How does this pinion angle look??

Joe473 · Aug 21, 2018

Getting a vibration 62-70ish. Measured angle with phone and shows it at 5 deg down from DS. Going to order 2 degree wedges to replace my 4's. Looks pretty straight up at 0 deg to me though. Vibration goes away by 75. Smooth as anything at low speed which has me thinking not the driveline. Doesn't change on deceleration accel. Problem is I feel like it started when I messed with the rear springs.

Centering pin is tight. Around 2.5 yrs 15k miles on tom woods shaft.

Already rotated tires. Checked u joints. Replaced one due to noise. Confirmed u joint phasing. Driveshaft shop said shaft is slightly bent but I'm trying to make sure that's the issue before shelling out $350 for a new one...

Never drove in FWD only with rear shaft removed. Any concerns doing that at 65 ish??

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Apogee · Aug 21, 2018

What did you change with the leaf springs? Are the U-bolts tight? Angle on the shaft should be 0 to 3 degrees down relative to the shaft based on what I've read. I'd be surprised if the shaft was the source of the problem unless the U-joints, double-cardan or splines were worn, but with only 15k miles, that seems less likely. How bent is "slightly bent"?

Joe473 · Aug 21, 2018

U bolts are tight. Ujoint are clean and smooth. No slop in splines. No slop in double cardan centering pin. I put in New springs and slid it back an inch.

Apogee said:
What did you change with the leaf springs? Are the U-bolts tight? Angle on the shaft should be 0 to 3 degrees down relative to the shaft based on what I've read. I'd be surprised if the shaft was the source of the problem unless the U-joints, double-cardan or splines were worn, but with only 15k miles, that seems less likely.

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Hozr · Aug 21, 2018

A bent driveshaft should be felt at all times, not speed dependent. How did they test for straightness?

Joe473 · Aug 21, 2018

Hozr said:
A bent driveshaft should be felt at all times, not speed dependent. How did they test for straightness?

Dial indicator and I agree I would think vibration would always be there just different frequency. They didn't give me the value for runout.

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Broncobowsher · Aug 21, 2018

Speed + load would be the factor. Load being the spring wrap (pinion rise).
Just making sure, there is a CV at the transfer case and not just a U-joint?
If the front end is capable of doing 65 in 4WD, it will be fine in FWD.
How does it drive with no shims? Try that before buying more.

Pa PITT · Aug 21, 2018

... I don't like that angle . TO ME IT NEEDS to be a drop of several degree in it .too straight .

Broncobowsher · Aug 21, 2018

If there was a torque arm on it, it would be great. The angle is all but locked in. But those leaf springs look flexy. Thus my suggestion to just remove the shims and see what happens?

Have a GoPro? Mount it under the truck pointed at the pinion and go for a drive. You will be amazed at how much that pinion climbs under load.

Steve83 · Aug 21, 2018

Have you read the TSB in the caption of this diagram?

(phone app link)

Dbteak · Aug 21, 2018

Don't rule out wheel bearings. I also chased a vibration that I thought was the driveline which turned out to be a wheel bearing. Doug

Joe473 · Aug 21, 2018

I think my next step is drive it with no rear driveshaft and prove it's in the driveline. I have seen the TSB's and agree mine looks too straight. If the FWD test agrees it's in the driveline I'll remove shims and go from there. If not road force balance of tires and check front wheel bearings.

I found a good chart that lists range of mechanical and audible vibration and possible causes.

https://www.ford-trucks.com/forums/1195169-vibration-diagnosis-details-w-chart.html

Thanks for the replies

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surfer-b · Aug 22, 2018

Did this just start, did you add a lift and the vibration start? Make sure the CV at the t-case is not binding at that angle. I had one do that, it was binding very slightly, couldn't see where it was hitting, but it was and causing a slight vibration. I swapped out the driveshaft with a high angle I had and problem solved. Also make sure all wheel bearing are good like others stated.
Driveline vibrations suck, its difficult to chase them down sometimes because it can travel through the entire vehicle.

Rustytruck · Aug 22, 2018

How tight are your drive shaft bolts? at 14 to 17 foot lbs that's snug with a short wrench and loctite on the threads. Make sure the yoke ears are keeping the driveshaft centered

http://www.dennysdriveshaft.com/p50..._u_bolt_set_fits_1.125_bearing_cap_diame.html

Joe473 · Aug 23, 2018

Ok, I removed the 4 degree shims. My ds to pinion angle differential went from -2 to -10. It doesn't look that severe but that's what I'm measuring. Driving feels different. The vibration in the shifter is gone. Pics below. Who makes a steel 2 degree shim? I feel like that would put me in a good spot as right now the shaft isnt deep enough into the splines for my tastes.

