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Old 01-11-2009, 06:17 PM   #1 (permalink)
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Question Pinion / Driveshaft angles

I bought a 1987 Suzuki Samurai tintop with a Trail Tough Spoa and Bonz-Eye springs already installed. I am guessing about 6" of lift total. I had some driveshaft vibration and was told that I needed to go to a CV rear driveshaft by a few vendors. Now my pinion angle needs to be adjusted AND I am looking to have some parts shipped overnight and would like to see if I can get some guidance on what size shims to have sent... This is my first time playing with this type of thing......is my thinking correct here ???

Driveshaft = 22 degrees
Pinion = 9 degrees

Driveshaft length is 19.75"
Pinion flange to center is 10"
So my ratio it 1:2 roughly ???
so for every 2 degrees of pinion angle changed it will change the driveshaft angle 1 degree ???
So I need 12 degrees "ish" to be where I need to be ???

if I go 8 degrees on the pinion then the driveshaft will move 4 degrees thus giving me my 12 degrees of change.

I SUCK at math and geometry so please HELP a newbie out....

8 degree shim and I should be good to go ???

Once again I am totally new at this so please be kind.
Thanks !!!
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Old 01-11-2009, 07:38 PM   #2 (permalink)
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Actually, you need to go at this in another direction. The standard (2 u-joint) driveshaft under a sammy needs to be set up so that both ujoint angles are exactly the same. You are trying to 'average the lower angle and that won't fix the problem.

Making the ujoint angles identical will allow one angle to offset the other. Unfortunately, the higher you go, the more angle you will end up with at both ends and that ain't good.

The suggestion from the vendors about a CV (or double cardon joint) style driveshaft is the easy way to make it work. It is not the least expensive, but is also the best to keep parts from breaking.

When going to an aftermarket double cardon joint shaft, you only have to point the pinion up at the output flange on the transfer case. Then the only angle is there, at the transfer case. You will still have to change the angle of your pinion, but in a good way, not adding to the problem. The double cardon joint puts two joints at that point and they will automatically be equal.
CV Driveshaft

Another good place to learn about driveshaft angles is at Tom Woods site:

Last edited by Billjohn; 01-11-2009 at 07:42 PM.
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Old 01-11-2009, 09:06 PM   #3 (permalink)
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Thanks for the info but can you offer any ideas or thoughts on if my math is correct.
Will or should an 8 degree shim put me inline ?

I need to overnight parts for a day in the dirt and I don't want to overnight the wrong size.

Thanks !!!
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Old 01-11-2009, 09:23 PM   #4 (permalink)
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You will need to tell us the angle of the tcase output flange relative to the pinion flange. That is the measurement that you left out. The difference is the degree of shim you will need. The two flange faces need to be parrallel (they will be offset, but they need to be parrallel). This will cause both ujoint angles to match up.
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Old 01-12-2009, 12:05 AM   #5 (permalink)
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Quote:
Originally Posted by Billjohn View Post
You will need to tell us the angle of the tcase output flange relative to the pinion flange. That is the measurement that you left out. The difference is the degree of shim you will need. The two flange faces need to be parrallel (they will be offset, but they need to be parrallel). This will cause both ujoint angles to match up.
NO, pinion needs to point up at the transfer case flange...
I am running a CV driveshaft so the two flanges will NOT be parrallel. The pinion will point up at the transfer case flange, but when the pinion is moved it will also move the driveshaft angle... thus a person cannot measure the two angles and just add a shim. The ratio of pinion angle to driveshaft angle needs to be figured in.... I am trying to figure this out before I order parts....

Maybe I am going about this wrong.... maybe this is just a guessing game with shim sizes and I should order a few different sizes and just go with a trial and error approach, but I don't want to believe that trial and error is the way the pros figure this stuff out.

All the articles I have read have laid out how to compute this info and I am looking for someone else that has done this and can confirm my numbers.

