I have a 98 ls1 that 3/4 clutch pack was shot trans worked good in r 1 2, we just rebuilt it and now r works fine and when you pull it in 1 or 2. Now if you star in 4 or 3 it acts like neutral if you start in 1 you can shift it and works in 1 2 3 and when you shift it to 4 it act like neutral again. When I place it in 2 it starts in 1 shifts to 2 then you can manual shift it to 3 a 4 is still like neutral . ON the rebuild we replaced pressure control and 1/2 and 2/3 solenoid also tested the 3-2 control solenoid took the valve body back off checked all valves any ideas would greatly be appreciated

 

These are the EXACT symptoms of installing the forward sprag upside down.
Sorry to tell you that - the trans will have to come out and be partially disassembled to fix that of course.
Unfortunately the forward sprag assembles equally well correctly and upside down.

The reason the car moves is that the overrun clutch is engaged in [D1] and [D2] and then in 3rd gear in [D3]. Once it shifts to 4th gear it doesn't use the forward sprag anymore.

 

mrvedit I’m not so the forward sprag is installed upside down. The two times that I installed it wrong, and yes I am ashamed that I did this twice, the trans would bind up when shifting from 1st to 2nd gear and smoke the band. I’m not kidding smoke was coming out of the trans. I think you are right in that the issue is with the forward sprag. I think it’s just not holding for some reason. May have two issues with no 4th gear also.

My diagnosing philosophy is to fix what you know is wrong and just maybe it will take care of the other problems. So I would start with the sparg. Make sure that it is installed correctly and that it holds. Look closely for wear on the races. If you did not install a new sprag the first time I would get a new one. This is one of the weak spots of this trans.

 

I don't know if this will help decide whats wrong but I just pulled the fuse and it will now start out in second when you put it in 1 2 or d and and shift up to drive.

 

When you pull the fuse, the trans is in "limp" mode, which is 3rd gear. Assuming it it the fuse that powers the +12V to the trans, it will not be able to shift either.

I missed that note that there is no 4th gear either - check that the 4th gear servo piston was installed correctly and not upside down.

A blown sprag gives the same symptoms as yours (except that 4th gear works):
https://ls1tech.com/forums/automatic...rking-wtf.html