Zf M/T 4TH Countershaft Gear 39 Tooth . 4th Countershaft Gear 6-Speed ZF Manual Transmission 39-Tooth Features and Benefits: 4th Countershaft Gear 6-Speed ZF Manual Transmission 39-Tooth Details: AAP UDA 4: 50 Application Summary: 1999-2010 Ford F-250 Super Duty (4th) (Transmission Code: S6-650 & Transmission Base Gear: 6 & Transmission Control Type: Manual / Qualifier: Replaces Oe Part Number(s) 1319-303-059, with 39 Teeth, without Tag # 1319-050-083, 1319-050-084, 1319-050-085, 1319-050-086 / Note: S6-650 4th Counter Shaft Gear, S6-650 4th Counter Shaft Gear, 39 Tooth) 1999-2010 Ford F-350 Super Duty (4th) (Transmission Code: S6-650 & Transmission Base Gear: 6 & Transmission Control Type: Manual / Qualifier: Replaces Oe Part Number(s) 1319-303-059, with 39 Teeth, without Tag # 1319-050-083, 1319-050-084, 1319-050-085, 1319-050-086 / Note: S6-650 4th Counter Shaft Gear) 1999-2010 Ford F-450 Super Duty (4th) (Transmission Code: S6-650 & Transmission Base Gear: 6 & Transmission Control Type: Manual / Qualifier: Replaces Oe Part Number(s) 1319-303-059, with 39 Teeth, without Tag # 1319-050-083, 1319-050-084, 1319-050-085, 1319-050-086 / Note: S6-650 4th Counter Shaft Gear) 1999-2010 Ford F-550 Super Duty (4th) (Transmission Code: S6-650 & Transmission Base Gear: 6 & Transmission Control Type: Manual / Qualifier: Replaces Oe Part Number(s) 1319-303-059, with 39 Teeth, without Tag # 1319-050-083, 1319-050-084, 1319-050-085, 1319-050-086 / Note: S6-650 4th Counter Shaft Gear)