Fed up with vibration issue

[Lowburb93]

I chased the same thing in a 64 F100 I lowered with axle flips (both). I even bought new wheels and tires. Couldn't get rid of it. My pinion angle was fine. BUT . . . my pinion angle and my tailshaft angle were mismatched. If your pinion angle is down 1.5° the your tailshaft needs to be UP 1.5°.

My pinion angle was a full degree off from the tailshaft angle. I made a 1/4" shim and put it under my transmission mount and that put it at the correct angle. Vibration gone - completely.

I just started chasing a high speed vibration in my unmolested c3500. Going through the same steps, so I feel your pain. I know I have wheel issues though, so I'm at the beginning of the process. Good luck, but I suspect driveline angle issues on yours.

I remeasured it yesterday with the driveshaft out and there was about a 2.5 degree difference between the two. I replaced the trans mount because due to a slow rear seal leak the mount had given out to the point of it being metal hitting the cross member. When i changed the mount i added 3 washers to each side as well which brought up the tail a good inch. I havent remeasured the angles yet but the vibration is still present. I might swap out a rear wheel with a spare or something to see if that does anything. The vibration isnt super bad but definitely noticeable especially on a flat road. Its enough to make the end of a cigarette in your hand on the wheel visually wiggle pretty good

 

[ed455]

2.5° of angle difference is huge. I only had 1° of difference and had a vibration. There are angle shims for the leaf springs available.

 

[Lowburb93]

2.5° of angle difference is huge. I only had 1° of difference and had a vibration. There are angle shims for the leaf springs available.

Alright ill try jacking the trans up more or buy some wedges soon. Thanks for the input. I didnt know how off the angles could be to make a vibration

 

[Uncle Ben]

Have a similar problem on my 97 extended cab. Vibration shows up at 60mph, then goes away at 70+

Truck is completely stock.

 

[sewlow]

Vibration probs! Aarrrgghhh!
I've swapped wheels, tires, driveshafts & axles chasing them.
New, & then machined before installed, brake drums. (New ones, even the OEMs, tend to be outa whack right from the box. Damn off-shore crap!)
New big-$ rotors. Again, machined before installing.
A complete urethane body mount & suspension kit.
Roadforce balanced the tires & wheels. 2x. 2 different sets.

These trucks have an inherent vibration problem. It usually occurs at between 30-40mph & then again at around 65-70mph.
It's called 'Beam Walk'. A resonant vibration between the two frame rails.
GM is aware of this. Their suggestion for a cure? 3-400lb.s of 'ballast' in the box! Huh? Really? Like WTF?
A sure cure, a permanent cure, is to box the frame. This can be as simple as an 2-3' foot plate on the inside of the frame over the diff, or as some have done, the Whole Hog route, is to box the whole thing from the rear cab mount to the shackle mount. Plating the frame crossmembers helps even more.
I've seen some frames where the owner has trussed the frame like a bridge's girders. Probably more work, but lighter in weight.

Have you checked the control arm bushings? Especially the top ones. They're now 25 year old rubber parts. If they haven't ever been replaced, they're probably about due. I'd recommend installing urethane ones. They have way less deflection than even a set of new rubber ones.
But they can be a major PitA to install. That requires the use of a mondo-huge press. We used a 20t press & it was still a bear of a job. Lots & lots of the supplied urethane bushing lube is needed. When you figure there's too much on the bushings, slop on some more.

But, there are some other things to check before doing all that

Had the driveshaft balanced? I had to get mine done & the re-n-re with the shop installing new universals, was $100 in Canuck Bucks. That's like what? $25.00 U.S.? Lol!

If you need to shim the pinion angle with some wedges, you have to install a leaf spring centering bolt with an extended head.
The factory bolt's head is not long enough to go through the wedge & still reach the hole in the spring perch.
GM lists 4 different lengths of centering bolts. 2 wheel drive 1/2 tons use the shortest. The bolts are cheap from the stealership. Couple of bucks each. I don't know if they're 'special' in any way, (gr.5? gr.8?) but they're the right ones as per GM. Buy the next longest in the list.
Crank a nut up to the head with some red Loc-tite, then grind the shoulders of that nut down to the bolt's head size. Install in the spring pack.


Since doing the drop, have you gone back & checked to see that all the nuts & bolts are still tight? Especially the ones for the shackles & hangars. Sometimes once the new parts settle in, a little re-torqueing is required. I had to tighten up the passenger side hangar a couple of weeks after doing the drop. It was tight at the time of install. Wasn't like it was falling off. Just a couple of ugga-duggas to get it tight. 6+ years later & it's still good.

Have you checked the wheel & axle bearings for play?
No rusty questionable/broken body mounts?

 

[sewlow]

I didn't know how off the angles could be to make a vibration

#2 is as good as it gets for these trucks.

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[deadbeat]

I boxed my frame, changed angles till they were right, changed carrier bearings, u joints, had 2 piece rebuilt, had it rebuilt another place and balanced, had it retubed, rebuilt by another place and balanced, still shook. Did the fluid nbs rear cab mounts, still shook. New rear end, new output shaft bushing, new wheels, new tires, rebalanced, new drums, new rotors, new hubs, new tranny mount. Finally I went and bought an aluminum shaft that was too long and had it cut down to fit mine and balanced and all my vibration trouble went away.

 

[deadbeat]

With the 2 piece driveshaft I could get it pretty good, but it always had 2 ranges it vibrated. Somewhere around 35 - 45 and somewhere around 68 - 78 which made me angry because I drove on country roads and the interstate and these speed a lot. Good luck with your journey, my truck is smooth now but it took 3 years. I am putting new bushing and supsension/steering joints in my truck right now, I fear it will vibrate when I am done but hope the ride stays the same.

 

[sewlow]

I went and bought an aluminum shaft that was too long and had it cut down to fit mine and balanced and all my vibration trouble went away.

When I went in to get the D/S balanced & whenever I've gone to buy universals, I've been asked whether it's steel or aluminum.
"Steel." Never thought any more about it.
Right about...now! DOH! (Just gave myself a big fat 'Homer' slap upside the head!)

Aahhh...WTH. Here Al. Have a couple more!
DOH! DOH!...DOH!

 

[Uncle Ben]

So is an aluminum driveshaft the answer?