Driveshaft vibration

[82TwoHeadlight]

For what it's worth, the Burban with the worn tail shaft bushing did not leak fluid. It did exactly what you describe, shake the floor. A glass of water in the console would definitely have rippled at the right speed.
You've been all over your truck diagnosing the problem, and unfortunately there's no smoking gun. You might try the cheaper of these options:
Balance the driveshaft
Replace the tailshaft bushing

Lastly, you've described this as not a tire or wheel issue, but have you inspected the drums? What about swapping the front tires to the rear?
A buddy had a car that kept coming back to the shop for a shimmy in the front. It turned out to be the brake rotor. At some point it became unbalanced.

 

[Bextreme04]

I have also had vibration issues caused by rotors out of balance. You would usually feel that in the steering wheel though. Bent axle or tube is a possibility.

 

[Raider L]

@SirRobyn0,

This may be out there in left field but have you checked your harmonic balancer? You reckon it's slipped some? That right there could cause a minor vibration. Check your timing and look closely at where your timing marks are supposed to be and where your timing tab is.
Ha, ha, and no, I didn't mean to actually go around with a open cup of water, just the idea of that much vibration. Like you could use a water bottle and look at the water while you're goin' down the road. If it's not the shaft or joints, not the rear end, not the trans., and not other minor stuff , it could very well be something like the balancer has come undone.

 

[SirRobyn0]

@Raider L So you mean all those cups of water I've put up on my dash and subsequently spilled out all over my interior..... You didn't actually mean for me to do that!!!! Of course I'm kidding. You just got me to think in a way I hadn't and that's a good thing. I'm able to time the truck using the balancer mark and tab, and it appears to run true.

@82TwoHeadlight Thanks for that. You are the first person to confirm a tail shaft bushing causing vibration like this and not leaking.

When I get to work on this issue again this is going to be my attack plan.
#1. Try to see if I have a bent shaft, using a straight edge. Possibly mounting a gopro under the truck if I can find my gopro.
#2. Transmission output shaft bushing.
#3. Look at converter bolts and re-examine the harmonic balancer.
#4. Get the shafts balanced, all the weights are still on the shaft, but even still I know it's possible. It'll just be inconvenient to be without the truck for 2 weeks.

There is no chance of this being a tire issue as the vibration was there with the old tires and the new ones. Wheels and tires ran straight and true on the balancer when I installed them. Drum or rotor issues seem unlikely. Obviously not a warped rotor, out of balance rotor or drum usually feels more like a tire balance issue than driveline.

I've been thinking more about this. If I had to make a bet I think I'm going to find a bent shaft or tailshaft bushing. Here is some additional info. When I was playing around with hose clamps, field balancing the drive shafts, adding them and moving them around on the rear shaft only resulted in no change or making it worse. With the front shaft, on the transmission end of the shaft I'd get it feeling a lot better and drive it for an half hour and it would start vibrating just as bad again. Move clamps around to where it is reduced, and again after a bit of driving it would be back. Finally I took all clamps off. I'm hopeful to put some time in on this Sunday or Monday. Of course whenever I get to it I'll report back what I find, in the mean time feel free to keep the ideas coming!

 

[Camatruder]

I'm absolutely no expert on chasing these vibrations, but i think it can still be your torque convertor. A damaged friction material ring can cause an unbalance in the TC even when not in lock up. In lockup however it will be worse

 

[jjester6000]

This is on my truck, 1984 C20 305 / 700R4 still running the 3.41 rear gears, but one day will be 4.56. Stock everything including suspension has the 14B semi-float w/ 2 piece driveshaft. I've had the truck for 3 years and it has had a driveline vibration since the day I bought it.

U-joints were the OE 37 year old joints until last weekend. They didn't have any slop in them, and weren't making any noise, but I'm taking enough longer trips 100 mile one way and returning loaded with feed, that I'd like to fix this vibration both because whatever is causing it I don't want it to give out on me 100 miles from home and it's also annoying. So I bought new u-joints and carrier bearing, thinking when I dropped the driveline I might find a stiff joint which I did not, but I proceeded to change the U-joints and carrier since I had it out. I saw no missing weights on the driveshafts, and everything went smoothly. And of course it is phased correctly. I put it back together and drove it today and the vibration is still there.

I guess I should describe the vibration. Feels pretty much like every other driveline vibration I've ever felt, it's at it's worst cruising or lightly accelerating in 3rd gear locked up 35 - 45mph. Unlocking converter reduces it, but it's still there. I can feel it at higher speeds and in 4th, but it's much less noticeable. Seems like it is not as bad during the first 30 minutes of driving, which to me seems odd for driveline vibration but I don't think it rules out driveshaft balance. It is not coming from the converter clutch.

Currently I'm playing around with hose clamp driveshaft balancing, for those that have not heard of this basically you start 6" from one yoke make a mark at 0, 90, 180, 270degrees on the shaft, using the head of the screw clamp as a weight you move it to each mark noting any improvements, and trying one or two clamps. I know I won't get the perfect balance this way, but if it is balance that is the issue I should be able to improve it at least. I did the end at the rear diff today with little change. I'll work my way over both haves of the driveline in the next couple of days.

I'd like to know your thoughts, if you have seen something like this before that wasn't the driveshaft, I'd like to know. I've done lots of U-joints at the shop of course, but I'm thinking I need some thoughts and maybe an idea or two from you guys. Thanks.

Want to swap rear ends?

My '86 Burb C20 has 4:56's, and I am wanting to go to 3:42's. I am really trying to make a highway cruiser out of this thing.

