didn't notice any big differences in mileage with the trans reset recall. on the out bound leg I averaged 91 mph over the 8 hour trip and 18.6 mpg. not bad....not bad at all.

 

If you felt any difference anywhere it would be at highway speeds, when you are in the top fixed mechanical gear. The clutch pack involved in the recall is only engaged when you are in that particular gear. No other time. The fact you were able to get almost 19 mpg at such high sustained speeds means the clutch pressure is still plenty sufficient.

 

KC135R, I spoke with my tech and with GM regarding the trans controller recall and none of them seemed to know what it did other than reprogram the controller with new software. Not questioning your knowledge, just wondering how you know which clutches were involved in the recall upgrade. Also don't understand your explanation very well. In my mind, at 91mph, I would think it is a direct mechanical link and the clutches are fully engaged. But I still wonder these things too...how was the engine speed at 91mph? How was the sound level? Jet1, did you look at the hybrid screen to see if you had any MG1/2 involvement or was it straight ICE? What did your instant MPG say at 91mph? Here is a simplified diagram of the 2-mode hybrid although it seems to be missing one of the clutches (aren't there 4?). I don't know where it came from really. I got it off of a 2 year old report on GM hybrids by the company GM did their setup with (their name slips me at the moment). It may be of no use to you but here it is anyway.

 

There are two planetary gearsets in the transmission with four clutches. The Transmission which incorporates the two electric motors is called the AHS-2 and is manufactured by Allison, who make the most reliable transmissions in the world. The actual two mode Hybrid design was completed by Global Hybrid Corporation which is a joint venture between GM/Chyrsler. This component is also used by BMW and Marcesdes. This technology has also been incorporated into buses that I believe operate in the Denver area.

 

Just go to the Global Hybrid Corporation website and it gives a good explaination of the 2Mode System.

 

Global Hybrid Cooperation (formerly called Advanced Hybrid System 2 or AHS2) is a set of hybrid vehicle technologies jointly developed by General Motors, Daimler, and Chrysler LLC, with BMW joining in 2005. It uses 2 or 3 planetary gearsets in an automatic transmission: one on the internal combustion engine side (input split) paired with a second (output split), forming the compound split, and possibly one third additional planetary gearset to multiply the number of fixed gear ratios (up to 4). General Motors has stopped using the "AHS2" name as of 2006, preferring to call it simply a "two-mode hybrid system"..

The name of the company that GM used their simulation software and math to develope the controller to run the hybrid drivetrain was Mathworks. It is amazing the amount of developement and the short time considering the hugh companies involved. Yes, I understand that the 2-mode hybrid was first developed and used in transportation buses and they are actually in use in a number of places, don't think Denver is one of them But...you can't believe everything you read. Still amazing technology.

 

how was the engine speed at 91mph?
I didn't really plot it but I don't think it ever turned over 2500 rpm...

How was the sound level?... sound was a non factor, I had the sat radio on and never noticed any appreciable wind noise except on the way back when I was driving in some 20 to 25 mph cross winds...

did you look at the hybrid screen to see if you had any MG1/2 involvement or was it straight ICE?... I didn't as I was using the straight nav to see if I could make it work better (ala BMW--I didn't) but I did look a couple of times and it was 90% ice except on the flats when the ice/elec option kicked in a few times, I'm sure it was 4v/elec a lot of the time after it got up to speed...

What did your instant MPG say at 91mph?... I was doing a straight speed run on a drive I have done a lot and my goal was to not really pay a lot of attention to the various on board options and I was not trying to achieve any specific goals I was just duplicating a trip I have done in various vehicles over the years....

I can tell you that most of the time the econ gauge was not happy!

 

ILMAO...I'll bet!

Speaking of that stinking little eco gauge. Ok, you have the thick radius line right dab in the middle from 11 to 1 o'clock. Then you have the three ticks along the thin radius line over to past 10 and 2 o'clock. When accelerating, and keeping it in the green, are they talking about all the way to the end of the three ticks on the thin green line? Or, are they just talking about keeping the needle at 12 o'clock or just past on the thick radius line? I have felt that accelerating at such a mild pace has to cost more than just getting up to speed more quickly (as is the case in the Prius..but it is MUCH lighter weight). Anyway, it wasn't until today with direct sunlight shining on the eco gauge that I realized the green band was past the three tick marks either side of the central thick radius line.

 

"Speaking of that stinking little eco gauge. "

I think the goal is to keep in the green zone the further outside the center you go the worse the performance. My reasoning is that if you use the cruise it purposely accelerates very modestly (staying well in the green) if you hit the resume button after defeating it momentarily. All of my other cars would accelerate pretty briskly (especially my corvette!) to get back to the set speed. Im pretty confident it is a design feature to get better mileage on the yukon

 

Any vehicle, it is just physics, the faster you accelerate, the more energy it takes. The further from 12 o'clock the lower the mileage on the gauge.