Thanks !!!
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Old 01-12-2009, 12:27 AM   #6 (permalink)
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Sorry, I misunderstood. The way I read your post was that you had been told you needed the CV, but you were going to try shims instead... Again, sorry about that.

I assume you don't have a welder, otherwise replacing the perches - pointing the pinion at the tcase and welding the new perches in place would be easier and much safer.

Your math is very very close. I have just never dared to use such a large shim. Make sure they are steel (not aluminum) and that you bolt them to the springpack. Don't just slide them between the pack and perch. If I had understood at the beginning then I would have just come right out and said it instead of beating around the bush... pros that build something that is meant to take a beating will not use more than a 3-4 degree shim - if they use them at all... large shims tend to fail and squirt out at the worst times.

I don't know what your experiance is, so I won't judge, but I have built and rock-crawled zooks for the last 13 years on the extreme trails in Las Cruces... I have never had a springpack/suspension failure on any of the suspensions I have built. I honestly wish you the best.

Last edited by Billjohn; 01-12-2009 at 12:37 AM.
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Old 01-12-2009, 12:55 AM   #7 (permalink)
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Thank you for all the quick info !!!!

Here is where I got my direction of thought from and just wanted to make sure I was following it correctly....

4Crawler Offroad Products - Custom Leaf Spring Shims

CV or double cardan driveshafts:
One complication arises if you are correcting the pinion angle on a CV or double-cardan driveshaft. This is because as you change the pinion angle, the driveshaft angle is also changing. Luckily, it is relatively easy to determine the relationship of the two angles. Basically the angles change by the ratio of the respective lengths of the driveshaft and the pinion extension from the axle center line. Lets say that you measure the distance from the center of the axle to the pinion flange or u-joint yoke and find it is 11" (as measured on a Toyota 8" axle). And lets say the driveshaft measures 55" long from the t-case output flange to the pinion flange. This results in a 1 in 5 ratio, meaning that for every 5 of pinion angle change, the driveshaft angle will change 1/5 of that or 1. This is easy to see if you sketch out the driveshaft and pinions to scale. Since the shim is tilting the axle at it's center line and the pinion sticks out away from that center line, it moves up and down as the angle changes. This means the bottom end of the driveshaft moves up and down by the same amount. But since it is much longer than the pinion length, the angle change is reduced by the ratio of the two lengths.
For a practical example, assume a 20 driveshaft angle and a 10 pinion angle, with a pinion length of 11" and a driveshaft length of 55", again your measurements will likely be different. So this gives a 1:5 ratio of angle changes. So, starting with the 10 difference, we want to end up with the pinion angle 1 - 2 less than the driveshaft angle. So, installing a 7 shim, we would find that the pinion angle would increase from 10 to 17. But at the same time, the driveshaft angle would decrease by 7/5 or 1.4, so it would end up at 18.6 (20 - 1.4). This leaves an angle difference of 1.6, which is within the 1 - 2 target we were shooting for.
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Old 08-26-2011, 09:41 PM   #8 (permalink)
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I have been having terrible wobble been searching everywhere online and found my caster angle to be off? way off?
have 88 samurai lifted with oldmanemu springs and 1'' extended shackles.
problem has been constant through the replacing of the steering stablizer, springs, shocks, shackles, and all bushings. all of it helped the wobble except putting on the 30'' which i just did and now i cant go above 40 or else will wobble to death.
anyways im trying to narrow it down and found the flange faces are definitly not parallel. is caster angle the only thing that will change this to make them parallel ?
Does anyone know what size shim i would need for this particular lift?
it seems way more than 6 degrees off more like 20 but im not sure just looks that way since the transfer case flange is facing up slightly towards the firewall and the other
is facing up towards the transfer case? is the transfer case supposed to be level?
this has been a huge expensive project to mainly stop this shit from wobbling.
any advise would be awesome. im trying to order shims or something asap cuz this is my Daily Driver! just ordered a 3'' drop pitman too hope that will help!
this vibration seems to have also made my transmission mount some loose as well
i can feel the shifter shaking with the wheels.
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