The Stovebolt Site Forums The Shop Area General Truck Talk Very bad low speed shaking going on

Okay guys and gals, here's question. A few weeks ago I reported that I had finished my '53 restoration. Engine runs great and sounds good. However, when I finally got her registered and insured and took her for the first drive, I found a very bad vibration and shaking going on at low speed. There is no vibration when idling and even when accellerating in neutral, so doubt it is anything to do with the engine being out of balance. I jacked up the rear end on stands, put it through all 4 gears and watched the driveline. I don't see anything that appears out of balance with the drive line and it has all new u-joints. The shaking is severe enough that I immediately turned around and brought it home from a block away. Remember, this is a ground up restoration, so the engine has been rebuilt and the tranny was removed. New cutch and throw-out bearing, etc. It almost seems it has to be in the transmission and shifting. If you recall, I had trouble getting the transmission to mate with the engine until I put the clutch in and then all slid together. The truck has all new rubber and wheels are balanced. It shakes bad enough that I am concerned it could vibrate apart, so it is no small problem. Any suggestions? I'm laid up with a broken leg right now, so it will be awhile before I can check out any suggested remedies. Thanks folks.

Is it an open drive shaft? When you had it up on jacks did you run it up in high gear & see if vibrates on the floor. It almost has to be in the drive shaft or tires. Did you check the wheels & tires for being out of round. If you used custom wheels sometimes they will not seat up against the drum with the original rivets holding the drums to the hubs. you have to grind down the heads.

Rick,

Sorry about the broken leg. If you can sit in the driveway (the truck), bring the RPM's up and nothing happens, then the problem isn't with the rotating mass of the engine and clutch assembly. You have already verified this...good.

If the thing goes nuts at low speed, my bet it isn't a tire. Does a 3/4 ton have a two piece driveshaft with a center support or center bearing? For something to shake as violently has you indicate, and a a very low speed, it must be way out of balance.

The driveshaft, if not assembled properly could fit the bill on the "whipping" at low speed scenario. If the rig was on jackstands, not under load, you might not get it to happen.

When your gam heals, grab a creeper and spend some time shoving and shaking on the drive train. Look for scraped paint where some support might have jumped around...you'll find it!

Stuart

You said, "a low speed" vibration. Were you able to get your speed up and see the vibration quit? Did it vibrate while moving with the clutch in?

Big Chevy, I wish I could remember on the vibration with the clutch in. My gut tells me it did not vibrate once the clutch was depressed, but I can't remember for sure. Stuart, yes, this truck has a 2-piece drive line with a carrier bearing. All was replaced. I did notice that the seal at the carrier bearing looks a little off center, but I tried loosening the two bolts that hold the bearing housing and prying it to see if there was any movement. Couldn't find any. Wrenchbender, I used all new tires mounted to the original rims and balanced professionally. I didn't check to see if the floor vibrated when it was jacked up. I'm fairly certain it has to be in the driveline as well, guys, but want to make sure I'm not overlooking the obvious. I'll be laid up for at least 2 months. Had a surgeon break my leg and cut out a wedge of bone. It was that or a knee replacement. That's the fun of getting old. The worst part is not being able to drive the '53!

Put the truck on jackstands under the rear axle so the suspension and driveline are in driving relation to each other. Then look underneath when it is in 1st gear. My guess is it may be a drive-shaft phasing issue if you took the 2-piece driveshaft apart and did not put it together in the correct phase.

you could also have a bum U-joint, output shaft bushings from the trans, or pinion bearings from the rear diff.

Good Luck.

Here is a chart of causes of vibrations at different speeds. It's from an old issue of Pickups 'n Panels 'n Print.

Hi Rick,
I don't know much about AD trucks but on my TF truck I had a vibration like you describe. It turns out I had a broken upper shock mount on the front. It caused a very violent vibration in the frontend. I thought the truck was going to come apart. Of course if yours stops when you depress the clutch then it's probably something else like driveline phasing. I hope that helps.

Does the steering wheel "walk" with the vibration? Arew the tires bias ply that may have been sitting quite a while? My first place to look would be tires. Borrow some known good ones, like modern radials, and swap them out to verify whether it fixed anything,
Scott

I was having much the same problem you were Rick. A lot of vibration at low speed. It would disappear at higher speed. I thought it was the transmission. Finally, the pinion nut fell on the road. Along with the pinion flange and back of the driveshaft and seal. I put it back together right on the lonely dirt road and it ran nice and smooth all the way home. I was lucky, this can be a deadly thing when this happens.

