Intermittent (speed depending) rumble/vibration

[porschpow]

I have tried to isolate it and had long since forgot about it (wasn't noticeable), but i notice that when i drive between 60-66 mph, under light throttle i feel vibration and rumbling in the rear (my butt feel this-not through the steering wheel)

Here's my thoughts:

Rear Wheel's not balanced (But why would it do the rumbling/vibration only under light to moderate throttle)
Drive shaft not balanced (Haven't observed it- Need to get it up in the air and have someone "drive" the car at that speed)
Tranny Mounts (Also seems inconsistent)


Anyone else been through this. This makes my 75 miles commute to work a little less undesirable

[sly]

check the tires for proper inflation and possibly get them re-balanced. If that doesn't sort it, then start looking at the spendy parts. May also be flat spots on the tires if the car has sat very long or you've locked up the brakes stopping for roadway shenanigans.

[porschpow]

Tire pressures are good and they were balanced. Now I will balance them again, but it wouldn't explain why it happens when i give it light to moderate throttle, its smooth when I let go of the throttle

[sxcpotatoes]

U joints? Can cause bad vibes too.

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[porschpow]

Yes!, I just had both U-joints replaced. I am sorry I forgot to mention that.

This happening most notably during throttle is what leads me to believe it had somethign to do with the driveshaft

[sxcpotatoes]

I had a coworker get both u-joints replaced on his ranger and one of them failed! Driveshaft jumped out on him and left him on side of road. Worth having the shop recheck them and make sure they're holding grease, etc.

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[porschpow]

I personally took off the shaft and brough tit to a shoip to have them replaced. I believe they were MOOG parts.

How can you check them? to make sure they are good. I am not sure if I bought the greasable ones

[nfldfordltd]

Just turn the driveshaft by hand and observe the joints for play/slop. The shaft will turn a little from the backlash adjustment of the rear axle, which helps in assessing the u-joints. Look at the driveshaft and see if there are balancing weights close to the ends or if they are missing. Mine are missing because I knocked them off by accident when I was changing the u-joints. I have seen people put hose clamps on over the driveshaft so the screw part is where the weights used to be for a better balance. I get a little bit of vibration as well and was thinking about trying the hose clamp trick to see if it helps.

[86VickyLX]

Did you balance them after I drove the car? I noticed a vibration at those speeds as well.

[porschpow]

no, John. I had them balanced before I brought it to you

[gadget73]

Check the trans mount and the trans crossmember out. If the mount lets you move the back end of the trans around, it won't be helping. Possible its letting the trans move to one side, causing the U joints to bind somewhat. If the trans crossmember is rotted at one end, you'll have similar problems. Just make sure it wont pick up off the frame, and that there is metal past the big bolt that holds it all together. When I replaced the trans in mine the first time, instead of a bolt hole in the end of the crossmember I found a big letter C and a pile of rust where the rest of the thing should have been.


Driveshaft balance problems will also cause very similar sorts of issues. I had a bad one in my car, and it vibrated like a cheap hotel bed in the 75+ range.

[L1011tristar17]

Interesting... my car has been having some of the same issues. I also got the u-joints replaced and had the tires balanced less than a year ago. Differential fluid was also changed in the last month.

[porschpow]

I will check out the mounting for the trany. Thanks