A/T - 700R4 Solid Teflon Sealing Rings/Turbine Shaft

TSB 88-22 (May)

THM 700-R4

SUBJECT:
SOLID TEFLON SEALING RINGS USED ON THE TURBINE SHAFT

Many technicians have questioned the use of solid Teflon sealing rings on the turbine shaft versus scarf-cut Teflon sealings rings. Both style rings have some advantages and disadvantages. Some important points need to be considered:

1. When the engine is not running, solid rings may help prevent torque converter drainback, since they don't collapse with the absence of pressure as scarf-cut rings do.

2. Scarf cut rings have a lot of side clearance in the groove; solid rings do not. When applying a clutch in the input drum, fluid pressure pushes sealing rings outward. Some of the turbine shaft rings have fluid pressure on both sides of the ring, not allowing a scarf cut ring to move easily from one side of the groove to the other.

When this happens, the ring may "float" in the center of the groove, causing a loss of clutch oil.

3. Scarf cut rings are easily damaged when installing the pump into the transmission. If the solid rings are sized properly, installing the pump into the transmission will not result in damage to sealing rings.

4. Solid rings may stick in the grooves of the input shaft, due to contamination and leak excessively, but there have been no reports of solid rings sticking on THM 700-R4.

Time will tell which style ring is best, but solid Teflon sealing rings do seal better when used on the turbine shaft, which handles valuable 3-4 clutch oil.

By the way -- what is the most common THM 700-R4 failure?