Hi ya Rick,
Been followin' this thread and your restoration, in fact I even have a Rick's folder with the pics that you have posted in it. Nice job! I'm interested because I'm a fellow 3604 (1950) owner and can appreciate what you've had to go through in order to keep a 3/4 or 1 ton original. The guys that have the half ton trucks mighn not think so, but they are on a cake walk compared to us poor guys who chose the 3/4 and 1 tonners!!! Poor us!!!! Ha!
Just joshin’ guys, but there are, some added problems with the heavies that ya don't encounter with the light trucks, availability of driveline parts probably being the biggest one.

So lets get back to the vibration. What tires did you end up mounting on the original rims???
I spent a bunch blasting and painting the split rims and mounted a brand new set of 7.00 x 15” Power Master Bias plies, with new tubes and flaps. I drove the guys and myself at three different tire shops nuts rebalancing the tires because of vibration. Of course everyone has heard the tale of square bias ply tires. Since I’m an old timer that’s all we had when I first started driving and for two decades I drove on bias ply tires before I saw my first radial tire. I can only recall there being a little thump with them after setting over night.

That my friend has changed! These Power Master bias plies were the lumpiest tire I had ever encounter. On a warm day it took a good 8 or 10 miles drive before they rounded out and even then I would get a lot of shuddering at different speeds. I could park the truck for a half hour while I did a little shopping and when I came out they would run flat for a couple of miles.
If I didn't drive the truck for a couple of days I would get such a severe vibration at low speed that I literally thought the front fenders were going to be shaken loose. If I pushed her up to 35 or 40mph it would smooth out quite a bit. In other words I could drive through the vibration, you know, like going through the sound barrier. It was kind of embarrassing if I happened to be in slow traffic when I first started out on a trip because the front end was just a blur for the first few miles.
Now jump ahead a few months and I now have a set of 1980 C20 rims with new Cooper tubeless radials on her and if it weren't for the 216 hammering away you would think you were in a late model truck. The only vibration I feel now is from the bumps in the road. I do still have a little annoying throbbing at 46mph but it only comes in and goes out at the speed and I truly think it’s from the frame flexing. I even have similar shudders on my new GMC Sierra at certain speeds.
Although I have tried, I really can't begin to tell you what a difference there is between the two types of tires.
I am absolutely convinced that the quality of the bias ply tires being produced today is vastly inferior to the tires of yesterday. So, I you're biased, look there for your problem, if not then maybe this will help some other poor soul down the road who is having a problem.
Denny Graham
Sandwich, IL

p.s. The split rims and bias plies are stacked in the corner and are to be used only for display while under the scrutiny of the VCCA judges.

Denny
Read your comments about bias ply tires being inferior today than in the past. Could be. I had Cooper bias 650-16 on the 49 for years and as they got older, harder and probably worn out in the belting, my ride shook at 40 mph exactly.
I changed for Firestone bias ply. I have never been happier with a set of tires. My ride is smoother and there is no 'good morning' bump.
However in this case Rick may have problems with his tires but I am inclined to think maybe something in the drive shaft or bushing.

All great suggestions guys. Thanks for the replies. I'm inclined to think it is the driveline as well. Scott, you mentioned the possibility of not putting the driveline together in the correct phase. What do you mean by that? By the way, I did have the truck jacked and resting on the rear axle as mentioned when I watched for something out of round as the driveline turned. I really don't think it is an issue with the tires and wheels in this case. I have some time to try to work through this. Any other ideas out there while we're on the topic? Thanks to all.

Rick,

Take the whole driveshaft and bearing to a driveline shop and they can validate the phasing as well as balance. It may cost you about $100 if they need to balance it.

The two piece driveshafts are splined together in the center by the bearing. If you get the front and rear section off by as much as one spline, you will have driveshaft issues. IF you have a perfectly level concrete floor, you can use a few steel blocks. Start at the front, block up the u-joint on an end cap, make sure it is square to the floor. Then the next joint (same shaft) should sit perfectly flush on the next block. Then the rear shaft joints should also sit perfectly flush on the last 2 blocks. If the rear shaft does not sit flush that indicates you are off a spline on on the bearing support and slider.

While you have the shaft out, check the U-joints to see if you have one that is brinnelled or frozen.

Also, if you changed springs, axle mounts, or other rear suspension components, you may have a rear pinion angle issue, however this is a remote possibility.

Scott

Hey that's great information Scott. I'm betting that is the problem. I probably installed wrong. I started with the front shaft to the intermediate bearing and then when I connected the rear driveline, the rear u-joint wouldn't line up, so I jacked up the rear end and turned the rear wheels until all lined up and then put it together. Sounds like I could have screwed up the alignment doing it that way. I'm still not sure of the sequence for putting it together and the shop manual instructions were a little confusing to me when they talked about making sure the driveline lined up properly. They didn;t say how that was done -- just that it was important. Prior to the rebuild I didn't have any issues with the driveline, so this is probably the source of my problem. Anyone have any photos showing this process Scott mentioned? Pictures are always helpful. Thanks again Scott.