YOKE AS 3624248 - Caterpillar

623B, 631D, 633D, 637D, 639D Tractors 641B, 651B, 657B Scraper 627 (P/P)SUPPLEMENT: 06/21/82SERVICE MAGAZINE, MAY 24, 1982, PAGE 3.In the article "Bow In Draft Arms" change the subtitle to read: "621B, 623B, 631D, 633D, 637D, 639D, 641B, 651B, 657B Scrapers; 627B (PP) Scrapers".--------------- END SUPPLEMENT ---------------There have been some reports of problems with bow (gradual curve) in the draft arms of the above scrapers. It is not necessary to make the draft arms completely straight.
The bow in draft arms is normal on new scrapers and will not decrease the service life of the component or decrease machine output.
The bow in a draft arm has the correct tolerances if it is between 9.5 mm (.38") and 12.7 mm (.50") as measured over the length of the draft arm. When draft arms are installed on a machine, the amount of clearance between the draft arms and the bowl sides will need to be adjusted. Shims can be added or removed from the wear shoes on the bowl sides to adjust the clearance from 1.6 mm (.06") to 3.2 mm (.13").