M109A3 30 MPH Bounce

[wsucougarx]

Took my M109A3 out yesterday. Not sure what it is. Whenever I hit 30 MPH she starts to bounce (has been doing this everytime I take her out). It's more of a rolling bouncing from the rear of the truck to the front or front to rear. She does it during acceleration or coasting. No issues at 27MPH and below and no issues at 33 MPH and above. Any ideas? My cargo trucks don't do this. Is this common with the 109 b/c of the extra weight on the rear?
I've rotated the steer tires to the rear and put newer tires up front...same issue. Please advise

I also noticed the driveshaft flange on the front axle was pretty warm (non driveshaft side). She was sitting at 110 degrees while the others were at 100 degrees. Have anything to do with the bounce? She's also leaking some GL-1 out the seal (just replaced the seal a month ago due to the leak, she still leaks)

 

[BadMastard]

A harmonic bounce is usually an out of balance item, typically a tire. Loose any tire chunks or lug nuts?

 

[wsucougarx]

Yah, I swapped out the steer tires with drive tires. Next step is to increase air pressure to see if that'll do it. If that doesn't cut it, I'll take the driveshaft to the front axle out.

 

[BadMastard]

Can I make an suggestion? Have someone drive beside you, and see what's bouncing. A tire will show on one side, an axle/etc should show on both. Did you drive over the neighbors cat and it's still there? (This is intended as comedic relief, and in no way reflects the disturbed mind of the poster.) Well, maybe it does after all.

 

[zout]

Just my .02 cents worth - when you can drive out of a vibration it is usually tire related. If you cannot drive out of a vibration - it is usually driveline suspension related.

 

[kastein]

Does the road have expansion joints?

The cement highways in Pennsylvania made me feel like I was on the business end of a 10 ton pogo stick on my drive back to Mass in the M54A2. If I stayed at 50mph the rear axles literally bounced, the guy I had following me in my backup vehicle said the intermediate axle and rear axle were bouncing up and down about 3 inches. If I dropped to 48 or sped up to 52-54 it stopped. My hips were black and blue from the seat belt when I got home. The speed I was going resulted in the expansion joints "pumping" the rear suspension at its resonant frequency.

I also get a pretty mean "death wobble" on the front axle when I hit a bump with the passenger side tire at about 20mph, the whole axle literally bounces back and forth. I believe it is due to some play in the steering linkages (working on fixing this), residual looseness in the steering box bracket, the slightly bent tie rod, and the badly scalloped front tires. All things on the list of stuff to fix before I take it for a serious drive...

 

[Barrman]

Check your dog bones on the rear. My Gasser started jumping one day and that is how I knew to start looking for something wrong. Found a broken dog bone. Been almost 2 years now, but I remember thinking "why is the rear of the truck trying to fly?"

 

[jatonka]

These are all good suggestions. I have 4 M109s, 1 with Goodyear 286 11.00R 20 radials, the rest on 9.00x20 non directionals and they all bounce at around 30 mph. My convoy light tubes rattled so bad at 30 that it just about drove me nuttser than I already am on the RT20 cross country in 2008. I fixed that this week for the Alaska trip, rubber taped the inner tube at the bottom of it. Now, no, that didn't fix the truck bounce, I just don't drive at 30 mph. JT out

 

[Wolf.Dose]

I think, Bad Masters said everything about the problem with balancing tires. It is uncommon, however really helps. And one mor thing:check your rims for propper runnig. I saw many US Army trucks with bouncing axles over here. If you look concentrated at the wheels, you will find out, that the rims do NOT run as propper as they should run. They are bend, running out of the round vertically and /or horizonally, simply scrap. And tire are not running round, inpropperly balanced due to"Who cares, just for the Army." allready during production.
If all this is in line, check all your suspension, your shocks, every piece of rubber, ever bolt for propper function / alinement / tightness / cracks / wear / smooth turning (And do not forget the bearings of the rear boggie mounting. Even they might be worn.). You are through all of this. Everything is really fine? The truck should run as smooth as never before.
Wolf

 

[LowTech]

I can tell that the "She Beast" is between 30 -35mph w/o looking at the speedo because she does her little hopping at that speed.

 

[phil2968]

My M109 bounces at 35mph, don't need to look at the speedo going through town!

 

[zout]

I get nothing from mine till it tells me it is time to back out of the throttle and let er settle down to a good road speed. I get no vibration - good steady steering wheel and holds the road tight with little play left or to the right. But eh - I know all my stuff is checked and tight and lubricated and no play in my steer box.

