Another Pinion Angle question I'm back!

[1LowToy]

Well after a long battle with working on the house I'm back to working on the truck. I did a flip of the rear end and have new perches to be welded on. I have it set at about 6 degrees, pinion down. Several people have said 2, 3 or 4 degrees down is fine. How about 6? I just hate to loosen everything up again for a nats ass

Yey Ney or????????

I may just have I welded up as is and may shim or shave down the lowering block.

[geezer#99]

6 degrees down puts it in severe u-joint bind.
Is your pinion above or below the centreline of the tranny.

[SkinnyG]

I have some vibration on my truck with a flip kit.

Trans is 5.5° down, and the diff was 0.9° up. The driveshaft was level. I shimmed the back of the trans as high as I dared (about an inch, I think), and put a 3° shim under the axle (makes the trans 5° and the axle 4°, ~close~ to parallel) and the vibration is much less. I will be shimming the axle another 1° to match the trans angle when I have time, and give that a try.

[1LowToy]

Yes lowering the trucks has created a driveshaft nightmare. I just figured out that I'm running about a 4 degree negative angle at the back of the tranny. (negative being that the tranny yoke is lower than the drive shaft) So I think the next step is to reduce that by a new tranny mount and a bit of spacer. I found some articles on this and I'm gathering I need to match it up with a positive pinion angle (pinion up). Like in the image?

It makes sense until you put a bunch of throttle on it. I have an inline six and the springs are beefed so I don't think I'll be getting any wheel hop soon.

[geezer#99]

What springs?
Leaf or coil?
You might be suprised how much the pinion moves up or down.
Some more info.
You might have these already.
http://www2.dana.com/pdf/J3311-1-DSSP.pdf

http://www.drivetrain.com/parts_cata..._problems.html

Leave the tranny where it is. You can't gain enough angle with raising it up an inch. Easier to do the pinion.

[SkinnyG]

I raised the back of my trans because I could, to try to reduce the operating angle of the forward u-joint. It did not change much at all, but even a little bit can't hurt.

[Keith Seymore]

Originally Posted by 1LowToy

Well after a long battle with working on the house I'm back to working on the truck. I did a flip of the rear end and have new perches to be welded on. I have it set at about 6 degrees, pinion down. Several people have said 2, 3 or 4 degrees down is fine. How about 6? I just hate to loosen everything up again for a nats ass

Yey Ney or????????

I may just have I welded up as is and may shim or shave down the lowering block.

It should match the engine/trans angle.

It's not just "6 degrees" in a vacuum, or related to the ground. What you are interested in is the U joint working angle between the pinion nose and the drive shaft. The difference in those angles should be minimized (statically, but will change with pinion nose windup during acceleration). Typically 1 -3 degrees for a coil spring and up to 5 or so for leaf spring.

K

[Ski-me]

Transmission and pinion angles need to be parallel with one another. Perhaps 1 degree lower on pinion to account for axle wrap on acceleration but ideally, parallel (not horizontal).

[1970pelle]

How are you measuring your angles? The correct way is at the U-joint caps. That is where the manufactures get there measurements. The pinion and tail shaft do not have to be in line with one another. There is a margin adjustment the U-joints handle.

This the style tool I have and use, made by Miller Tools.

[wilkin250r]

It's my understanding that it's more a RELATIONSHIP, rather than a single number.

Any angle at all causes the driveshaft to change speeds through it's rotation, it's not uniform, it accelerates and decelerates every 90 degrees of rotation. No problem at slow speeds, but can cause a shutter as speed increases.

Because of this, driveshafts are designed so the u-joints at opposite ends are exactly opposite phase, so the acceleration and decelerations will exactly cancel each other out IF (and this is important) the angles of the u-joints are the same.

You're always going to get SOME mis-match, because you can't keep everything perfect and rigid through suspension travel, axle wrap under acceleration, and other factors, and small angle differences have very little effect. But the greater the mis-match, the greater the effect becomes.

So it's not about a single number at a single point (like pinion angle). It's a relationship with ALL the angles involved.

[1970pelle]

Yes and no. The fix isn't tilting the transmission and engine back and down.
You may have to go to a CV type drive shaft, which can better handle the job.

[Keith Seymore]

Originally Posted by wilkin250r

It's my understanding that it's more a RELATIONSHIP, rather than a single number.

Any angle at all causes the driveshaft to change speeds through it's rotation, it's not uniform, it accelerates and decelerates every 90 degrees of rotation. No problem at slow speeds, but can cause a shutter as speed increases.

Because of this, driveshafts are designed so the u-joints at opposite ends are exactly opposite phase, so the acceleration and decelerations will exactly cancel each other out IF (and this is important) the angles of the u-joints are the same.

You're always going to get SOME mis-match, because you can't keep everything perfect and rigid through suspension travel, axle wrap under acceleration, and other factors, and small angle differences have very little effect. But the greater the mis-match, the greater the effect becomes.

So it's not about a single number at a single point (like pinion angle). It's a relationship with ALL the angles involved.

This is exactly correct. That relationship is, at the least, the U joint "working angle" and at the most the working angles across the whole system.

We would say that a U joint issue is a "second order of driveline" disturbance, because you get two "kicks" per rev of the shaft. The disturbance is increased as the working angle is increased, and as the torsional load is increased.

This is in contrast to a driveline imbalance issue, which is one "kick" per rev (or a "first order of driveline" disturbance). The two are often confused and fixes for one are often applied to the wrong problem.

Well said.

K

[Keith Seymore]

Originally Posted by 1LowToy

Yes lowering the trucks has created a driveshaft nightmare. I just figured out that I'm running about a 4 degree negative angle at the back of the tranny. (negative being that the tranny yoke is lower than the drive shaft) So I think the next step is to reduce that by a new tranny mount and a bit of spacer. I found some articles on this and I'm gathering I need to match it up with a positive pinion angle (pinion up). Like in the image?

It makes sense until you put a bunch of throttle on it. I have an inline six and the springs are beefed so I don't think I'll be getting any wheel hop soon.

Take a look at this:

http://67-72chevytrucks.com/vboard/s...d.php?t=522180

If you can follow this logic then you can fix any vibration problem.

K