2manytrucks Posted January 8, 2012 Share Posted January 8, 2012 (edited) have you tried running it up on jack stands? very carefully, of course. at least then maybe you could figure out if it was front or rear. Edited January 8, 2012 by 2manytrucks Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97109 Share on other sites More sharing options...
Olivetroad Posted January 8, 2012 Share Posted January 8, 2012 have you tried running it up on jack stands? very carefully, of course. at least then maybe you could figure out if it was front or rear.Just don't hire some guy named Ferris Bueller to help set it up. Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97128 Share on other sites More sharing options...
leversole Posted January 8, 2012 Author Share Posted January 8, 2012 have you tried running it up on jack stands? very carefully, of course. at least then maybe you could figure out if it was front or rear.Yes...ran all four rear corners...even tighened up the brakes and ran each wheel individually at the "bounce" speed..have not figured a way yet to test the front...it would probsbly be easier to replace the entire fron axle than to build some powered variable speed roller setup... Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97138 Share on other sites More sharing options...
leversole Posted January 8, 2012 Author Share Posted January 8, 2012 Frustrated again...I took a bunch of videos today and can see no significant movement anywhere...the trunion bushings are not moving, doesn't look like there is any play in trunions or front spring bushings. I even shot the back of the transmission to make sure it is not moving around. All the while the front end is moving a couple of inches up and down! (the cab too!)Maybe I am looking too deep and ignoring the obvious...I am going back and start looking at the rear tires...If I had to describe the feeling, it would be that one of the rear tires is boken inside or way out of round at speed...If I remember correctly, when I first got the truck on the road it bounced at 40 mph only...after 8 used (90% tread) rears (6 alike and 2 alike) it developed the 22mph and 44mph bouncing that is driveing me nuts!...I have had everything off of the front except the wheels, I ran without drums, I put the fronts (new) on the rear, no change. I have run the rears in the air, but if a tire problem, not running under wieght may hide the issue. I also believe it to be a single tire, as it bounces all of the time at the certain speed, before, during and after curves which changes the wheel to wheel relationships.So, I will ask you experienced folk out there if you have ever heard of a faulty tire exhibiting issues at such a narrow speed range, AND half of that speed?My next move is to get the tire store to round me up some used rims (no tires) so I can run with four tires on the rear, swappin my tires out till I either find the source or go insane and commit hari-kari!Leslie Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97208 Share on other sites More sharing options...
Rob Posted January 8, 2012 Share Posted January 8, 2012 Fashion a platform to strap a chair to, or yourself to and look around while someone else drives.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97209 Share on other sites More sharing options...
leversole Posted January 8, 2012 Author Share Posted January 8, 2012 Fashion a platform to strap a chair to, or yourself to and look around while someone else drives.RobI think the truck would rot away to nothing quicker than I could teach "the wife" to drive it! Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97210 Share on other sites More sharing options...
Rob Posted January 8, 2012 Share Posted January 8, 2012 I think the truck would rot away to nothing quicker than I could teach "the wife" to drive it!I'm up against the same roadblock there. One other note is make sure the drive yoke pinion nut is tight and cotter pinned on the rear of the trans. I've seen those loose with Nylock nuts and they do strange things in the driveline. Have you had the driveshafts out? I've seen brinneling to the bearing surfaces and it acts strange also. On a final note; have you always been in the same gear at the same engine rpm when you notice the vibration? If so, change something either up or down to evaluate.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97211 Share on other sites More sharing options...
leversole Posted January 8, 2012 Author Share Posted January 8, 2012 On a final note; have you always been in the same gear at the same engine rpm when you notice the vibration? If so, change something either up or down to evaluate.RobIt will do it in other gears AND with the engine idling (in neutral or with clutch in)...it is speed related... Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97212 Share on other sites More sharing options...
