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My pinion angle

Eddie Greenlee

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Hey y’all. To the best of my ability and with a Klein digital angle finder.
Rear pinion to driveshaft is 17.5 +- each.
Front pinion to driveshaft is 7.7 & 10.5.
What do you think ?
Do I need to drop my rear pinion one degree?
Do I need to raise my front pinion angle 2 degrees ?
Thanks
 

Gollywomper

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Hey y’all. To the best of my ability and with a Klein digital angle finder.
Rear pinion to driveshaft is 17.5 +- each.
Front pinion to driveshaft is 7.7 & 10.5.
What do you think ?
Do I need to drop my rear pinion one degree?
Do I need to raise my front pinion angle 2 degrees ?
Thanks
Do you have vibrations?
 

Jerry Bransford

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If you have a SYE kit installed your rear pinion angle needs to be essentially the same the driveshaft angle. Ideally the rear pinion angle is 1/2 to 1 degree lower than the driveshaft angle when the driveshaft is an aftermarket DC driveshaft.

On the front axle what's important is its caster angle. If you Jeep tracks straight and steering has good return-to-center after completing a turn, and you don't have any front driveshaft vibrations, the front axle's pinion/caster angle is fine.
 

Jerry Bransford

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I do have a super short SYE and both are double cardan drive shafts
Should look like this... rear pinion angle should point about 1/2 to 1 degree lower than the driveshaft's angle.

You can remove the front driveshaft to isolate the vibration to the front or rear.


CV Driveshaft Angles.gif
 

Gollywomper

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That speed range is a bit odd for a DS vibration. Have you had your tires checked and rebalanced?
You need to identify which drive line is giving you vibrations. Start by removing the front and taking it for a drive. You should be able to just disconnect from your front axle and tie it up to your frame. Be sure your tcase is in 2hi. If vibrations continue then reconnect your front and remove your rear DS.
 

Shawn at Tom Wood's

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JMT

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After you've done what @Gollywomper said above, and if you've isolated the vibes to the rear (40-50mph is low speed for a driveline vibe), but if it is THEN...

Ideally you want the rear pinion to be 1* less than your rear driveshaft.

In the front you want 5* caster. The angles don't have to match, but if you have a problem, try putting the front pinion 1* more than the rear driveshaft. If it doesn't work, take it back down till when under full front axle droop you don't get binding. That will give you the most caster you can have
 
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eastbloc

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That is indeed unusual speed for vibes from what i have read so far and experienced myself, typically 55 - 60 is when party starts.
As mentioned above, start with diagnosing rear, go through different angles in 0.5 increments. That should resolve or give you best angle that gives least amount of trouble. If you cant find angle that works, try rotating ds inside the yoke in tc and axle, that can resolve the issues.
If you have exhausted rotations and angles, take DS to a local drive line shop, have them check balance.

I am currently going through interesting situation with a new rear driveshaft, so far smoothest operation i got out of it at 0 degrees, which is a bit puzzling, but i am still vibrating/shaking past 55. Local shop told me that it was way out of balanced, so they decided to rebalance it without letting me know. Alright, cool, but i am still vibrating/shaking past 55.
From the transmission towards back everything has been replaced and renewed, there is nothing left to point fingers at besides the drive shaft. Will be sending it back to maker this week to see what they say.
 
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Eddie Greenlee

Eddie Greenlee

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So with my 32RH 3speed automatic transmission and 35” tires I do believe 4.10 gears would be the preferred ratio for on and off road.
Right now I have 4.88 and at 2800 to 3000rpms and 55 to 60 mph , things sound and feel over reved. I may have to swap out transfer cases one day to find the 4:1 ratio in low gear that I want on the trails