I did a LSx swap into my 70 Camaro. I put in an LQ4 with a 4L60e .. including a factory computer from a 2003(i believe) chevy truck. Once installed the transmission would not shift into 4th gear but would go back down to 2nd gear. I thought the 3-4 servo or clutch bands were out so I had the transmission rebuilt and its put back in and the same thing. no 4th gear. What I mean by no 4th gear .if I put it in "D" it goes from 1st to 2nd, then to 3rd and then kicks down and revs up like its back in 2nd gear. I thought then maybe i have some pins messed up in the harness to the computer but I have not seen any issues.

Is this a computer tune issue? or is there something else I am missing? Help please, I want to drive my car..

 

Check which gear is being commanded with a scanner. If you think the rebuilder is reputable then I would look towards wiring/tune.

But stuff can happen even on fresh rebuilds.

If you think it's internal, the relay valve would be a good place to look. Decent leaks in this area. If installed backwards you will also not have 4th.

 

I forgot to add that i have a monster transmissions 2500-2800 stall converter as well.

 

Jeff's transmissions in Tampa is pretty reputable. The car is with them right now and they are troubleshooting the wiring. I purchased this Camaro where it had a 5.3 w/ 700R4 in it. so I swapped it with my worked up 6.0L Iron block and a 4L60E. and had a guy wire in the cables to the ECU. it immediately had issues with no 4th gear so I felt a rebuilt was in order to stiffing it up for more power so it has a brand new rebuild.

• possibly it was wired incorrectly?
• also wondering if the fuse/connection to brake pedal could be causing this?
• possibly the 2500-2800 stall converter causing issues?
• ECU setup incorrectly for shift points/RPM/Speed?
• TCC issues?

just shooting in the dark things I have heard can cause issues like this.

Has anybody else encountered this issue?

 

If the shop has the capability, I would ask them to test drive the car (or you drive it with them) and have them shift the trans via a scanner. Ideally a standalone handheld controller but not all shops have that.

That would be the easiest way to rule out the trans mechanical side of things.

Otherwise just have them stay the course. Track every wire and make sure it is going where it's supposed to in the PCM then check the tune and make sure it is correct with correct tire size/gear ratio.