Charlie C
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| posted on 27/7/17 at 08:26 AM |
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Nasty vibration, worn prop UJ
My Haynes had a nasty vibration in 5th gear and a clonking when coming on/off the throttle, I thought it was the gearbox on its way out, the diff is
new rebuilt and the back lash appears ok.
My Haynes has an MX5 engine/gearbox and the boxes are as cheap as chips I have two spares so the cost of changing the gearbox wasn’t an issue it was
just the thought of pulling the engine out which wasn’t very appealing. So I started working my way back from the rear axle to see if the problem was
something simple and easy to fix, by the way the axle is from a sierra.
Firstly, I noticed some of the CV bolts had come lose and one of the CV joint didn’t feel great so I changed both drive shafts as they had excessive
play along with the CV joints.
There was still a clonk from the rear end, with the rear jacked up rotating the wheels without the drive shafts on there was a slight nock which was
coming from the rear upright lower pivot. I took the upright off and measured the lower pivot whole and it was ½” but the bolt is M12 also the tube
that goes between the two pivots was more like m14, the uprights were bought as part of a prebuilt chassie pack from a well know supplier, I wont name
because they normally have a good reason for doing most alteration to book speck and have been really helpful in the past. I cut the M14 tube out and
welded in an M12 tube and that has cured the clonk when coming on/off the throttle.
After all this the nasty vibration was still there so I took the propshaft out and the front UJ had a very very slight notch feel on one of the axis
at TDC, the Mx5 UJ aren’t easily replicable so I sent it back to Bailey Morris they replaced the UJ and upgrade the shaft. It’s the second time I’ve
used Bailey Morris and the service and been great both times. This solved the vibration and I didn’t need to take the gearbox out after all.
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Angel Acevedo
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| posted on 27/7/17 at 04:37 PM |
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quote:
Originally posted by Charlie C...
After all this the nasty vibration was still there so I took the propshaft out and the front UJ had a very very slight notch feel on one of the axis
at TDC, the Mx5 UJ aren’t easily replicable so I sent it back to Bailey Morris they replaced the UJ and upgrade the shaft. It’s the second time I’ve
used Bailey Morris and the service and been great both times. This solved the vibration and I didn’t need to take the gearbox out after all.
Maybe by replacing your propshat you erased the source of vibration, but...
Was that the root cause?
If UJ are installed with no angle, they may wear a "notch" on the bearing races of the UJ.
If your new shaft is installed like that, the problem will come back again unless as stated above was designed out with the new propshaft.
Beware of what you wish.. for it may come true....
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Charlie C
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| posted on 27/7/17 at 06:57 PM |
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The UJ is at an angle and the car has only done about 300 miles also the propshaft was a used mx5 prop cut down to size. So I'm guessing the UJ
on the second hand prop was worn before i fitted it.
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alfas
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| posted on 4/8/17 at 06:11 AM |
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ususally when prop´s are sent to a specialist for refurb, they are balanced after the repair....means the problem might have been more related to an
unbalanced prop rather than the worn u-joint.
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Charlie C
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| posted on 4/8/17 at 07:35 AM |
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The prop was originally shortend by Bailey Morris I would be suprised if they are sending out poorly balanced props.
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