Wheel hop at 45 mph

[rwoods]

I have a 1986 M1008 with a 4" (maybe 6") Rough Country lift and Kelly 285/75R 16 tires. At 45 mph the truck shakes as if the tires were not balanced. Tires and wheels are brand new. Had the same "hop" with old tires and wheels so I don't think it is the tire/wheel balance. Smooths out around 50 mph. This is not a front-end wobble just an annoying shake/hop - kind of like this guy .

Any thoughts as to the cause?

Thanks, Ron

 

[Anubis8472]

First guess would be front end alignment.

How did the wear look on the old tires?
Too much toe in can cause a 'hop' as the tires bind and release.

Is this with power applied, let off, or all of the above?

If it's only under heavy accel it could be spring wrap ... lift blocks in the back?

You'll also want to check all your U-joints, it could be front axle U-joints or even drive shaft U-joints binding.

 

[4x4 Forever]

U-Joints out of phase or going out.
The dreaded Kingpin dilemma.
Front crossbar worn.
Bad Shocks.
Bad steering stabilizer.

Those are the first things to come to mind...

 

[cheiser666]

i get that shake at the same speed when I am at 35 psi. If I run the recommended 45psi i get no bounce.

 

[Carpenter]

I've got a similar setup w/ a 6" and 37s and I get the same shake at 47-48mph. Doesn't matter if I'm speeding up, slowing down, or just coasting.

I'll be curious to hear what you find. I haven't had a chance to look into mine yet.

 

[rwoods]

First guess would be front end alignment.

How did the wear look on the old tires?
Too much toe in can cause a 'hop' as the tires bind and release.

Is this with power applied, let off, or all of the above?

If it's only under heavy accel it could be spring wrap ... lift blocks in the back?

You'll also want to check all your U-joints, it could be front axle U-joints or even drive shaft U-joints binding.

Old tires were evenly worn across the tread; no cupping.

Begins at 45 mph. Diminishes as you speed up or slow down from 45 mph. It does have lift blocks in back but the hopping is not the classic acceleration rear wheel hop. The whole truck just has a rhythmic hop at 45 mph.

Front hubs are unlocked so this should eliminate all but the rear driveshaft. I thought maybe with all the GL forklift bent drivelines someone would point to the rear shaft if this was a common symptom of an out of balance shaft. There is no discernible "clunk" in the driveline. But I'll check out the shaft for play this weekend.

Thanks, Ron

 

[allenhillview]

Truck Mystery

Mine does this, all stock truck, can't wait to read as this thread goes on down the line.

Working toward my fix now if there is one?

So far done all the above, except the king pin, its on the way with spring bushings also, (ord) even the shaft has been balanced, front end set, working out a 1/2 degree camber now.

Its just like he said above, nothing bad, truck drives great just this bounce at 47mph, driving me nuts, spent around 1200.00 so far, to much to list, thought I was crazy till tonight when read this thread.

 

[rickycotte]

I have been working in a very similar problem on my stock '99 Dodge Ram 2500 w/Cummins. I have changed to new stock size tires, new stock wheels, new shocks and the hop is there all the time at around 50-55 MPH. I checked with a vibration monitor Android app on my smartphone and pinpointed the fact that the vibration is mostly vertical with some component to the rear/front of the vehicle. Negligible sideways vibration gives me the idea that it is not driveshaft related.

I have been looking on information on how bad brake drums can be unbalanced and I have been surprised to find that this is a very common problem. Since 3/4 ton trucks can have fairly large drums, I suspect that could be the culprit. It is the only thing left which rotates there!

So, my next move is to balance (somehow) or replace the rear brake drums. I will post my results/findings.

Any ideas are welcome.

 

[rickycotte]

BTW, has anyone here tried those Counteract balancing beads that you put inside your tire and allegedly balance your tire/wheel forever? Sounds interesting but would like more info before trying them. I understand this technique is familiar with semi-trailers.

 

[allenhillview]

Want to keep this thread alive so to rickycotte stay with me here?

I'm going to work this week some on front end, soon as parts get here (waiting now) then I'm looking into the drum balance, suspected this also, took a rubber band (large one) put a lifter in one of the flutes on outside of drum and it fell out before I got a reading. So anything in this direction will help, please chime in,Ok.

 

[Cletus09]

BTW, has anyone here tried those Counteract balancing beads that you put inside your tire and allegedly balance your tire/wheel forever? Sounds interesting but would like more info before trying them. I understand this technique is familiar with semi-trailers.

