Vibration when hit 32 mph

johnhjohnson2 · May 21, 2018

Hey guys I have a strong vibration in truck I can't figure out. It happens when I hit 32 mph and disappears at as I get to 35 mph. It also hits again if I get truck to 64-65 (with a breeze going down hill lol). It has been that way since day I got from auction. It is precise enough that I know when I am going exactly 32 mph without looking at speedometer. Since then I have replaced all 4 tires, put on centramatics (did not help at all), replaced all ball joints upper and lower, replaced all tie rod ends front and back, replaced pitman and idler arms, new alignment, all new shocks, replaced transfer case, and had driveline inspected at two shops. The truck obviously rides much better but the vibration is still there. Any ideas?

orgnal · May 21, 2018

johnhjohnson2 said:
Hey guys I have a strong vibration in truck I can't figure out. It happens when I hit 32 mph and disappears at as I get to 35 mph. It also hits again if I get truck to 64-65 (with a breeze going down hill lol). It has been that way since day I got from auction. It is precise enough that I know when I am going exactly 32 mph without looking at speedometer. Since then I have replaced all 4 tires, put on centramatics (did not help at all), replaced all ball joints upper and lower, replaced all tie rod ends front and back, replaced pitman and idler arms, new alignment, all new shocks, replaced transfer case, and had driveline inspected at two shops. The truck obviously rides much better but the vibration is still there. Any ideas?

Only thing I can think of is transmission. At 32-35 the transmission might be trying to shift from 2nd to 3rd. I don't know all the internals of the HMMWV's 3 speed transmission to speculate what part might be the issue during the shift from 2nd to 3rd.

McReddy

Dock Rocker · May 21, 2018

My guess would be that you have a driveshaft that is out of balance.

You need to take it to a driveline shop that can put it on the rack and run it up to speed the shutter happens and observe where it’s coming from.

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johnhjohnson2 · May 21, 2018

I have had two different shops look at the drive shafts. The last shop told me the rear drive shaft was out of phase but I have been told that the two rear drive shafts only got together one way and that is normal. I haven’t taken it to a driveline shop I will try that out. Thanks.

lowell66dart · May 21, 2018

If you had a buddy with another HMMWV shaft to try that would nail the driveshaft question quickly.

Milcommoguy · May 21, 2018

Not sure? Remove it and run out on the front or remove front and run the rear. One or the other could tell if it's a drive line / carrier bearing, extra wobble issues. A little bit of work could point to the problem. And maybe discover something else while crawling around under there. There's always something.

Bulldogger · May 21, 2018

The others have covered it. I was going to say hubs, control arms, crossmember, or propellor shafts, but other beat me to it. Am replying to subscribe and see what solution you end up at, hopefully. Best of luck.

Bulldogger

johnhjohnson2 · May 21, 2018

I would think it would have to be something rotating since it presents and dissappears in such a tight window of speed. As soon as I hit 32 mph I can see brush guard wobbling like crazy. As soon as I hit 34-35 it goes away.

Thanks for the help guys.

tomcata3 · May 22, 2018

My buddy had a similar problem with his HMMWV, he took his truck to a large truck tire shop. It turned out his tires were slightly out of round they put each tire / rim on a machine and it cut out the high spots. Then they also balanced them. He said it rides great now

suzukovich · May 22, 2018

Sounds like tires need to be balanced.

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gringeltaube · May 22, 2018

suzukovich said:
Sounds like tires need to be balanced.

x2!
I don't think a propeller shaft out of phase or balance would cause the whole front end/brush guard to wobble "like crazy"...

suzukovich · May 22, 2018

I would also check the idler arm. They are notorious for going bad.

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johnhjohnson2 · May 22, 2018

The idler arm has just been replaced. I have not had tires balanced. I have tried but haven’t been able to find a shop to do it locally including big truck shops. That’s why I bought the centramatics. Tires are wrangler mt’s from surplus w 90% tread. I would have thought the centramatics would have helped at least some but I don’t think they made any difference. But w surplus tires I’m sure there is a reasonable chance the issue could lie there. Only thing is I just replaced them and had same issue w previous tires.

suzukovich · May 22, 2018

Is there any play with the steering. There is a remote possibility the steering box is getting worn out..

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johnhjohnson2 · May 22, 2018

The steering is great since I had pitman and idler arm replaced.

Milcommoguy · May 22, 2018

And now the rest of the story. "Paul Harvey" How easy it is to go down the rabbit hole when learning the tire were not balance in the first place and the magic of the Centramatic are not matic or magic. There is a lot more mass in the rotten 37 inchers and bent rims, on all four comers going places not necessarily in the same directions. Rock and roll.

johnhjohnson2 · May 22, 2018

The tires and rims are in great shape. Agreed that’s a lot of mass for the centramatics to overcome if greatly unbalanced. But there are a lot of guys rolling on rims and wheels like mine that don’t have the same issue and I would think the centramatics would at least have some sort of effect on an unbalanced tire. I hope the issue is as simple as an unbalanced tire i was just hoping someone else had combated something similar in the past. The trouble shooting manuals all seem to point to bad idler arm which I have already addressed.

Thecaptain · May 22, 2018

Do you happen to know if you replaced your pitman and idler arms with the moog problem solver? If not, the non problem solvers are known to fail quickly. It’s a pretty easy diagnostic to see if those components are (still) good.

Action · May 22, 2018

At what speed to the Centramatics need to rotate to become effective? Meaning, having the c-force push the weight where needed and not just sitting at the bottom.

johnhjohnson2 · May 22, 2018

Well I’m not sure they do become effective lol. But I believe they claim the low 20’s on their website. I purchased them as I was having a lot of trouble finding a shop that would balance my tires and I had this issue which I thought at first was likely an balancing issue.

Vibration when hit 32 mph

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