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U-Joints and Vibration |
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CamJam
Moderator Group Joined: Jan/04/2014 Location: Arizona Status: Offline Points: 6553 |
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Posted: Jul/12/2017 at 8:35pm |
I replaced the U-joints on my '72 Javelin today trying to cure a drive line shudder. While I made a big improvement, it's still not perfect. I have the same problem to a smaller degree in my '69 AMX and wonder if it's something I'm doing. I made the mistake in the past of tightening the u-bolts too tight and distorting the bearing cups, so I know not to do that, and I marked the position of the driveshaft today when I took it off to make sure that the yoke and drive shaft went back together oriented the same way. I also know to make sure that the U-joints are not binding after they are pressed back together. I did notice that one of the U-joints I got today was made in China. The other (a Spicer) was US made, and the cups seemed to be stronger. Anyone else had problems with the Chinese U-Joints from places like O'Reilly's and/or Auto Zone?? I'm going to try switching the drive shaft 180 degrees tomorrow, but just thought I'd ask for some ideas from you guys before I start chasing my tail.
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'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST '69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD |
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304-dude
AMC Addicted Joined: Sep/29/2008 Location: Central Illinoi Status: Offline Points: 9082 |
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I donno, but long ago some where I read about how to check balance of the drive line (Chilton or AMC) on installing a large band clamp may assist in seeing if there is an out of balance.
Marking 1/4 sections with a marker and placing the screw end on the mark. Rotate 180, 90 either way to see were between the marks to place it. Some times 2 bands is needed for balancing.
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71 Javelin SST body
390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker |
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CamJam
Moderator Group Joined: Jan/04/2014 Location: Arizona Status: Offline Points: 6553 |
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Thanks, James. I do know that trick. I'm also going to loosen the U-bolts just to make sure I got the cups properly seated in the saddles.
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'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST '69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD |
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POWERSTROKER7.3
AMC Apprentice Joined: Feb/15/2012 Location: Winnebago MN Status: Offline Points: 91 |
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When does the shudder appear? Is it when you accelerate from a stop, on deceleration or is it a constant vibration reguardless of vehicle speed? Does it change if you are at speed and put the vehicle in neutral does it go away or still there? Is it at slow speeds or high speeds? These answers will help with the diagnois of your issue.
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Airdrie AMX
AMC Nut Joined: Aug/08/2010 Location: Alberta, Canada Status: Offline Points: 329 |
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If you haven't already, check and see if there is any weights missing of the driveshaft on either end they are usually welded on washers. A couple of other things to look for is a worn or broken trans mount, movement or worn splines on yoke, tailshaft bushing, driveshaft too short (not enough spline contact), loose pinion/ carrier bearings. Could be anyone of a number of things, just some things i'd look for.
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72 amx javelin 401 4spd
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CamJam
Moderator Group Joined: Jan/04/2014 Location: Arizona Status: Offline Points: 6553 |
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This shudder is sort of a pulsation, and the frequency of it increases with speed for the most part. Seems a bit more pronounced under acceleration. It's still there when coasting in neutral or decelerating, but it becomes more constant rather than pulsating. You don't notice it under about 40 mph. I can wedge my hand under the rear seat while I'm driving and the vibration feels quite strong there. That's right about where the rear u-joint is. Thanks for the tips so far. There is a weight at the back of the drive shaft. I don't see any at the front. I'll check the tranny mount first as that's an easy one. Guess I should also check that the rear diff has enough gear oil. I just bought the car a few weeks ago and haven't gone through everything yet. |
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'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST '69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD |
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CamJam
Moderator Group Joined: Jan/04/2014 Location: Arizona Status: Offline Points: 6553 |
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The TSM does have some good information on diagnosing this problem. I checked my pinion angle measurements and don't see anything out of the ordinary there, so I'm going to pick up a dial indicator from Harbor Freight today so that I can check the shaft run out too. |
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'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST '69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD |
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CamJam
Moderator Group Joined: Jan/04/2014 Location: Arizona Status: Offline Points: 6553 |
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I actually think I might have two things going on here. I have some wheel wobble on the left rear. It's not the wheel, so it's either a bent rear axle or hub-- and I have some engine vibration too. When I'm going down the road, at highway speeds, at a certain speed it seems the two get in phase, which is when I get a sort of cyclic shudder. How much engine vibration is normal, I don't know, so I'll have to have someone more knowledgeable than me check it out. When the car is parked it causes the steering column to vibrate at what I estimate to be around 2,500-3,000 rpm. There's no tach in the car so that's just a guess. How hard is it to replace a bent rear axle and/or hub? I guess I should just replace both pieces? |
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'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST '69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD |
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mmaher94087
AMC Addicted Joined: Apr/01/2008 Location: Arizona Status: Offline Points: 1690 |
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Cameron, pull the rear wheels and see if the hub balance-weigh is interfering with the seating of the rim against the hub.
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Mike
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CamJam
Moderator Group Joined: Jan/04/2014 Location: Arizona Status: Offline Points: 6553 |
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That's a great thought, Mike. I'll check it out in the morning. I don't remember the drum having a weight, but I could be wrong. In the meantime, I made things a whole lot better by inverting the drive shaft 180 degrees at the rear U-joint. I also ran the car in gear on some jack stands and added some hose clamps to the drive shaft (following the instructions in the TSM) until I found the sweet spot. I also found a vacuum leak causing a little miss in the engine. It's not perfect yet-- I think I need to replace the carb spacer-- but it's an improvement. Anyway, all-in-all the vibration's much better, though the LR tire is still definitely wobbly, so I'll look for a weight on the drum.
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'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST '69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD |
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