I do still have the overall shaking of the truck 65-75. I'm starting to lean toward bad tire and going to try road force balancing and check front wheel bearings.

U joint end caps were done with very short wrench and loctite. U bolts and spring center bolts are tight.

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Boss Hugg · Aug 23, 2018

My shaft lines up with the pinion just like yours did with the shims. I have a vibration also starting at about 67mph. I'm not sure what the vibration is, but I know its related directly to speed and torque. It feels the same where cruising or accelerating, but goes away when I let off the gas. Everything I read says that if you have a double cardan shaft, the shaft needs to line up with the pinion--otherwise you'll have a vibration. So IDK what you're solution is.

But I will say... IF you have a bad tire, don't just road force balance it. Replace it. imagine blowing a tire apart on the hwy. How well will you respond to whatever change in direction it might cause? I had one separate (as I would later find out) as I was making a long sweeping exit ramp at 70. Once I was able to get it slowed up, I wound up only able to drive 20mph for the next 4 miles to get home--after work at 4:00AM. I got home and went straight to bed. When I woke up, I went out and looked it over and that's when I saw the problem. I'm lucky it didn't split the tread. It only bubbled out. But you never know....

Joe473 · Aug 23, 2018

Boss Hugg said:
My shaft lines up with the pinion just like yours did with the shims. I have a vibration also starting at about 67mph. I'm not sure what the vibration is, but I know its related directly to speed and torque. It feels the same where cruising or accelerating, but goes away when I let off the gas. Everything I read says that if you have a double cardan shaft, the shaft needs to line up with the pinion--otherwise you'll have a vibration. So IDK what you're solution is.

But I will say... IF you have a bad tire, don't just road force balance it. Replace it. imagine blowing a tire apart on the hwy. How well will you respond to whatever change in direction it might cause? I had one separate (as I would later find out) as I was making a long sweeping exit ramp at 70. Once I was able to get it slowed up, I wound up only able to drive 20mph for the next 4 miles to get home--after work at 4:00AM. I got home and went straight to bed. When I woke up, I went out and looked it over and that's when I saw the problem. I'm lucky it didn't split the tread. It only bubbled out. But you never know....

Thanks. Using the road force machine to find the bad tire. I have a good spare that will go in its place if it's only one tire. If its 2 or more I guess I'm breaking the bank for new tires and wheels....

I agree everything you read says line up pinion but from what I feel down a few degrees is better. I do wish I had a go pro

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Boss Hugg · Aug 23, 2018

I can see the advantage to the u joint with a difference in angle. It makes absolutely sure that the cups (bearings) are moving enough to stay lubed and not freezing up. But that should also be happening as your suspension moves around during regular driving.

Anyway, good luck with it.

DirtDonk · Aug 23, 2018

Boss Hugg said:
...Everything I read says that if you have a double cardan shaft, the shaft needs to line up with the pinion--otherwise you'll have a vibration. So IDK what you're solution is.

You don't read that here. Or hopefully not!
Likely on sites that discuss rigs with 4-link or other linked suspensions that don't allow axle wrap. Those with Jeep TJ's for instance would go for zero degrees relative to the shaft center.
With Broncos, the proper angle is 1-2 degrees down from the centerline of the shaft.
It's enough so that you don't vibrate under hard accel, but not so much that you vibrate under decel.

Paul

Joe473 · Aug 24, 2018

DirtDonk said:
You don't read that here. Or hopefully not!
Likely on sites that discuss rigs with 4-link or other linked suspensions that don't allow axle wrap. Those with Jeep TJ's for instance would go for zero degrees relative to the shaft center.
With Broncos, the proper angle is 1-2 degrees down from the centerline of the shaft.
It's enough so that you don't vibrate under hard accel, but not so much that you vibrate under decel.

Paul

Paul, do you guys have 2 degree shims? With mine there was a pretty large change from 4 degree to no shims. I'm concerned even though it feels better now ujoint life may be impacted if I don't reduce the angle some.

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Boss Hugg · Aug 24, 2018

Paul, I WILL be doing an antiwrap bar. I picked up a cold duck and was advised I would need it.

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How does this pinion angle look??

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