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| I think rear shackles hit frame on hard bump. https://slantsix.org/forum/viewtopic.php?t=56512 |
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| Author: | Sam Powell [ Wed Nov 05, 2014 4:13 am ] |
| Post subject: | I think rear shackles hit frame on hard bump. |
The rear shackles sit pointing slightly rearward at rest with very little space between frame and shackle. When I go over a speed bump there is a substantial thunk from back there, and I can find nothing else that could be doing this. I have fiddled with exhaust and tightened all bolts. When I changed the springs out, I put the alignment shims from the old springs back in between the left front spring perch and the box frame which pushes the spring back about 1/4" on that side. This was needed on the old springs. I assumed the error was in the frame, but now think it was in the old springs, as it handles very oddly coming out of a left hand turn and the left shackle is closer to the rear frame than the right one. The shackles both sit pointed rearward by maybe 10- 15 degrees. It seems they should point frontward a bit. Can someone look at their rear shackles and tell me what their attitude is? Do they point straight down, front wards, or backwards slightly at rest? I suppose I should take the car and put it on an alignment rack, but just am feeling cheap right now. I have a bunch of other things I want to spend money on. I am suspecting the alignment shims are going to come out of there. Removing them would create a little more space for the left rear shackle. Does anybody know a DIY rear end alignment check? One solution if the noise is coming from the shackles and frame is to put a pair of boomerang shackles on the rear. I see them on Jeep Wranglers all the time. Thanks. Sam |
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| Author: | Dart270 [ Wed Nov 05, 2014 6:56 am ] |
| Post subject: | |
It would take a huge spring excursion to change that angle much. It is normal for the shackles to sit angled toward the rear a little unless the car is really jacked up. 5-10 deg? Never measured it... Lou |
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| Author: | Greg Ondayko [ Wed Nov 05, 2014 8:01 am ] |
| Post subject: | |
Time for a witness mark. Smear grease, pasint, chalk etc... on the top of your spring where it rolls around the bushing.. if the grease transfers to the frame then its hitting. if not then its something else,. Greg |
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| Author: | makapipi [ Wed Nov 05, 2014 8:14 am ] |
| Post subject: | |
could there be something loose in the trunk that hits the bottom when the car hits speed bump? |
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| Author: | Sam Powell [ Wed Nov 05, 2014 8:14 am ] |
| Post subject: | |
It does this on speed bumps, which are plentiful around here. I think there is only a quarter inch between the back edge of the shackle and the box frame. I can throw some math your way later, and you can likely tell exactly if hitting the frame is possible. Sam |
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| Author: | Dart270 [ Wed Nov 05, 2014 11:42 am ] |
| Post subject: | |
Greg has got it - measure it. I would just smear some BJ grease on the point where it might hit and drive/clunk around then take a look. Lou |
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| Author: | sandy in BC [ Wed Nov 05, 2014 2:53 pm ] |
| Post subject: | |
It would seem to me that the problem is really speed bumps....... |
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| Author: | Sam Powell [ Wed Nov 05, 2014 7:41 pm ] |
| Post subject: | |
I guess I could drive around the speed bumps. Early in the post spring swap, the shocks were hitting the exhaust. I managed to get that out of the way, and test drove it with great confidence I had fixed it. Alas, no. However, it takes a much more serious bump in the road to make it clunk now. I will do some version of the grease or chalk to test for transfer. Thanks for the ideas. I will still measure the arc of the spring, the length of the spring, and see if math will predict if it will lengthen enough when flattened out to push the shackle back into the box frame. My eye says yes. Sam |
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| Author: | Sam Powell [ Mon Nov 10, 2014 4:04 am ] |
| Post subject: | |
Lou, You are right. The springs sit almost level now, so flexing upward moves the shackle forward, way from the frame, not rearward towards it. I saw rub marks on the pass side tail pipe where it sits beside the spring there, and was able to move the pipe over to create a little more space. I took it for a test ride last night to calibrate the electronic speedometer, and it definitely is quieter now. I did not drive far enough to find a speed bump so do not know if the big bumps will still create the noise. I am hopefully optimistic on this one. Maybe that was the culprit. I forgot to mention I had already removed the unneeded alignment plates I had put between the d side front spring perch and the frame. When I held a long straight edge against the rear tire, it was very obvious that the left rear wheel was toed out. AFter taking the shim out it drives better, and the straight edge test looks better. Some day I will get it on an alignment rack again. Taking out the shim did move the D side spring slightly forward, and put more space between the rear shackle and the frame. Thanks, Sam |
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| Author: | Dart270 [ Mon Nov 10, 2014 4:33 am ] |
| Post subject: | |
Wonderful! Lou |
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| Author: | sandy in BC [ Mon Nov 10, 2014 6:54 am ] |
| Post subject: | |
I like your science! |
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