98 Ram vibration

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

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

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?

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.

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

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?

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

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.

Loose wheel? Happened to me...

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

I checked all the lug nuts and they are fine.

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.

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

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.

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

Yeah, how many miles on your truck, trainman?

Based on the vibration going away when you downshift, it sounds like it may be something in the lockup that's not staying engaged. Your initial posts said at highway speeds and up a slight grade, which is where your TC would disengage lockup to get a bit more power to handle the hill. I had an AT vehicle that shuddered up hills or in the 45-50 range while accelerating in 4th; I left it in 3rd unless I was going to go on the highway and be above 50 mph for awhile.

It diffently is not a hesitation, you can hear the vibration and it sounds and feels like I am driving over the rub strip on the side of the highway. I have no codes deplaying and no check engine light.

The truck has 68000 miles on it and for what my 2 cents are worth I too think that it is the TC

It does sound like a mechanical problem in the TC. Hopefully you have the 7/70 powertrain warranty....and can take it in!

Unfortunately no, my warranty ran out at 60,000 miles. I do have another question though as to what the powertrain contol module does?

Bummer about the warranty.

I'm not the resident expert, but I believe the PCM is responsible for when/how the transmission shifts. If there's a problem in there about the lockup, it could conceivably cause the problem, but again I'm not 100% sure. Hopefully one of the folks that's good with auto trans will check this thread.

Not sure but your original post did say on acceleration and deceleration is this correct just trying to rule different things out such as possible missfire with a partially plugged injector very common on these trucks and you get the same sympton but only on acceleration and worst in o/d and did you try rotating your drive shaft 180 degrees i'm urging you to try this as we have seen this cause the same type of problem or pull all your plug wires off of the distibutor cap and check for heavy corrosion on the cap towers i realize your engine lamp is not on but your pcm is probably not counting miss fires for different reasons such as improper fuel gauge readings or did not learn addaptive numerator these things defeat miss fire counters and will not turn your engine lamp on eaven if you took the plug right out and drove the truck did you get the vehicle checked on a scan tool by a known good tech that knows the values of the sensors or voltages because some guys will only know to read codes and could not determine a fault ahead of time as the threshold of some sensors are so great that a sensor could be faulty but not turn the engine lamp on because it did not cross the required voltage to turn lamp on i can go on for days on this but i think you get the ideal and i don't want you to spend a bunch of cash on something that may not be required but only trying to help because Dodge is my bread and butter for 30 years and i thik these are about the best trucks out there and the more you like your truck the better job security for alot of us techs because word of mouth is excelent advertising

Like I said, you needed a resident expert. :)

Thanks 1thunder.

just hope i can help out i guess you know how hard it could befredjacksonsan to diagnose this type of problem without seeing or driving the vehicle it could be anything posted so far and the trick is to try to fix efficiently

The vibration occurs between 42 and 48 mph, and occasionally at higher speeds. The vibration goes away if I accellerate or decellerate. I have been driving the truck the past few days with the OD off and the vibration has not occured at all. One of the trans shops that I took it to did a scan and found nothing. I have had the driveshaft checked and the cause of the problem is not there. If the problem is with the PCM then it is covered under the warrenty for 80,000 miles. I will check the plug wires and cap for corrosion and go from there.

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
Change you plugs and wires and cap and rotor

I changed the plugs,wires,cap,rotor, but the vibration is still there. I have noticed that with the Overdrive off the vibration does not occur. Any suggestions as to where to go from here, maybe a stick of dynamite would help.

Change you plugs and wires and cap and rotor
Alright the next thing I would do is look into your torque converter. If its only doing it in overdrive mybe your clutch pack in the torque converter is bad. Any shop will have the computer to check this out and to tell you if that is the problem...

I took the truck to another trans shop and yes it was the TC. This seems to be a typical problem for Dodge. Thanks for all input and help. Have a good day.