Transaxle Refinements
REACTION SHAFT SUPPORTEarly 1989 transaxles were made with a three sealing ring reaction shaft support. The three-ring support was upgraded to a four sealing ring support as a running change in February of 1989. The three seal ring configuration could cause clutch failures due to internal leakage between the underdrive and overdrive circuits. The additional ring allowed the third and fourth seal rings each to perform a single sealing function and provided dual venting to the sump.
INPUT CLUTCH HUB
Reference: TSB 21-08-89
The input clutch hub bore was deepened to accommodate a new reaction shaft support length in February of 1989. The revised input clutch hub (453163737) must be used with the revised (4-ring) reaction shaft support.
The input clutch retainer was machined flat to allow more travel of the overdrive/reverse piston. The change occurred in February of 1989.
During 1989, the O-ring compression, or crush, was increased by making the hub O-ring groove shallower to increase the sealing between the O-rings and the input clutch retainer. The original black O-rings were replaced by orange and green Teflon coated, tear resistant O-rings. Some remanufactured transaxles received fight blue and yellow O-rings that had a 0.007" larger cross section than the original. The change increased O- ring compression while still using the original hub.
TRANSAXLE LIP SEALS
Reference: TSB 21-09-90 (Rev. A), HL-18-89, and HL-37-89
Some overdrive/reverse piston and input clutch hub outer lip seals were out of specification. Some 1989 and 1990 A-604 Ultradrive Transaxles may slip during 2-3 upshifts due to these seals. These seals can be found in other transaxle locations that are within specifications. The seals were only dropped from overdrive/reverse piston and input clutch hub outer lip seal applications. The seals can be identified by the marking "IPC".
TRANSMISSION CONTROL MODULE
Reference: See TSB 18-24-95
PARKING SPRAG GUIDE BRACKET AND PAWL
Reference: TSB 21-25-89
The parking sprag bracket and pawl was changed in May of 1989 from a stamped steel unit to a precision cast unit. The cast guide bracket reduced the effort required to move the shift lever out of the park position.
INPUT CLUTCH HUB O-RINGS
Reference: December 1989 Master Tech
In July of 1989, the input clutch hub O-rings were changed from a 0.070" to a 0.103" cross section and the groove on the hub is deeper. This change was made to eliminate the possibility of O-ring damage during installation. The latest O-rings are red and blue.
L/R SNAP RING ORIENTATION
When installing the low/reverse reaction plate tapered snap ring, be sure to follow the removal or installation guidelines. The ends of the snap ring should end up opposite the oil pan face and when installed, be located under the case metal, not by the
COOLER BYPASS VALVE
Reference: TSB 21-28-89
An external cooler bypass valve was introduced in December 1989 to prevent potential transaxle damage due to a lack of lubrication. Under very cold conditions the transaxle fluid may get cold enough to resist flow through the oil cooler and deprive the transaxle of lubrication was made an integral part of transmission.