leversole Posted December 2, 2011 Share Posted December 2, 2011 A minute and a half under my truck!http://youtu.be/9j822LpeVj0 1 Quote Link to comment Share on other sites More sharing options...
shortstack Posted December 2, 2011 Share Posted December 2, 2011 You're right, don't see any bounce back there. One wheel had a slight wobble but didn't seem to be too bad. Quote Link to comment Share on other sites More sharing options...
DCR Posted December 2, 2011 Share Posted December 2, 2011 Great videos! What about shocks on the front? Bad or no shocks can cause a hop. Quote Denny330-550-6020A "Mack Pack" Charter Member Link to comment Share on other sites More sharing options...
Mike Posted December 2, 2011 Share Posted December 2, 2011 Great videos! What about shocks on the front? Bad or no shocks can cause a hop.That was the same thought I had. I just can't put any faults on the hub, spindle or wheel. By seeing the video......it reminds me of the days of older cars floating up and down and they needed shocks. I've been thinking this for a couple of days now, hoping Freightain would put some highlight on this subject. Seems he had an issue with a broken shock some years back.mike Quote Link to comment Share on other sites More sharing options...
41chevy Posted December 2, 2011 Share Posted December 2, 2011 I was thinking the same thing on the hub or drum, they would both be constant and would also have gone away on light braking. Paul Quote "OPERTUNITY IS MISSED BY MOST PEOPLE BECAUSE IT IS DRESSED IN OVERALLS AND LOOKS LIKE WORK" Thomas Edison “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’” P.T.CHESHIRE Link to comment Share on other sites More sharing options...
Freightrain Posted December 2, 2011 Share Posted December 2, 2011 I had a front shock arm bend up as the upper ball/socket fell apart allowing it to drop down and get bent around axle. There are no real "shocks" on a B model, just these oil filled dampers(like a model T Ford had). Kinda a friction thing with an arm that attached down to the axle by a rod.I replaced both rods with typical Heim ends and threaded rod. The mounting hole was 9/16" so the 1/2" bolt I used with the 1/2" heim ends has a touch of slop. I was going to work on making bushing, but never got to it(go figure). I cranked them down tight and seem to still be tight. I also removed the "shock" and put some oil in them and I was able to make them move. I'm sure they aren't perfect, but at least they do move.I know one rear bushing is locked up in the spring mount, I've been wanting to tear it apart and fix them. LF spring clamps are blown off and the pack is puckered up. Sure that is not helping things. Mine still has a slight hop to it, but nothing like before I replaced the tie rods ends.Not sure if you checked yours, but get a big bar and pry UP on tie rods and see if they are loose. Mine didn't seem bad til I put a big bar on them and realized how loose they were. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment Share on other sites More sharing options...
Lmackattack Posted December 2, 2011 Share Posted December 2, 2011 I rebuild shocks for race cars. and here is what I can add.. The biggest issue with suspension found on old trucks is 3 things.1) axel weight. (unsprung weight)2) they have huge tires that have lots of side wall flex. this is a big issue when the side wall flex fights the spring and damper. you will get a shake or excess movement of the suspension.3)that they used huge springs that take alot to flex (bump)and thus when they try to return (rebound) to their resting position they do so in a violent movement. When the spring is seeing any movment it causes the shock to resist that movement. the faster the movement the harder the shock attempts to resists that motion.now add in the tire flex and the axel has lots of vibrations(simple explanation!). The shock trys to control movement in both directions and is sometimes valved to resist diffrently in one direction vs the other. For most automotive applacations the bump valving is softer than the rebound valving. even tho a shock is constantly absorbing vibrations it is doing it diffrently depending on its direction of movement. An out of balance tire or wheel can be fixed easy with weights. a weak or soft spring on the other hand will often flex more than is needed in a constant fight to find its level resting point. If the shock cant control the spring then you get vibrations and un needed movement. the old leafs did very little to reduce movement. you had 12 springs that all want to do there own thing. even 3 leafs fight each other. if you notice most truck MFG that set up an axel now use 3 or less springs or just a spring to support an air bag. less things moving the simpler to control vibrations. If vibration is the concern try adding a stiffer shock. if ride quality is also the problem swap in a 2 or 3 leaf front spring it will improve ride and should have less vibrations.Trent Quote Link to comment Share on other sites More sharing options...
leversole Posted December 3, 2011 Author Share Posted December 3, 2011 The "shocks" are MIA...I am still unsure how an out of balance wheel/drum...cound be the cause of all my woes but the video doesnt lie! Plus, it is only one side, as the speed is completely repeatable and even has a "harmonic", and if it were both wheels the speeds would have to change as they came in and out of phase with each other...I just thought the video was cool...I like seeing the mechanical things that make em move! Quote Link to comment Share on other sites More sharing options...
mackcl96 Posted December 4, 2011 Share Posted December 4, 2011 Is it just me .......Your slack adjuster never moved when you came to a stop?My thought on front bounce.....Spring pins and bushing,,Are they tight and no slop up and down Quote Thanks for hearing me out.You can have the soap box now---------JIM Link to comment Share on other sites More sharing options...
slpwlker Posted December 4, 2011 Share Posted December 4, 2011 It isn't just you I never saw it twitch Quote Link to comment Share on other sites More sharing options...