These are 11 x 20 on the unit and I hold 60 lbs pressure in all the tires. And I do have a ton of chit in the box without even sticking anything else in it.

 

[wsucougarx]

Ok thanks guys. Looks to be a common issue w/M109A3's to bounce around. I was really racking my head as this truck had only 1100 original miles on her. When she gets past 33 MPH she smoothes right out for a decent ride. At 30 MPH it feels like I'm driving over speed bumps..literally.

 

[wilber]

Can I make an suggestion? Have someone drive beside you, and see what's bouncing. A tire will show on one side, an axle/etc should show on both. Did you drive over the neighbors cat and it's still there? (This is intended as comedic relief, and in no way reflects the disturbed mind of the poster.) Well, maybe it does after all.

Hey pal, I find that very offensive. I happen to love cats, especially with a honey mustard dressing on a bed of greens.

 

[BadMastard]

Wilber I'm going to have to disagree with you. Ranch is a WAY better dressing.

WSucougarx, Although lots of people have tire bounce, I will have to say that I don't. There may be a couple of factors involved. I have 11's in stead of 9's on it, I've singled out the rear tires, and I run about 55 psi in them.

Now, I strongly suspect what we have is tire imbalance, and here's why. We don't balance our tires.

If I had to guess, and I do, I'd say that if we happen to put two imbalanced tires on the same hub, then we will end up with bounce. Now, if their imbalance is opposite, then it's perfect! Not likely, but possible.

My thoughts? Two possible fixes. I heard that if you put slime in the tire, it acts as a liquid balance. Secondly, we find someone who can spin balance our tires and have them check it out. I'd bet we are WAY off on them, but that's just my guess.

If you lived in utah, I'd say all you have is ice in your tires, and wait till summer. But that's just my twisted sense of humor again.

 

[Katahdin]

I've experienced the bounce, what helped mine greatly was equalizing the tire pressure on each dually with a pair of air hoses going to the same regulator set at 50psi. I used the 1/4" NPT tire hoses with the cheap plastic clamp-on chucks from Tractor Supply, its a little tricky getting the chuck on the inner tire valve stem but its doable. I use the same set of hoses (with extensions) to equalize the tire pressure in the steering wheels.

But yeah, that seems to point to a tire balance/air pressure problem.

 

[stumps]

I've experienced the bounce, what helped mine greatly was equalizing the tire pressure on each dually with a pair of air hoses going to the same regulator set at 50psi. I used the 1/4" NPT tire hoses with the cheap plastic clamp-on chucks from Tractor Supply, its a little tricky getting the chuck on the inner tire valve stem but its doable. I use the same set of hoses (with extensions) to equalize the tire pressure in the steering wheels.

But yeah, that seems to point to a tire balance/air pressure problem.

Hopping at slow speeds on tandem trucks, with locked 4WD axles in the tandem (like all unneutered deuces) is often caused by having different tire sizes between the middle and rear axle. This can be caused by using tires with different brands, sizes, ages, conditions, etc... and by having different tire pressures among the tires.... which changes the circumference of the tire slightly.

The two axles wind up and give a little hop when they release the wind. If the truck's speed is just right, it puts the whole suspension into a rocking sort of oscillation. This can show up especially nicely if the torsion links are worn out.

In any case, having different tire sizes on tandem axles will eat the tires, eat the gas mileage, and rob the power from the deuce.

-Chuck

 

[wsucougarx]

Took my truck out for a spin last saturday. It is the first time since I added the aux 50 gallon fuel tank. Currently she has about 30 gallons in there (45 gallons in the main tank). I noticed the harmonic bounce has really tamed down with the extra weight

 

[jimk]

I have this problem on my 813 (1400x20's). The motion is a resonance. It is being stored/released in spring or tire in frt/behind. The latter is causing the pair to bounce like a teeter totter. It is always 30mph +/- 5mph. 1 tire on each side (rear) has 1/4" radial run-out. Adding max air (95) made it worse. If you jack up one axle you can spin bolt tires (one fwd one backwards). I used a 5 gal bucket in frt (or behind) the tread center and gauged it with a hardware bolt. I used a screwdriver on pail to check the rim flange and tire bead. I am looking for a local re-capper that can buff out some of it.

 

[mightymanx]

Of the 3 I have driven long distance in I would have to classify it as "normal"

My budy in the chace car pulled up super close and watched and the back axle "chatters/bounces" up and down and that seems to cause the 109 feeling.

I am guessing that the suspension works much better when the boxes were loaded to the gills with parts and tools.