LBZ: No reverse after rebuild

gmac32

Member
Dec 8, 2009
288
3
18
bellville ohio
I just refreshed a customer's trans and now there is no reverse. Goes forward in the shop but haven't drove it. Doesn't throw any codes at all. That is what has me stumped. I put it in reverse and it says " shift range inhibited" is there a way to make it go hydraulic reverse or third like the 5 speeds?
 

Cougar281

Well-known member
Sep 11, 2006
1,806
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63
St Louis, MO
No codes at all when you put it in reverse and get shift range inhibited? A LONG time ago, I had something similar happen where when I put it in reverse that would happen but there was a code (don't recall what it was). Problem was an o ring for one of the pressure switches in the psm was out of place and leaking pressure.

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Mattsmax

Member
Jul 27, 2013
90
0
6
Barboursville, VA
I’m no genius but I’d guess valve body since there is no codes. Check your springs and make sure all the valves move freely.
Make sure your speed sensors are hooked up as well

But start the truck. Pull the main harness on back of trans. If it doesn’t have third and reverse like that then something internally is wrong somewhere
 

SoCal66

New member
Sep 15, 2019
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Not to spoil anyone’s fun but...
Me thinks it’s time to check your NSBU Switch...
Start simple, go from there

Also check battery voltage (and each battery to check for bad one), fluid levels, etc.
 
Last edited:

Mike L.

Got Sheep?
Staff member
Vendor/Sponsor
Aug 12, 2006
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Fullerton CA
Not to spoil anyone’s fun but...
Me thinks it’s time to check your NSBU Switch...
Start simple, go from there

Also check battery voltage (and each battery to check for bad one), fluid levels, etc.

It's a 6 speed, no NSBU. Battery voltage would inhibit forward gears as well; so would low fluid.
 

SoCal66

New member
Sep 15, 2019
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^ Good Catch...
Guessing now...Pressure Switch Manifold related?
Possibly TCM related, broken/backed-out wires?

Bowing out. Good luck. Hope you get it fixed quickly.
 

gmac32

Member
Dec 8, 2009
288
3
18
bellville ohio
I tried another tcm and no change. Took the valve body out and everything stroked freely. Speed sensors are working right. It will power brake and spin the tires so i know i have enough pressure for reverse. I have done all these things and this is why i am confused.
 

Mattsmax

Member
Jul 27, 2013
90
0
6
Barboursville, VA
I tried another tcm and no change. Took the valve body out and everything stroked freely. Speed sensors are working right. It will power brake and spin the tires so i know i have enough pressure for reverse. I have done all these things and this is why i am confused.

Crank the truck then pull main harness on back of trans, put it in reverse. Does it have it then?