4L60E Speedo shift problem

1999 Chevy Express. Trans went completely bad about a year ago. Installed rebuilt trans and didn't shift correctly, speedo too fast (reads 60 when going 30), shift too soon and no codes. Chevrolet replaced reluctor wheel and seemed to work fine for 6,000 miles. Now doing same thing again. Rebuilder provided another trans and Chevrolet shop installed with same problem. Speed sensor replaced, no codes, shifts too soon as the speedo reads too high. The Anti-Lock light is on but we believe this is because wheel sensors don't jive with computer. Chevrolet has no answer and I am at a loss. Bad wiring? Bad VCM? This was not a problem with the original trans, it simply had a clutch pack seal go bad as it just starting slipping and quit. Where do I go from here? Start pulling wiring harnesses? Pull Computer Module? What besides the speed sensor effects the shift? Could I have a ground problem? Please help.

needs to be put on a transmission/engine capable scanner and check for codes and sensor readings.

Does the speed sensor in scanner match truck MPH?

Speed sensor signal need to match the truck MPH to shift right but also check all engine running sensors.
Engine has to be runniing right for transmission to shift right.

Well forgive me, I am not sure of the equipment required to do what you suggest but I have had it to a Chevrolet Dealership twice (recently lost their franchise, another story). The first time was with first rebuilt trans and they immediately concluded that the reluctor wheel was bad. After fix it worked about 6,000 miles. This time they are at a loss. I am not afraid to spend money to get it fixed, but I am in rural Central Illinois and not sure where to go or what to ask when I call around. Do I ask if they have a certain diagnostic machine? If so, what is it called? Chevrolet had some kind of machine as they told me readings looked good and no codes were appearing. What kind of machine they used, I do not know. There are several trans specialist in nearby towns, but two I do not trust. I have seen their work on some 350thm and 400thm from years past. They obviously are out for the buck, as their rebuilds were simply partial fixes (1 clutch pack rebuilt and another was not). Anyway, I really appreciate any info you can offer as I am lost as to how these electronic trans work. Thank you for all you do on these message boards.

Any good repair shop has a good engine /transmission capable scanner that will test out the engine running and transmission operation.

But the key to that is to find a good repair shop that has trained techs that can use the scanner and read out the readings and know what the scanner is telling them.

Yes a lot of transmission places are rebuild/repair happie or out for the buck.

Tips on finding a good repair shop.Check around Ask around
Word of mouth.
Family friends coworkers neighbors business people and delivery people.
Mailmen and parcel delivery people get around and notice a lot of stuff.
Even a good parts house knows what shops are good and not good.
Chamber of commerce and better business bureau and city hall.
If you find a good referral to a repair shop go look them over and talk to them.
Look for a clean looking busy place with nice people running it.
Ask a few questions and ask about their qualifications and training.
Not all places have trained tech/mechanics.
If they do not find a place that does.
Even all dealers do not have all trained techs/mechanics.

Let us know how it goes.
Good luck
MT

I don't mean to be hard headed, but the Chevrolet Garage it has been to is a "good repair shop" and they haven't a clue as to the problem. So, back to my original question with modification. Where do I go from here when all else checks out. Could this be a ground problem? Bad Computer? Bad wire harness? Or, will I be wasting my time pulling wires and chasing such a possible cause. Could a bad computer act this way (show no error codes yet be bad)?

Thank you again for the ideas and help.

If they are good they would be able to find the problem.
If they can not fix it.

Find another repair shop.
Let us know how it goes.

I decided to try the "Just Answer" feature linked at the top of this page. A very nice GM Tech ask that I check the resistence in the wire from the VSS to the computer and compare that to the resistence at the VSS. The good news is that it appears the wire is good, no loss. Bad news is there is another problem. I am waiting to hear back from him as to what I should do next, but I am real close to purchasing a PCM. Woops, there he is. He now wants me to check the ground. Better get to it. Thanks guys, I'll let you know how this goes.

I decided to try the "Just Answer" feature linked at the top of this page. A very nice GM Tech ask that I check the resistence in the wire from the VSS to the computer and compare that to the resistence at the VSS. The good news is that it appears the wire is good, no loss. Bad news is there is another problem. I am waiting to hear back from him as to what I should do next, but I am real close to purchasing a PCM. Woops, there he is. He now wants me to check the ground. Better get to it. Thanks guys, I'll let you know how this goes.

Let us know how it goes.

Update: The GM Tech had me check the wire from the VSS to PCM to see if it is running to ground or to the power (battery disconnected of coarse) and the wire passed the test with flying colors. He then said it could only be one of two things 1) the transmission or 2) the pcm. So, I purchased a pcm and installed it this evening and it fix the problem. I do have service engine light on and I have to wait til my son gets home with my truck so I can get the tool to read and clear codes. The van now runs out good and shifts as it should. The speedometer appears to read exactly right. My experience with Just Answer was great. It helped me eliminate the problems and narrow down the possibilies. Thank you for your help.

The Service Engine Light is caused by a DTC P1336. After research it sounds that there is a learn proceedure needed to make this go away. Simply clearing the codes does not do it, they come back. My scan tool does not appear to have the capability to implement the Learn Proceedure. Is there another answer? Should I take the proceedure to the local garage and have them do it? Any suggestions? I am soooo close.

Thanks

The Service Engine Light is caused by a DTC P1336. After research it sounds that there is a learn proceedure needed to make this go away. Simply clearing the codes does not do it, they come back. My scan tool does not appear to have the capability to implement the Learn Proceedure. Is there another answer? Should I take the proceedure to the local garage and have them do it? Any suggestions? I am soooo close.

Thanks

If it is running good drive it a while and see if it will relearn on it own.
If not it is find a repair shop that has the proper scan tool to reset and relearn it.

Good luck