drive line angle

[miked]

I thought I would update what I did with my drive line.

I decided to check all my angles, starting with the engine as per chart above.
This chart came from a 1994 manual.
To be clear, I installed a zf5 with transfer case into a 2wd automatic truck, but I am keeping it as a 2wd. Just like the option for a lower gear range.

My modified transmission support bracket had set my engine at 6.5 degrees. It took a 3/4 thick shim on top of the transmission mount to bring the engine to the 5.5 angle found in the chart above.

It then took a .200 shim under the support bearing to bring the first driveshaft to the 4.6-degree angle.
I attribute this partially to the fact that the transfer case brought the front drive shaft to a lower position.

The second drive shaft ended up at 7.3 degrees instead of 8.6 which I believe is probably caused by 30-year-old spring sag.

Anyhow, I decided to do some research on how to do the calculation for a 2 piece drive shaft and only found some vague a+b=b+c formulas that did not work for me.

But I did find an online calculator at Spicer called the torsional analysis calculator in which you put in your driveline angles and drive shaft lengths, and it gave you a pass or fail with explanation.
Needless to say, I spent more hours than I want to admit playing with it.

Found that when I put in the numbers from the ford chart. The drive train was good until you passed 3100rpm on the drive shaft. Then it received a fail.
But when I put in the numbers from my drive train with the 7.3-degree angle rear driveshaft, it was good passed 4000 rpm. Ford must like their trucks loaded.

Anyhow, I thought this calculator might be of interest to others who like going down rabbit holes.

 

[u2slow]

The other variable is how well the shaft itself is balanced in the first place.

 

[IDIBRONCO]

To be clear, I installed a zf5 with transfer case into a 2wd automatic truck, but I am keeping it as a 2wd. Just like the option for a lower gear range.

Nothing at all wrong with that. I'll be doing the same thing to my 1987 dually some day. My 1985 4X4 with 3.54 gears sees almost exclusive pavement use. The front hubs are rarely locked in. I do use the 2lo option for backing up trailers and backing into my driveway.

 

[miked]

Sometimes it is just nice to go slow.

The transmission mount and drive shafts that I used in my truck, came off a truck that had been converted from 2wd to 4x4.
Thinking back to that truck, it’s drive line angles must have really been messed up. Especially as it also had the axle spacers installed, could explain why all the u joints were completely trashed in it. I originally thought it was just someone who never did maintenance.