Jackstands + no wheels = heavy vibration?

[bob8619]

Is there something I'm not aware of that would cause heavy vibration when putting the truck in drive while on jack stands and the back wheels removed? Drums are off too.

Does the lack of resistance of the wheels being amplify possible drive line issues or is it just a known thing that running without tires causes vibrations?

[harpo231]

Not normal....

Does it shake on the road ?

[weq92f]

Well, I've never done that before so I have no direct experience, but... I can't think of any reason why you'd have such a vibration. Even without the wheels, there are quite a few moving parts that could cause the issue. Most suspect in my mind would be the stuff inside the pumpkin, axles, ujoints, drive shaft and components and then up into and through the tranny.

I would first check your u-joints and then your pinion angle.

[bob8619]

I've got a hopping type feeling throughout the cab between 50-53mph give or take a couple. This falls somewhere between 2100-2400 rpms. The tires are cheap but new, my mechanic says its excessive runout on two of the tires so I brought it back to Tire Kingdom but the claim they're fine. I trust my mechanic more than them but they weren't willing to replace them.



I tried two old smaller tires on the front and test drove, same issue at same speed and rpm. Then, I put those tires on the back and the issue persists at the same rpm but now at 47mph. Its always possible though that the 2 smaller tires are out of balance and its only by coincidence that the hopping is occurring at the same rpm range. But anyway because of this test I started to question the driveline . However, if I keep it in 2nd gear and get into that rpm range, it doesn't happen. Only once it gets into 3rd gear.

Since its confusing me I figured I'd just try it without tires on and the rear end jacked up, and thats when I discovered it is worse without tires than with them on. So now I don't know if its tire issue, drive shaft issue or tranny issue.

[palallin]

U-Joints &/or carrier bearing would be first on my list to eliminate.

[bob8619]

My yoke was questionable when I replaced the u joints a few weeks ago, I thought it had it squared away but perhaps I didn't.

[bob8619]

Heres what I mean by questionable. Its hard to see in the pics but If you notice, the two caps that are going into the yoke are not even, this makes it seem like it would be off center but if you look at where the u joint lines up with that notch in the center of the yoke, it makes it appear as though its centered.

[jradford]

U-joints and carrier bearing would be the first thing I would check.

[Stocker]

Originally Posted by jradford

U-joints and carrier bearing would be the first thing I would check.

x3, and being on jackstands with the rear wheels off, it seems like you might be able to actually see what's moving around causing the vibration.

[bob8619]

I found that one of the u joint caps in the yoke has side to side play in it. I overnighted a new yoke so we will see if that was the only problem.

[special-K]

Originally Posted by bob8619

Heres what I mean by questionable. Its hard to see in the pics but If you notice, the two caps that are going into the yoke are not even, this makes it seem like it would be off center but if you look at where the u joint lines up with that notch in the center of the yoke, it makes it appear as though its centered.

That'll do it, not centered as well as unseated bearings in cap. Could it be the needle bearings got dislodged in the cap, causing incomplete bearing with the one or ones that fell out laying in the cap preventing it from seating? Did you get the clips in both sides?

[Overdriven]

I don’t see it mentioned anywhere so I figured I would ask. When running your test on jackstands, is the rear axle on jackstands supporting the weight of the truck as if it were on its wheels?

[bob8619]

Originally Posted by Overdriven

I don’t see it mentioned anywhere so I figured I would ask. When running your test on jackstands, is the rear axle on jackstands supporting the weight of the truck as if it were on its wheels?

Yes

[bob8619]

Originally Posted by special-K

That'll do it, not centered as well as unseated bearings in cap. Could it be the needle bearings got dislodged in the cap, causing incomplete bearing with the one or ones that fell out laying in the cap preventing it from seating? Did you get the clips in both sides?

I had to modify the clips to get them both in but it wasn't due to the caps not going into the joint completely. I checked and rechecked and the needles hasn't fallen. The caps were seated on the joint completely just appeared to be uneven in the yoke.

[100%Chevy]

I had some bad vibrations on my 78 C-10.Finally replaced the center carrier bearing and still vibrated(about 60/65 mph).
Found the pinion nut was a little loose!Tightened it up and the problem is gone.
Mike.

[davepl]

Assuming stock parts installed and phased correctly, if I ever have another vibration, are the steps I follow regardless, because logic and troubleshooting have always failed me on drivelines:

1) Replace carrier bearing
2) Replace u joints
3) Balance driveshaft
4) Service slip yoke on 2-piece

For me I had to go to #4 (with many other stops along the way) before it got fixed. They said there was wear in the spline, that I couldn't feel. I was highly dubious but they replaced it and the problem went away.

[bob8619]

New yoke came in, installed with new moog joint and no luck , still vibrating. One piece drive shaft so no carrier bearing. U joint at the axle is only a month old and has no play in it so I didn't replace that one today. I guess I'll check the pinion angle and then after that just go get the shaft balanced.

[jeffahart]

Originally Posted by harpo231

Does it shake on the road ?

This question was never answered, or did I miss it? My take is... who cares! If it performs on the highway under load with no symptoms then I think you are fine. It's a truck... not a pine wood derby car. Get it off the jacks and run it, give it some torque. If it performs, run it. If it vibrates, then chase the problem. Anything else seems to be an exercise!

My two cents, worth the price paid!



j

[bob8619]

Originally Posted by jeffahart

This question was never answered, or did I miss it? My take is... who cares! If it performs on the highway under load with no symptoms then I think you are fine. It's a truck... not a pine wood derby car. Get it off the jacks and run it, give it some torque. If it performs, run it. If it vibrates, then chase the problem. Anything else seems to be an exercise!

My two cents, worth the price paid!



j

Yeah I answered it up there. In a nutshell: It does shake between 50-53 mph. 2 month old tires, been balanced 3 times. Mechanic blames excessive runout, tire shop says he is wrong so wont swap them out for more.

Tried some old tires and got the same feeling at the same rpm but different mph since the tires were smaller. So thinking it was rpm related as opposed to speed, I went into that rpm range while in 2nd gear and it doesn't shake. Thats when I tried without tires and found it shakes even worse without tires.

[bob8619]

When I got the truck the guy had chunks of 2x4s in each of the rear shocks, I didn't think much of it and removed them. These are how the shocks look now, could their condition result in improper driveline angles which could cause the speed/rpm dependent vibrations? Sorry for the sideways pics.

[jeffahart]

OK, happens on the road; that said and that picture! No angle! Post #3 center rendering; the angels cancel each other out. Let's see the front. Or maybe you can get a shot of the whole drive line. You need to get your drive angles correct. As stated above. Unhook the drive shaft and see it it still vibrates. Just so you know! Easy and you can rule out anything up stream. Assume nothing!




j

[jeffahart]

Also, after you verified, no vibration from upstream. While your shaft is unhooked, whole shaft. Turn the shaft 180 degrees then, Re-install it! You want it connected on different sides of the yokes! Simple test, and it my show progress or degradation. After that.. it's those pesky angles!



j

[bob8619]

With the shaft unhooked I get no vibration. I stuck blocks in the springs just to experiment and it seems it moved the vibration up to 53-56mph range now instead of the 50-53. I can't get the whole drive line in one pic but I took 3 pics.

[bob8619]

I raised it even more with wood between the coils the vibration is gone as far as I can tell. So this gives me two thoughts, the changing of the pinion angle is helping OR the wood is stiffening my springs to the point where I can't feel whatever is vibrating?

[jeffahart]

I see something new, I see something new! Did it vibrate before that new yoke? Did you turn the shaft? See if that changes anything. I always put my shaft back in the way it came out.


j