This is an older hull 74 Sleekcraft Rebel but the pump is upgraded with an AT 9.25 bowl and 9.25 SST impeller. The berk. 12JC suction housing has the AT HP angular bearing with the AT HP shaft. Engine is a turbocharged 496 BBC. The coupler is rattling big time from idle to about 2000 so I changed the u-joints, no joy and seems even worse. It has always rattled a bit at idle but it's really knocking. The only thing I did was to freshen up the pump softgoods, check clearances, and reset the thrust bearing preload. I checked the crank end play and it has increased from 0.006 to 0.010 (don't have this one figured out yet). As a note with the new packing the pump rotates very freely by hand. I'm thinking on pulling the pump again and making sure the thrust bearing is OK but really could use your expertise here. As an observation when idling there seems to be no visual crank lateral movement. Also there is about 0.25 inch of sliding clearance on the pump splines when coupled to the motor.
When you rebuilt the ujoints did you install a new yolk?
Wen you rebuilt the ujoints did you replace the yolk? Your problem is in this area. As soon as you give the engine enough throttle to lock the splines against each other the noise goes away. Not sure if you will ever get ride of the rattle completely but I feel it can be improved on.
thanks Greg, seems to be the consensus all around - with the reduced rotating friction in the pump and the inertia that the SST impeller carries coupled with the solid roller cam and what it does on crank accelleration and decelleration the splines are crying out.