Rebuilt transmission shifting hard

[NGAneer]

First post in a long time.

Had a rebuilt trans put in a few months ago. From the beginning, it would shift really hard but only occasionally.

Took it back to the shop and they ran a full diagnostic and showed a bunch of codes that would lead back to ground problems, even some that were not transmission related. The transmission related codes were P0700 generic MIL request and another that was for the rand on the ISS in the trans.

I read that the TCM can sometimes not give a reliable ground and causes issues with the ISS and it needs a dedicated ground. So I spliced into the ground (pin V on the trans case connector) and put a ground on the frame and another near the TCM. That yielded some improvement, it would go a few days before shifting hard again.

I then went throughout the whole chassis and cleaned all the grounds and I'm going through the engine grounds now.

Here's my question... Has anybody had this issue and resolved it?

 

[petethepug]

Yes, last year on a trans rebuild by my local Indi shop, 6L80. A quick visit had all the codes reset and a recalibration on something with the scanner. Two weeks later I brought it back and got …

Yea, damn. I know what it is I didn’t tighten the jubba dibby tab down tight enough on the skibidibby doo bob.

This is on me. Bring it in and I’ll rebuild your orig trans and install it. No push back and no absurd accusations against me like the dealerships do like …“been driving it in manual 1st gear a lot?”

Can’t mess around with a trans rebuild and minor symptoms. Keep them informed and let them know you can’t be responsible if it breaks again. The signs are there, ask them if they’ll honor the warranty if it dies when it’s covered? We’re really already there aren’t we?

 

[j91z28d1]

the P0700 is trans related, but not the tranny codes. I'm sure a shop scanner would pull them up, they just chose not to show you for some reason. the p codes are just the standardized obd2 codes and then non standard codes take a little better scanner to read. but every module on the truck has its own fault code.

my first thought would be take to a shop that isn't the one that didn't rebuild it and see what they say.

 

[NGAneer]

It's actually a Jasper reman and I went back to the shop twice. They showed me all the codes and gave me a printout. I'll pull the obd codes tomorrow. Thought I could remember but I can't.

 

[Joseph Garcia]

@NickTransmissions is our resident transmission expert, and he may be able to provide some insight into your issue.

 

[NickTransmissions]

First post in a long time.

Had a rebuilt trans put in a few months ago. From the beginning, it would shift really hard but only occasionally.

Took it back to the shop and they ran a full diagnostic and showed a bunch of codes that would lead back to ground problems, even some that were not transmission related. The transmission related codes were P0700 generic MIL request and another that was for the rand on the ISS in the trans.

I read that the TCM can sometimes not give a reliable ground and causes issues with the ISS and it needs a dedicated ground. So I spliced into the ground (pin V on the trans case connector) and put a ground on the frame and another near the TCM. That yielded some improvement, it would go a few days before shifting hard again.

I then went throughout the whole chassis and cleaned all the grounds and I'm going through the engine grounds now.

Here's my question... Has anybody had this issue and resolved it?

What Transmission? I'm assuming a 4L60E based on what you have in your signature line but you can confirm/deny.

Once you respond, I'll provide a response with first steps you can take to get to the bottom of the issue. If it's intermittent, it's more likely to be a C3 issue but anything's possible at this point (at least until I know more about your problem). A priori, turbine speed sensor; my speculation is that Jasper simply reused it (a huge no-no, if so).