pinion angle help please

[88Stanger]

Ok, so i have a 1969 C10 that is lowered 4" in rear with springs and 2" blocks, the front is dropped 2.5 with springs and drop spindles. At say around 40 to 45 miles an hour there is a vibration, harmonics. The drive line is new single piece that replaced a 2 piece that did produced the same vibrations, so this tells me it is Pinion angle. Here are the angles:
4L60E tranny is from front of truck to rear = 7 degrees down
Drive line is at 1 degree down (from front of tranny looking to rearend)
Rearend is 5 degree up (from rear of truck looking towards the front)
all measurements are done with truck on 4 separate blocks, so suspension is fully loaded. I have trailing arms not leaf springs
Where i get lost here is what to do. Should i install wedges to rotate the rearend to decrease the "positive" pinion angle? If i am not mistaken, if i move the 5 degree pinion angle to "Down" to 3 degrees of up angle, then the Driveline angle would increase to -3 degrees. This would then take the rearend pinion angle to a net "0" pinion angle, is this correct? If that is correct, that would then make the transmission angle increase correct? damn i am confused here and i know it is something simple i am just missing.
Thanks for any and all help here.

[kwmech]

A perfect rear angle will be parallel to the trans angle. So theoretically you'll have to move the pinion down 12 degrees. A 2 piece driveshaft helps with these angles as you can fudge them a little more. I would start with a 6 or 8 degree shim on the rear diff. Or if you can push the trans up? (not usually)

[geezer#99]

Originally Posted by kwmech

A perfect rear angle will be parallel to the trans angle )

That is correct.
However your numbers aren’t!
Tranny is down 7 degrees so pinion should be up 7 degrees. You need to shim the pinion up 2 more degrees.
Don’t worry about the driveshaft angle. It isn’t a factor in your case.

[HO455]

In my opinion you should try to move the tail of the transmission up a bit if you have room. It will extend the life of your U-joints. Less angle less wear. That being said you need a minimum of 1.5 degrees of angle on each end of the shaft for things to work correctly. As it was stated earlier try to match the angles as close as possible.
If you are interested I have some information posted on my WBM thread (page 14) below of what I did to mine.
Good luck

[57taskforce]

TREMEC has a smart phone app that helped me set the angles on my K20

[p0508]

https://youtu.be/gmV4qwLfOMY

Watching this might help you make sense of it in your head.

[88Stanger]

So, tonight I was able to make some tranny shims, moving the tranny down angle to 5 degrees, the driveline is now at 2 degrees down and the pinion is at 5 degrees up. What does everyone think of that?

[cornerstone]

Originally Posted by 88Stanger

So, tonight I was able to make some tranny shims, moving the tranny down angle to 5 degrees, the driveline is now at 2 degrees down and the pinion is at 5 degrees up. What does everyone think of that?

From what I have come to understand it should work... although I was thinking you need a working angle of 1-2 degrees. In other words, if the front is down 5 and the pumpkin is up 5 then your working angle is 0 degrees.... they cancel each other out.

The drive test will tell us for sure. Please report back after you run it through it’s paces.

[88Stanger]

Cornerstone i update after I drive it. I hope it is gone a d the issue is fixed. If not, then I have axle shims in the mail to adjust the pinion angle slightly, 1 to 2 degrees.

[Bigdav160]

Originally Posted by cornerstone

From what I have come to understand it should work... although I was thinking you need a working angle of 1-2 degrees. In other words, if the front is down 5 and the pumpkin is up 5 then your working angle is 0 degrees.... they cancel each other out.

The drive test will tell us for sure. Please report back after you run it through it’s paces.

Just a slight correction in terminology. The working angle is the angle difference between the transmission yoke and the driveshaft. Or the pinion yoke and driveshaft. Too much working angle and the u-joints wear out prematurely. Ask the lifted 4x4 crowd. Too little working and the grease doesn't move in the u-joint and they can wear.

The difference in the working angles should be close to 0 to cancel each other out.

[bloo]

Originally Posted by 88Stanger

So, tonight I was able to make some tranny shims, moving the tranny down angle to 5 degrees, the driveline is now at 2 degrees down and the pinion is at 5 degrees up. What does everyone think of that?

Sounds good to me. The trans angle and the pinion angle need to be equal. So, if your trans tail is down 5 degrees, your pinion flange should be up 5 degrees. This is what it takes to make the speed variations of the u-joints cancel.

One caveat is that no u-joint should run completely straight. If a u-joint runs with no angle at all, it will wear or pound little slots in the bearing surface on the cross, and then THAT will vibrate.

The angles on the u-joints really shouldn't be over 3 degrees either.

[88Stanger]

Thank you for the response Bloo. Also good to see a local on here

[88Stanger]

Originally Posted by p0508

https://youtu.be/gmV4qwLfOMY

Watching this might help you make sense of it in your head.

Awesome video, and damn that helped me alot to understand!!

[p0508]

https://www.speedwaymotors.com/Rear-...sku=91016072-2

I would buy 2 degree and 4 degree ones. Install. Drive.

[tj1970cst]

Fender or alignment shims under trans mount

[88Stanger]

I appreciate all your comments!! Thanks guys. The micro vibrations at about 40 to 45 are just killing me. My tuner is taking the truck to set up the LS tune next weekend so I'm trying to fix this now.
I am first going to try everything I have to raise the tranny up. Not sure what I have available, hopeful for 1/2" min, 1 " if possible maybe? Get the angles down, then I bought the 2*, 4* and 6* shims for the pinion. I'll post how it's going.

[bloo]

Anytime. I am in Wenatchee most of the time now and Seattle the rest. I was just revisiting this pinion angle problem the other day on a truck I did an axle swap in a long time ago....

Good luck 88Stanger, I hope you get it sorted out.

[bloo]

Sounds good to me!

[HO455]

Good work. How does it drive? I know the ride (NVH) in my Burban got much smoother once I got the angles right.

[88Stanger]

I honestly have yet to get it out. I had to cut the tunnel alot and will be installing the high hump this weekend, then get the cold air induction completed, then its driver. I'll post how it is after I get it out. Thank you for all the help guys!!

[Daaaanz67]

Waiting to see also.

[88Stanger]

thanks for all the great input. Now my only issue is what to do with the center console that no longer fits!!! DAMNIT. And the carpet does not Fit!! Damnit!! Oh well, .....