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Vibes after 1" lift, what to do??
- Thread starter srimes
- Start date
The 2.5* shims came in yesterday and I installed them to move the pinion angle down. The vibes are worse now than before!
I guess I'll flip them around to move the pinion angle up and see what happens then. This goes against the theory I've been working off of, and as an engineer I'm interested in why things work the way they do.
Here's my hypothesis: I assumed that the vibrations were caused by miss-alignment of the driveshaft ends. The ends of the driveshaft are supposed to be parellel while offset so that the u-joint phasing cancle each other out. But that's not what cause my vibrations in the first place. My vibrations were caused by the angle between the tcase output shaft and the driveshaft, as the output shaft is poorly supported and subject to vibration at higher angles. When the pinion angle is adjusted the pinion not only rotates but moves vertically, so when I decreased the pinion angle I lowered the pinion which increased the driveshaft angle at the output shaft. So if I increase the pinion angle I can decrease the driveshaft angle. This will help reduce vibrations at the tcase output shaft but may increase them from the driveshaft u-joints. I'll see what happens after work.
I guess I'll flip them around to move the pinion angle up and see what happens then. This goes against the theory I've been working off of, and as an engineer I'm interested in why things work the way they do.
Here's my hypothesis: I assumed that the vibrations were caused by miss-alignment of the driveshaft ends. The ends of the driveshaft are supposed to be parellel while offset so that the u-joint phasing cancle each other out. But that's not what cause my vibrations in the first place. My vibrations were caused by the angle between the tcase output shaft and the driveshaft, as the output shaft is poorly supported and subject to vibration at higher angles. When the pinion angle is adjusted the pinion not only rotates but moves vertically, so when I decreased the pinion angle I lowered the pinion which increased the driveshaft angle at the output shaft. So if I increase the pinion angle I can decrease the driveshaft angle. This will help reduce vibrations at the tcase output shaft but may increase them from the driveshaft u-joints. I'll see what happens after work.
I flipped the shims around. It was alot better than with them the other way, but no better than without them. The vibes were different: different "tune" at different speeds. So I'm back to no shims.
I'm thinking I'll do a small crossmember drop, maybe 1/2 an inch. Won't be much clearance lost, and with the bastard pack the xj rides and handles these crappy oklahoma roads a ton better as it has twice the up travel.
I'm thinking I'll do a small crossmember drop, maybe 1/2 an inch. Won't be much clearance lost, and with the bastard pack the xj rides and handles these crappy oklahoma roads a ton better as it has twice the up travel.
TwistedFocus
NAXJA Forum User
- Location
- Ohio
Dumb question here, and maybe you've already addressed it and I missed it, but...
Did you have the front end alignment checked?
I realize the ZJ springs likely only raised the front around an inch, but I'd think that could still be enough to cause issues with the alignment. It seems shims helped, but maybe its a compund issue. It's probably worth getting on an alignment rack to at least check it. Most places won't charge for a check if the alignment isn't needed.
Did you have the front end alignment checked?
I realize the ZJ springs likely only raised the front around an inch, but I'd think that could still be enough to cause issues with the alignment. It seems shims helped, but maybe its a compund issue. It's probably worth getting on an alignment rack to at least check it. Most places won't charge for a check if the alignment isn't needed.
TwistedFocus
NAXJA Forum User
- Location
- Ohio
Ah, I see. I have been looking into swapping out my rears and have read so many threads obout springs lately that I must have mixed your situation up with someone else.
I thought you had added ZJ coils at the same time.
I thought you had added ZJ coils at the same time.
