98 Ram vibration

[trainman]

I have a 98 Ram 1500 4x4 that has a vibration between 42 & 48 mph. This vibration goes away if I accelerate or decelerate. I was told that it was the torque convertor, but I had it to 3 different transmission shops and all have told me that this is not trans. related. I have checked the u-joints, motor mounts, trans mount, had the tires rotated, and rebalanced. This has me baffled, any suggestions as to what it could be? Thanks in advance

[fredjacksonsan]

So, it's just cruising at those speeds? Very odd. Are there any harmonics, vibrations at multiples of those speeds, like 22 or 90?

[fredjacksonsan]

Additional thought:


How rapid is the vibration? That may give you a clue as to where it is, but you've tried almost everything.....could be an unbalanced driveshaft...have you had that checked?

[trainman]

I have just had the driveshaft checked and it is normal. The vibration also has happened at highway speeds of 55 or 65 depending on the speed limit at the time. This usually occurs when going up a small grade. I still think that it might be the tc, but the trans shops say no.

[1thunder]

have had the rear shaft out of phase 180 degrees just try it it's free and have nothing to lose just a little labour

[fredjacksonsan]

1thunder's idea has worked for me before, so it's worth a try.

When experiencing the vibration at highway speed, is it rapid or slow?

[trainman]

The vibration feels like I am driving over a wash board. The vibration is fast.

[fredjacksonsan]

I'd have to say driveshaft. When the dealer "checked" it, did they say what they did? I've taken driveshafts to driveline specialty places, they've balanced and straightened them to take away vibration.

[BleedDodge]

Loose wheel? Happened to me...

[fredjacksonsan]

It's surely possible. (I tighten my own wheels 99% of the time, though) Worth a check.

[trainman]

I checked all the lug nuts and they are fine.

[fredjacksonsan]

One other test I can think of: when the vibration starts at highway speed, I'm thinking you're in top gear. Try downshifting to the next gear and maintain speed. If it's the driveshaft, you'll keep the vibration and if the TC, then it will likely go away. Play with it a bit to vary the load on the drivetrain, if it goes away try to recreate it in the lower gear.

[trainman]

Sounds like a plan, right now I will try just about anything, even a stick of dynamite.

[trainman]

I tried the downshift idea and the vibration went away. The vibration will not occur below 42 mph. I quess it is time for the stick of dynomite.

[A97]

are you sure that it is a vibration and not a hesitation? i have a `98 with the 5.2 and at about 75000 miles my coi wire broke internally. to make a long story short i did a complete tune up and after 20,000 miles or so later i had a hesitation in the same speed range along with a ticking sound i figured it was spark knock, i replaced my plugs and it went away. since then every 15,000- 20,000 miles i have to replace my plugs the same problem comes back and if i put off the plugs long enough on a grade my check engine will flash giving me a code for cylinder 8 misfire. put new plugs in and im good for about the same amout of miles no one has been able to figure out why after the same amout of time i have to replace the plugs. you may be having the same problem that i have had