GMC C1500

Truck details: 1990 GMC K1500 (4WD), 5.0L, 4-spd auto (700R4/MD8), SB/EC, one piece driveshaft. Approx 150K miles.

Replacing badly worn factory-type (non-greasable) U-joints (which made the usual clunking sounds) with greasable type so I can lube at the recommended 5K/10K or 3 month intervals. Of course I marked which end was rear and front and spline yoke orientation, etc. - With the brightest yellow grease pencil in my artist's box I could find. Thankfully I'd noted which end had the casting dimples on the aluminum yoke or I'd be totally lost, but during handling the marks came off and it took some time with my old worn-out brain to remember that and re-establish which end was the front when it came time to put the splined yoke back on.

However, because it's possible this is a replacement & I've found other previous repair/replacement mistakes on this truck from prior owners and/or 'mechanics', I wanted to make sure I do have the front & rear identified correctly. So after much research online - even after spending many hours on the Dana-Spicer website - I have yet to find any way of positively identifying which end is which.

More details: Spicer driveshaft assy p/n 915802-5920 now obsolete & superceded by a few times, most recently by p/n 921518-6116. The end pieces have an older part numbering system - what I think is the front is cast with " F3-309" and (rear?) With " F3-329". Other than the slightly different shape of the casting and length of the tube yokes (see dimensions below), there is nothing which would make a positive identification possible - to anybody who is not a driveline specialist or Dana engineer. The tube is straight from end to end (not stepped down in diameter, as are many of the ones I saw online).

Dana's new numbering system does not have these tube yoke numbers in any catalogs or web pages I've seen, so I can't even look at specs and do the math to figure torque, angle, critical speed, etc. As if specifying a driveshaft for a new application. I'm sure that somebody else has run across this problem from not marking the driveshaft at all and figure my question in general might help others across all topics when it comes to this.

How does one positively identify the front and rear ends of a driveshaft?

F3-309 tube yoke (poss. Front) is more " squared", approx. Distance from center of bearing hole in the yoke ear to center of tube-yoke weld: 1.9"
(date stamp? &Quot; 90 20" )

F3-329 tube yoke (poss. Rear) is longer and more tapered from tube to ears. Approx. Distance from center of bearing hole in the yoke ear to center of tube-yoke weld: 3.6"
(date stamp? &Quot; 88 96" )

Note to self: use a permanent marker on the aluminum part of the tube next time.

-D. Van Dijk
March 9, 2007.

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