I have a 2011 Tahoe Hybrid with just under 78,000 miles. It's basically been problem-free since it was new.

I'm now noticing a thud when the AFM disengages when cruising at highway speeds (this is most noticeable going from V4 to V8 and less noticeable when engaging — V8 to V4..) The thud seems to be more noticeable when under load (small highway incline, etc.)

I don't have any alerts or codes (I don't have a way to scan but there are no messages on the console) and I don't have any engine miss (that is noticeable, anyway). I know there's a lot of info online about VLOM and AFM lifter failures but I don't see this being the case — it really feels like it's transmission/torque converter(dampener assembly)/lock up—related... I'm not noticing any other transmission-related issues though. Shifts fine under hard acceleration, etc.

On a side note: I just had a full transmission, differential, engine oil (basically all fluids) changed at around 75K (shortly before noticing this behavior) but I can't come close to pinning it on that, specifically.

I scanned the forum to see if there were related topics but didn't see anything that directly related. Any ideas?

 

I'm seeing a lot of new, useful advice in other threads but nothing in this one after nearly a month...

I can't be the only HyHoe owner that has ever experienced consistently rough, clunky AFM disengaging/engaging at highway speeds.

I definitely want to be proactive with this vs. waiting until something breaks.

Any help is appreciated.

Thank you.

 

Have you replaced the small oil filter under the pressure sensor that feeds oil to the lifters? Wonder if a partially clogged filter could be starving the lifters of oil and causing what you are seeing.

 

Thank you for the reply, Jaime.

It is just freshly off a factory Chevrolet extended warranty so I haven't wrenched on it myself yet.

Is this small oil filter something that would get changed during normal (dealer) service? As indicated in my original post, I had all fluids changed this June, just as the warranty was expiring.

-b.

 

I don't think it is part of any regularly scheduled maintenance. The oil pressure sensor has to be removed to replace it. The Engine Valve Lifter oil Filter part # is 12585328.
Rock Auto has it listed as an "Oil Pressure Filter".
Check this video for an example of a very dirty filter:
If all this oil/lifter stuff checks out OK, I would then check the drive shaft U-joints.

 

Hello again, Jaime.

I really appreciate the insight. I will replace that filter right away seeing that it probably never happening during the scheduled maintenance and I'm approaching 80K.

I'll update the thread if it makes a difference.

Would you say that's about all I can check at this time since I don't have any codes?

Thank you!

-b.