8L90 Swap Lockup Issues

[gofast321]

Hi everyone. I just finished an Gen V L83 / 8L90 swap in my 1988 Suburban. I love the swap; power and gas mileage are both awesome!

My question is... When coming to a stop in the truck it feels like the torque converter lockup doesn't let go until the very last second and causes a little bit of a lurch in the truck as it stops. Has anyone else had this issue in their 8L90 swaps? Is this expected behavior from this trans? If not, does anyone have a suggestion on what I should start looking at (my transmission knowledge is terrible)? I do have the torque converter control wire from the harness hooked up to the brake light switch in the truck to show the ECM/TCM 12v when I step on the brake.


Thanks in advance for the help.


Chad

[Ziegelsteinfaust]

When I got my 18 Silverado I had the V6 6 speed, but as I was doing my research on the various sub models. The 8l90 had tuning issues where people were not happy with them. Do not remember exact details, but your problem maybe linked to the factory issue. Many people complained about.

[Hart_Rod]

Originally Posted by gofast321

Hi everyone. I just finished an Gen V L83 / 8L90 swap in my 1988 Suburban. I love the swap; power and gas mileage are both awesome!

My question is... When coming to a stop in the truck it feels like the torque converter lockup doesn't let go until the very last second and causes a little bit of a lurch in the truck as it stops. Has anyone else had this issue in their 8L90 swaps? Is this expected behavior from this trans? If not, does anyone have a suggestion on what I should start looking at (my transmission knowledge is terrible)? I do have the torque converter control wire from the harness hooked up to the brake light switch in the truck to show the ECM/TCM 12v when I step on the brake.


Thanks in advance for the help.


Chad

Originally Posted by Ziegelsteinfaust

When I got my 18 Silverado I had the V6 6 speed, but as I was doing my research on the various sub models. The 8l90 had tuning issues where people were not happy with them. Do not remember exact details, but your problem maybe linked to the factory issue. Many people complained about.

What Zieigel said. It needs someone with experience to clean up the transmission tune. Let us know how that goes.

[buffydores]

Every time I've run a tuned 5 speed or 6 speed, they've had that lurch you describe. It's a tuning deal. Nothing wrong with the transmission. Just need to find someone who can massage it.