L86/8l90 Issues

I have a L86 with the 8l90 swap in a project. I am having issues with the transmission, and have the ECM and TCM matched up with the TUN number.

The problem I have been fighting is the truck will go in reverse, but wont go into drive. The Scanner shift PID show Park, Reverse, Neutral, then when I put it down in Drive it says Unknown:82, then Low gear says Unknown:81.

Does anyone have any insight into this, because I am at Wits end. This was a custom built harness by a large harness outfit and I have been through all the pinouts and everything. Any insight would be appreciated, also would be interested in talking to anyone that's a 8l90 transmission Guru.

Did you ever get this fixed? Im having the same trouble with a GMPP crate 8L90.

You most likely have a newer 8l90. These will only work using a T87A controller. Are you using a non t87A controller?

I have run (and tuned) a 2015.5 T87 on a 2017 8L90E Silverado. I bought the T87 new and set it up on a 2015.5 L86 8L90E Yukon Denali XL with the same gears (3.23) with MDI. No problems, no codes.

I'm having a similar issue. New crate 8L90 from GMPP, their harness and controller T87. Everything works as far as driving goes. The customer supplied a paddle shifter from PCS. I cannot get it to work to shift the trans. Everything else works on it, MAP, RPM, TCC lock %, a bunch of stuff. So I know its on the BUS and communicating. The issue I'm having is when the shifter is in Drive it shows unknown 82 and Low it shows unknown 81. In the file you can select what gear position you want the TUTD active. D1-D6, N, R, P, and 9. I cannot get the scanner to show D or anything else that would make sense for the TUTD to be enabled. There is no codes. Anyone that has an idea I'm all ears!!! Here is the paddle shifter in question if it helps.

https://www.powertraincontrolsolutio...fter/A-PS2006/

PCS doesn’t have anything that will work with the 8 speed! You will need GM paddle shift setup

Figure anything out same issue here?

Im late to the party but I have been able to get the PCS paddleshifter to work on an 8 speed. Itll shift through the gears but the gear indicator will stay on 6 when you shift past 6th gear. In the tune, set TUTD to hardwire and adjust the TUTD shift scheduling tables.