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Discussion Starter #1
I tried researching this online and couldnt' find anything. Everything comes back to if you have vibrations, get it checked out.

So my truck has the Ford Racing springs up front and Hotchkis leafs out back with stock height shackles. A lot of you guys recommended checking the pinion angle but truth be told I have been lazy about it and haven't really had time lately. I have driven my truck a few times since and have probably gotten it up to around 100 mph on the highway and I'm not getting any vibrations of any sort. I called Hotckis to see their opinion on this and they said if I didn't get vibrations at any speeds, low or high, that I should be fine. Opinions?
 

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Wile E. Coyote, Super Genius!
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Numero Uno, do you have long bars on your truck? IIRC, you do. Seen the pic with the differential cover and the bars. I ask because they almost make pinion angle a moot subject. As long as when you view the angle of the driveshaft to the pinion from the side, it looks like a flattened "V". That's the correct angle. If it appears as a flattened "A", it's incorrect. Flattened "V" is negative angle. Flattened "A" is positive. You don't want it to be positive when sitting still. That's not good.

Remember that when you get on the happy pedal hard, the driveshaft Moves upward. You want the driveshaft to be slightly below the pinion, so that when you're hard on it, it becomes straight as an arrow. If the driveshaft is already above the pinion, when you get on it hard, it makes the angle even worse. But long bars practically prevent any movement of the angle at all. So if it's slightly negative, you're good.

I've never measured mine. But when I dropped my 04 two inches in the back, I simply removed the tapered shims. With the shims in place, the shaft to pinion was practically zero, straight. Removing the shims corrected it. Your 02 likely never had any shims at all. They were installed in 2003/04 models since they were two inches higher in the rear than the previous four years. On 99 - 02, I suspect you would need the same shims I had, but installed backwards of how mine were installed. IIRC, mine were installed thick end to the rear, thin end to the front. By removing them, it tilted the pinion down a hair.

Is that pretty clear?
 

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When you change the height with leafs you are not actually changing the pinion angle you are changing the drive shaft angle. The change with a one piece drive shaft should be close to the same front and rear so it should be no problem. When you use rear shackles only You are raising the rear of the spring which pushes the nose of the pinion down which needs to be neutralized. Changing both front and rear hangers would be closer to just your spring change. Usually pinion angle causes a harsh vibration at slow speed below 35mph on acceleration. For U joints to work smoothly they need to be in phase and at the same angle.
 

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Wile E. Coyote, Super Genius!
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Yeah, I think are correct. When I did the shackles on mine, it dropped the pinion down and made the angle too much. The thick end of the shim was in the front. I removed the shims, thus raising the pinion up a hair. Reduced the angle to a more user friendly angle. I used to have pictures, but I think they got lost when I deleted all my pics from FailBucket and put them in a folder in my computer. Some of them didn't make the transition. Oh well.

What's funny, is that in all the stuff Tim Skelton's page has on suspension mods and lowering, not once does he mention pinion angle. I just browsed all his suspension articles, SQUAT! 3-link, 4-link, Blackwood suspension, fiberglass leafs, lowering kits, etc. not one word on pinion angle. Hmmmm.

https://web.archive.org/web/20160310130105/http://timskelton.com/lightning/race_prep/index.htm
 

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Discussion Starter #5
Based on what you guys are saying, it looks like I'm fine then. Previously, I had the 2" drop shackles with stock 02 leaf springs. I think the previous owner removed the OEM shims because I didn't see anything there on either leaf. Make sense since the long bars uses it own leaf brackets and U-bolts.
 

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Sir,

Desired pinion angle is when the centerline of the trans is parallel with centerline of pinion. Setting pinion angle requires taking into account of movement of the pinion during acceleration. With long bars, that usually means 3-4 degrees negative angle. 4-link...1-2 degrees negative angle. Positive angle during acceleration results is vibration, loss of horsepower to the ground, and damage. Vibration or not, get off your butt and check it!

Keith
 

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local painter
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Sir,

Desired pinion angle is when the centerline of the trans is parallel with centerline of pinion. Setting pinion angle requires taking into account of movement of the pinion during acceleration. With long bars, that usually means 3-4 degrees negative angle. 4-link...1-2 degrees negative angle. Positive angle during acceleration results is vibration, loss of horsepower to the ground, and damage. Vibration or not, get off your butt and check it!

Keith
Welcome to LR! :bigtu
 

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Pilsung
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Like everyone above mentioned

Here is how I have always done it.

JL recommends -2 @ the pinion

Setting Pinion Angle

There are two angles to deal with:


1) Driveshaft angle
2) Pinion angle


You subtract pinion angle from driveshaft angle to get TRUE pinion angle, here's how you do it:


Using an angle finder place it on the underside of the driveshaft and record the angle indicated from the driver's side of the vehicle.


Next, place the angle finder under the flat surface of the pinion yoke (this surface is parallel with the pinion shaft) and record the angle indicated. Record both angles from the driver’s side of the vehicle. On the driveshaft anything to the left of 0 is positive, on the rear end anything to the right of 0 is negative.


Subtract the pinion angle from the driveshaft angle. The result is "TRUE Pinion Angle". In order to apply preload you need negative TRUE pinion angle. Adjust so that the front of the pinion goes down; continue to check each angle until the pinion angle is more degrees down than the driveshaft angle.
 

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Wile E. Coyote, Super Genius!
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Hell with all that, I just eyeballed mine. When I lowered it, the angle was severe. Removed the shim, no longer severe. Good enough for me. I have no vibration at any speed. Didn't even have any vibration when the angle was too severe. But it was never positive.

YMMV
 

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Discussion Starter #11
I don't put a lot of miles on my truck and it was lowered before I got it and still fine. I may have put 1K miles since I bought it about 8 months ago. Based on what chuck said, I'm probably better off now than I was before I did my Hotchkis springs being that it was lowered with shackles before in the rear. It's not like I got an extra 2-3 inches out of this...barely got a little more than 1/2" but it definitely feels sportier. Rode like a granny Cadillac before. I'll focus being off my butt with things I got going on in life which includes getting my house ready for sale. Once that's done and settle into a new place, I'll look into the angle for a little piece of mind. I mainly brought this up because I couldn't find anything on angles with no vibration.
 

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If you are drag racing with a positive pinion angle it will effect your 60ft and put a lot of strain on the u-joints. If you add not having long bars it will eventually be catastrophic. Even with the long bars, once you get into sticky slicks and some higher HP you will be moving the angle into a more positive position. Like the others stated lowering the truck will create a positive pinion angle. Using the shims is the best way to correct the angle. Ultimately you want it down (Negative) 2* so when you launch the angle is 0. Basically you want the trans to driveshaft and driveshaft to rear angles to be 0. Straight line gives you the best power to the wheels and no vibration. Here are some pics of my pinion in the positive position then eventually using the shims (Thick part facing forward) to rotate the rear down to a negative position. Don't forget the truck must be sitting flat on the ground when measuring everything. Having a drive on lift is key so the suspension is not hanging.
 

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Bringing this thread up because I'm trying to get rid of what I think is a driveline vibration. I'm getting a little confused with which direction I need to go with my pinion angle. At the driveshaft I'm 2.7 - 3.0º up and pinion is 1.2º down. If I do like stated above then I get ---> 2.7 - (-1.2) = +3.9º But If I follow what Wolfe Race Craft states then I get -1.2 - 2.7 = -3.9º. So my questions are
1. Is this within specs for my suspension with longbars? I see lots of different numbers thrown around as to what is ideal.
2. If it's not within spec then which direction do I need to go with the pinion?
 
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