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Old 03-17-2015, 07:12 PM
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Help with pinion angle

So I finally got my driveshaft today and installed it and I'm having slight vibrations. I'm pretty sure I'll need adjustable control arms but was hoping some of you with a good eye can tell me how much my angles are off(roughly). I have a 98 with the DPG kit, advanced adapters SYE, ford 8.8, and a front tj driveshaft cut and rebuilt. The pictures might not be the best so if you need more just let me know

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Old 03-17-2015, 07:12 PM
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Again
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Old 03-17-2015, 07:22 PM
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Sorry, app only lets me post one pic at a time
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Old 03-17-2015, 07:22 PM
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Old 03-17-2015, 07:23 PM   #5
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Looks like pinion must come up some.
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Old 03-17-2015, 07:23 PM
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Old 03-17-2015, 08:27 PM   #7
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Your rear pinion angle is way too low... it needs to look like the below drawing. With CV driveshafts as you have, the rear pinion angle needs to be at the same angle the driveshaft is at. Absolutely no higher and at at the lowest, pointing 1-3 degrees below the driveshaft.
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Old 03-17-2015, 08:27 PM   #8
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Originally Posted by 2004jeeptj View Post
Looks like pinion must come up some.
^x2 the pinion come up more
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Old 03-17-2015, 09:00 PM
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Thanks for the help guys. Now to find a good set of control arms
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Old 03-17-2015, 09:18 PM   #10
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Looks really low. It should be 2 degrees lower than output yoke.
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Old 03-17-2015, 09:57 PM   #11
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What is your lift? A 4 inch lift should have 16-17 degree pinion angle. It looks like yours is the stock 6 degrees.
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Old 03-17-2015, 10:44 PM   #12
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Correct pinion angle depends on wheelbase, lift height, transmission model due to their various lengths, type of SYE kit, and rear axle type... all of which affect the resulting driveshaft angle. There is no single correct pinion angle for any particular lift height. Not to mention measuring angles can be more confusing than just eyeballing them. I haven't used my angle finder for setting a pinion angle in probably 10+ years.
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Old 03-19-2015, 07:31 PM   #13
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^ I have read that from more than one person. They got the angle close and it worked out fine. I had a hell of a time with mine and I have a very small lift and still don't have all the vibe out. Started with a one of those Jorgensen angle finders and eventually moved up to an electronic version. This is where I made the most progress. 1 degree is actually quite a bit.

Finding a good spot to measure was also a challenge. The driveshaft is easy enough, its the axle that was giving me trouble. In the end, I had the best luck putting one leg of a square directly on the differential cover bolt heads and laying the angle finder on the other leg.
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Old 03-19-2015, 08:00 PM   #14
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The pinion angle itself is as easily measured as the driveshaft is.

Place your angle finder with a 90 degree base on it so it is positioned on the two flat machined surfaces as shown below. Those flat surfaces are 90 degrees from the pinion angle so if you position the angle finder properly, it will directly show the pinion angle... no need to add or subtract 90 degrees.

The holes inside those flat surfaces are there for a case spreader for when doing ring & pinion work.

Once you develop your eye for the pinion to driveshaft angle differences, you'll stop needing an angle finder.

The top surface of the angle finder in the second photo is equal to the pinion angle.
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Old 03-19-2015, 08:57 PM   #15
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^ In my case I have those measuring points restricted by the gas tank in the rear and the tie rod in the front. I assume the differential cover is also also machined on the same plane as those holes for the case spreader?
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Old 03-19-2015, 09:10 PM   #16
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Extend the measuring surface down with a ruler or 1" wide scrap steel and measure from that. Make it work just think it through.
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Old 03-20-2015, 05:44 PM
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Does anyone know how much you can change your pinion angle before you run into issues with re welding your brackets?

I still need to measure my angles this weekend but am just curious if how much adjustment I can make
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Old 03-20-2015, 05:56 PM   #18
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You can make enough pinion angle change to work with the CV driveshaft without problem. Once you do that, you won't have to mess with it again.

That said, it's always nice to have the coil spring bucket so the spring isn't curved as it will be after raising the pinion angle but it's nothing that must be done. I keep thinking I should do that to my TJ but between my previous and current TJ, I have 14-15 years of running it that way without a problem.
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Old 05-04-2015, 10:27 PM   #19
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just got my new shaft in tonight, test drove, starts a vibe at 70 or so, get a lil worse as speed goes up, as a rule of thumb on a TJ does the rear end come up on acceleration or go down? I forget that one?? just wondering if I need to go up a little or not, it is slightly down right now.
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Old 05-04-2015, 10:33 PM   #20
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just got my new shaft in tonight, test drove, starts a vibe at 70 or so, get a lil worse as speed goes up, as a rule of thumb on a TJ does the rear end come up on acceleration or go down? I forget that one?? just wondering if I need to go up a little or not, it is slightly down right now.
Usually 2-3 degrees low is a good starting point.
Pinion angle will go higher with acceleration in the rear.
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Old 05-05-2015, 12:10 AM   #21
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Quote:
Originally Posted by 98SaharaTJ View Post
Does anyone know how much you can change your pinion angle before you run into issues with re welding your brackets?

I still need to measure my angles this weekend but am just curious if how much adjustment I can make
You start running into problems when you add a TT. You will hear the more experienced folks say to run a SSSYE instead of a regular SYE for that purpose. Every bit of length you can add to a driveshaft will help.

I swapped in a rubicon 4-1 t-case into mine and did a Rokmen TT. That was enough to cause driveshaft bind (not a good thing). I found a different D44 and stripped it bare and added new 3/16" brackets. I accounted for the extra pinion angle and welded them on. Another problem I ran into with clocking the old axle back was that the axle side track bar mount interfered with my Poison Spyder GTS. Problem solved by rewelding brackets and swapping in a new Savvy GTS. Along with all that I relocated my upper and lower spring perches to get it back to somewhat normal.










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