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Author Topic: Not so good vibrations  (Read 5760 times)
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Melbourne VIC

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« Reply #20 on: April 04, 2022, 03:30:12 PM »

So, to close out this post I should advise the solution to Miss Mullum's vibration issues.

From the advice offered there seems to be 3 areas that need to be checked or considered. The first is tailshaft balance. Luckily for Miss Mullum, this was the final answer. Next on our list to check was to check the tyres for balance/buckles, Robbie is still going to do this as they have not been checked for a long time. Last was going to be diff/tailshaft/motor angles (Fraser's solution).

The tailshaft imbalance on Miss Mullum was a tricky one. When Robbie got the car around 7 years ago it had a bad vibration around 55mph. He had the tailshaft balanced by a company in Cheltenham VIC - there was an improvement but still a definite vibration from 55+, still there at 65mph (GPS speed). So we swapped it with another newly balanced tailshaft from the same workshop. This made a slight but noticeable change. Robbie decided to get the original shaft rebalanced again but at a different workshop (Knox Driveshafts in VIC) requesting they pay particular attention at the revs for 55mph+. The engineer also replaced the front uni (although wear was very minor.....) and balanced the shaft for $220. We reinstalled the shaft and Robbie tested it to almost 70mph (on a 110 road of course  Wink) with no signs of vibrations. So it was 3rd time lucky in this case!

With regard to the diff/tailshaft/motor angles, we measured tailshaft at 3.7 degrees and motor at 3.9 degrees (diff obviously at 0 degrees). This results in a front uni angle of 0.2 and rear of 3.7 degrees. Using a CAD package I was able to find the best compromise for wedging the diff on Miss Mulum was at 2.5 degrees which gave around 0.7 degrees at both unis so the wedging option would has some benefits. Fortunately we did not have to go down this route.

So Robbie is now happy (and so are his fellow Club members who were getting a little frustrated going on Club cruises at 50mph  Cheesy)


FC Sedan, Ute & Wagon .... only a Panel Van required to make the set
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« Reply #21 on: May 23, 2023, 08:07:51 PM »

The steel  caster wedges I had made to order arrived inside a week, $35 each plus a bit extra for delivery is a good deal I reckon. I fitted them today, just undid the u bolts, jacked the axle up, slipped the wedges in, making sure that they engaged with the lugs on the insulater plates, lined up with the axle pad, tack welded the wedges to the axle pads to give permanent positive centering, did the whole lot up again and job done. I took the car out on the Motorway for a test run and am absolutely delighted with the end result- I was able to push speed up over 100kmh with no trace of vibration. In fact the FC is noticeably smoother from 80kmh.
The dimensions I used were 110mm x 60mm with 25 mm centre hole and 3 deg angle for my car. I bought the wedges from Industrial Tools and Wedges In Nelson Bay NSW. Just google “steel wedges”
Cheers, Fraze
Thanks for this Fraze. I’m ordering a pair of 4 degree wedges for the FB ute. 63mm wide for the FB springs. My diff pinion axis is currently horizontal, with the crankshaft pointing up 6 degrees. There is a slight vibration at 60mph under load, increasing on over run. I want to leave the pinion pointing down a couple of degrees static as they ride up under load. We are doing the drive from Willunga to Echuca and back next month so should be a good test.

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