Re: BigKev's 1937 115-C Convertible Coupe

Posted by DavidPackard On 2023/1/13 15:00:05

Axle nut torque:

The desired torque should be a function of the tread diameter and pitch. For the later cars both the 3/4 X 16 and 7/8 X 14 had a call-out of 200 – 270 ftlbs. If the ’37 has something smaller than 3/4 inch diameter then the later torque specification IMO would not apply. My ’35 – ’42 Motor’s Manual is silent on the subject as is the ’40 – ’54 version of the manual.

My tool handbook (circa ’49) lists the failure torque of a 3/4 -16 as 390 ftlbs, and 7/8 – 14 as 625 ftlbs. If the ’37 Packard has a smaller axle thread diameter/pitch of say 5/8 – 18 that failure torque is listed as 220 ftlbs. It would appear that Packard was comfortable pushing the fastener to about 70% of the failure torque for the junior cars, but the senior cars pushed only to 43% of yield. If you find the axle thread is 5/8 – 18 then consider 110 ftlbs (50% of 220), otherwise for the 3/4 -16 shoot for the low side of the later car specification 200 ftlbs (≈50% of 390). There was no mention of lubrication, so I’m assuming dry thread and washer surfaces in the above data.

I would ‘stone’ the nuts to get the cotter pin to fit versus ramping-up the torque.

dp