 

[SirRobyn0]

I'm absolutely no expert on chasing these vibrations, but i think it can still be your torque convertor. A damaged friction material ring can cause an unbalance in the TC even when not in lock up. In lockup however it will be worse

Absolutely possible, it's on my list but not high. When I have driven vehicles that have a damaged friction material in the TC, the vibration is usually violent when the TCC engages. While the vibration I have is bad enough to be annoying I wouldn't call it violent.

Want to swap rear ends?

My '86 Burb C20 has 4:56's, and I am wanting to go to 3:42's. I am really trying to make a highway cruiser out of this thing.

Damn, I take it you have seen the other thread from a while back where I decided I'd like to go FF and 4.56 To bad your in Illinois and I'm in Washington or I'd be all over that offer. We could park next to each other and swap parts!

 

[SirRobyn0]

Checked out the driveline with my straight edge this morning. The front part of the shaft is perfectly straight and shows absolutely no unevenness. The rear shaft has just the teeny tiniest of deflection in one spot. The only way to possibly measure it would be with a feeler gauge maybe a thousand of an inch. I don't think it's enough to cause a vibration, but I'm putting in the notation category.

What I did find @82TwoHeadlight is there is some slop at the transmission I had not noticed previously. If I put the truck into neutral and grab hold of the drive shaft yoke right at the tranny I can move it up and down. Not tons, but maybe a 1/2 inch. Enough so that I can make it go clunk, clunk when I move it. So I think replacing the tailshaft bushing is my next move. Is it just as simple as it looks? Unbolt the tailshaft, drive out the old bushing and seal, install the new stuff. Do you think I'll need to replace the yoke? I didn't notice it having a lot of wear when I had the shaft out. Thanks.

 

[82TwoHeadlight]

The replacement is straightforward, remove the driveshaft, then the tailshaft, and remove and replace the bushing. I tried replacing the bushing on my own and ruined the new one. Rather than buy another and ruin it too I went to the salvage yard and got a "good" tailshaft off an astro van and bolted it up. I didn't have the right tools to press the new bushing into the original tailshaft without ruining it.

Good luck! Post up and let us know how it goes.

 

[SirRobyn0]

Good luck! Post up and let us know how it goes.

Thanks for the info. I will be sure to let you all know how it goes and if it fixes my vibration. I'm not 100% convinced that it will, but it I can see that's an issues.

 

[SirRobyn0]

Not much of an update yet. We had some near 90 degree weather mid-week and on Tuesday I had trouble with the truck getting hot at idle. Looks like I need to replace the fan clutch, which is simple enough, but with as much and as far away as I drive this truck, with the trailer to sometimes, I'm going to go though the cooling system tomorrow morning. Plan is replace radiator hoses, heater hoses, thermostat and depending on how the inside of the radiator looks when I drain off the coolant it might be coming off for a semi-home brew chemical flush.

I did pick up the bushing and seal kit so if time permits I'll do that as well, just not sure if time will hold out and the cooling system takes priority right now.

 

[Raider L]

@SirRobyn0,

I'd say that the tail shaft bushing is worn enough to raise it at all is enough to make it vibrate. To bad you couldn't down it to do what I was telling you about, the roller bearing tail shaft bearings instead of a bushing. But if you could move it a half inch...man! Yeah, I know that guys kit was probably expensive, but a new bushing will get you going.

Being science minded about a lot of this stuff even though it's auto mechanics, I'd be interested in finding out what would cause such wear in that bushing. I've never had that problem even after over three hundred thousand miles on my truck I guess I still wasn't putting enough of whatever it was to cause that kind of wear. I know these transmission guys on this forum would know. I have a little squeak in the frame from time to time. A chassis guy said after as many miles as I have on the truck the rivets here and there might be loosening. I think that's funny because it sounds like my body, it squeaks every once and awhile to, from to many years on my frame. lol

 

[SirRobyn0]

@Raider L I know what you mean about being science minded with auto mechanics. So here is the really interesting thing. The driveline before I changed the U-joints still had the original factory non-greaseable U-joints, held in with the Teflon stuff. None of them were loose and none of them were binding, except the one by the differential which did have a small bit of play in it. So I went ahead and changed all the u-joints and carrier just so I'd know they were all new. My truck has 235K on it, I'm reasonably certain that is accurate. So what would cause that kind of wear in the tailshaft? we'll never know for sure. But it would be fun to know. It's also a 36 year old truck, maybe that's not the original driveline. Maybe someone ran a bad u-joint until it exploded and grabbed this driveline out of a wrecking yard, but the damage was already done to the tailshaft bushing.

I might have done the roller bearing, but when I was ordering my parts for the cooling system, I asked about the bushing a national bushing and seal kit was $10 in stock. My transmission isn't doing anything it shouldn't be, but at high mileage, and towing with it, I'm expecting it to be likely to need to be rebuilt in the next few years anyway. Which will raise the question keep the 700R4 and upgrade it or go to a more heavy duty transmission like the TH400, or a heavy duty built TH350. I do like the overdrive and low first gear of the 700 though.... I guess what I'm saying is I don't want to invest to much money into the 700R4 until it's rebuild time. I guess I'll cross that bridge when it's time.

 

[Rusty Nail]

**** is the status of the Check Engine light?
Is there any TCC code present?

Wait a minute....it's 1984 with a 700r4?

TCC yes?

I haz another good add!

Looking at the distributor cap.. What are the orientation of the #5 and #7?



At no time reading the entirety of this thread , did I have even one thought imagining a rotating driveline culprit will be found.

BUT! I DID wonder about sticking distributor weights and swapping 5 with 7.



Hope this helps!

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How does John Anderson help?!

 

[Rusty Nail]

* if it's "all stock" then you haz intact EST system?

Did I say TCC solenoid already? Ain't it frickin Hard AF to set that code, whatever it is? I don't remember the trick.