US 12,007,019 B2
Modified vehicle transmission hydraulic valve circuit for forward sprag protection
James A. Dial, Springfield, MO (US)
Assigned to Sonnax Transmission Company, Bellows Falls, VT (US)
Filed by Sonnax Transmission Company, Bellows Falls, VT (US)
Filed on Jun. 22, 2023, as Appl. No. 18/339,634.
Claims priority of provisional application 63/354,515, filed on Jun. 22, 2022.
Prior Publication US 2024/0026970 A1, Jan. 25, 2024
Int. Cl. F16H 61/02 (2006.01); F16H 61/00 (2006.01)
CPC F16H 61/0276 (2013.01) [F16H 61/0009 (2013.01); F16H 61/0267 (2013.01); F16H 2061/0062 (2013.01); F16H 2061/0279 (2013.01)] 15 Claims
OG exemplary drawing
 
1. A modified hydraulic circuit for an OEM vehicle transmission,
the transmission having a forward clutch, a forward clutch hub and a forward sprag having an inner sprag race and an outer sprag race, an overrun clutch and an overrun clutch hub, the forward clutch and the forward sprag providing a link to a planetary gear train to propel the vehicle forward, the forward clutch hub defining the outer sprag race, the overrun clutch hub defining the inner sprag race,
the OEM vehicle transmission, when operating in a D4 mode, applying the forward clutch but not applying the overrun clutch,
the OEM vehicle transmission further including a hydraulic valve body having a plurality of passages and a separator plate, and further including a 1-2 shift valve, a 2-3 shift valve, a 3-4 shift valve and a 3-4 relay valve, and a gear shift valve,
one of the plurality of passages fluidically connecting the 2-3 shift valve to the overrun clutch via a first check valve, the first check valve having a body and a movable element ball,
another of the plurality of passages fluidically connecting the gear shift valve to the 2-3 shift valve,
the modified hydraulic circuit comprising:
a first blockage in the passage fluidically connecting the 2-3 shift valve to the overrun clutch;
a second blockage in the passage fluidically connecting the gear shift valve to the 2-3 shift valve;
removal of the movable element ball from the first check valve body; and
a passage from the gear shift valve to the overrun clutch via the first check valve body,
wherein when operating in the D4 mode, the forward clutch is applied and the overrun clutch is applied and are locked to one another, such that the forward sprag is ineffective.