Opinion on Drive Line Correction

I installed a 2.5ish inch lift (front and back), and took some angle readings before and after. Before I list my angles, I want to note that Spicer has the following to say about u-joint angles:

• Universal joint operating angles at each end of a driveshaft should always be at least one-half degree
• Universal joint operating angles on each end of a driveshaft should always be equal within one degree of each other (one half degree for motor homes and shafts in front of transfer cases or auxiliary devices). Note: the angles don't have to cancel each other out, they can be equal in the same direction.
• For vibration-free performance, universal joint operating angles should not be larger than three degrees. If they are, make sure they do not exceed the maximum recommended angles.

Driveshaft RPM - Max. Operating Angle

5000 - 3.2°
4500 - 3.7°
4000 - 4.2°
3500 - 5.0°
3000 - 5.8°
2500 - 7.0°
2000 - 8.7°
1500 - 11.5°

Points to remember:

• The angles shown on the above chart are the maximum u-joint operating angles recommended by Spicer engineers and are directly related to the speed of the driveshaft.
• Any universal joint operating angle greater than 3 degrees will lower universal joint life and may cause a vibration.

With stock 3rd gen 2.93 gears, 32" tires, and recording RPMs on the highway at my target max. speed of 80 mph, I get the following driveshaft RPMs (Shaft RPM = Engine RPM × Gear Ratio):

4th Gear - 1.0 Gear Ratio - Engine RPM 3400 = Shaft RPM 3400
5th Gear - 0.69 Gear Ratio - Engine RPM 2300 = Shaft RPM 3333
6th Gear - 0.58 Gear Ratio - Engine RPM 2000 = Shaft RPM 3450

Doing the math and referencing Spicer's table above, it appears the maximum u-joint operating angle I want to allow would be 5.2 degrees, but try to stay under 3 degrees if possible.

I measured the following on my truck before and after the lift in the first table below. The next two tables with red text was estimated by measuring driveshaft lengths and mocking up the geometry in CAD.


Based on 4Crawler's recommendations on 2-piece drive shaft angles (https://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml#2-Piece), I can go one of two ways:

Second Table: Add 3 degree axle shim and achieve Setup 1 (B = C)
Third Table: Add carrier bearing drop shim and achieve Setup 2 (A = C)

The axle shim option maintains B = C, regardless of weight in the bed, and all angles are near or below 3 degrees.

For the CB drop option, at some weight in the bed between 0 and 500 lbs, the middle U-Joint will be at 0.0 degrees. This is concerning, as I might get vibes at that weight by violating the 0.5 deg min. rule. It is also noted that my first U-joint would be running at a greater angle all the time, and the third U-joint would also be running at a greater angle than 3 degrees when unloaded.

It is lastly noted that I currently don't have any vibes, although once I get up to 80 mph and beyond, according to Spicer, I should start to get vibes.

 

Welp, for those who might come across this post while trying to figure out how to correct drive line angles and vibes, I ended up going with the 3 degree shim option. New angles after driving around the block a couple times after install are:

0.0
3.3^
3.3DN
1.9^
5.2DN
1.6v
3.6DN

I have driven the truck around town and gotten it up to 70 mph, no vibrations whatsoever (but then again I didn't have vibes before either). I ended up with about 3.5 degrees of correction with the shim, but things might still settle a bit more, and bring things more in line with 3 degrees of correction. While U-joint operating angles might not be perfectly opposing on the second shaft, I think keeping the angles below 2.0 degrees is helping as much as anything. All done and said, I feel a lot more comfortable not running the pinion U-joint over 5 degrees.

Update: After almost 2 years, with bed weight ranging from 0 to 1300 lbs, speeds up to 100 mph, and all sorts of terrain, I am blessed to say that I'm still vibration free. I believe the key is to have U-joint 1 = U-joint 2 (same sign convention), and U-joint 2 = U-joint 3 (opposite sign convention, cancel out), with up to one deg difference OK, while also keeping all U-joints between 0.5 and 3.0 deg, if possible.

 

I haven't measured any angles on my truck. That being said, I recently installed the TRD OEM lift kit shocks and a 2" AAL. 2" increase all around as you had attained. I had previously purchased an Old Man EMU C.B. drop kit but have not installed it yet. This is because I'm not getting any vibrations at all from the driveline. This is indicating to me (at least) that I don't have any problems with change of angles at the moment.

I do have the ECGS Bushing ready for install if needed for the front, but again I do not have the vibrations indicative of a sloppy needle bearing in the front differential.

Still watching and observing my truck post lift.

 

https://www.tacomaworld.com/threads/just-fixed-driveline-vibration-for-free.153050/