0836

And then from the transfer case I’m getting—
U1255, u1000, c0306, c0327, c0359, c0379, c0550, b0790, b2725, u1301


Sent from my iPhone using Tapatalk
 

Duramaxrig

New member
Aug 17, 2023
2
0
1
Texas
Hey y’all, so i just installed a built transmission and it simply won’t go into gear. When I put it in drive it shows range shift inhibited on the dash, and throws 35 codes (incorrect ratios for all the gears, shift solenoid stuck off, pressure switch low control circuit, etc). I installed a stage 4 kit from dmax store. My truck is an 03 but the transmission I built is an 05, however I reused my existing 03 valve body and all my existing electrical harnesses. Any ideas what could be causing this?
I’m having the same problem but my truck is an 08 duramax did you find a fix for it?
 

Duramaxrig

New member
Aug 17, 2023
2
0
1
Texas
The trans got rebuilt when I broke the output shaft on it and no forward gears work only revers. I did a relearn on the trans and didn’t help, and got a used tcm and got it flashed and it’s still not working. Any help would be great. Truck has been sitting for 7 months now and can have nobody here find the problem.
 

Jdherron

New member
Aug 12, 2023
4
3
3
Tennessee
I’m having the same problem but my truck is an 08 duramax did you find a fix for it?

It was the stupidest thing man, I didn’t have enough fluid in it. I didn’t realize I had a deep pan, I filled it up with like 14 quarts and checked it and it was good but I didn’t give it a chance to actually circulate before I checked the fluid level, so it looked good when I checked it but after a few minutes it quit sucking up fluid cause it was below the internal filter. Anyway I finally figured out I had a deep pan which takes 4 extra quarts and filled it with the correct amount of fluid and it’s running great


Sent from my iPhone using Tapatalk
 

PureHybrid

Isuzu Shakes IT
Feb 15, 2012
3,330
365
83
Central OH
The trans got rebuilt when I broke the output shaft on it and no forward gears work only revers. I did a relearn on the trans and didn’t help, and got a used tcm and got it flashed and it’s still not working. Any help would be great. Truck has been sitting for 7 months now and can have nobody here find the problem.

Who rebuilt the trans?
 

Al313

New member
Oct 10, 2023
1
0
1
Lovegod15
It was the stupidest thing man, I didn’t have enough fluid in it. I didn’t realize I had a deep pan, I filled it up with like 14 quarts and checked it and it was good but I didn’t give it a chance to actually circulate before I checked the fluid level, so it looked good when I checked it but after a few minutes it quit sucking up fluid cause it was below the internal filter. Anyway I finally figured out I had a deep pan which takes 4 extra quarts and filled it with the correct amount of fluid and it’s running great


Sent from my iPhone using Tapatalk
Quick question brotha,

I just changed the valve body on my 07 gmc 5500, took it to the shop and these guys have no idea what they’re doing and regretted it after paying them $1200 for nothing. I did the valve body, nsbu switch, speed and oxygen sensors and changed to all new solenoids with new body. Having same symptoms of reverse but no forward. Would it be a broken output shaft? They’re saying it’s transmission but this thing was babied, I don’t mind paying for one but don’t want to spend if it’s something much smaller. Truck is 8.1 vortex v8 gas 24 footer box truck. Allison 1/2k. Please any advice would help. Used to blink under the RND321 but now solid line after new installments and won’t go forward. It does but I have to seriously seriously rev it which can blow engine and only goes 2-3 mph most.
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
21,178
4,967
113
Phoenix Az
Pull the main trans bail connector at the back of the trans on the pass side, then start the truck and see if you get any forward movement when put in gear. You will get codes and it will probably clunk hard but if it does, that means you have 3rd gear and mechanically you don’t have a broke shaft. If it doesn’t go, you have an internal hard part issue
 
  • Like
Reactions: 1FastBrick