Editing TH700R4 through 4L70E tips and tricks (section)
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== Pump modifications == ===Drain back holes=== Drain back holes from behind the converter hub seal at the bushing should be enlarged in some pumps. This is year dependent since GM enlarged this hole in the late 1980s. [[image:Drillhole2.jpg]] The matching hole on the pump cover stator support (shown in yellow circle) should be enlarged too. [[image:Drain_back_hole.jpg]] ===3-4 clutch oil passage=== Early 700R4 - 4L60 pump covers (stator support) have an extra bleed hole in the 3-4 clutch circuit that can be plugged off. ===Modification for better 3-4 clutch pack apply=== On early pumps the circled hole can be tapped and plugged with a 5/16 inch set screw. GM deleted this hole in later pumps [[Image:3-4_hole.jpg]] ===Stake the pump bushing (for pre-1987 model year 700R4 )=== Photo shows drill bit location to stake bushing. Pump bushing is removed for this operation. 1/4 inch drill bit works well here. [[Image:Stakebush3.jpg]] This photo shows the small spot made with the drill bit to stake the pump bushing in place. The spot doesn't need to be very deep. [[Image:Stakebush4.jpg]] This photo shows the pump bushing edge dimpled into the location created with a drill bit. Use a suitable rounded chisel or the side of a screw driver and hit it with a hammer to bend the bushing edge into the recess area. [[Image:Stakebush.jpg]] ;{{Note1}} The #732 pump (manfactured since October 1986 which includes some early 4L60Es without the 2 piece bellhousing) has a cast in step to help retain the bushing. The early pump had an issue with the pump bushing walking out, requiring staking and/or Loctiting it in place. Also, the #732 pump has an additional oil drain hole which is a connection for the oil transfer tube used with the auxillary valve body. The early and late pumps do not interchange (same with the pre- and post-October 1986 transmission cases (the late 1988-1993 cases have a "St. Louis Gateway" arch casting and the absence of 3 oil pressure fittings). Also pump assembly from 4L60E (PWM (pulse with modulator) or non-PWM) does not interchange with nonelectronic 4L60 and early 700R4; oil pump gear (esp. the 13 vane pump from the later 4L65E/4L70E) and later design Teflon bushing will fit 700R4 pump. ===Pump rotor clearance check=== Photo shows the depth micrometer at 0.0015" showing clearance on the rotor. This is an ideal clearance. Set it at 0.001" to 0.002" for good pump performance. [[File:700r4_rotor_clearance.jpg]] A wide angle view photo of the depth micrometer in use. [[file:700r4_rotor_clearance01.jpg]]
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