I'm converting my '39 Merc rear to open drive, but don't want to dis***emble it. For reasons unknown, early Merc banjo rear ends did not have a separable drive shaft - their drive shafts were basically a pinion gear with an eight-foot stem. The first pic shows the Merc with the torque tube removed and all but a foot of the drive shaft (1.125" diameter) cut off; the pinion gear is supported by a pair of tapered bearings, which are held in place by a nut and washer. The second pic shows the hat I'll use to contain a drive-shaft seal (and maybe another support bearing). Question #1: I'd like to weld a short section of spline onto the drive shaft near the hat, and then support a u-joint yoke on the spline with a nut. Does anyone know where I can get a suitable donor spline shaft, and a bolt-on yoke? (Note: I can machine threads onto a suitable splined shaft.) Question #2: What's the best way to weld the donor spline to the drive shaft stub? I'm thinking of making a drill bushing to drill a 1/2" center hole in the drive-shaft stub, turning an inch or so of the spline shaft to a press fit, and weld into some deep V's on the drive shaft and splined shaft. Question #3: The pinion shaft has two or three degrees slack in it (i.e. you can turn it a few degrees before it engages the ring gear) - is that too much, or normal for an old banjo? Question #4: Should I decide to rebuild the rear end, is there a comprehensive set of instructions available? I've seen bits and pieces of the process on the HAMB and in the rod mags, but never an A-to-Z write-up.
You are lucky to have the shaft on the pinion. Find a 'u' joint & drive shaft that can fit when a spline is cut on the remaining shaft. Take the unit apart & go to a machine shop & have the shaft splined to the "u"joint.
Is that "you don't want to dis***emble it ". Or " you don't really want to dis***emble it" As you will most likely have the 3.54 merc ratio gears the best way is to dis***emble it clean it up lop off the extra length merc shaft and machine a standard six spline into the pinion shaft. Not sure who else sell open drive adapters but speedway do. I cut off my own 39merc pinion shaft a few years ago and got it repsplined, but for a torque tube. I wouldn't think the pinion bearings would take to kindly to any welding.
Still looking for a promising welding idea. Will weld slowly enough that pinion bearings are not affected. But suppose I did choose to spline the pinion shaft - does anyone know of a suitable machine shop in Central Texas? And does anyone have a complete set of banjo-rebuild instructions?
HAZ should not be an issue if welded slowly with plenty of time to air-cool - also good ideas for keeping the coupling true. Still looking for the best idea on how to prepare for the weld, and part number(s) for the u-joint coupling.
One question???? How do you plan to get that bearing retainer/seal carier over a welded on coupling??? Re-splining sounds like a better fix.
Not thinking of a coupling; welding withing the OD of the 1.125 shaft. Otherwise, would use o-rings and a two-piece retainer.
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