Any of you who've seen my posts within the past year might remember that I've been triyng to diagnose a road vibration issue summer of last year (2020). Ealier this year (2021) and late fall of 2020 I have been trying to diagnose a whinning/grinding/groaning sound somewhere in the drivetrain. And recently earlier this year I've started diagnosing a strange RPM surge between 3rd and 4th gear. There was also a time back in 2018 where the acceleration felt sluggish. It sort-of does today still feel sliggish. All of these I've identified as a wearing out torque converter possibly. There would also occasionally be random engine stalls at idle RPM when braking. I know I don't have a vaccum leak.


Here's the previous posts I made on those topics. More or less identifying the times these symptoms happened.

Slow / sluggish acceleration:
https://blazerforum.com/forum/2nd-ge...ragging-97064/

Engine stalls:
https://blazerforum.com/forum/2nd-ge...arness-102379/
https://blazerforum.com/forum/2nd-ge...ut-off-102149/

Road vibration:
https://blazerforum.com/forum/2nd-ge...speeds-102080/
https://blazerforum.com/forum/2nd-ge...speeds-102872/

RPM surging:
https://blazerforum.com/forum/2nd-ge...55-mph-102944/

Strange groaning noise:
https://blazerforum.com/forum/2nd-ge...-right-102683/


I stumbled across this article here, and realized that all these things I've mentioned on this forum before are common symptoms of a wearing out torque converter.
https://itstillruns.com/signs-bad-to...r-5073640.html
https://rxmechanic.com/symptoms-of-a...que-converter/


I just want to confirm with the community if my suspicion seems valid.

My fixes so far:

Slow / sluggish acceleration:
I didn't really do anything about the sluggishingness. I just dealt with it thinking that running the AC on a hot day is the cause.
After doing a transmission fluid / filter change, and bringing the fluid up to the correct level, this symptom feels very much resolved.
Acceleration and shifts are smoother.

Engine stalls:
The engine stalls I thought were bad sensors or vaccum leaks. I have done a complete leak-down test and found no vaccume leaks.
Mass air flow sensor, manifold pressure sensor, idle air control valve, and throttle position sensor have all been replaced.
I still occasionally get RPM dipping below 300 when coming to a stop and almost stalling.

Road vibration:
Complete suspension rebuild. Shocks, ball joints, tie rods, bushings, and steering arms. Also brand new Cooper Evolution HT tires.
All were valid repairs because the those components were indeed worn out. Factory original with 160k miles. The previous set of Cooper Adventurer AT tires were starting to cup on the inside tread.
All of this was an attempt to completely get rid of the road vibration, but it still occasionally happens suddenly then quickly goes away. It seems to very much depends on the quality of road I'm on too.
The same road always produces the same effect, so I've just accounted that to just how things are given the heavy duty Bilstein shocks I installed.
I've found that making sure the front suspension has the proper amount of lubrication reduces the vibration. All of my joints are servicable.
There's still some vibration today. No play in either of the drive shafts. Vibration still felt at speed in netrual.
I also want to clarify that when I say vibration in this context, I mean bumpiness. It feels like I'm driving over rocks and gravel.

RPM surging: (Now what I know to be shuddering, rather)
I had no idea what was causing this. I just knew it was something transmission related.
I read that this happens on low transmission fluid, but at the start of this post when I checkd the fluid level (incorrectly) it seems fine.
It wasn't until that I realized I was checking the fluid level incorrectly that I did a proper "hot" check and had no fluid on the dipstick at all.
So I did a transmission fluid / filter change, got the fluid to the correct level on a "hot" check, and the shudder is completely gone.

Strange groaning noise:
I've done nothing special to address this specific issue. I was hoping a transmission fluid / filter change might solve it, and it did at first, but it's come back now.
This happens primarily when slowing down from high speed. The sound is then amplified if you're making a turn like going around a bend on an exit ramp.
It's not a consistent groan though. It's a low pitch whomp whomp whomp sound that increases in rate with vehicle speed.
There's no groaing noise at all while stopped, and you can pick out the noise rolling along at 15 MPH with your foot bearly applying acceleration.
Also when I'm not wearing thick-soled shoes, I can feel a grinding vibration in the floor while accelerating.



So after all of that, here's the remaining symptoms:

• Occasional acceleration sluggishness when at operating temperature
• No engine stalls lately, but RPM dips dangerously close to stalling when coming to a stop
• Occasional vibration / bumpiness at highway speeds (could just be the nature of the road and suspension with HD shocks)
• Groaning noise when slowing down from high speed OR when giving enough throttle to maintain speed. Accelerating fast produces no noise.
• Vibration feel in the floor when accelerating

 

In response to specifically vibration felt by tranny operation
you checked out that trans mount recently?
as far as sluggish running is the engine up to snuff on maintenance, this is a stupid question of me to ask you but, may as well. What did the fluid look like when you serviced it?

I'm assuming it got a new filter so did you look at the old one for how bad the contamination was? Converter failure dumps trash into the tranny up front and in the front of the pan, and into the pump, which circulates alot of it to the back of the tranny, Contaminating the whole thing. Sometimes leaving larger pieces in the pan and in the case, It will start to act like a burnt clutch in a Manual transmission rig combined with the fact that you don't have direct control of the bite point.

The RPM surging could be slipping of clutches in whatever gear you are in, if its 3rd gear i would not be surprised as 4L60Es are known for 3rd gear clutch failure. is it gradual surging or harder more felt disconnect in the drive-train from loosing torque to the rear

 

The fluid was pretty dirty, but on a paper towel it still has some pinkness. It didn't feel gritty and ot didn't have a burnt smell.

The slippage went away after the fluid change. Shifts smoother than it did before.

My father who knows Chevys pretty well gave it a test drive, and he doesn't think its transmission related. The noise while driving straight is more coming from the rear he says. He thinks its differential, ujoint, or wheel bearing. However the noise being made while turning is coming from the front left wheel. Like it's rubbing on something. I'll rotate the tires and see what that does.

I will inspect the transmission mounts next. Forgot about that last I had it up.

Vibration could be ujoints, but when I inspected them I didn't feel any play.

I'm mostly trying to figure out what the possible causes are of the noise and vibrantion (which could be 3 separate things really) before I take it to a 4x4 expert for a professional diagnostic.

 

After troubleshooting the grinding noise and vibration further, it has lead me to believe that it's a front differential problem.
https://blazerforum.com/forum/2nd-ge...60/#post734470

 

I've confirmed that that the noise and vibration is a rear differential issue.
Considering this subject closed.