Front end Chassis Issue, 97 Ford Super Duty

[jeffwhite]

Since you guys ALWAYS ( what a clever bunch) have a fix for everything.....I have a 97 Rexhall Airbus (30')with the Ford Super Duty Chassis F53, 30K miles. I get a rumbling between 25-40mph. Clears up at higher speeds. Definitely feels like the front end area. Truck mechanic said I have a noticeably out of round tire that was also wearing badly. He then checked out the RV as I had just purchased it, and replaced the driveshaft support. Took the RV to America's tire and they replaced the front 2 tires(MichelinXPS), as they were both old anyway. Spin balanced. Still rumbles. Mechanic rechecked, can't figure it out. America's Tire rechecked the spin balance, all good. Still rumbles. DW drove next to me and said the tire wasn't 'wobbling". Looked fine. Really feels like it's a balancing issue, but doesn't seem to be. Spin balance should have shown a bad rim, right? When rumbling, if I put it into neutral, no change. Accelerating, decelerating, coasting, neutral coasting...no change.
The rumbling frequency is similar to riding too far to the right and hitting those "rumble strips". Any ideas? jeff

[Ductape]

I've had several vehicles that required spin balancing and tire trueing on the vehicle to cure vibration. Sometimes the vibration may feel close, but may in fact originate from the rear.

Driveline out of phase or misaligned possibly.

TCC ruled out by testing in neutral and coasting.

You may need a truck shop that can run it on a chassis dyno or on a lift at speed to find the cause.

[jwmII]

When all else fails. Check for worn U joints. That chassis probably has a 2 part drive line since you noted that the center bearing had been replaced. Also check the drive line halves where they make up for timing marks. Some are marked, some are not. If marked the idea is to assemble the drive line with the marks matched.
If there are no marks try assembling the drive lines 180 degrees from where they are presently assembled. If this is the problem you may have to change the driveline around a couple of times to smooth things out.

[Golden_HVAC]

How about the rear tires? How old are they?

It sounds like your front set was pretty old, and where already changed out.

Sorry to hear about your problems. I also have a 97 Bounder 30E model, F-53 and 460" engine.

The transmission filter also is the 1996 4X4 F-350 with the same engine. Brake pads also fit the F-450/550 of the same timeframe - 1996 -1997 used the same pads . ..

Good luck,

Fred.

[Wills6_4_Hemi]

Tie rod end. jmo

[fivejackie]

We ran over a truck tire, after that we had the same problem. RV had a thumping at slow speed and cleared up after 45 mph. I also thought as you that it was something in the front wheels. Ford dealer found the problem, a bent drive shaft. Ford replace the exhaust system which was also damaged and the drive shaft for $2200. Auto Club paid it all.

[John_Joey]

jeffwhite wrote:
..snip... Could it really feel like it's in the front end if the Drive shaft is out of balance? jeff

Never seen it or used it, but there is a tool/device they put on the dash of the car to help determine exactly what you are having. Based on the vibration it is smart enough to point the tech into the correct area. Yes, the drive shaft is one of those areas that the machine can measure.

I'm guessing harmonics is what is happening and I think that is what the mechanic thought also. Whenever you have a two part driveshaft you can not rule it out. YMMV

[dodge_guy]

Yes, a TCC would make that type of noise. Try touching the brakes (riding the brakes) and see if it goes away.

[jeffwhite]

TCC: Would this make a vibration like I described? Wouldn't it go away when I let off the gas, or shifted into neutral? jeff

[topflite51]

dodge guy wrote:
I would lean more towards drive line. It may be a bearing in the trans.
Now that I think about it it sounds like the lockup torque converter may be slipping! I had a 95 Explorer that had a similar issue as you describe and it turns out the TCC (torque converter clutch) was slipping. At certain speeds it goes into partial lock up and the PCM lets it slip a bit, (yes they design them this way).The fluid was dirty so I flushed it. The problems was fixed and I got another 60k miles out of it before it lost O/D.

Check your trans fluid and have it flushed with Merc V. It may very well fix your problem.

X2.

This is where I would be looking.

[wolfe10]

While you mentioned tire balance, did they check RUN-OUT with the wheels mounted on the coach?

If not, easy to do yourself: Use jacks to get front wheels off the ground. You are not crawling under the coach, so jack/safety stands are not required.

Use a 4X4, metal angle or similar that you can move up to the tire as you slowly rotate it. You want to check both "front to back" and "side to side" of the tire.

As you slowly rotate the tire, move the "measurer" in toward the tire until it just touches at the part of the tire with the most run-out. While holding the "measurer" firmly in place, rotate the tire slowly until you find the place with the largest gap between tire and "measurer". Use feeler gauges to measure gap. You really want run-out under .035". At .050" you will really start to notice it.

[dodge_guy]

I would lean more towards drive line. It may be a bearing in the trans.
Now that I think about it it sounds like the lockup torque converter may be slipping! I had a 95 Explorer that had a similar issue as you describe and it turns out the TCC (torque converter clutch) was slipping. At certain speeds it goes into partial lock up and the PCM lets it slip a bit, (yes they design them this way).The fluid was dirty so I flushed it. The problems was fixed and I got another 60k miles out of it before it lost O/D.

Check your trans fluid and have it flushed with Merc V. It may very well fix your problem.

[jeffwhite]

Wheel bearings were checked, I would also think that there would be other typical bearing symptoms like sonically in turning corners, physical play etc. All checked. Driveshaft was a thought of mine, though they check universals (my first thought when tires weren't the problem). Could it really feel like it's in the front end if the Drive shaft is out of balance? jeff

[John_Joey]

I would pay attention to the drive shaft more. Good call on his part about the support, but it might be the drive shaft itself.

[DrewE]

Wheel bearing? though I would have thought that someone would have checked on them in the midst of all this checking and head scratching.