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Jeep Wrangler YJ
YJ General Discussion
Driveline angles and new vibration
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<blockquote data-quote="Shawn at Tom Wood&#039;s" data-source="post: 438646" data-attributes="member: 21069"><p>I am predicting that rotating the pinion down to match the transfer case will make things worse. This is because it will increase the angle of the drive shaft too, by about 4-5 degrees. That will increase the operating angle of the joint at the transfer case end from 14 to around 18-19. That is too much angle for the shaft to run smoothly, even if they yokes are parallel. Spicer says that the max operating angle of a single joint at 3,000 rpm is 5.8 degrees. This limit can be pushed a little with good success but tripling the limit does not usually work out well. The way things are now, the yokes are a few degrees off from being parallel but that pinion rotation helps to mitigate the driveshaft angle and the overall joint angles. It's not quite right for either the parallel or the less than 10 degree joint angle rules but it is only a little off for each instead of extremely far off for one or the other. Anecdotally, most people have better success with having the pinion raised a little in this type of scenario than they do if they keep the pinion at the 6 or so degrees that it would be stock. But, a lot of this has to do with dumb luck and how a certain set of parameters happens to play out in a certain vehicle. Perhaps rotating the pinion down would make things better in this specific Jeep but It might also prove to be a waste of time and money that only makes things worse than they are now. If parallel yokes was the only part that mattered slip yoke eliminators wouldn't be such a popular thing for lifted Jeeps. That is explained in better detail on the page in my second link above. </p><p></p><p>To the OP, if you want to try rotating your pinion down a couple/few degrees it might make things better. But as stated above it might also make things worse. You won't know until you try but as long as you know the risks of possibly wasting a little time and a little money on shims it might be worth a try.</p></blockquote><p></p>
[QUOTE="Shawn at Tom Wood's, post: 438646, member: 21069"] I am predicting that rotating the pinion down to match the transfer case will make things worse. This is because it will increase the angle of the drive shaft too, by about 4-5 degrees. That will increase the operating angle of the joint at the transfer case end from 14 to around 18-19. That is too much angle for the shaft to run smoothly, even if they yokes are parallel. Spicer says that the max operating angle of a single joint at 3,000 rpm is 5.8 degrees. This limit can be pushed a little with good success but tripling the limit does not usually work out well. The way things are now, the yokes are a few degrees off from being parallel but that pinion rotation helps to mitigate the driveshaft angle and the overall joint angles. It's not quite right for either the parallel or the less than 10 degree joint angle rules but it is only a little off for each instead of extremely far off for one or the other. Anecdotally, most people have better success with having the pinion raised a little in this type of scenario than they do if they keep the pinion at the 6 or so degrees that it would be stock. But, a lot of this has to do with dumb luck and how a certain set of parameters happens to play out in a certain vehicle. Perhaps rotating the pinion down would make things better in this specific Jeep but It might also prove to be a waste of time and money that only makes things worse than they are now. If parallel yokes was the only part that mattered slip yoke eliminators wouldn't be such a popular thing for lifted Jeeps. That is explained in better detail on the page in my second link above. To the OP, if you want to try rotating your pinion down a couple/few degrees it might make things better. But as stated above it might also make things worse. You won't know until you try but as long as you know the risks of possibly wasting a little time and a little money on shims it might be worth a try. [/QUOTE]
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Jeep Wrangler YJ
YJ General Discussion
Driveline angles and new vibration
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