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Damn Transmission….

GMC-AT

By GMC-AT
in Troubleshooting & Recalls

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GMC-AT Senior Enthusiast

GMC-AT

Posted
  • Author
Posted

how does it save gas by downshifting ? The RPM's go higher every time... seems like it would eat more gas.. versus when you left off the gas.. RPM drop to near nothing..

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svtkidd23 Enthusiast

svtkidd23

Posted
Posted
how does it save gas by downshifting ? The RPM's go higher every time... seems like it would eat more gas.. versus when you left off the gas.. RPM drop to near nothing..

The rpm is not going up from inducing extra fuel its going up from the tires rolling.. There fore when you hit the pedal to go again your not giving extra gas from idle to say 1400 it's downshiftimg to bring rpm higher therefore when you get in gas in theory no extra pedal effort..

Rpm matching.

fondupot Senior Enthusiast

fondupot

Posted
Posted

The rpm is not going up from inducing extra fuel its going up from the tires rolling.. There fore when you hit the pedal to go again your not giving extra gas from idle to say 1400 it's downshiftimg to bring rpm higher therefore when you get in gas in theory no extra pedal effort.. Rpm matching.

 

Good explanation.

svtkidd23 Enthusiast

svtkidd23

Posted
Posted
The rpm is not going up from inducing extra fuel its going up from the tires rolling.. There fore when you hit the pedal to go again your not giving extra gas from idle to say 1400 it's downshiftimg to bring rpm higher therefore when you get in gas in theory no extra pedal effort.. Rpm matching.

 

Good explanation.

tried lol
TorkFaze Enthusiast

TorkFaze

Posted
Posted

how does it save gas by downshifting ? The RPM's go higher every time... seems like it would eat more gas.. versus when you left off the gas.. RPM drop to near nothing..

 

Sorry you don't like the way the trans works.

 

The trans is allowing the vehicle to back-drive the engine when coasting. This allows the engine to use very little if any fuel when coasting. You see RPM increase because when the engine speed gets low enough in a certain gear, the trans needs to downshift (while still backdriving the engine and still not using much if any fuel) to slightly increase the engine speed to keep the eng speed high enough to make sure that if you step on the throttle, you're in a decent gear and RPM to accelerate.

 

When the engine is being backdriven like this, it uses less fuel than just dropping to idle.

 

Hope the explanation helps.

 

TF

GMC-AT Senior Enthusiast

GMC-AT

Posted
  • Author
Posted

That does make sense when you think about it. I know they do every possible thing to squeeze the most MPG..

I still hate the trans though..

MR. DRAG SLEDDER Enthusiast

MR. DRAG SLEDDER

Posted
Posted

I hate how mine doed exactly what your saying.. It feels like it chunks... And the -1-2 shift feels like it slips to second

SAME HERE!!!! tjhought it was me...

svtkidd23 Enthusiast

svtkidd23

Posted
Posted
I hate how mine doed exactly what your saying.. It feels like it chunks... And the -1-2 shift feels like it slips to second

SAME HERE!!!! tjhought it was me...

drives me nuts
fondupot Senior Enthusiast

fondupot

Posted
Posted

tried lol

 

it was good. for real. :thumbs:

 

For everyone complaining, im sure a custom tune will be able to tune this out. If it bothers you that much. Tune it out.

svtkidd23 Enthusiast

svtkidd23

Posted
Posted

This thing is going to dealer Monday my 1-2 shift slips than jams in..

In traffic the v4 to v8 clunk.. Wtf... I am starting to miss my f150 with this transmission

Stex Senior Enthusiast

Stex

Posted
Posted

Just wait for the 8 sp tranny...that will be fun. You really hate to tune a new truck and risk powertrain wty problems. My 09 trans function has been a pita since about 1000 miles. I held off because of wty on power train. Finally tuned with about 6 months to go on wty....

 

If tranny not setting any codes and not easy for dealer to replicate the issue, you are stuck. We road many miles with scan hooked up and service mgr could not replicate. I would leave the dealership and it would act up within the hour.

 

I would now try just the range to cut off AFM and see if that helped. If not and If dealer not able to replicate issue, then I would give it a yr/12,000 or so and see if gm issues a fix. If not, go see a good tranny shop. If they find nothing then tune it. My 09 is nice with an 89 oct tune.

2014 Sporty Shorty Enthusiast

2014 Sporty Shorty

Posted
Posted

This thing is going to dealer Monday my 1-2 shift slips than jams in.. In traffic the v4 to v8 clunk.. Wtf... I am starting to miss my f150 with this transmission

How the hell could you miss it? The trucks ok but you get craptastic engines. Ones a unreliable, fuel drinking pig that sounds like a camry with hairdryers, the others an anemic dog with junk car only DOHC. Ford used to make great motors until they went the modular route, nothing but problems since then.

svtkidd23 Enthusiast

svtkidd23

Posted
Posted
This thing is going to dealer Monday my 1-2 shift slips than jams in.. In traffic the v4 to v8 clunk.. Wtf... I am starting to miss my f150 with this transmission

How the hell could you miss it? The trucks ok but you get craptastic engines. Ones a unreliable, fuel drinking pig that sounds like a camry with hairdryers, the others an anemic dog with junk car only DOHC. Ford used to make great motors until they went the modular route, nothing but problems since then.

That 5.0 is a damn good motor.. The thing has more power than the current 5.3. Low end not as much but wot the 5.0 kills this.

 

The transmission in this truck is jerky. Ever since the reflash.

I keep finding issues as the day goes by

1. Back left seat rattles unless weight is on it or up.

2. V4 TO V8 is rough.

3. In v4 mode truck surges and vibrates under 50mph

4 . top end passing power not as much as the f150

5 . steering wheel is made of cheaaaap material. Ive knicked the wheel 2x and now have a nice mark from my fingernail which drives me crazy now I know its there.

6. The truck is very quiet when driving.. Except hitting rumble strips before the bridge i drive every day. (wife and 2 friends mentioned it also) 7. Tires need re balancing.. (could also be #6 problem to.. Hard ass tires)

Those are my irritations

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