something is wearing out... 60-65mph highway rumble

[N2BRK]

Hi all -

Recently I developed a problem, and I'm looking for advice please. My truck starts to shake like I'm driving over rumble strips under light throttle at about 60-65mph. If I chop the throttle off it goes away. If I drive faster or slower it stops.

So far I have made sure that the tires are road-force balanced, and had an alignment done. I'm not sure what's wearing out... wheel bearing? U-joint? I greased the front end (it was fine) and jacked and yanked on the wheels at 12 and 6 and 3 and 9 o'clock with no odd play or noises.

I'll be using it pretty hard Friday evening and all day Saturday, and I'd be happier if I had this licked by then

Any advice would be appreciated!

Thanks!
Wally

 

[N2BRK]

could TCC be doing this too? Or would it keep doing this at higher speeds and not disappear as I go over 65?

 

[N2BRK]

one last thing; not sure if this is related but I'll fix it tomorrow. I noticed that the lower bushing on my driver's side front Bilstein shock is worn out. WHen I grabbed the shock it had tons of play and clunked. Maybe it could give a little wheel shake, but not this right?

 

[Big Block 88]

Does the noise get worse while turning at highway speed? 4wd make it worse?

 

[N2BRK]

That's on my list of things to try tomorrow. For now, I don't know. TNX!

I am reading about a lot of folks having this complaint when the ujoint at the axle to rear end is going. It sounds exactly like my problem. Hopefully that's it... would be simple to replace.

 

[MarkBroviak]

What are you running for tuning? If you log it and see this vibration in the log then it is a tuning issue. Unfortunately this seems to be an lmm thing as I personally saw two lmm's this week doing the same thing. Go log it and see if it shows up in the vss and pulse and calculated main rate mm3. Report back!

 

[N2BRK]

I am having some tuning issues. I put in 40 overs and I'm having a lot of trouble trying to get the tuning right. I didn't give it a thought when this popped up... hmm.

I can log it tomorrow with the v2 and see. BTW - my long-term plan is a built trans and your 3794 Stage 2 VVT!! I hope to be about 2 years out on those goals

Thanks!!
Wally

 

[Harbin_22]

Since the day mine was tuned, it did some weird stuff at 55mph in 6th gear. I changes the shift points around so it will downshift to 5th at 55 and haven't had a problem since
Seen quite a few lmms like that.

 

[gmduramax]

Frame beaming? How are your rear cab mounts?

 

[Awenta]

It's mad at you for keeping such low rpms

Sent from my SM-N910V using Tapatalk

 

[MarkBroviak]

Like I said, this is something that just popped up in the last couple of weeks and had me pulling my hair out trying to figure out what was going on. Both trucks I have are over grown trucks, one has big semi wheels and tires the other is on 37's and big lift kit. Both trucks had some tire shake so it was very difficult to pin point this issue but once I did it sent up a red flag. Both trucks are big power and over sized injectors. I have not seen this on stock fuel trucks yet and it seems to only be an LMM thing. Yet another LMM querk it seems.

 

[N2BRK]

I'm on 285/70/17's, so not huge but oversized.

My truck is running LBZ tips honed 40 over. I am unsuccessfully trying to get it to run "right" in the range of 2000rpm but it seems fine at cruise. I'll get that log done very soon today and post it up!! Thanks!

 

[catman3126]

What exactly is the "frame Beaming" I keep hearing about?

 

[N2BRK]

a little different; covered that with new GM cab mounts.

Ok, I did a log. There's a stretch in the log at 61mph where it was shaking like mad in the truck

I also tried (didn't log) where I used the DTV tool to shut off the TCC when it was doing it, and it stopped. I don't know if that's just confusing the issue though.

I'll attach the log... thanks!

 

[MarkBroviak]

Yeap, looks almost exactly the same. If you highlight a good section of the log file where it shakes and open your tune file it will be highlighted in the tune. What you will want to try is to back the timing down to 2.2-3.5* of timing in that range and bump the rail pressure up some in that area. Also smooth the pulse width table out in that area and see if that doesn't calm it down for you. Let us know if it fixes yours.

 

[N2BRK]

I got home and made up the changes that you recommended, into my base tune. i loaded up and took the highway to take my daughter to tap dancing (yep, I'm a DAD first!).

This was a very short trip, but I was able to see the new tune was holding 3 degrees of timing at 11k psi. The truck was still acting up. I switched to tune 2 and back to the base and there was no difference except the added timing etc.

 

[N2BRK]

Mark is right. He pm'd me to put the stock tune in. For some reason the truck is ok running down the road at -1 or -2 degrees of timing but then out of the blue it starts adding timing and then the rumble comes up.

I am on the road now (stopped). I had it happen. I got off the highway and flipped a uturn. It went back to -1 or -2 degrees and didn't shake.

Crazy LMM's!

 

[The Neens]

Nice troubleshoot Mark!!! :thumb:

 

[Chevy1925]

What exactly is the "frame Beaming" I keep hearing about?

It's when the truck hits expansion joints in the highway and causes the truck to bounce. It's a combo of things that cause it, worse of it happens in cc/lb trucks unloaded. With the stiff rear leaf packs, only so much shock will get the suspension to move right, from there it transfers into the frame and to your seat. Cab mounts help fix it but unless you do a air ride setup or run softer rear leafs, you won't fully get rid of it.

I ve combated mine with a deaver mini pack and the rancho adjustable shocks. Stil has some so at some point I'll be hooking up with Ben (dmaxmafia) to do a link/air bag setup

 

[Big Block 88]

Wow mark! A true badass. I would have never even guessed man