I just got my 400 back together last weekend after rebuilding the TA. I put in a new main clutch, TA clutch, new bearings in the TA and a rebuild overrunning clutch. With all the seals and oil the cost for parts was just under $800. In the term ramp clutch, you have 8 rollers and springs to push them up the ramp to lock the gear cage up on the back of the gear case. In the sprague overrunning clutch you have about 20 rollers that run up the ramp to lock up the gear cage with no springs. I went with the original overrunning clutch that was rebuild by BMD for about $117 and use Hi-tran for the lube in the transmission. So far everything is working wonderful and I can not see any advantage over the two if you use them right.
John In Iowa