Rob Posted January 8, 2012 Share Posted January 8, 2012 If certain the problem is speed related there would need to be some rotating mass out of parameter. This would not dissappear at differing speeds. However, a bind, (as in a bad universal joint) would, and could set up a vibration as a harmonic of the original and those are even in symptoms and multiples of the same symptom. I'd dissassemble the driveline to and evaluate along with the carrier bearing, (if there is one) for any rotational binding.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97216 Share on other sites More sharing options...
leversole Posted January 9, 2012 Author Share Posted January 9, 2012 If certain the problem is speed related there would need to be some rotating mass out of parameter. This would not dissappear at differing speeds. However, a bind, (as in a bad universal joint) would, and could set up a vibration as a harmonic of the original and those are even in symptoms and multiples of the same symptom. I'd dissassemble the driveline to and evaluate along with the carrier bearing, (if there is one) for any rotational binding.RobIf something were in a bind, wouldn't the problem present itself with the rears in the air? Not doubting what you say, but with the back of the truck jacked up it is smooth at all speeds...Also, not saying it means they are good, but I got a little spurt of grease from each cup when I greased the universal joints (no carrier bearing) Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97245 Share on other sites More sharing options...
David Posted January 9, 2012 Share Posted January 9, 2012 Is the driveshaft in phase? Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97247 Share on other sites More sharing options...
Rob Posted January 9, 2012 Share Posted January 9, 2012 If something were in a bind, wouldn't the problem present itself with the rears in the air? Not doubting what you say, but with the back of the truck jacked up it is smooth at all speeds...Also, not saying it means they are good, but I got a little spurt of grease from each cup when I greased the universal joints (no carrier bearing)Not necessarily. When the truck is in the air supported on stands, it takes a lot less force to rotate the rears than everything as in actual operation. Pushing the truck through the friction of the tires rolling, and overcoming the resistance of the air takes a lot of power right off the top. If you can, adjust the rear brakes to drag pretty good while you accelerate with the wheels on stands to load the driveline.You should be able to start off in the same gear you experience the vibration in or the brakes are too tight.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97249 Share on other sites More sharing options...
Lmackattack Posted January 9, 2012 Share Posted January 9, 2012 here is an idea/ remove the inside duals and then go for a drive. If the bounce is still there start swaping out tires with others untill it smooths out, could also have all balanced just for kicks and to elimanate the tires. The drums may be out of wack also They use to just weld weights to them, sometimes they rotted away and fell off tho?Trent Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97255 Share on other sites More sharing options...
miro Posted January 9, 2012 Share Posted January 9, 2012 Like you all said it is speed related and I still say you are getting harmonics in the frame because of the missing cross members. Remember you said it got worse tightening the frame bolts!!! Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97281 Share on other sites More sharing options...
220cummins Posted January 9, 2012 Share Posted January 9, 2012 If something were in a bind, wouldn't the problem present itself with the rears in the air? Not doubting what you say, but with the back of the truck jacked up it is smooth at all speeds...Also, not saying it means they are good, but I got a little spurt of grease from each cup when I greased the universal joints (no carrier bearing)If there is no carrier bearing you could have too long of a driveshaft with worn or binding u-joints. Measure your driveshaft and check with a driveshaft shop on recommended max length. I buddy of mine had a 84 KW tandem with air ride that had a bounce and Henry Farmer, good friend of my dads who was a rep for rockwell looked at it and recommended putting in a carrier bearing. He did and noticed a difference. Also if you wedges(wheel lugs) aren't set right and a set of wheels wobble like the passanger side intermediate axle has in the video it will bounce and shimmy. One set on my b61 (passanger drive) were out a about 3/8" and it shook and bounced to hell and back unloaded. Check you front fan shroud for tightness. The adjustment rods the crisscross can loosen up over time. Like miro said check you crossmember distances and add one if necessary. You seem to have a lot of little things that need attention and to be fixed the right. Do one thing at a time and by process of elimination you'll figure it out. Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97292 Share on other sites More sharing options...
Pawel Posted January 9, 2012 Share Posted January 9, 2012 Hello!I see there's a real problem to solve. While I can't help you with specific details, I thought I could offer some theory. For one - this effect where the bounce dissapears above 22 mph and returns at 44 mph. The physics describe similar effects as resonance. Resonance appears, where an object receives a vibration at a specific frequency - or it's multiple (called a harmonic). Then it starts vibrating very violently, sometimes to the point, where it gets destroyed. In school they often cite the unit of soldiers, marching on a bridge. If they "hit" the specific frequency of the bridge with their marching, they can even collapse the bridge (that even happened a few times before the army got trucks for their soldiers). So in your case the wheels turning are always slightly out of ballance - no perfecion in this world. Changing speed changes the frequency of vibration, that is transmitted through the suspension to the frame and so on. Once this frequency meets the specific or resonance frequency of something (yeah - tha's the big question - what is vibrating exactly?) it starts vibrating like shown on the video. How do you think - what could be that something? Is it the frame? Or is it the front suspension? Maybe it's the cab on its mount? Did you try your truck heavily loaded? Is it stil bouncing under load? How to stop that? Normally the theory says you should introduce more damping in the setup. If the frame was vibrating, you should make it stiffer - tighten the bolts, install another crossmember? If it's the front suspension, maybe a damper could help? Anyhow, I hope you can save the day, wish you good luck with your truck, and have a nice dayPaweł Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97301 Share on other sites More sharing options...
