Vibration Experts-Chime In
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Vibration Experts-Chime In
Well I've been chasing vibrations on my 50 F-1 for the last 3 years. I've put on new tires and rims, balanced the tires on the truck, and most recently I rebuilt the transmission but there still is a vibration at 50 mph and over. It happens probably half of the time. The odd thing is that if I work the clutch in and out a few times I can usually make it go away. The clutch (Weber) and pilot bearing was also new when I restored the truck 3 years ago. The pinion angle looks OK but I'm wondering about the driveshaft. I had it lengthened and balanced when I put in the 9" rear. The first time I got the driveshaft back it vibrated horribly so I brought it back and had it done over. Can you tell I don't trust these guys.
Other than taking the driveshaft somewhere else to check the balance again I'm out of ideas. So what do you think?
Other than taking the driveshaft somewhere else to check the balance again I'm out of ideas. So what do you think?
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Originally Posted by ALBUQ F-1
I assume this has the stock drivetrain other than the 9"?
Check the tailshaft of the tranny for slop. Also the trans mount for deterioration.
Check the tailshaft of the tranny for slop. Also the trans mount for deterioration.
Lead Driver
Joined: Oct 1999
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From: Kalispell, MT
If it didn't vibrate before the driveshaft was lengthened and it did after..........
I'd take it to another shop - ask local race track drivers who they trust with driveline alterations and go there. Might double check your u joints to make sure everything is lined up evenly.
I'd take it to another shop - ask local race track drivers who they trust with driveline alterations and go there. Might double check your u joints to make sure everything is lined up evenly.
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I probably will take my driveshaft to the other place around here that does them to verify balance and phasing.
I guess the part that really puzzles me is why it doesn't always vibrate and why working the clutch can make it disappear. Is it possible the flywheel/clutch is a little out of balance and when that matches up with the "high" spot on the driveshaft it vibrates and when they are opposite of each other they cancel out? OK, I'm grasping at straws here.
I guess the part that really puzzles me is why it doesn't always vibrate and why working the clutch can make it disappear. Is it possible the flywheel/clutch is a little out of balance and when that matches up with the "high" spot on the driveshaft it vibrates and when they are opposite of each other they cancel out? OK, I'm grasping at straws here.
Fleet Owner
Joined: Jul 2004
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From: NM
What angle did you set the 9"-er's pinion at? And where does the pumpkin sit, side to side? Is it near to center (at the yoke) or offset significantly? Some 4x4 9"ers have an offset pumpkin. I'm suspecting angular misalignment, although the de-clutching thing is puzzling.
What shape is the pinion of the 9"er in? What ratio is it?
My experience with out-of-balance driveshafts is that they have a small range of mph's that they vibrate badly at, but there are a lot of variables here -- axle ratio, tire size and type, etc.
What shape is the pinion of the 9"er in? What ratio is it?
My experience with out-of-balance driveshafts is that they have a small range of mph's that they vibrate badly at, but there are a lot of variables here -- axle ratio, tire size and type, etc.
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More Turbo
Joined: Jun 2003
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JDMick-
I had the exact same symptom with my '56 3 speed column shifted light duty trans. After going through clutches, driveshafts, motor mounts, pinion angles, and everything else you can name, I had the trans rebuilt. The rebuilder discovered that the output shaft was bent, and I guess depending on how and where the clutch disc was clamped the vibration could be cancelled out or made worse.
Try removing the driveshaft, and then turn the output shaft with your fingers. I'll bet you will see some up and down movement as it goes through 360 degrees. I did this before I ttok my trans out and told the rebuilder I thought he should check the shaft with a dial indicator. He said he had never seen a bent output shaft but that he would check. Anyway, the problem was solved with a straight shaft.
Steve
I had the exact same symptom with my '56 3 speed column shifted light duty trans. After going through clutches, driveshafts, motor mounts, pinion angles, and everything else you can name, I had the trans rebuilt. The rebuilder discovered that the output shaft was bent, and I guess depending on how and where the clutch disc was clamped the vibration could be cancelled out or made worse.
Try removing the driveshaft, and then turn the output shaft with your fingers. I'll bet you will see some up and down movement as it goes through 360 degrees. I did this before I ttok my trans out and told the rebuilder I thought he should check the shaft with a dial indicator. He said he had never seen a bent output shaft but that he would check. Anyway, the problem was solved with a straight shaft.
Steve
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Joined: Oct 2004
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From: Durham NC
In addition to the straightness and balance of the driveshaft also check the angle of the output shaft and pinion. They should be parallel but not pointed directly at each other. in other words ther should be a small same angle thru each universal, neither should be straight. same goes for looking straight down on the driveshaft, if the engine is offset side to side it should not be angled to point at the pinion. As for phasing, both yokes on the driveshaft should be parallel. Many larger heavy truck repair shops are equipped to do driveshaft work since few commercial trucks use the same length driveshafts. Did they make the driveshaft the correct length? With the truck sitting on it's wheels the slip joint should be 1/2 way into the tranny, if the length was measured while the truck was jacked up it may be too long. Too long a driveshaft or one where the splines are burred, rusty, dirty or not greased so the slip joint binds can cause symptoms like you describe.
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****UPDATE*****
Thanks for all the helpful replies. Since you guys also seemed suspicious about the driveshaft I decided to take it to the other place in town yesterday. Well they already found a couple of interesting things. They said there was some side play between the u-joint and the housing (something I didn't notice) and that the yoke looked peculiar. The guy says it looks like the yoke has angled (he had a fancier term for it) splines which from his experience weren't common until the late 60's. The splines were usually square when you look at them from the end. Well I just looked at my transmission tailshaft and yes, by my eye they look square. Too bad my dad isn't around anymore so I could ask him if he did any driveshaft repairs in the late 60's, shortly before the truck was parked. The problem wouldn't have been apparent when driving around the farm though. I'll double check all the pinion angles when I reinstall it. Thanks again and I'll keep you posted.
Thanks for all the helpful replies. Since you guys also seemed suspicious about the driveshaft I decided to take it to the other place in town yesterday. Well they already found a couple of interesting things. They said there was some side play between the u-joint and the housing (something I didn't notice) and that the yoke looked peculiar. The guy says it looks like the yoke has angled (he had a fancier term for it) splines which from his experience weren't common until the late 60's. The splines were usually square when you look at them from the end. Well I just looked at my transmission tailshaft and yes, by my eye they look square. Too bad my dad isn't around anymore so I could ask him if he did any driveshaft repairs in the late 60's, shortly before the truck was parked. The problem wouldn't have been apparent when driving around the farm though. I'll double check all the pinion angles when I reinstall it. Thanks again and I'll keep you posted.
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Well it looks like the problem is solved. I found a good used yoke to replace the original (the new one the driveshaft place found didn't fit). Between that and the other new parts and rebalancing it seems a lot smoother now. The pinion on the rear end is off about 2 degrees so I'll have to fix that sometime.Thanks again.