Vibration at 75km/h, not u joints or tires what next?
 

1993 F150, ext. cab flareside, 5.0L auto, 199 565 km:

Here's the problem: Starting at 75km/h a vibration starts, it increases intensity untill around 80 then eases off at around 90 when it then turns into a low vibration that continues on past 95, 100 ...but it isn't a hard vibration at the higher speeds.

I have had all 3 u joints replaced the rear one was really shot and the middle one was only slightly better, I think it lessened the problem a little bit but it still does it, and the carrier bearing was inspected and they said it was fine as well. All the tires were rebalanced too, their new. They said it now might be the rear wheel bearings, can you tell just by spinning the tire and listening or do you need to disassemble stuff? Oh, and you feel the vibration through the seat and the floor but not really in the steering wheel? Any opinions you guys have would be great, I'm sick of spending money and not getting the problem fixed. Thanks

Hi speed vibration can be caused by several things. You covered the most obvious ones. Warped disc brake rotors cause significant vibration. Bad suspension bushings cause them also. Weak suspension components like shocks can add to the problem. It's always a challenge to find them when it is not the most obvious choices. Good luck.

my dad used to have brand new tires lathed to make them truely round....you'd be surprised how out-of-round a new tire can be. Anyways it always helped his F-350

forgot to mention....he always got 10,000 miles more out of a set of tires than I did with the same truck

Check the alignment...warped rotors usually are felt when applying the brakes...

Check your motor and trans mounts. Also check torque converter bolts, and see if weights are still on flywheel.

I have the same problem with my F150 except it occurs from 70 - 75 MPH only. Not sure how that compares to km/h.
I have a one piece driveshaft. Replaced u-joints and had the shaft balanced but still no change.
I have ruled out tires and wheels since I have rebalanced them all and have rotated from back to front. It must be something with the rear drivetrain because front drivehaft & axles are not locked in while the vibration is there. I can feel it throught the gear shift and also through the clutch pedal.
Someone posted on this subject about "road force balancing tires" but I still think it is something else.

How do you check the tranny mounts?

vibrations
 

have your rims checked to see if one of them is warped. i have the same problem and it is caused by a warped rim. of course i have a set of obscelete chrome rims. i am also looking to sell them if anyone is interested.
holla:-X06

My last truck was a 95 f150 6 cylinder 5 speed. I too started to get a slight vibration at around 75 kilometers/hour. I spent a year and about $1500 to finally find out it was due to a problem with the rear end gears. (posi) I never did fix it, just sold the truck and got a bigger one. this too has vibration problems that I'm working on. Good luck

It might be the driveshaft itself. A dent, or a lot of dried mud caked on one side can cause the shaft to be out of balance.

Clean off all the junk on it and see if that helps. If not, you can take apart the front u-joint, rotate the driveshaft 180 degrees, and reinstall.

Only change the phase of one u-joint, front or back, not both. More than likely you'll find the vibration goes away.

If not, your driveshaft might need to be balanced. Might also be why your u-joints were shot in the first place.

Mine is fine until I hit about 50mph, vibrations kick in something fierce, then lessons around 70mph. Rotating the driveshaft 180 degrees solved my problem, didn't have to have it balanced.

The reason why some of us experience these vibrations at different speeds is due to the gear ratios and tire diameters being different as well as the shaft lengths. I have a crew cab, thus I have two shorter shafts.

Hope that helps.

I have seen postings about screwed up driveshafts before, the driver had new everything in the driveshaft and it turned out to be lousy technicians. They looked at the driveshaft a second time and finally found the problem. Don't eliminate your shafts, ujoints, carrier bearings, just yet.

I think your problem is transmission/drive component related. If you don't feel it in the steering wheel, then it must be the back rotors/drums or tires or drivetrain.

Belts can break inside multi ply tires and give you a wobble, this might have been eliminated if a good tire tech has checked the wheels carefully.

If you have any aftermarket brake disc rotors or drums, then have them replaced with Ford parts, I have seen too many Pep boys, etc. etc. rotors and drums fail way too early. They easily warp and score, especially if you are also using bozo brand pads. Use ford pads or equivalent.

[QUOTEIf you have any aftermarket brake disc rotors or drums, then have them replaced with Ford parts, I have seen too many Pep boys, etc. etc. rotors and drums fail way too early. They easily warp and score, especially if you are also using bozo brand pads. Use ford pads or equivalent. [/B][/QUOTE]

What about us cheap sumsabitches who get used rotors out of the junkyard?

<grin>.

But I agree about pep boys remanufacturered brake parts, would make me nervous too.

I have one that is intermittent at about 75 mph. I thought it was the tire (cause it was worse on the front, till I rotated em) but now have different wheels and tires on the truck and still have it. I suspect the U-joints but asked the local front end shop to check it when they were doing the inspection and they could not find anything.
Suppose it is the rim?? The only reason I say that is that these rims (oem steel) had a vibration when I took them off more than a year ago. The tires were balanced.... but a 'warped' rim would not always be caught by balancing. I guess I am lazy or I would swap out the rear tires/rims and see if that made a difference (but I don't know which tire has the bad belt! and my compressor is 200 miles away)
Anyone ever hear of a drive shaft loosing the balance (welded on weights)??

They can lose their balance if they get slightly bent or dented. I suppose the weights could fall off too. I bought my truck with a slight vibration at around 30, 55, and 75 mph. I put up with it and didn't really notice it anymore till I changed my carrier bearing, which made it much worse. Balancing my driveshaft fixed it, and I couldn't tell anything was wrong just by looking at it.

It could be a broken leaf spring too, or a bad shock. Driveline vibration at that speed would be at a higher frequency than a tire vibration. Have you hit any potholes lately? How about a puncture? Water can get into a puncture and cause steel belting to rust and delaminate.