Hi I've got a 89 TN wagon that I've swapped from Carb to EFI. I noticed before I did the change over that the gearbox would jolt when changing gears and once it got to 4th and would slam back and stay at 3rd ( not nice when I'm drunk iced coffee at that time)also when I'm at a dead stop and go again it takes off in 2nd . I hoped when I did the change over it might fix it but with no luck ( only the jolt has gone).So yesterday the fluid and filter and it ran smooth for about 3kms I even got overdrive then it slipped back to 3rd

Any help would be great thanks

first try replacing the computer module

because carby ecu and efi ecu are different

its under the carpet below the radio

your TPS might be sticking

next overdrive slipping not staying in 4 th
make another post and we can fix that