I have not tried them my self personally. However, at work we put them in bigger truck tires that won't fit on our computer balancers. Customers seem to be happy with them from what I have been told. I'm not sure, but I don't think this will solve your brake drum problem. Ask your tire shop.

 

[engineman2]

Bouncing

I have a M1008 with a 4 inch lift on 35's and it does the same thing. At about 46 or so it'll bounce up and down and it smooths right back out at about 48. It does it regardless of acceleration, coasting down or constant speed in that range. I had just been assuming it was the fact that the tires were getting old but it seems it may be a different issue than that now. I'm sure if it was an imbalance in either driveshaft or brake drums it would get worse as I sped up not come and go at a certain speed. As a side note, when I tow the trailer in my avatar it seems to be less apparent. And, when I load up the truck and trailer with firewood it goes away. Strange issue...

 

[197thhhc]

Drums are not very hard to balance. We do it all the time on a tire balancer. Its a very common problem.

 

[wallew]

I just finished replacing the U-joints on my 1991 Suburban - and with the help of my buddy Randy, he noticed that the rear yoke at the diff was actually slightly loose (you could wiggle it very slightly). So we removed the nut, cleaned the threads on both the nut and the bolt, applied red locktite and then tightened her down to spec. AND replace both front and rear u-joints.

It's a 4x4 truck and it used to vibrate at about 60 mph up through 70 mph - NOW I have found myself having to watch my speed because it no longer vibrates at all.

I've also had the similar issues when I bought my M1028A2 dually and it also vibrated at about 55 - 60 mph - the drive shaft was not bent or dented, it was just out of round - so a new drive shaft later, it's also smoooooth all the way PAST 65 and I gotta be paing attention so I don't over rev the engine.

 

[allenhillview]

Drums are not very hard to balance. We do it all the time on a tire balancer. Its a very common problem.

Can you tell us the procedure used to do this balancing of the drums.

 

[natem]

Spin your tire/wheel on a tire balance machine, you might be surprised at how out of round your wheels are. When we mounted my 285's we clocked the tires around the wheel till we got the best balance and run out.

I have never tried the balance rings, but I always use the balance powder in the tires in my work trucks (10X22.5).

 

[allenhillview]

My wheels have been checked on the truck with no tire, with dial indicator.

Also with tire on for run out, clocked tires also still this 47mph hop.

Many tire shops don't have LUG centric balancing eguipment, they use the center of wheel with the cone shape device to center wheel on machine not lugs, they are hard to find.

 

[mudman]

It sounds to me as a "Rotating Mass" problem. Four things that are rotating at this speed..."Tyres"...Now with at said..Balancing??, Bent wheels, or my favorite, the bead to wheel line up. if the bead to the tire is not set right on the wheel...all **** brakes loose. Not a drive line, not a loose lug nut, think about what is moving when you are driving at that speed. You can and I have seen it, get bad tires from the start. good luck!!

 

[rickycotte]

I will be performing further testing this Thursday. Yes, I found out that brake drums may be balanced on a tire/wheel balancing machine. It just has to be set to static mode to perform the task. I will find out if my local Pep Boys has such setting on their machines.

I am almost convinced that, in my particular case with my Dodge 2500, the drums are to blame since I have changed now the tires for the fourth time and this last time I went thru the pain of purchasing stock steel wheels for testing. I even changed the shock absorbers.

These drums are fairly big and heavy. My rear suspension is stock and it is not anything to awe at. Honestly, I find it somewhat flimsy and very prone to vertical movement from any unbalance.

Lastly, a phenomenon called resonance might be setting on this particular arrangement of leaf springs, rotational speed, unbalance acceleration and an unloaded truck bed making it more noticeable. However, if indeed there is an unbalance, it will be there even if you do not feel it at higher/lower speeds.

I will keep posting until I find the cure!

 

[allenhillview]

Thanks rickycotte, So far we have done alot in this area, spent a ton of money. Its like unless we find the problem were not very good at anything. Funny huh.

Guy above talks about bead line up, we have moved tires and wheels around trucks so many times its un-real, taken tires off each truck put on others, taken same size tires (235-85-R16) off our cattle trailers, used them, nothing, you're not going to get

unlined bead that many times with exact same results. We have my truck,1008 , 92 w-250 with 4500lb axles doing the same thing, currently working this out on both.

We are considering a set of centrimatic balancers, have you read anything on those yet? Se Ya later on this week.

Also tires are all in good shape with three manufactures, michenlin, uniroyles,generals, all good running tires on that cattle trailer.

We have about ruled out tires since we've moved stuff so much, created so many different combinations.