Overdrive vibration

[nasty51ford]

Well, started driving my B67 this week after getting it insured and tagged, slowly sorting out little issues it has. Whenever I get it into overdrive (which isn't often in the 18 mile drive to my shop ad back), it has a vibration it seems to diminish somewhat when I let up on the throttle, what would cause this, will it do this if the transmission is low on lube?

[r686st]

I had a similar issue and kingpin adjustment as well as new steer tires virtually solved the problem. My truck is a 1991 RD690S if that helps.

[nasty51ford]

I can understand that BD, but this happens only when I drop it into overdrive

[hatcity]

yes it may happen due to low fluid level.

But, I would think a bearing issue on that gear.

[j_martell]

U joints??

[theakerstwo]

Like he said u/joints or loose yoke nut.

[nasty51ford]

I thought of those things, but U joints or a yoke should do it through all the gears, not just overdrive I would think, I know it is still a little low on lube though

[mrsmackpaul]

If it was a little low on lube I wouldnt think it would make much difference because the oil is fairly flying around the box once your moving that fast if it is only one gear I would lean towards a crook bearing in the box however I would check the uni's and make sure the yokes are tight (as said above) before I would get all keen and drop the box out could also have a crook carrier bearing perhaps ?

You see I have always found that with drive line harmonics??? sought of can give false indications of were the problem lies and quite often I can spend bucket loads of time looking in the wrong direction

Paul

[j hancock]

I thought of those things, but U joints or a yoke should do it through all the gears, not just overdrive I would think, I know it is still a little low on lube though

With the increased shaft speed of OD, imbalances or looseness sometimes show up that don't seem present at a lower speed.

While under the truck checking the yoke nuts and greasing the u joints, also check the center bearing rubber for deterioration, lots of age cracks or slop.

[nasty51ford]

Thanks JH, but this truck has a single driveshaft, no carrier bearing.

[HarryS]

N51F, I have the same vibration you describe in OD only (TRD 720). There is also a high pitched noise in that gear that is not present in any of the others. I have drained the trans and changed fluid. There were no filings or debris that came out, also nothing on the magnet. I pulled the PTO covers and nothing unusal. The U joints were replaced along with the slip joint and rear output shaft bearing. The shaft was also balanced. I've had it on jack stands running in gear but can't hear or feel anything. I can't think of anything else to check without pulling the trans.

[nasty51ford]

Yeah Harry, it can be aggravating, I checked my U joints, they were dry, and the slip yoke also, I greased them all, and I checked the yokes, there is a very small amount of play in the rear end yoke. I was going to drop the driveshaft, but when I took the bolts out of the caps, and tried tapping them to spin them around, it was like they are welded in there. I put the bolts back in for now, I am going to buy another set of u joints before I attack those old ones! Lol ! I'm hoping that little bit of play in the rear yoke is my problem. I have felt a lot of different vibrations in my life, and this feels just like a driveshaft related vibration. I can make it come and go with the throttle also, which points to the rear yoke or a bad u joint as well. I hope you find your vibration problem.