Driveshaft vibration

[SirRobyn0]

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.

 

[shiftpro]

Rotate your tires.

 

[SirRobyn0]

Rotate your tires.

Good idea, but all 4 tires have been replaced, wheels are true, new tires made no change to vibration.

 

[Magna86]

Check your engine and transmission mounts. Do you feel it in the wheel, thru the cab, or a certain area?

 

[Keith Seymore]

A couple thoughts:

The fact that it is worse with the converter locked up leads me to believe that it is an interaction between the driveline and the engine; specifically engine firing frequency (fourth order of engine rpm) and driveline u joints (second order of driveline) are often very close together and stepping on each other.

Since you can't make the engine firing frequency go away (or you will cease to motivate) that means you need to attack the driveline. I'd check U joint working angles to make them straight as possible, or look for a bad u joint causing a problem.

K

 

[Bextreme04]

Take a look at carrier bearing placement. On my 74 C20 I had a slight vibration even after replacing the ujoints, and I could change the vibration by sliding the carrier bearing left or right to change the driveling angle.

 

[SirRobyn0]

Thanks for the ideas so far. Here's my morning update:

Check your engine and transmission mounts. Do you feel it in the wheel, thru the cab, or a certain area?

Checked and double checked, Does not feel like an engine or trans mount vibration. Definitely comes though the floor / Cab.

Take a look at carrier bearing placement. On my 74 C20 I had a slight vibration even after replacing the ujoints, and I could change the vibration by sliding the carrier bearing left or right to change the driveling angle.

I know my carrier will slide forward and back thus changing the amount of travel on the splines, but I don't think I have much side to side movement, but I will look at that to see if it's an issue.

A couple thoughts:

The fact that it is worse with the converter locked up leads me to believe that it is an interaction between the driveline and the engine; specifically engine firing frequency (fourth order of engine rpm) and driveline u joints (second order of driveline) are often very close together and stepping on each other.

Since you can't make the engine firing frequency go away (or you will cease to motivate) that means you need to attack the driveline. I'd check U joint working angles to make them straight as possible, or look for a bad u joint causing a problem.

K

New U-joints, so I wouldn't think that would be the issue, but as you know a defective part or a error on my part during installation is always possible. The thing is that the vibration seems the same both before and after replacing the U-joints and carrier bearings. Stock ride height so I wouldn't think that there is an angle issue, but it is something I should probably look at anyhow.

Additionally here is my hose clamp balancing findings from this morning. Working back at the differential I tried 8 different combinations. 4 positions with both one and two clamps. In some positions it seem that it made little to no change, in others it seemed like I was creating a different vibration. My take away whatever the issue is I don't think it's on that end of the driveline. So I moved to the front of the driveline by the transmission. By this time I was running out of time so I did not get much experimentation done. I only used one clamp in 2 positions, but adding weight there and moving it around definitely changed the intensity of the current vibration. My take away is that whatever the issue is it is with the first shaft from trans to carrier. I will play around with it tonight I'll take a look at the angles of the shaft as well and see what I can come up with. Thanks.

 

[Bennyt]

Not trying to be an a$$ but why not have it balanced professionally at a shop so you aren't playing a guessing game? I believe it's only $20-30 to have it checked. They do it same day usually and can probably spin it up and check it while you wait.

I paid $105 last week to have the one piece shaft on my sons C10 straightened, balanced, and new high quality U-joints installed. I had already removed the old joints and powdercoated it.

Is your truck lifted/ lowered?

 

[Craig 85]

It's been 20 years since I've had a 2WD Square, but I thought I recalled at least 1 of the 3 C20/30 trucks I had, had a shim between the carrier bearing and the crossmember. Maybe I'm just smoking something...

 

[SirRobyn0]

Not trying to be an a$$ but why not have it balanced professionally at a shop so you aren't playing a guessing game? I believe it's only $20-30 to have it checked. They do it same day usually and can probably spin it up and check it while you wait.

I paid $105 last week to have the one piece shaft on my sons C10 straightened, balanced, and new high quality U-joints installed. I had already removed the old joints and powdercoated it.

Is your truck lifted/ lowered?

Stock everything. Thank for the reminder I meant to call the driveline shop this morning to get some info like cost and turn around time for a professional balance. Basically the hose clamp thing came about because it was something I could try, starting last night.

It's been 20 years since I've had a 2WD Square, but I thought I recalled at least 1 of the 3 C20/30 trucks I had, had a shim between the carrier bearing and the crossmember. Maybe I'm just smoking something...

Mine does not have a shim, no idea if it should.

 

[SirRobyn0]

Not trying to be an a$$ but why not have it balanced professionally at a shop so you aren't playing a guessing game? I believe it's only $20-30 to have it checked. They do it same day usually and can probably spin it up and check it while you wait.

I paid $105 last week to have the one piece shaft on my sons C10 straightened, balanced, and new high quality U-joints installed. I had already removed the old joints and powdercoated it.

Is your truck lifted/ lowered?

Here's a good one for you, and this is just par for the course in this area anymore. The only driveline shop I'm aware of still left is Drivelines NW, I was just quoted $120 to balance a 2 piece driveline, and 6 days. No not 6 days until I can drop it off, they need the driveline for 6 days after it's dropped off.

Seem a little ridiculous to you? Yea me to, but I also expected that.

 

[shiftpro]

Good idea, but all 4 tires have been replaced, wheels are true, new tires made no change to vibration.

I just had to mention this because I chased driveline vibration for a long time on my dually (avatar pic<<). Higher tire pressure helped, weight in back helped but it was still there. Finally changed out rear tires and vibration is gone.

 

[SirRobyn0]

I just had to mention this because I chased driveline vibration for a long time on my dually (avatar pic<<). Higher tire pressure helped, weight in back helped but it was still there. Finally changed out rear tires and vibration is gone.

No I appreciate all ideas and this is how I always look at it when I'm trying to help someone out. If it doesn't help them, it might help someone in the future that reads the thread, I mean all this stuff is open to view on the internet after all.

 

[SirRobyn0]

I had a small amount of time after work tonight, now this is just like an extra 15 minutes, keep in mind I work the day job at the shop plus own a farm. So an extra 15 minutes is what I was left with. I spent that time stopping on the side of the road to adjust the clamp on the driveline to different positions, this is nearest the tranny yoke. There is one spot where it seems to reduce the vibration somewhat and also move the speed at which the vibration occurs up a bit. So the next time I get a few extra minutes I'll try adding another clamp in the same spot and see if a little more weight will help a little more or not.

I have had no time to look at angles, that will probably have to wait until this weekend so for the time being it's just going to be playing with the weight a little to see what effect that may have.

 

[SirRobyn0]

Ok I'm going to ask you guys silly question. On my truck the rear shaft to front shaft slip joint is keyed and will only go on one way, however on the front the driveline has the missing spline for a key to go into, but the transmission is not keyed. I marked the driveline to the transmission housing so it went back in the same way it came out, but what about in the past? No idea what has been done, and not really even sure if it matters. The mechanic in my has always said it doesn't matter, I've always marked that stuff when possible just to play it safe. I guess the question is do you think it matters? If the shaft wasn't keyed at the tranny I wouldn't even be thinking about.