Originally Posted by OldSub
Why are they failing? It may be good to be sure you know before switching.
I'll second that, and guess it's a balance or angle problem.

If you want to redesign the driveline have a look at this Tech Tip and the manuals linked in it http://www.stovebolt.com/techtips/driveline/setup/index.html
A driveshaft may look simple but there is a lot thought that goes into getting the right one for the job and installing it properly so it will last.

Before just swapping stuff around at least skim through the manuals and or ask a good driveshaft shop for help/recommendations.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-