I have an irritating vibration coming through the drivetrain somewhere. It has done it ever since I bought the truck in August. It only occurs between 65 and 75 mph and goes away completely when either above or below that range. It is most noticeable when deaccelarting through that speed range. I can hear it as a droning sound and can feel it with my hand on the gearshift or through my foot on the clutch.

I have ruled out the engine because it is not dependent on RPM and it still vibrates after I push the clutch in.

I thought it may be a wheel or tire but I now have new wheels and the rears got moved up to the front. No difference between the old tire/wheel setup and the new.

I thought for sure it must be the driveshaft. Had it balanced at a good shop and they also put new joints in. Same problem after all that too.

I have tried rotating the driveshaft 90 degrees to the next holes on the differential yoke. Doesn't seem to matter where it is.

I have noticed that there is slight side-to-side movement in the shaft where it goes into the rear of the tranny. The driveline shop said some play is normal. Is this true?

Also the dealership that I bought the truck from said they replaced the seal on the front of the differential. Is there a way they could have screwed something up when they did this? I'm not familiar with how to replace that seal.

Any suggestions are appreciated.

Dan

 

I have kinda the same problem but between 30-40mph on my 88 f150 4x4 302 aod. I have also ruled out drive shaft. I'm thinking because it's 4x4 could it be the shaft or ujoint on shaft from trany to the front ?

 

yea... i have the same problem in the same speed zone with my 1992 straight 6 f-150... i've posted on this and i got a little bit of advice.. saying that it could be anything from the transmission to a bent rim to a bad tire.. hope this helps a little bit.

 

I had a similar problem with a 73 F100 I restored. After spending $1,000s on this truck to restore it had a vibration at about 50 - 70MPH that made driving a disappointment. I tried everything, balance drive shaft, new rims, tires, etc. I had two problems that when fixed stopped the vibration. First, I had the tires road force balanced. It cost more but it uncovered a defective tire that regular balancing did not catch. The computer running the machine also told which tire to put at which corner of the truck to make it run the smoothest. After that it was MUCH better but not perfect. I then consulated a mechanic specializing in vibration issues and he worked with adjusting the angle of the drive shaft from the trans. to the rear end. He made several shim adjustments and after about 3 tries the truck was as smooth as a baby's bottom. It was great! Hope this helps.

 

What is road force balancing?
I was thinking that my problem wasn't a tire balance because the vibration didn't change when the rear tires went to the front. Maybe it is balance after all.

I know my hubs are working so that should rule out the front driveshaft since it isn't spinning.

How did your mechanic adjust the d/s angle? Where do the shims go?

I did have a similar problem on my Ranger but that was due to the lift. It had a two piece d/s and I had to adjust the height of the center carrier bearing.

 

Road force balance is a computer operated machine that you place each tire on and looks similar to regular balancing but the tire rotates much slower and a roller applies road pressure to the tire as it rotates and the computer monitors the process. If a tire has the least bit of irregularity it will catch it. If the tire is not to bad the machine will tell you where place that tire on the vehicle to get the least amount of vibration. I had one tire that had a cord problem that would have never been caught otherwise. The draw back is that you may have a hard time finding a shop that does this and the cost is about $25 a tire. If your problem annoyed you as much as it did me the cost will be worth it.
On the drive shaft, it was a two piece affair and the shims were placed under the carrier bearing. The road force balance was the thing that made the biggest difference for me. Good luck!

 

I would almost be willing to bet it is an axle bearing. Jack the truck up and put the rear on jack stands. Remove the tires and put the lugs back on backwards to hold the brake drums on. Run it up to the problems speed and see if it still vibrates. If the front seal was replaced I bet the rear end was run low and the axle bearings are the first to go. my 2 cents

 

Thats a good idea. I'll try with and without the wheels on.

Could they have messed anything up when the front seal was replaced?

What's involved in changing wheel bearings on an 8.8 reae end?

 

They could have overtightened yoke messing up the pinion adjustment how it meshes with the ring gear. Axle bearing are easy on a 9" but I have never done a 8.8 before. I just swapped the whole rear when I did it.

 

I spent allot of money trying to find the vib in my truck. The road force balancing found the tires to be defective. Spend the extra 100 bucks for the road force and take the tires out of the picture.

John

 

Follow up post - hope this helps someone else with this problem.

I finally fixed it!

Replaced the tailshaft housing ($120) and the vibration was better but it was still there.

Replaced the slip yoke shaft ($65) and that took care of the rest of it.

I figure that the d/s must have been out of balance for a long time and it just progressively wore things out. I think the one piece d/s probably vibrates more since the greater mass/longer length amplifies the vibration worse than the shorter shafts on a two piece setup.

Dan

 

Danz.... that is great news. Vibration is hard to resolve. Thanks for the heads up.

I inspected my my xfer case rear output shaft last nite. It moved side to side or up and down about 1/8". How much play did you have in yours. Why did you need to replace your slip yoke shaft, was it wear out badly due to vibration ? TIA.

Later,

 

underDAWG,

The play on my shaft was much less than yours, maybe 1/16 at the most.
If you are having driveline vibrations start by getting your d/s checked/balanced. If it was out of balance it is probably the culprit for causing the excessive wear.

There is a bronze seal in the tailshaft housing and it will wear out much quicker if the vibration is beating on it all the time. I found that the new housing held the shaft with much less play but evidently there was still enough for me to still feel the vibration through the gearshift at 70 -75mph.
When I had the tailshaft housing off I checked the shaft by sliding the yoke on and checking the play. Didn't know how much was too much but I hoped that the new housing would fix it.
After the housing didn't fix all of it I decided there must excessive slop in the splines of the output shaft and the slip yoke shaft.
I replaced the slip yoke because it was much cheaper and easy to do. For all I know the output shaft could still be a little worn but it's good enough at this point.

In hindsite it may have worked to just balance the d/s and replace the slip yoke. The housing may not prevent movement as much as making sure those two shafts spline together properly.

Let me know if you decide to replace the housing as Ford does not make a replacement housing that is identical to stock. You have to use a later version and plug the speedo opening.

Dan