8 Speed TSB update

[CounterMeasure]

All jokes aside, I think a good after market tune is your only option to get these to work properly. GM has got so wrapped up in maximum fuel economy numbers that they tuned these transmissions to go into the top gear as soon as possible, causing less than optimal shifting and sensation of the same.

 

I think it is more than that. They were inspired by the ZF 8HP transmission. Externally, it even looks like a ZF unit to me. But then tried to take that one to the next level in the middle of their bankruptcy run. From my personal experience, that hasn't gone smoothly.

 

An interesting technical read can be found at http://www.thetruthaboutcars.com/2014/04/saturation-dive-the-gm-8l90-transmission/.

[redwngr]

Interesting that the patent filing date for the 8L90 was May 2009.

 

Authors of the article seemed to be impressed.