Odd stumble at highway speed, or wind turbulence?

[redfishsc]

Ok gents this is a head scratcher for me. I'll put my Suburban specific info below.

I cannot tell if my Sub has developed a stumble at highway speeds or if for some reason wind turbulence feels different/more noticeable.

This is only felt at about 65+ cruising and feels very much like a misfire. A slight hesitation. NEVER feels like a stumble at WOT.

I'm out of town at the moment so I don't know if I'm throwing a misfire CODE (engine light rarely comes on even when it should so no help there).

At sub-65 I don't feel a thing. If I'm driving through a highway lined with trees, I feel nearly no stumble. Any vehicles passing, I feel it.

I've driven this old girl across my state and back at least 25 times, gone from West Virginia to Marathon Key, Florida. She didn't display wind turbulence like this in the past.

No floppy body panels, no floppy noises.


Vehicle info;
5.7 Vortec, 250k miles
4l60e, probably not original.
Trans fluid is definitely full and clean, clear red.

No drips/leaks

Recent service:
March 2022, New fuel pressure regulator
July 2022 New distributor cap/rotor.
September oil change Penn Platinum 5w30.

Suspension redone 3 years ago (Moog ball joints and tie rod, New control arms, KYB Monomax shocks, professional alignment afterwards).

Tires are all Cooper Discoverer HT C Class about 2 years old.


The only mod on this truck is the rear end which has 410 Motive gears and an Eaton Trutrac which I keep checked annually for gear oil. This was my first rear end rebuild but it's been doing great for 5 years now.


Other than reading codes, anyone have any suggestions?

 

[454cid]

Are you driving N/S and have heavy crosswinds? I don't recall ever feeling it in my truck, but I sure have in my cars. There has been a few times where I thought the car maybe wasn't running right, and then realized it was the wind. I would think a Suburban would get pushed around more then a my pickup truck.

 

[HotWheelsBurban]

Probably the wind, I have noticed this with my Burb and crew cab on occasion.

 

[redfishsc]

Yeah actually I do a lot of N/S driving at highway speeds when I'm in the Sub.

It just feels different, I've put a lot of miles on this truck in 8 years and never felt it quite like this. I'll pull codes tomorrow if the local parts store will give me a loaner scanner.

 

[95burban]

Maybe torque converter?

 

[tsr2185]

I noticed a very consistent and odd surge when my AC compressor was short cycling on cruise at hwy speeds. Felt very similar to increases and decreases in headwind. I dont think most people would have noticed, but I pay attention to stuff like that, especially something that subtle.

 

[redfishsc]

Maybe torque converter?

Interesting suggestion. Any idea on how to test that?

 

[95burban]

I had a similar problem. It would shutter goin into overdrive and kinda hunt and buck at light throttle. Might put a tube of shutter fix (not joking) i did that and my horrible shutter went away and that helped my trouble shoot. I pulled my trans and replaced the converter and shift solinoids.

Long story short the shutter at lock up felt like a hwy rumble strip, once it locked up it would hunt and buck making it fell like it had a miss.

 

[L31MaxExpress]

I had what felt like a misfire at high speed, low load cruising. Ended up being a knife edged worn distributor gear. Step on the throttle it would go way, back off and it would come back.

 

[redfishsc]

Well crud, yesterday I noticed a rumbling sound coming from the rear when I let off the gas. I suspect some tomfoolery in the rear end, which is potentially courtesy of yours truly since I rebuilt the rear end myself a few years ago (first rebuild ever).

Assuming she doesn't break down on the way home, I'll pull the diff cover and look for wear and check for slack in the pinion.

Glad I have AAA. I'm 240 miles from home lol.