flatheadsix1950

thank you, kindly. I did check after many rotations with a drill driving the pinion that the minimum spot seemed to stay in the same place on the ring gear. That would seem to me to suggest a high spot on the ring gear, and not a problem with the pinion? or is that not right? Good point on the axles!

Greetings, experts. I’m rebuilding a B-1-B and came across an NOS ring/pinion set with a 3.54 ratio. This is a “Formate” gear set for a Chrysler, and fits fine in the original Dodge truck differential case. With my rebuilt 218, a 3-speed, and 16-in wheels it won’t pull stumps, but I’m expecting reasonable highway road speed. I do plan to take some trips, so the target is something more than to just make it to a show. I’ve installed all new bearings in the third member, and done the setup. Pinion pre-load gives 20-25 in-lbs drag as it should. The ring gear has about 0.0025-0.003 runout, which is within spec. The backlash has a distinct minimum in one area. I’ve been able to adjust the backlash to 0.006 at the minimum, but it increases to 0.010 at the maximum as the ring gear is rotated into other positions. In most positions, the backlash is around 0.007-0.008. My question is whether this variation in backlash is OK to just run, or should I take it all apart and try to figure out where it’s coming from. The service standards say backlash 0.006-0.008. The standards say to start setting backlash from the gear side at the point of minimum backlash, which sounds like some variation is expected, but the standards or the shop manual don’t otherwise talk about backlash varying. It seems to me because I started with 0.001 and adjusted the minimum to 0.006 (per the shop manual) that the minimum backlash is on spec, that the differential bearing preload is therefore OK. To my untrained eye, the contact patterns look OK after spinning with an electric drill with some friction on the ring gear to load it (I guess they’re OK - see the photos), but since this is the first differential setup I’ve done, I humbly request the opinion of you folks that have done this and ended up with a rear end that lived to tell the tale!