Darn Vibration
 

I have this vibration in the peddle of my truck, more so when i go to let off the gas, just before i let the peddle up as far as it can go, the vibration will get worse (sometimes). My u-joints have been changed, any idea on what it could be? If im going real slow, say as if im driving up my hill, It seems like once i hit a certain speed or rpm, the truck will really start to shake, i kinda kinda feel the bed shake with it, unless i give it more gas to go faster. Do my driveshaft be all messed up or something? Im clueless.

Mic -

Is your driveshaft balanced? If it once was, the balancing weights may have come off.

When I brought my 56 home, it also had a vibration that got really bad at certin speeds. I didn't have to spend anytime diagnosing the problem, though. The driveshaft fell out on the way home! The driveshaft guy pointed out the problem immediately when I took him what was left of the shaft. :-X07

I went to a driveline specialty shop and got a whole new custom driveshaft fairly inexpensively. If your current one is in good shape, just checking it out and rebalancing won't cost very much.

Did you mark the yoke and shaft when you changed the u-joints? If not, I would try taking apart the shaft at the re-placed u-joint and rotate it 180*. That may correct the possible balence problem. You might also want to check and see that all the pins in the u-joint cups are properly positioned, sometimes on or two will fall over and cause problems.

you're right about the pins huntsman, and when they do they're a gooey mess to get right again. I pulled my tranny a few months back and in the process dropped one of my pin bearings from one of the u-joints. I almost went nuts looking for it. and had to re-position all the others just right to get it back together.

im not to great with hands on stuff, im 22 years old and im pretty much getting started with the hands on, the u-joints were changed by somebody else and i would assume they did the job right..The driveshaft is kinda old lookin though, i took a look at it and it looks like it wants to fall out lol, i mean i dont know all that much, it could be working fine, but it looks realllllly old...Any idea on how much a driveshaft would cost? I would like to get a brand new one if the price is right, im tryin to get things new so i can win at shows lol

If the rearend has been changed your pinion angle may be out of phase with the transmission. This will cause vibration at certain speeds. If you have someone check the driveshaft and u-joints ask them to check the angle also.

micginish, one thing you could check is if there are any not-so-old looking places on the driveshaft. If there are any in the shape of a square or rectangle it's a dead givaway that your driveshaft slung some weights (and is therefore out of balance). A cheap new one won't win any shows, a billet one would win shows but not be cheap.

It sounds like you are talking about a vibration at slow speeds? It's more likely a bad motor mount, even a bad water pump, than driveline.

You haven't told us what year truck this is, what engine, trans, etc. Is it an automatic? Could be the torque converter if so.

Yes! Ross beat me to it.

A bad motor mount was my first thought, a bad trans mount is a lesser possibility.

Mike

Old does not mean bad - but sometimes mud and gunk can cause a rotating mass to get out of balance. Why don't you start your "hands on" experience by dropping the driveshaft, wire brushing it clean, and repainting it?

You likely will need to do it twice - once putting it back exactly as it was, and, if you still have the same vibration, again but this time rotated 180 degrees. If you want you can have your driveshaft balanced, but I doubt that will help.

It is an easy job, well within your abilities. The only danger is the possibility of dropping an end cap off one of the U joints. Just wind some tape around the joint to hold the caps and you will not have any problems. If you should drop a cap it is not the end of the world, just make sure the needle bearings are all there and in the right position when you put it back.

While you are under there, give everything a good shake and tighten anything that wiggles.

The only way to get "hands on" experience is to jump in and get your hands dirty. And don't confuse a parts changer with a mechanic - almost anyone can replace everything in sight, very few can fix something.

i have no idea how to drop my driveshaft, i wouldnt even know where to start..Ive only done things like change my oil and the basic stuff like that...I have a Chiltons guide for my Blazer that i look through every once in awhile but nothing has happened to give me the chance to try anything in there yet...

Some info about my truck..56 F100..351 Cleveland engine...obvious chop..Grand Torino IFS..The tranny is a 3 spd cruiseomatic (automatic)..

I'd take it to a shop, you're likely to waste time and money trying to figure it out here

Micginish -

I have a 56 that is set up almost identically to yours. Before buying it, I hadn't worked on any cars for 30 years. If you have very deep pockets and can find someone qualified to do the work needed on a 50 year-old custom truck, you are in business. You can afford to avoid learning mechanical skills.

If, like me, your funds are more limited, you need to get busy and learn by doing. There is a tremendous amount of experience among the forum members. However, at one point every one of us knew NOTHING about mechanical stuff.

Dropping a driveshaft is certainly a simple place to begin the learning. Take a crayon and mark a line accross one end of the rear universal joint and it's journal. Back out the four bolts that secure the clamshell universal clamps at the differential. Shift the shaft forward (toward the tranny), then drop the aft end down and slide the forward yoke out of the tranny. Voila! Driveshaft out. Carefully remove the universal joint, clock it 180 degrees, then reinstall it and reverse the procedure above.

You're on your way to being a journeyman mechanic. :-D

I would tend to agree with that as long as you know of a good shop. Vibration problems can be very difficult to pinpoint. Ask me how I know. I've spent a lot of time and money trying to rid my 50 of vibrations. In my case it's been a combination of problems from an out of balance driveshaft to an unbalanced imported brake drum and bent wheels. Next on the list is a transmission rebuild to get rid of what vibration remains. Good luck.:)

yeah driveshafts are easy. After an hour of staring I figured out how to get mine out. Randy has it covered. Mark the line on the tranny end, bull four nuts, slide forward, slide aft, and you're done.