4 Speed Shifts Funny.

2zl · February 19, 2011

My 2007 silverado has a 4.8 and the 4 speed auto.

I bought it with 125000 Km and I have put on about 3000 KM on it so far.

What i find strange is some times is when rolling to almost a stop, and i start to accelerate again its also like its out on gear, and takes a second to start pulling again.

I had the same tranny in my wifes Envoy and although i noticed it slightly in her vechicule I really notice it in my silverado.

I have also noticed that there was a sticker under the hood saying that Jiffy lube did a tranny flush and fill at 115 000KM. Is it possible that they filled it with the wrong oil?

brainpause · February 19, 2011

Many will say that a flush is bad, unless done frequently or on a newer tranny.

Could it be that it is the torque management that you are noticing?

Larry

8.1HD/ALLISON · February 19, 2011

Check you fluid level and check for leaks. Sounds like the trans fluid could be a little low to me. They will act exactly like that till you build a little pressure then it will go.

2zl · February 19, 2011

I will check the level.

It shifts and acts perfectly with no slipping and good shifts.

never even thought about the level.

98 Z71 SLT · February 19, 2011

I will check the level.
It shifts and acts perfectly with no slipping and good shifts.

never even thought about the level.

sounds like good ol' torque management

bc_gavin · February 19, 2011

My 2010 sierra 4.8L doe's that all the time i think its a gm thing pedal to the metal buddy

williamoneal · February 19, 2011

They are prob. Correct about the torque management. I had the same problem in my 5.3 4 speed. A BB tune completely fixed the problem that you are describing.

[email protected] · February 19, 2011

Mine does the same thing,and it still shifts at a complete stop in traffic.

Doug_Scott · February 20, 2011

It is actually a very simple thing. The trans is downshifting to first gear automatically, and since it not in 1 on the shifter, the low/reverse band is not applied, and it is using the over-running clutch to get first gear. Since it is using the over-running clutch (some call it a "sprag" clutch) it is freewheeling on deceleration, once you step on the gas, the engine will rev up to the speed the trans is actually going, making it appear to be either slipping, or banging into gear.

Note that the over-running clutch is a one way clutch, it locks in one direction (acceleration) and free wheels in the other direction (decelleration).

Maybe this is not that simple after I re-read this... so to make it more clear, it is normal.

chrisjr123 · February 20, 2011

It is actually a very simple thing. The trans is downshifting to first gear automatically, and since it not in 1 on the shifter, the low/reverse band is not applied, and it is using the over-running clutch to get first gear. Since it is using the over-running clutch (some call it a "sprag" clutch) it is freewheeling on deceleration, once you step on the gas, the engine will rev up to the speed the trans is actually going, making it appear to be either slipping, or banging into gear.
Note that the over-running clutch is a one way clutch, it locks in one direction (acceleration) and free wheels in the other direction (decelleration).

Maybe this is not that simple after I re-read this... so to make it more clear, it is normal.

mine does it too and it feels terrible 40,000mi 07 gmc oh yeah and it eats oil like the gulf coast.