1938 WC transmission gear ratio.
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=171680
Printed Date: 04 Sep 2025 at 3:01am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: 1938 WC transmission gear ratio.
Posted By: Alanv8
Subject: 1938 WC transmission gear ratio.
Date Posted: 01 Jun 2020 at 11:38am
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Hello everyone!! I own a 1838 Unstyled Allis Chalmers Speed Mantainer and i would like to know the gear ratios of the transmission. Been searching in the forum and in the Owners manual, and can't find that info. Does anyone know that?? thank you very much in advance!!! Alan.
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Replies:
Posted By: Alanv8
Date Posted: 07 Jun 2020 at 6:43pm
| help!!!!! |
Posted By: DrAllis
Date Posted: 07 Jun 2020 at 6:51pm
| First gear from the flywheel/clutch thru the transmission output shaft is 13.32 to 1 ratio. Second gear is 9.20 to 1. Third gear is 6.93 to 1. Forth gear is 1 to 1 direct drive. |
Posted By: DrAllis
Date Posted: 07 Jun 2020 at 6:57pm
| Ring and pinion is probably 6.6 to 1, but could be 4.7 to 1 if it is a farm tractor rear end. Final drives are 4.0 to 1 ratio. |
Posted By: Alanv8
Date Posted: 09 Jun 2020 at 12:53pm
Hello DrAllis, thank you very much for your response. I've been searching on the internet and found this article http://antiquetractorpullguide.com/wp-content/uploads/2010/04/Allis-Chalmers-WC-with-RC-Ring-and-Pinion-Ground-Speeds.pdf" rel="nofollow - http://antiquetractorpullguide.com/wp-content/uploads/2010/04/Allis-Chalmers-WC-with-RC-Ring-and-Pinion-Ground-Speeds.pdf  Assuming that the 4th gear es 1:1, then 26.4 / (6.6 x 4) = 1 (Ring and Pinion, and Final drives) So making the same math to the rest of the First, Second and third gear, the ratio would be 3.70:1 ; 2.54:1 and 1.92:1 respectively. Could that be possible?
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Posted By: DrAllis
Date Posted: 09 Jun 2020 at 4:27pm
| Whomever wrote all those numbers up is wrong !! A WC has a ring and pinion ratio of 4.7 to 1. The RC has a 6.6 to 1 ratio. Everything is wrong because of his wrong numbers. |
Posted By: DrAllis
Date Posted: 10 Jun 2020 at 6:53am
| I've got to recant. I didn't read my own hand written notes correctly. My numbers included the ring and pinion gears For a WD and not the final drives. So, he is correct on some things. For an RC rear end (6.6 to 1 ring and pinion) my numbers are 97.68....67.39.....50.79...and 26.4 to 1. For a WC rear end (4.7 to 1 ring and pinion) my numbers are 69.56.....47.99......36.17....and 18.8 to 1. Where he is dead wrong is claiming there is 10% difference between an RC and WC rear end. From 6.6 to 1 in an RC to 4.7 to 1 in a std WC is 29% difference, not 10%. Anyone who tractor pulls a WC seriously always has narrow 38 inch rear tires. They know that low gear at stock high idle RPM's is right at 3.5 MPH. The only variable is the actual tire diameter which varies from brand to brand and cut versus un-cut lugs. You asked the question. Why are these gear ratios so important to you ??? |
Posted By: Alanv8
Date Posted: 10 Jun 2020 at 10:39am
| Thank You very much DrAllis!!! I am trying to adapt a new engine and transmission to the grader so before doing anything i would like yo check those ratios to ensure that the speeds Will be similar to the Originals. Thank You again!!!!!!! |