2014 Transmission problems

[micha]

Hey everyone,it's my first post here, need some advice with my 2014 Tahoe 5.3L 4x4.

I’m running into a few issues:

After coming to a stop, when I press the gas to start driving again, the truck moves forward with a loud, aggressive thump — feels like something’s engaging hard or late.

At red lights, if I take my foot off the brake, the Tahoe starts rolling backward like a manual car.

At medium speeds, I’m getting a noticeable vibration when the transmission shifts gears.

I also noticed a medium-sized oil leak coming from the front of the transmission area.


My mechanic says the transmission needs to be replaced, but I'm not 100% convinced — we’ve all had our share of trust issues with mechanics

I’ve been digging around a bit and I’m starting to suspect it might be related to the torque converter. Has anyone here experienced something similar? Could it be something else — like a mount, U-joint, transfer case issue, or maybe just low fluid?

Appreciate any insights!

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

What is the truck's mileage? Which transmission do you have? Is you transmission fluid at the full level?

My first thought is that your torque converter is failing. If this is the case, you need to get it replaced fast, before it grenades (if it hasn't started already), and sends metal fragments throughout your transmission, and grenading that as well.

@NickTransmissions is our resident transmission expert, and he will chime in with his thoughts and perspectives.

 

[OBSandaNNBS]

I'm agreeing with Mr. Garcia, and Nick will probably too.
I would stop driving it immediately until the TC is replaced or problem is ID'd. The TC is a bit of a weak spot on these trucks. Fortunately there are some good aftermarket solutions.

 

[rdezs]

Agree 100%.

 

[NickTransmissions]

Hey everyone,it's my first post here, need some advice with my 2014 Tahoe 5.3L 4x4.

I’m running into a few issues:

After coming to a stop, when I press the gas to start driving again, the truck moves forward with a loud, aggressive thump — feels like something’s engaging hard or late.

At red lights, if I take my foot off the brake, the Tahoe starts rolling backward like a manual car.

At medium speeds, I’m getting a noticeable vibration when the transmission shifts gears.

I also noticed a medium-sized oil leak coming from the front of the transmission area.


My mechanic says the transmission needs to be replaced, but I'm not 100% convinced — we’ve all had our share of trust issues with mechanics

I’ve been digging around a bit and I’m starting to suspect it might be related to the torque converter. Has anyone here experienced something similar? Could it be something else — like a mount, U-joint, transfer case issue, or maybe just low fluid?

Appreciate any insights!

Your mechanic is probably right, given the myriad of symptoms - what about him is not trustworthy (i.e. what did he do or say that would make you feel that way)?

Do you have a bi-directional scan tool that can render live data and give shift commands to the trans and TC? If not, either invest in one or take it back to your mechanic to have him diagnose it for you. But if you told me what you wrote above, I'd be inclined to think along the same lines (trans, TC failure).

 

[micha]

Thank you all for the answers.
The truck has 124,000 miles and a 6L80E transmission.
@NickTransmissions — he didn’t do anything blatantly untrustworthy, but the bills were inflated, and a few times he replaced parts and charged me without asking, which I would’ve preferred he cleared with me first.

I also spoke with my current mechanic, and he agrees that the symptoms I’m experiencing are likely due to a failing torque converter. However, he mentioned that just replacing the torque converter probably won’t last long, since the root of the problem is likely the transmission itself — it may have sent metal shavings into the converter, ruining it. So unless the transmission is rebuilt or replaced, the issue is likely to return.

Do you guys agree with that, or could just replacing the torque converter and doing a full fluid and filter change be enough to fix it for a while?

 

[swathdiver]

From the shop manual:

Harsh, Soft, Delayed or Slipping 1-2-3-4 Shift:

Harsh, Soft, Delayed or Slipping First or Reverse Gear:

Have you been changing the transmission fluid? Have you checked the level when HOT and COLD?

 

[OBSandaNNBS]

I also noticed a medium-sized oil leak coming from the front of the transmission area.

If you are talking engine oil, make sure you get your rear main done while you are into the tranny. Would be good to think about if it wasn't leaking too.