Iain M Posted June 28, 2017 Report Share Posted June 28, 2017 I recently read an article regarding UJs in propshaft applications that recommended that the working angles of each UJs should be between 1/2 and 3 degrees for longevity, and that the difference between the two angles at each end should not be more that half a degree to avoid vibration. My 6 has terrible vibration at motorway speeds so i thought it worthwhile to check them (inclinometer apps on mobile phones provide accuracy to 0.1 deg). I found working angles at the gearbox- and diff UJs of 2.5 degs tail down and 5 degrees nose up respectively. In order to get the rear UJ angle down to 2-3 degrees to meet the guidance i have tried to lower the diff nose. Changing the front upper diff rubbers made the latter worse (became +6 degs) as the new ones proved thinner than the old ones, raising the diff nose instead. Im now looking for thicker upper rubbers, but i note that theres not a great deal of thread remaining on the front pins to achieve the drop required. I guess raising the diff rear would also work, but i can only see this being achieved through packing washers between the diff casing and the rear rubbers, which is a bit of a bodge. Has anyone any experience or advice with this? Have you checked/adjusted your UJ angles to within the 3 degree/ 1/2 degree recommendations or am i seeking perfection where it never existed with in the first place? Thanks, Iain Quote Link to post Share on other sites
Motorsport Mickey Posted June 28, 2017 Report Share Posted June 28, 2017 (edited) Well Hardy Spicer (who MIGHT know something about them ) recommended to me a max of 7 deg and 1/2 deg between ends on a TR7 V8 racecar, so I think on that basis yours as is would be ok. Sounds like a balance issue to me, If you're bored try a jubilee clips on your propshaft and turn around maybe 20 deg a time after trying a road test to see if it reduces. Mick Richards Edited June 28, 2017 by Motorsport Mickey Quote Link to post Share on other sites
Iain M Posted June 28, 2017 Author Report Share Posted June 28, 2017 Well both UJs are individually within a 7 degree spec, but the diffence between ends 2.5 degrees. Quote Link to post Share on other sites
Iain M Posted June 28, 2017 Author Report Share Posted June 28, 2017 If 7 degrees is acceptable i suppose i could drop the gearbox tail a tad to get it to 5 degrees though! Thanks. Quote Link to post Share on other sites
Guest ntc Posted June 28, 2017 Report Share Posted June 28, 2017 You should need to drop nowt,the std prop and ujs work well if in good order. Quote Link to post Share on other sites
Waldi Posted June 28, 2017 Report Share Posted June 28, 2017 Ian, Are the rear rubber mounted correct? You can install them above or below the flange of the diff cover. Waldi Quote Link to post Share on other sites
Alec Pringle Posted June 28, 2017 Report Share Posted June 28, 2017 Useful Spicer guide . . . . . http://spicerparts.com/calculators/driveline-operating-angle-calculator Don't overlook the tendency of knackered engine and/or gearbox mounts to influence the gearbox angle. Remember to measure with driver and passenger in place . . . . . Avoid cheap UJs which tend to vibrate of their own accord . . . . Cheers Alec Quote Link to post Share on other sites
Iain M Posted June 28, 2017 Author Report Share Posted June 28, 2017 Waldi, They're below the flange as per the moss catalogue illustration. Quote Link to post Share on other sites
TriumphV8 Posted June 28, 2017 Report Share Posted June 28, 2017 Humming in the seats like somebody is acting below with a grinder at 130 Km/h is mostly blaimed to the propshaft. Problems in the driveshaft are more a rumble and similar to fast hammering if I should explain. I could destroy the joints in my V8 within a month. Over a longer period I changed them every year, never had to grease them because they are destroyed quicker. When they die they give a rumble under load and get quieter off throttle or the other way round. Last possible culprit is the splined piece. It gets play and locks under load in different position/angles. Sometimes they are okay and sometimes they rumble. Best way to avoid driveshaft trouble buy a CV jointed shaft and forget about loosing wheels, too Somebody is just selling a set from CCDC here at the forum Quote Link to post Share on other sites
Guest ntc Posted June 28, 2017 Report Share Posted June 28, 2017 Useful Spicer guide . . . . . http://spicerparts.com/calculators/driveline-operating-angle-calculator Don't overlook the tendency of knackered engine and/or gearbox mounts to influence the gearbox angle. Remember to measure with driver and passenger in place . . . . . Avoid cheap UJs which tend to vibrate of their own accord . . . . Cheers Alec +1 and do not forget the wheels. Quote Link to post Share on other sites
Iain M Posted June 28, 2017 Author Report Share Posted June 28, 2017 Thanks all. The vibration (felt like it was under the seat) would occur above 70mph in OD top, and could sometimes be reduced by decelerating and quickly reapplying power. I am in the process of changing the worn driveshafts for the uprated rislan-coated type, and have now fitted the uprated GKN-type UJs throughout the drivetrain. I haven't road-tested since, but hope that these changes, together with replacement of a sloppy-fitting wire wheel spline, may have already reduced or removed the vibration regardless of the UJ angles, but i wanted to be sure I had removed all possible causes. To be honest, I would still prefer to get the prop UJs operating at the lower end of the working angle tolerance band anyway in order to get maximum life out of them so will give the gearbox and engine mounts a check too. Quote Link to post Share on other sites
RogerH Posted June 28, 2017 Report Share Posted June 28, 2017 Hi Iain, I think you are looking too hard at the prop angles. The relative position of the GB and diff is fixed so assuming the GB rear mount is OK and the diff rubber bushes are OK then the set up is as it left the factory. Has the propshaft been balanced.? Roger Quote Link to post Share on other sites
Iain M Posted June 28, 2017 Author Report Share Posted June 28, 2017 No Roger, but now ive refitted it (and the diff etc) I am tempted to see how the other upgrades have changed the vibration before dropping it all again. Thanks. Quote Link to post Share on other sites
MostEasterlySteve Posted June 29, 2017 Report Share Posted June 29, 2017 Hi Iain, I think you are looking too hard at the prop angles. The relative position of the GB and diff is fixed so assuming the GB rear mount is OK and the diff rubber bushes are OK then the set up is as it left the factory. Has the propshaft been balanced.? Roger This. Sounds like classic prop out of balance to me. Everyone else's box to diff angles will be much the same as the OP's but they don't have problems. Over-thinking that for sure. Quote Link to post Share on other sites
Andy Moltu Posted June 29, 2017 Report Share Posted June 29, 2017 Are you sure the prop U/Js are in good condition fitted properly? Quote Link to post Share on other sites
stuart Posted June 29, 2017 Report Share Posted June 29, 2017 TBH I would have just gone for a new prop from Proptech Kidderminster as the problem with IRS cars is the sliding section gets a wear spot due to the fact that it does nothing unlike a prop on a live axle that does move in and out. Stuart. Quote Link to post Share on other sites
Stag powered Posted June 29, 2017 Report Share Posted June 29, 2017 Make sure the yokes are aligned on opposite ends of the shaft. When I first got my 250 I replaced one of the joints on the shaft as it was knackered. I did this without separating the two halves of the shaft. A couple of years later after much high speed vibration the same joint failed again. This time I decided to separate the two halves of the shaft to make the job easier, but when getting ready to mark the shaft before I split it, I realised the shaft had been assembled one spline out. Having replaced the knackered joint I reassembled the shaft with the yokes aligned properly and found the vibration had disappeared and the joints are still good 20 years and many tens of thousands of miles later Neil Quote Link to post Share on other sites
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