Driveline Vibe Diagnosis Help

Working on diagnosing drive line vibes after 2"+ lift and pretty stumped on how to proceed.

Here is my process and angles:
1) zero on TC and measure rear pinon flange: 10.2 degrees
2) measure 1st (front) shaft: 4.2 degrees
3) measure 2nd shaft: 5.4 degrees (1.2 degree CB working angle)
4) zero on 2nd shaft and measure rear pinon flange: 3.1 degrees

So, when I think about how to solve the angles, I could start with a 3 degree shim to resolve the 2nd shaft/rear diff working angle. But, I would still have a 7 degree offset between the TC output. and the rear diff input. I am seeing several methods across TW, but don't know how to proceed. Anyone have thoughts?

 

could be needle bearing

 

Already replaced with ECGS. Definitely driveline issues

 

Okay, have you isolated to front or rear? So many things it could be as I am dealing with the same with one of my cars. And was it ONLY after the lift or before as well?

 

vibrations are only after the lift. I have some shutter at acceleration and some steering wheel vibrations at 10-20MPH and ~60MPH. I think it is rear driveline -- i have messed around with CB drop and vibes change but are not resolved, hence why i started measuring to be more scientific

 

I would first tighten everything down again and make sure its aligned. What lift do you have

 

From your slope measurements, your working angles are:
A=4.2
B=1.2
C=-4.6

I derived C=-4.6 from your t.case zero...
I realize you re-zeored on the 2nd shaft and got C=-3.1.
Point is, something's fucky with your measurements/measuring. But I'll procede, as is.

C is expressed as a negative number since it is a upward angle(...for method 4, below). Anything over 3 degrees, accelerates wear. I'd take the carrier drop out before you procede; but, you're really close as is. Up to you...

That said, there are 4 ways to equalize a two-piece shaft with 3 standard u-joints:
1.
A=0
B=C

2.
C=0
A=B

3.
B=0
A=C

4.
A+B+C=0

As is, you have(with method 4):
4.2 + 1.2 - 4.6 = 0.8
Or, a 1 degree shim positioned to increase the C working angle 5.4-5.6.

 

Thank you, this is the kind of information I was trying to calculate! One question, where does the -4.6 come from?

 

Just saw that you added the explanation. Thanks!

 

No. Disregard that 4.6; I fucked up. Sorry.

You have:
A=4.2
B=1.2
C=-3.1

4.2 + 1.2 -3.1 = 2.2
Or, a 2 degree positioned to increase C by 2-2.2 degrees...as you sit now.

 

It might help or maybe not, mine I ended up getting the drive line the same angle from front to back, I don’t remember what I ended up at but that helped me out. I know I posted it somewhere. I used stainless steel fender washers for the CB. Also, check that the front and rear shafts are aligned. The cb can be moved slightly left or right.

Cough cough, if you end up wanting to buy a set, I’ve got slotted 3° shims here- https://www.tacomaworld.com/threads/spc-3°-axle-shims.742794/

 

Thanks all for the input. This has been an all day project and quite frustrating. trying to resolve driveline with what i have readily available. I think I will be taking @splitbolt recommendation with the 1 degree shim. The math works out perfect, but what I found today is that the angle of the shim doesn't necessarily change the axle that same amount. Assuming the interaction of the leafs + the shim amplifies the true angle adjustment.

 

May want to look at post #10...

I really recommend removing the carrier drop, though. Why increase A, requiring you to increase C to cancel it?

But yeah...trig...cosines...2+2 don't always equal 4.

 

I missed that. will report back without the drop. Thanks.

 

I chased this a bunch when I removed some 2" tapered blocks and put in a 3 leaf aal. what ended up working for me was the following. Have since swapped in some deaver u402 stage 1’s and still good. This was with the arb fk29 cb drop and no pinion shims.

 

Part art, part science.
I think yours is using th A=C, B=0 method with the aid of axle wrap. As the pinion lifts, it's reducing B closer to 0 and bringing C closer to A; basically mimicing a 1-piece shaft with 2 standard u-joints.
No vibes on decel?

 

Does it change at all when in 4hi?

 

no vibes on decel. I played around with mine a bunch. Tried 2 different size pinion shims and multiple different amounts of pinions drop. I haven’t remeasured after doing the deaver springs but it doesn’t vibrate so I figured why bother.

 

can i get in on this? i have a 2014 double cab. serious VIBES 55-65mph.. its a 2nd gen, but i believe the numbers are prolly the same or similar. i have a 2.5" spacer kit in the front, and i have a AAL in the rear, also, im 2WD, and these numbers recently taken, were after a CDB spacer was installed. i think its 8MM thick. so i see a almost 4 degree difference,.. is that too much, not bad? im wondering if i should relpace the center carrier bearing. i don't think it feels bad, i yanked on it both sides of the bearing, it feels snug. i wonder if angle shimming the rear diff will cure some vibes. it will add more final degrees on the ujoints and pre-wear them, but thats what i get for modifiying the damn truck in the first place.

can someone help, sorry to threadjack.



after i posted this, i went to the spicer webapp, and put in my numbers, can anyone explain what this means, or where i should be concerned? thank you





or does this mean i have a 10 degree inbalance?

 

When inputting the figures into the spicer page are you I’m putting the up/down based upon measurements from left to right? I get that the pinion is probably pointing up 8.2 degrees but I believe you have the slope put in backwards. The slope on each measurement should be defined by up or down from left to right or right to left on every angle. The driveshaft at -6 degrees down and pinion at + 8.2 should be 2.2 degrees not 14.