86 C-30 Dually Vibration Issue....

[dustykey]

Hopefully someone here can help me. This is wearing me and my wallet out!!!!
86 C-30 Dually Crew Cab Choo Choo Custom is vibrating and it starts phasing in at around 35-40 mph. That is when it is at its worse....but it never goes away, it just lightens up as speed increases. Truck was in rough shape when I got it. I have rebuilt the entire front end. By this I mean...tie rod ends, ball joints, steering arm, idler arm and steering gear as well as replaced a worn out rag joint. I have replaced front wheel bearings and races. Replaced all U-joints and the carrier bearing and had driveline balanced. Replaced all 6 tires with new BF Goodrich and had balanced. Transmission output shaft has no movement and I have checked the harmonic balancer and it seems fine. Will not vibrate when in neutral and engine revved up.....
Is a lost weight off of a rear drum a possibility? Bent axle?
Any help is greatly appreciated.....

[77 350 Shorty Wide]

Good Morning, It could possibly be that one or more of the new tires is out of round. Was this problem present before new tires? Hope you find your problem and have a blessed Christmas season.

God bless, Terry

[Puke160]

Try having the tires rebalanced. A guy a work with have a weight come off his highboy and he said it was almost undriveable over 45 mph.

[dustykey]

These are actually the second set of new tires on it. I originally bought ultra cheap tires and had the problem. Took it to have them rebalanced and was told that 2 were a little out of round. I sold that set to a buddy for his RV and bought this new set. It did help with some vibration but ultimately it is still there and hasn't changed from one set of tires to the other.

[mattybilt79]

Don't know the best way to describe a vibration but does it sound and feel like a rhythmic whir whir whir whir?

[dustykey]

Yes it does do the rhythmic thing once I get up to highway speed....over 65mph.....

[Domer]

i know what you are talking about.. my 97 dually did it when i bought it. the previous owner had no idea.. i through alot of money and parts at my truck before i accidently figured it out. I have aftermarket wheels on my truck. Chevys are hub centric wheels, (wheel centers off the hubs). My were for a ford with a bigger hub. I had my truck on jackstands and was running it and cycling the gears, i could see my wheels basically bouncing up and down..i machined some hubcentric rings that fit my wheels to the hub, and have never had a problem since. good luck on your hunt.

[mrolds88]

Also check your carrier bearing. Try to eliminate one thing at a time. Put the rear up on jackstands, start it up and put it in gear, see if you still have the vibration at speed. Have plenty of room in front just in case. Then if you still have the vibration, pull the wheels and tires. Also have someone watch from the side to see what the driveshaft is doing.

[suxtobu65]

Even tho you have replaced your u-joints. I firmly believe your issue resides there. Even new u-joints can accidently be messed up and cause an issue.

Test.....

Get the truck up to speed on an open road (somewhere with little or no traffic, highway at night, etc).
Once at speed (where vibration is worse) shift trans into neutral. If vibration goes away, it pin points the driveline (driveshaft) as your source of issue.. If vibration remains. The issue is somewhere in your rolling stock. (ex. diff, axles, brake drums, wheels, tires..)

Good luck. I hate vibrations.

[mrolds88]

Was the driveshafts put back together in phase? Any of them that have the slip splines on that aren't lined up would make a vibration. As would a u joint that wasn't centered in a yoke.

[dustykey]

The driveline cannot be put back together out of phase on this one. That's the first thing I checked. Had it balanced after carrier and u-joints were replaced. I have put it in Neutral while rolling down the road and the vibration remains.
The idea of the wheels being wrong makes sense. These are just steel wheels that were on it when I bought it, but I am the 4th owner. No telling what has been swapped. I will check the wheel fitment to the hub this weekend.

It had flat spots on tires due to brakes locking up, it had bad wheel bearings, and everything else bad on it that could cause a vibration. I am just knocking them out one at a time.

[mattybilt79]

I asked about the rhythmic vibration because my 85 does that too. I figured its probably some where in the rear end. Your problem does sound tire/wheel related would start there. Ford/dog dually wheels are roughly 1/8-1/4" bigger in hub diameter than gm wheels. Will be a visible gap all around the hub to wheel. The flat spots in your tires seem to hint you have an issue there they are not always from the brakes.

[mrolds88]

Another thing I just thought about was the pinion angle. Should be parallel to the trans output.

[dustykey]

I'm pretty sure the pinion angle is fine. Nothing has been done that would change the angle of the driveline or the input yoke of the rear diff. I'm leaning towards the idea of a wheel being the issue. There's a pretty good chance that it may have one odd ball wheel on it that doesn't seat to the hub correctly. I will be able to check that tomorrow and let y'all know

[craig113]

84 CC here, had that issue years ago, I ended up changing the drive line angle, dropped the carrier bearing a couple inches and it fixed my problem.

[dustykey]

I was able to find the issue this weekend!!! I removed all 4 rear wheels and found that one of the wheels had the center hub hole quite a bit bigger than the hub on the truck. It needs a spacer. There were 2 wheels that had egg shaped lug nut holes. I will be getting new wheels this week and should be rolling vibration free next weekend!!!

[SCOTI]

Originally Posted by dustykey

I was able to find the issue this weekend!!! I removed all 4 rear wheels and found that one of the wheels had the center hub hole quite a bit bigger than the hub on the truck. It needs a spacer. There were 2 wheels that had egg shaped lug nut holes. I will be getting new wheels this week and should be rolling vibration free next weekend!!!

I picked up some steel wheels from a board member earlier this year & came across a similar situation. Of the 4 steel wheels off the rear, 2 were from a later model truck & 2 others had the holes ovaled from excess play.

I sold the 2 later model units to a guy needing them & was able to even sell the wheels w/the ovaled holes as rollers to a guy building a dually chassis.

I found 2 more correct, super clean steel wheels this weekend so check Craigslist or there's always alum aftermarket wheels.

[Domer]

glad you figured it out.. it took me forever.. never thought that would be the problem.