Posted by Keith in Washington [172.71.147.94] on Monday, March 04, 2024 at 15:14:12 :
In Reply to: Divorced T-case question posted by bucky [172.68.27.25] on Saturday, March 02, 2024 at 17:49:27 :
Yes it is nice to have the jack shaft in phase with the rear driveline. Is it a matter of life and death, No. It is much more important that the drivelines are in phase. As the bearings and bushings become more worn in your driveline the vibrations will become more noticeable.
Case 1
That said. I keep my drivelines in phase. Especially on my Carryall as it has a centered rear axle which means the Transfer Case output is directly inline with the input. Basically, this means that you may have a driveline at each end of a shaft that are putting pressure in different directions which is going to shake that shaft and cause wear. Yes I know that this is not a solid shaft from input to output in the TC. However, they are basically two shafts where the nose of one shaft fits into a pocket in the second (which is a shaft with a gear attached with the pocket in the gear). Bearings providing a rotation surface between the shaft nose and pocket. Out of phase input and output drive lines will put a lot of stress and wear on the shaft nose, bearings and pocket.
Case 2
If you are running the standard PW offset rear driveline, I can believe that the jack shaft and being out of phase may cause less issues. However, both shafts will be out of phase and putting stress on the transfer case in different directions. I don't know how the offset drivelines will affect the intermediate gears and etc in the transfer case. I know that the offset drivelines put a lot of stress into the transfer case as the power is turned 90 degrees twice in this setup. I can't see that drivelines vibrating at different phases would not cause additional issues.
Case 3
I caught that you are using drive flanges in your front axle. This means that the front driveshaft is always spinning. With this setup I would make sure that the front, rear and jackshaft are all in phase. Like in case 1 above you have 2 drivelines attached to the ends of a shaft. The same issue would be seen here as in case 1. There are drive flanges available at several vendors that are known to us all. You can get one machined so that it is free spinning. You can swap the original flanges and the free spinning ones as needed if you using 4 wheel drive all the time.
Two general comments: 1)any vibrations and wear will increase with the drive line angle. That's why short wheel base jeeps that are lifted have to go to specialized joints in their drivelines. 2) Vibrations and wear will increase with speed.
Hope this helps. Comment are welcome.