Highway speed vibration

[zach_carver]

Hello everyone I would like to pick your brains for a minute. I have recently bought a 77 c10 and lowered it by flipping rear axle and drop spindles and springs. I used bell tech shocks and springs. Since then I’ve gotten a pretty bad vibration while driving at highway speeds. 65 mph or so my butt and seat shakes very bad even my seat belt on passenger side shakes against cab. I’ve rechecked u bolts, replaced u joints, rebalanced all wheels and all. Is there anything in rear end that can cause a vibration? I just flipped rear axle so I didn’t think my pinion angle would be too bad. Any guesses guys?

[mongocanfly]

I was gonna say check your pinion and trans tailshaft angles...they should be the same except one is +and one is -

[Kudzupatch]

If nothing else changed.... pinion angle is the most likely. Easy to check just makes sure it is under load when you check it.

[Dannyboy1966]

Here is another thought for you that I ran into. I have the two piece drive shaft, I had to have the front half off to get the spline end replaced, when I put it back in I had a wicked shaking at highway speeds. I had been balanced, it turns out all I had to do was drop the rear half, give it one half a turn and put it back on, shaking all gone. I hadn't marked them to rephase it when I put it back in.

[zach_carver]

When this started I replaced my U-joints just in case, but it didnt seem to make a difference. Im gonna check pinion angles and report back. I have lowered about 5 of these trucks just like this with no issue but who knows with these things. haha

[SCOTI]

Originally Posted by Dannyboy1966

Here is another thought for you that I ran into. I have the two piece drive shaft, I had to have the front half off to get the spline end replaced, when I put it back in I had a wicked shaking at highway speeds. I had been balanced, it turns out all I had to do was drop the rear half, give it one half a turn and put it back on, shaking all gone. I hadn't marked them to rephase it when I put it back in.

Agreed. This is a very common mistake. Make sure the u-joints are phased correctly.

[kwmech]

Did you separate the 2 piece driveline from itself or the diff? It is probably pointing too high. You may need a degree shim in either 2 or 4 dergree

[dagnabbitt]

Dumb question, but did you get a wheel alignment after you replaced the spindles?

[zach_carver]

When I flipper my rear axle I didn't remove my driveshaft. I removed it to replaced my u joints but I marked it so i knew which way to put it back in. My truck has a one piece driveshaft not a two piece. But my vibration started before I replaced the u joints. However my pinion angle may be my issue I guess. Ill check it and report back

[zach_carver]

Originally Posted by dagnabbitt

Dumb question, but did you get a wheel alignment after you replaced the spindles?

Yes sir I did. I even swapped back to my stock wheels to see if it was in my 20s but it didnt change anything. Because I put new wheels and tires on the same time I lowered it.

[Ski-me]

I'd say pinion angle/driveline angles. Generally what happens when ride height changes (up or down). I went up and had to shim my axle just a touch.

[zach_carver]

Originally Posted by Ski-me

I'd say pinion angle/driveline angles. Generally what happens when ride height changes (up or down). I went up and had to shim my axle just a touch.

Did you have a vibration also? Everyone I talk to tell me a pinion angle being off will not cause a highway vibration. Im not sure but its driving me nuts.

[Ski-me]

Yes, much more noticeable at highway speeds. I don't know if you have a one piece or two piece type of driveline, but for me, I have a single piece. U-joint at axle, slip joint at transfer case. And I went up by 2.5".

On short wheelbase vehicles, moving the suspension just a little can create some vibrations.

So, in your case and assuming you have one piece drive line, your axle pinion angle needs to be parallel to your transmission angle. Or maybe one degree in the downward direct for axle pinion. this allows for a little axle twist on acceleration.

If your axle pinion is pointed up by 6 degrees, your tranny should be pointed down by 6 degrees. Not parallel to the ground, parallel to each other.

The other potential could be what was discussed earlier about phasing the u-joints.

[mongocanfly]

I now this has been shown more than once but its always good to tag this video with vibration issues....
https://www.youtube.com/watch?v=Idk3BVDVHq4

[zach_carver]

I'm going to try and attach some photos so you guys can look also. It appears as if my rear pinion angle is almost angled up toward the bed rather than lower than the driveshaft.

[zach_carver]

Of course my pictures are sideways but maybe y'all can tell something by them.

[mongocanfly]

if your angle finder is seated good on the pinion yoke and the trans yoke, that looks odd...
I'm also wondering why your getting different readings on the driveshaft itself...those should all be the same...

[mongocanfly]

this looks odd...sideways pics are messing with me...
looks like the trans tailshaft is to high...it should be down 5. ...to match the diff which is up 5

make sure your angle finder isn't sitting on anything but the yoke...it may be hitting trans tailshaft in pic..and the other on diff and d-shaft

[mongocanfly]

did you rotate the driveshaft to see if its bent...in the first pic it looks like your angle finder is sitting on the weld....but the angles you show are 0...+5....-8...those should all be the same regardless ...
your second set of pics shows driveshaft at -2.....0......0
those don't match your first set of angles...

[Kudzupatch]

Did you check it with the truck level and then suspension under load?

[zach_carver]

Originally Posted by mongocanfly

did you rotate the driveshaft to see if its bent...in the first pic it looks like your angle finder is sitting on the weld....but the angles you show are 0...+5....-8...those should all be the same regardless ...
your second set of pics shows driveshaft at -2.....0......0
those don't match your first set of angles...

No I didnt rotate it. It was hard to get an accurate measurement I felt like due to the yoke wasnt level itself, and I wasnt 100% sure where to measure it at. Everywhere online showed something different. Yes I checked it under its own weight loaded.

[mongocanfly]

I've got a angle finder like yours..it should be a magnet on one side...you can stick it on the bottom side of the driveshaft and just let it hang there...just keep it on the tube....regardless the angle of the yokes the tube angle should be the same....
on the yokes its gonna be tougher to get a accurate measure...you need a good flat surface....would be much easier with the d-shaft out so you can stick it on the yoke face and trans tailshaft....
just keep in mind if you can, a imaginary line from the pinion centerline and one from the trans centerline....those 2 imaginary lines need to be parallel...

[mongocanfly]

heck....I just realized I was looking at your pics upside down.....
so now to me the angles you show looks like the trans angle is down...which is good..but so is the pinion...which is bad...if your getting good readings then it shows the pinion angle to low....

[zach_carver]

I really appreciate all your help man, I think I’m just gonna burn the truck hah. Just kidding let me get better pics and accurate angles. I’ll report back. I’m just gonna measure like you said on the drive shaft.

[mongocanfly]

the driveshaft angle isnt going to show your pinion and trans angles...but I was curious as to why you were getting such diff angle readings on it..every reading you get on the tube should be the same