Plymouth Owners Club

General Category => Technical Discussion => Topic started by: Dave123 on July 21, 2022, 11:51:56 PM

Title: 31 plymouth differential ratio
Post by: Dave123 on July 21, 2022, 11:51:56 PM
Anyone out there know of a replacement crown and pinion gear set that could be installed to replace the PA's 4.33 ratio?
Ideally without disturbing the originality or appearance of originality?
Would not want to make a huge change, maybe something in the 3.9 or 4.0 to 1 ratio.

Dave
Title: Re: 31 plymouth differential ratio
Post by: TodFitch on July 22, 2022, 12:55:35 AM
Looks like 30-U, PA and PB used the same ring and pinion. The only ring and pinion sets I see for those in the 1928-33 Master Parts set are for 4.33:1 ratios. Well, not quite true, the 7 passenger and taxi used a 4.62:1 set which you probably don't want even if it would fit (the 7 passenger, etc. vehicles often used totally different running gear).

There was a major redesign of the running gear, including the rear axle, for Plymouth in 1933 (and another one in 1937 or so) so it is highly unlikely that a ring and pinion set for Plymouth later than 1932 would fit.

You might want to find parts books for the same era DeSoto or Chrysler cars and see if they used the same carrier and maybe had a ratio that you could use. Sometimes the coupes and business trim versions of Chrysler built cars had a better ratio than the sedans. At least then you might have a list of cars that could be donors.
Title: Re: 31 plymouth differential ratio
Post by: Dave123 on July 22, 2022, 07:25:55 PM
Thanks good advice

Dave Eddie