Reply to "half shafts and u-joints"

My Spicer u-joints, for F-350 and F-500 Ford trucks, mic at 1.18" OD on the cups while OEM u-joints mic at 1.261"OD. The assemblies are also 0.035" longer for OEMs than for Spicers so no mixing of parts is possible- the OEM yokes are wider with bigger holes. I see no problem using two different half-shafts in a street car, except for the obvious requirement of remembering which is which when parts are needed. But if I understand your question, mixing a Spicer male spline-section to an OEM female spline-section might cause some difficulties since presumably one is SAE and one is metric. I guess it would depend on whether the male & female splines in the slip-coupling fit correctly; too loose and the splines could tear out while too tight would prevent the halfshaft from telescoping under driving conditions. Congratulations- this possiblity has never been brought up before!