Code 72 VSS

[Ike99]

1994 K1500 5.7L, 10k on rebuild transmission

I’m getting the dreaded code 72 VSS output speed loss with rough shifting mostly out of 2nd, it requires high RPMs to shift when it does. I have a functioning speedometer and tachometer. I have no problem with a Brake or ABS light on the instrument cluster. I’ve replaced the VSS and checked the VSS buffer. They all check out to be good. I’ve looked at the wiring including grounds and I could not find anything wrong.
I’ve looked at various diagnostic aids and performed the steps outlined and still no luck. I’ve even replaced the ECM with no luck.

I need to mention that I also get the following codes from time to time.

69 TCC STUCK ON
72 OUTPUT SPEED L0SS
73 FORCE MOTOR CURRENT
79 TRANSMISSION HOT
81 TRANS SOL B FAILUREN

Any ideas on what else I could look at?

 

[NickTransmissions]

1994 K1500 5.7L, 10k on rebuild transmission

I’m getting the dreaded code 72 VSS output speed loss with rough shifting mostly out of 2nd, it requires high RPMs to shift when it does. I have a functioning speedometer and tachometer. I have no problem with a Brake or ABS light on the instrument cluster. I’ve replaced the VSS and checked the VSS buffer. They all check out to be good. I’ve looked at the wiring including grounds and I could not find anything wrong.
I’ve looked at various diagnostic aids and performed the steps outlined and still no luck. I’ve even replaced the ECM with no luck.

I need to mention that I also get the following codes from time to time.

69 TCC STUCK ON
72 OUTPUT SPEED L0SS
73 FORCE MOTOR CURRENT
79 TRANSMISSION HOT
81 TRANS SOL B FAILUREN

Any ideas on what else I could look at?

Did you continuity test the transmission harness, solenoids and pressure switch manifold assembly?

Those all should have been replaced at time of the overhaul with AC Delco / Rostra components so if they were not one or more may be failing.

 

[Ike99]

Thanks for the reply Nick. I have not continuity tested the harnesses, solenoid, pressure manifold assembly. I can only hope they used the manufactured parts you mentioned.

I had the truck towed to the transmission shop yesterday. I can ask them to check what you suggested above. I spoke to them today and they are check checking wiring and harnesses much like I did.

In the mean time i continue to look at /research for problem areas that I overlooked. I’m sensing this one will pose a challenge.

 

[Ike99]

I forgot to mention that the code 72 does not clear when I use the scanner to clear the codes. I have to disconnect the battery to clear it.

I’ve also removed and checked the ECM and Transmission fuses and they checkout good.

 

[NickTransmissions]

Thanks for the reply Nick. I have not continuity tested the harnesses, solenoid, pressure manifold assembly. I can only hope they used the manufactured parts you mentioned.

I had the truck towed to the transmission shop yesterday. I can ask them to check what you suggested above. I spoke to them today and they are check checking wiring and harnesses much like I did.

In the mean time i continue to look at /research for problem areas that I overlooked. I’m sensing this one will pose a challenge.

If it's still under warranty, i wouldnt worry about it. If it's not or if it turns out to be a problem outside of the trans, you'll likely be billed for the repairs; if that is the case, hopefully it's a relatively minor problem.

Also please quote my posts if you would like me to reply. I dont watch the threads I post in so dont get notified...

 

[Ike99]

Thanks Nick. Unfortunately, it is not under warranty. I’m new to the forum and learning how it all works. I’ll quote your posts as suggested.