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"Revised" 6-speed


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Posted

"Powertrain grade braking is now included in all six-speed automatic transmissions. This feature reduces brake rotor temperatures 100 degrees Celsius on grade tests by downshifting transmission gears, thereby reducing brake applications on long downhill conditions."

 

After reading up on grade braking, it appears that this feature is now active whether you're in Normal or Tow/Haul mode. However, I'm not sure if that's what I'm experiencing b/c the DIC isn't giving me any indication (on the GMT-900's a message pops up indicating when it's happening). They say if you press & hold Tow/Haul button for 3+ seconds it deactivates it... I'm going to test that out on my way to work.

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Posted

Update: pressed and held Tow/Haul button a few seconds then released. DIC indicated Grade Braking Off. Transmission still rough downshift when braking, so that wasn't it. Looks like I'm back to Wait & See until 2500 miles.

Posted

Yeah dic will let u know when it comes on. I get that every day going down the. 1-10 bridge here locally.

Posted

My 04 Acura tsx has this...tap the brakes on a down hill and it will put in hill descent....its trans programming is way ahead of my 09...my 09 will free wheel down a hill requiring one to use brakes or drop in to manual and downshift...and 5-6000 lbs. going down a good hill can really get rolling...

Posted

My 04 Acura tsx has this...tap the brakes on a down hill and it will put in hill descent....its trans programming is way ahead of my 09...my 09 will free wheel down a hill requiring one to use brakes or drop in to manual and downshift...and 5-6000 lbs. going down a good hill can really get rolling...

GM hasn't been a tech leader in any sense for the last 50 years unless you count Delphi magnetretoricial(sp) shocks. GM owned them at the time.

 

Its mind boggling when you think of the incredible stuff they did in the first half of the automobiles existence, and then..... it turned into a giant corporation.

Posted

MotoMedic: Have you noticed if they corrected the shudder problem caused by checking the O2 sensor? There was a TSB for the 900s that under decal around 40-50 mph it would check the O2 sensor and if interrupted by giving gas etc could cause a shudder. I think it checked the sensor after every restart??? My 09 has problems with bucking on such a decal.

Posted

... Totally normal. ...

I get goose bumps when I read quotes like that regarding to problems with a GM product...

 

so long

j-ten-ner

Normal operation of a transmission, or any other vehicle system, is not a problem just because its operational characteristics are different than what you perceive to be as normal.

Posted

Your 4 speed was not a clutch to clutch transmission like the 6 spd is. Totally normal.Not sure what you are saying as I am not a tech...my 09 does not do this but it does buck on decal around 50-40...ops seems to rev to high on down shifts?

ALL GM 6 speed automatic transmissions are a clutch to clutch transmission that means absolutely no slippage or freewheeling on downshifts. I'm sure certain years are different than others and I'm sure certain vehicles are slightly different than others due to ongoing calibration changes and owner driving habits. I'm not driving the op's vehicle but considering that I deal with these vehicles everyday on an above dealership technical level, my opinion of what he is describing, is a normal operational characteristic of that transmission.

Posted

Normal operation of a transmission, or any other vehicle system, is not a problem just because its operational characteristics are different than what you perceive to be as normal.

I guess you did not quite get my point.

 

But anyway in a late model truck I would never "always trust the instruments" more than my butt...

 

:)

so long

j-ten-ner

Posted

Normal operation of a transmission, or any other vehicle system, is not a problem just because its operational characteristics are different than what you perceive to be as normal.

I guess you did not quite get my point.

 

But anyway in a late model truck I would never "always trust the instruments" more than my butt...

 

:)

so long

j-ten-ner

Then maybe you, like many others these days it seems, should get an engineering degree (if you don't already have one) and go to work for GM calibrating their Powertrain components. They are hiring for those exact positions right now at their proving grounds.

Posted

Yesterday, I used the Tow/Haul mode for the first time pulling my boat. Grade braking kicked in coming down an overpass and I have to say it's a nifty feature. Also, when on the boat launch, the Hill Assist kicked in and my truck/trailer didn't roll back, even an inch, when I released brake to hit the gas. I really like this feature! On my old truck, I'd hold the brake with left foot, rev up a bit with right foot, then release the brake to stop from sliding back towards the water.

 

 

ALL GM 6 speed automatic transmissions are a clutch to clutch transmission that means absolutely no slippage or freewheeling on downshifts

 

I don't think what I'm experiencing is due to the type of transmission, but is instead due to when the transmission chooses to downshift. If you've ever driven a manual, you know downshifting early will cause the revs to jump up b/c the engine is suddenly forced to match gear/wheel speed (that's why racers blip the throttle on downshifts). I believe now that GM intentionally uses low-level engine braking at all speeds/grades, and just increases the amount when you're in Tow/Haul or on a steep surface. I understand why they would b/c it does reduce braking required. I've just been slow to adapt, and given the choice, would rather use my brakes to provide 100% of the stopping force. But it is what it is... like the poll I posted on the new trucks name, I'm probably just being too OCD! ha

 

I do appreciate everyone's feedback and I'm really glad we have a sweet a$$ forum like this one when questions arise! :thumbs:

Posted

Grade braking is on all the time to some extent unless turned off by holding the tow/haul button for five seconds or using the manual shift mode. Had mine kick on this weekend when driving in very hilly terrain, cruise set, no tow/haul mode and no load on the truck.

 

Also used the hill start assist to pull the jet ski out of the water this weekend. Defiantly handy for sure.

Posted

Normal operation of a transmission, or any other vehicle system, is not a problem just because its operational characteristics are different than what you perceive to be as normal.

 

The normal, no code, bucking and jerking of my 09 on decel from 50- 40 mph is just my perception not the pos trans and programming, now I understand. Been to dealer many times on the matter.

Posted

Then maybe you, like many others these days it seems, should get an engineering degree (if you don't already have one) and go to work for GM calibrating their Powertrain components. They are hiring for those exact positions right now at their proving grounds.

 

They're hiring? Is there a demand? Too many complains in the past?

 

so long

j-ten-ner

 

Edit: Sorry OP. No further disruptions.

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