Did a search and got too many results to read thru on this.
I was checking the SD over last night getting ready for a trip. Was under the car checking the driveshaft and could feel what I thought was slop in the center U-joint. Oh great! Took off the cover and found to my relief it was not the joint, but the spline coupling that was a bit sloppy.
So, the question. How tight should that nut be? I checked the repair CD, and it didn't really say. I just snugged it down until I couldn't feel and movement or slop in the spline. Is it supposed to be tight? Or should the spline be able to slip in and out at all? I would think not, since these cars have indie rear suspension.

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past MB rides:
'68 220D
'68 220D(another one)
'67 230
'84 SD
Current rides:
'06 Lexus RX330
'93 Ford F-250
'96 Corvette
'99 Polaris 700 RMK sled
2011 Polaris Assault
'86 Yamaha TT350(good 'ol thumper)