General Motors 8L90 hydraulic operation

This video is part three of a seven part series on the GM 8L90 transmission. In this video, I cover the hydraulic operation of this impressive transmission. I describe the valve components, pressure regulation, pump operation, solenoid control, and much more!
Here are the other videos in this series:
8L90 Overhaul - part one covers disassembly: • General Motors 8l90 Ov...
8L90 Overhaul - part two covers assembly, including clutch and gearset assembly and measurements: • General Motors 8l90 Ov...
8L90 Overhaul - part three covers valve body: • General Motors 8L90 me...
8L90 Mechanical and powerflow: • General Motors 8L90 me...
8L90 Electrical theory and operation: • General Motors 8L90 el...
8L90 Torque Converter: • General Motors 8L90 to...
8L90 Rebuilding Particulars:
8L90 Modifications and Tuning:
Special thanks to Precision International, TransGo, and Sonnax for providing me with product to use in these videos. Also thanks to KB Cores and AA Midwest for providing me with a few 8L90 cores at a good price!
0:00 introduction
0:51 upper valve body components
3:54 actuator feed limit valve
7:31 solenoid operation
9:50 clutch exhaust backfill
13:16 oil pump
15:11 pressure regulation
22:03 surge accumulator
24:14 solenoid valve body
26:28 clutch control
34:48 solenoid accumulators
36:31 checkballs
37:41 vacuum testing
42:59 conclusion and summary

[@SouthpawAutoworks]

6:19 (AFL Circuit) (Orifice #10)
That's very interesting, Sean.
I look forward to circling back and watching the rest of this video.

[@blancosilverado9795]

Appreciate you making this,

[@taha.al-dulaimi1461]

Excellent explanation, thank you for your effort, and we hope for more information about the most important malfunctions?🎖

[@Aintright890]

Thank you very much for this video.
You sure are smart.....!!!!!!

[@brianbunch3577]

Excellent videos on 8L90. We have one in the shop with “Transmission Control Solenoid 3 Stuck Off” before and after rebuild. I was wanting to see the video on pump not wanting to prime discussed at end of this video. Is that video still being developed? I can’t locate it. Thanks,

[@user-my3bq9xt4l]

Thank you for your video, which allowed me to understand the logic of the 8l90 transmission. May I ask where I can obtain the 8l90 oil pressure control logic diagram

[@thecitiots]

This is great content thanks for the brain dump. 👍

[@jraydelatorre]

Have you ever done a tutorial or seminar on the Sonnax vacuum test stand kit and how to use it specifically on General Motors 60 70 80 and 90 Electronic three speed four speed and six speed transmissions

[@siuautomotive]

No, just the 6L80/90 and the 6T70. You can go to sonnax.com and view their vacuum test guides. The expected results can be found in the instructions for the replacement valves.

[@jraydelatorre]

@@siuautomotive Nice just got through opening the box to my new Sonnax Vac test kit. I know a little bit about how to use it I used it before very little and then it was stolen this is my replacement it will never leave my house/shop again Now to start replacing all of my reaming tools.

[@siuautomotive]

Wow! Sorry you were robbed! Those reamers are expensive too! If you are a Trnw.net member, he usually has the best prices. Actually, his prices are still probably better even if your not a member.