Transmission Slipping

[AirJordan613]

Recently purchased this ‘09 Tahoe with the 6.2. About 140k miles on it. Trans started slipping after having the fluid flushed and filter changed (OE fluid and filter at Chevy dealership). Seems to only be slipping under WOT, otherwise it seems to behave pretty normally. Does this look toast?

 

[swathdiver]

Have you seen this before Randy? @randeez @BlackBearPerf

Should he run the Service Learn Adapts?

 

[Bill 1960]

I would drive that very gently back to the dealer and have them hook up a scanner and drive it. Could be just a malfunction in a control circuit (electronic or hydraulic) caused by some debris that was dislodged during the flush.

Could be it’s toast. What was the initial reason you took it in and had the flush/change done?

 

[AirJordan613]

Reason was that I didn’t see any records of transmission service, so I figured that I should. Also had some weeping trans cooler lines and those were replaced.

 

[alpha_omega]

The sound heard other than the engine, was that your swinging keys striking the dash as you accelerated?

 

[AirJordan613]

Yes, just the keys

 

[AmunRoo]

Hey, I'm new here and I'm kind of having the same issue you are. I experienced the same type of problem when going WOT. Everyone other than that, normal City driving causes no issues whatsoever. I'm considering changing my fluids but not a flush. I have an 07 Denali with the 6.2 AWD

 

[Foggy]

Exactly the reason I don't recommend "flushing" the trans...
If the fluid is that bad, it's prob toast... If the fluid is that bad, drop the pan
and replace fluid --- then do it again in just a couple thousand miles..

 

[swathdiver]

@iamdub @Doubeleive @mikeyss @gooffeyguy

Have you guys taken a look at this yet?

 

[Doubeleive]

def an issue, I have no input other than it's in the range of where the torque converter starts to go, probably needs a deeper look, have pan dropped and check for metal/inspection
could it be a relearn issue? not sure when mine was relearning it did some weird shifts but not that bad

 

[AirJordan613]

So I took it to both my local Chevy dealer and an independent transmission shop. Both were able to reproduce the symptoms but neither observed a slip when they had their scanners hooked up. And neither recommended rebuilding the trans, but didn’t know what else could be causing this issue. Recently during a “slip” I seem to have momentarily lost electrical power. Dash flickered dark and airbag light came on for a few seconds afterward. Then returned to normal. Still mostly above 4k RPM but sometimes noticing a bit in upper 3000s. Anything electrical that could be causing this? The loss of power thing was bizarre. I’m pretty stumped myself. Hard to justify rebuilding the trans when two separate shops couldn’t confirm a bad trans.

 

[CaptainAmerica1]

Battery health? Checked the alternator? Pulled battery and cleaned and replaced grounds? Checks the battery cables for corrosion? All these tests are free and won’t change the fact your transmission may be toast but start ruling out the stuff you can check yourself….

 

[AirJordan613]

Battery is brand new. Grounds looked good last time I checked. Dealer recently checked those too.

 

[AirJordan613]

It certainly seems like there’s a transmission problem. Just scratching my head since both the trans shop and Chevy dealer thought the trans was mechanically OK.

 

[the blur]

Flushing a tranny with 140k. Nah... I'll pass.

 

[AirJordan613]

Flushing a tranny with 140k. Nah... I'll pass.

Your help is greatly appreciated…

 

[donjetman]

Flushing a tranny with 140k. Nah... I'll pass.

Your help is greatly appreciated…

While doing a rear main engine seal job, I changed the tranny filter and 100% of the fluid (Dexron6) in our very used new to us 132k mile Denali. 3yrs and 40k miles later it's still going strong.

 

[AirJordan613]

While doing a rear main engine seal job, I changed the tranny filter and 100% of the fluid (Dexron6) in our very used new to us 132k mile Denali. 3yrs and 40k miles later it's still going strong.

Glad to hear it! My tuner is going to take a look at it and see if there’s anything that can be corrected by tune. If not, I’ll probably just rebuild the trans.

 

[swathdiver]

Flushing a tranny with 140k. Nah... I'll pass.

Why not? This is not a TH350.

 

[mikeyss]

I'm just seeing this too, and that definitely should be checked out with a scanner soon. I see the CEL is not on, so the computer isn't detecting slippage between the input and output sensors. The thing my 6.2/6L80 has been doing is the shift flare between 2-3 shift and sometimes the 4-5 shift. I also hear my trans shift moreso than feel it shift