I have a ST400 switch pitch pump that has pump gears that measure .625 thick vs. a normal TH400 .727 thick gear. I’m not sure what this pump with thinner gears is from but I’m wanting to use it for a replacement for a ruined pump that has the thicker gears. I not sure if reduced flow with the thinner gears is an issue that I need to be concerned with. So far I really have not found out much info on what this pump is all about . any input on this would be appreciated. Thanks
What I have seen, is the TH400 originally used the thinner pump gears, in the switch pitch (65-67) transmissions. For about 68 they went to the thicker gears. Other changes were made in the 67-70 period as well, such as filter and pan, valve body, center shaft spline, center section protection ring, clutch pack piston, and 9 element sprag. All of these individual or as sets will interchange in all TH400s. My transmissions are made of parts from which ever was the best (in my opinion) of these parts. Since I am committed to switch pitch transmissions, I must use the thinner pump gears. The one exception is the TH425 FWD trans from Toro and Eldo. The pump assembly of these may be removed as a set, between the 2. My TH425 switch pitch has the thicker gears. Bruce Roe
Bruce, thanks for the reply. The pump that I have that is destroyed has the thicker gears and oddly the gear set is slightly larger in diameter than the thinner pump gear set. Do you know if this also on one of these 425 pumps? Thanks
"I have a ST400 switch pitch pump that has pump gears that measure .625 thick vs. a normal TH400 .727 thick gear. I’m not sure what this pump with thinner gears is from but I’m wanting to use it for a replacement for a ruined pump that has the thicker gears. I not sure if reduced flow with the thinner gears is an issue that I need to be concerned with. So far I really have not found out much info on what this pump is all about . any input on this would be appreciated. Thanks" The .625" gear set is from the "fixed" stator TH 400 from '64 & '65. Yours is not variable pitch. As per ATSG manual and General Motors Corp.