| 47Jack | -- 05-03-2011 @ 9:31 AM |
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Now that the weather is warmer I've been putting some miles on my 47 1 and 1/2 ton flatbed. I'm getting a vibration as decribed by other posters in the 35 to 45 mph range. What is unuasual is I can take it out of fourth gear, double clutch and return it and the vibration disappears. Sometimes I have to do this several times before the vibration goes away. The vibration will return only after I have stopped and after I get into high gear. I replaced the center bearing a while back and the "U" joints seem ok. My car mechanic thinks it harmoncs in the engine but I don't think so. Is this something any of you have come across? Thanks, Jack
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| 37RAGTOPMAN | -- 05-03-2011 @ 9:44 AM |
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Was the vibration there before you worked on it,???were the u-joints free and not binding or sticking,? any rust on the bearing surface, are they greased.? a binding U-JOINT will cause many problems, even if it was not installed correctly. off center, a spacer or snap ring different size thickness etc,??? any loose engine mounts. or trans mounts? hope this helps 37 RAGTOPMAN
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| deluxe40 | -- 05-03-2011 @ 9:57 AM |
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Here's a theory (or wild guess as the case might be). Your pilot bearing is worn and it allows the front shaft of the transmission (with the clutch disk riding on it) to land in different places when you let the clutch out. If it lands in the center you don't get a vibration; if it lands off-center you get the vibration because the clutch disk is off center and out of balance. Lots of things can cause vibration, but most of them wouldn't change when you use the clutch.
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| supereal | -- 05-03-2011 @ 10:11 AM |
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Given that almost all problems arise from the last work done. I suspect you reinstalled the driveshaft "out of phase" after the center bearing was replaced. It is always important to mark the halves of a driveshaft before removing them so they can go back in the proper phase. Remove the back half and rotate it 90 degrees and see if the vibration goes away. If not, turn the shaft another 90 degrees. Vibration occurs when out of balance shafts end up with the heavy parts on the same side. Our shop shortens or lengthens truck frames and makes up driveshafts to fit. It isn't rare to have to change the position of one part of the assembly to get it to smooth out. Also check all u-joints for any play. a loose joint cap bearing can account for the change when the load is removed. You can't check u-joints by sight.
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| 47Jack | -- 05-03-2011 @ 2:50 PM |
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Thanks for the replies guys. I'll try to answer your questions. You all bring up some very good points. It did vibrate before I changed the center bearing, rust came out when I first greased it that's why I changed it. I did make soapstone marks when I disassembled the drive shafts but it's possible I didn't mate them up when reassembling but I was aware of supereal's advice before I started the project. I only had the U bolts apart by removing the bolts and didn't remove the clips to check the other two journals on each U joint. This I need to do. There are four because of the two shafts. The pilot bearing concept is interesting but I think I will double check the driveline before considering that. Thanks for all your good advice and I'll let you know when I find the remedy. Jack
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| supereal | -- 05-03-2011 @ 3:06 PM |
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That narrows it down to a rusty and/or dry u-joint. When they run out of grease, the needles break up quickly. I doubt that an engine or transmission problem is involved, as you would have vibration in all gears.
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