steamer Posted January 9, 2012 Share Posted January 9, 2012 Are your front shocks good Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97347 Share on other sites More sharing options...
leversole Posted January 10, 2012 Author Share Posted January 10, 2012 Talking to the last flurry of posts...No front shocks...driveshaft is only 43 inches, and has a nice little blalance weight and is relatively new with a shiny sticker from a driveline shop in CT. I have closeup video of the driveshaft and I cannot discern any movement or binding (just saying!)I have to have some blank rims to remove the inside duals correct? I will try that, and also cranking the brakes and running in the air...I would love to build some rollers to set the fronts on, then the rears, may induce the bounce as the truck is a whole system....Will put up some videos...Thanks for all of the ideas and comments! Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97390 Share on other sites More sharing options...
David Posted January 10, 2012 Share Posted January 10, 2012 Rule of thumb is 60" max for a driveshaft. Is it in phase? Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97394 Share on other sites More sharing options...
fxfymn Posted January 10, 2012 Share Posted January 10, 2012 I also don't have any specific advice on what to look for, but my bet is it something relatively simple. My experience when troubleshooting almost any issue is that something serious jumps out at you and that we all tend to look for the most serious problem we can imagine if the problem is not obvious. Often the real problem is something so simple we overlook it while we convince ourselves that whatever is wrong must be something serious and costly.I think you are correct in re-evaluating the tires. If nothing else they should be the simplest to check. Any chance you can borrow a set of tires from someone to try?In one post you imply that the truck has done this since you have owned it. If this is correct have you tried to contact the previous owner to see if he had the same issue? If not, the obvious implication is it is something you did when you were preparing to put it back on the road. Change of tires? Rotation of the driveshaft out of it's original yoke positions? Tighten or loosen spring shackles? Etc.?Good luck. Quote Money, sex, and fire; everybody thinks everyone else is getting more than they are! Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97408 Share on other sites More sharing options...
Rob Posted January 10, 2012 Share Posted January 10, 2012 I also don't have any specific advice on what to look for, but my bet is it something relatively simple. My experience when troubleshooting almost any issue is that something serious jumps out at you and that we all tend to look for the most serious problem we can imagine if the problem is not obvious. Often the real problem is something so simple we overlook it while we convince ourselves that whatever is wrong must be something serious and costly.I think you are correct in re-evaluating the tires. If nothing else they should be the simplest to check. Any chance you can borrow a set of tires from someone to try?Soon as I get that sleeper bought, he won't have to be worried about it any longer.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97411 Share on other sites More sharing options...
fifth wheel Posted January 10, 2012 Share Posted January 10, 2012 I am with Miro and Pawel on this, a harmonics issue. Put some weight on the frame to deaden it, that will tell if it is.FW Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97414 Share on other sites More sharing options...
leversole Posted January 10, 2012 Author Share Posted January 10, 2012 Soon as I get that sleeper bought, he won't have to be worried about it any longer.RobDoes that mean you are bringing me an R Model to trade?!? Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97415 Share on other sites More sharing options...
Rob Posted January 10, 2012 Share Posted January 10, 2012 Does that mean you are bringing me an R Model to trade?!?Being cognizant you are a busy man, I'm going the distance to lessen your load.Quite casual of me ehh?Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97419 Share on other sites More sharing options...
leversole Posted January 10, 2012 Author Share Posted January 10, 2012 No matter what others say...you are a good man! Quote Link to comment https://www.bigmacktrucks.com/topic/21884-bounce-slow-motion-video/page/3/#findComment-97428 Share on other sites More sharing options...
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