I'm trying to help a friend with a 1998 automatic ls1 trans am ws6. He tells me the car sticks in a gear. Sometimes 1st sometimes 2nd and sometimes 3rd. he has replaced the transmission and the ecm and the problem still exists. I was thinking it sounded like a vacuum issue but I didn't think these transmissions ran on vacuum? Any help would be greatly appreciated

 

did you test tps, reset shift cable?

 

Instead of a Vacuum feeding the transmission Modulator directly the PCM uses the information from the MAP sensor to determine the engine load.It could be a vacuum issue but that would be a MAP issue or the line feeding the MAP.

Is the speedometer workking right. Is it the same issue before and after he changed the transmission?

Scan tool would tell you is the PCM is trying to shift the the transmisiion is not doing as told. As a general rule the delayed shifting comes from weak seals in the clutch packs. It is a common issue and if he bought a used trans that has been sitting around for a while It would not surprise me if it had the same issue.

 

Well he said the transmission he put in was completely rebuilt

 

if it was a different trans i would say its electric, wiring, wire connection, not sure what controls the trans shift on a 98 but if its the bcm i would look at it as well. also make double sure the shift cable is adjusted correctly http://shbox.com/trans/A4_trans_linkage.html

 

Who rebuilt it and why is this not their problem? A transmission shop that takes more then hour tracking down what the issue is has no business working on computer controled transmissions.

 

I believe he bought the tranny rebuilt, and installed it himself

 

Is his speedometer working right and is it the same exact problem he had before he swapped in the rebuilt trans?

One of the most common screw ups do it yourselfers make is not flush out the cooling system for the transmission. The lines get metal in them from the old failing transmission and that metal is on the wrong side of the filter. Start up the car and you have the same problem with the new trans as you had with the old on. I am not saying that is what happened just that I have seen it before.

If it is a defective trans he is going to have to prove it to the rebuilder, that would mean a trans shop would need to agree it is a trans issue.

 

He said the speedometer works, and that the transmission both did the exact same thing

 

I don't see a way around it, he needs a scan tool. He needs to see the Map reading and he needs to know what it should look like he needs to be able to drive the car and see if the computer is telling the car to shift and it is not shifting or if the computer is telling the transmission to not shift until high RPMS.

Since he has never done this before it would be worth it to spend the money and go to a good trans shop and have them look at it.