39 Baby Mack Posted December 4, 2011 Share Posted December 4, 2011 I was wondering the same thing, never saw the slack move?Ron Quote Link to comment Share on other sites More sharing options...
leversole Posted December 5, 2011 Author Share Posted December 5, 2011 Is it just me .......Your slack adjuster never moved when you came to a stop?My thought on front bounce.....Spring pins and bushing,,Are they tight and no slop up and downI noticed that too! It was a very light application...If I give a full brake application, they all move...probably the quick release valve needs cleaned out...I have lots of oil to make my air slipprier! Quote Link to comment Share on other sites More sharing options...
leversole Posted December 5, 2011 Author Share Posted December 5, 2011 My thought on front bounce.....Spring pins and bushing,,Are they tight and no slop up and downNever checked them...The last time I greased them, they did not appear worn at first glance...but once I get situated, I will jack the front up by the frame and check them... Quote Link to comment Share on other sites More sharing options...
mackcl96 Posted December 5, 2011 Share Posted December 5, 2011 Never checked them...The last time I greased them, they did not appear worn at first glance...but once I get situated, I will jack the front up by the frame and check them...Yes its a pain dragging timber under the truck with a bottle jack,,,,or if you have a stubby bottle jack put it between the spring and frame Quote Thanks for hearing me out.You can have the soap box now---------JIM Link to comment Share on other sites More sharing options...
leversole Posted December 5, 2011 Author Share Posted December 5, 2011 Yes its a pain dragging timber under the truck with a bottle jack,,,,or if you have a stubby bottle jack put it between the spring and frameI took two 8 foot 2 x 8's and cut into 1 foot pcs for my timbers! Quote Link to comment Share on other sites More sharing options...
220cummins Posted December 5, 2011 Share Posted December 5, 2011 Check your tires for any bulges or bumps you could have some tread seperation. Check the diameter of the tires to compare if any differences between. Ive seen tread seperation start doing the same thing and it only gets worse. Also check you steer tires the same way. Add some balance beads to see if helps. You slack adjuster should be moving some even pulling out. Quote Link to comment Share on other sites More sharing options...
leversole Posted December 5, 2011 Author Share Posted December 5, 2011 Check your tires for any bulges or bumps you could have some tread seperation. Check the diameter of the tires to compare if any differences between. Ive seen tread seperation start doing the same thing and it only gets worse. Also check you steer tires the same way. Add some balance beads to see if helps. You slack adjuster should be moving some even pulling out.Tires (front) are brand new, it did the same thing with the old tires. Steers were balanced at the mack dealer, though at a much higher speed than the bounce occurs.Thanks Quote Link to comment Share on other sites More sharing options...
220cummins Posted December 6, 2011 Share Posted December 6, 2011 Tires (front) are brand new, it did the same thing with the old tires. Steers were balanced at the mack dealer, though at a much higher speed than the bounce occurs.ThanksAre the rear tires new or checked for bulges? Ive seen a freightliner single axle exhibit the same shake...The virgin inner tire on the drive side (passanger) side had a slight bulge in the center of the tread about 3"x1/2" high this was tread seperation. This tire was only a year old with low miles. Replaced the tire and the shake went away. Quote Link to comment Share on other sites More sharing options...
leversole Posted December 6, 2011 Author Share Posted December 6, 2011 Are the rear tires new or checked for bulges? Ive seen a freightliner single axle exhibit the same shake...The virgin inner tire on the drive side (passanger) side had a slight bulge in the center of the tread about 3"x1/2" high this was tread seperation. This tire was only a year old with low miles. Replaced the tire and the shake went away.The drives tires had some miles on them...but looking at the videos I shot, the rear is not bouncing at all! Whatch this video of the front...as soon as I hit 44 mph, the bounce comes, and as soon as I get above or below that speed, the bounce stops! I will get a better video of the front the next nice day! Quote Link to comment Share on other sites More sharing options...
Mike Posted December 7, 2011 Share Posted December 7, 2011 I can only believe it is still a tire out of balance or some separation inside the tire causing an out of balance.mike Quote Link to comment Share on other sites More sharing options...
MACKS Posted December 7, 2011 Share Posted December 7, 2011 Watching the vid you can see the axle its self bouncing up and down,that tells me its and out of round tire,also put you pointer on the brake drum and you can clearly see it bounce up and down along with the axle and the rest of the front end,swap out the tires and rims if you can and see what happens. Quote Link to comment Share on other sites More sharing options...
41chevy Posted December 7, 2011 Share Posted December 7, 2011 Did you look at the spider for cracks or flex marks where it bolts to drum? Had a cracked spider on a trailer and it sort of acted the same. Paul Quote "OPERTUNITY IS MISSED BY MOST PEOPLE BECAUSE IT IS DRESSED IN OVERALLS AND LOOKS LIKE WORK" Thomas Edison “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’” P.T.CHESHIRE Link to comment Share on other sites More sharing options...
leversole Posted December 8, 2011 Author Share Posted December 8, 2011 Just to rule them out, my next step will be to take the frums off of the front and take it for a ride...Hopefull the bounce will go away...if not I will look for replacement wheels...of course, it is snowing like a ^$^#*#( so I dont know when I can work on it again! Quote Link to comment Share on other sites More sharing options...
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