Yesterday I took my 2010 Suburban to the dealer about a problem with the truck shuttering or trembling at slow speeds when shifting gears. Got a call back telling me that GM had a fix, but I had to approve the computer update because it would give me worse gas mileage? Anyone ever heard of this and why would a 50k car with 29k miles on it have to have a fix that would decrease the gas mileage in order for it to shift right????

 

I have never heard of this before! Possibly changing the shift pattern might result in lower gas mileage, but that hardly sounds like a "fix" to me. I would suggest getting some more information out of them as to what exactly their "fix" entails.

 

probably because it wont shift so fast to the higher gears - and keep the revs up a bit longer kind of like in tow/haul mode. the newer 6 speeds seem to try to get to the 5th or 6th gear as quick as possible to keep RPMs down but that makes driving them tricky until you get used to the shift paterns

 

Sometimes a malfunctioning torque convertor lock-up clutch produces the effect you describe.

 

Can you say "PCM for less"? PCMforless.com

 

Of course the reprogramming of my transmission did not work. Just messed up my gas mileage. GM is going to replace the torque converter, and reprogram my transmission back to the original program. Waiting on the part and the computer program to be sent to the dealer.

 

interesting mine has just started vibrating when crusing at highway speeds, but only when getting to a slight hill. basically seems to be the torque converter having issues. the service guy couldnt get it to do the same today because traffic was so crazy on the highway. but he thinks it will be the tq converter and I am going in in a couple weeks to get them to check again and most likely replace it.
considering you have the 6 speed I am sure the TQ converter is different than mine with the 4 speed but still may be a weak point?

 

Well, new torque converter did not fix the problem either, then the dealer found a GM bulletin #06-06-05-001E 'information on change in exhaust tone or sound for active fuel management", that goes on to say a slight vibration may be felt when engine switches to V4 at low speeds. This is normal and no repair should be attempted!...

 

Have they test drove it with you to see/hear/feel the vibration(s)?
or are they shotgunning parts?
Seems like they jumped at the TC awful quickly....

 

Neither of mine exhibited any vibration associated w/ the V8/V4 mode change and very little change in the exhaust tone.