A/T Oil Pump Seal Assembly - Leaking
Number: 83-T-59Section: VIIc
Date: June, 1983
Subject: OIL PUMP SEAL ASSEMBLY LEAKING - THM 700-R4 ALL
FIGURE 1 - OIL PUMP BODY:
TO: ALL CHEVROLET DEALERS
Beginning March 7, 1983, all THM 700-R4 transmissions were built with a revised oil pump body (P/N 8642986). As shown in Figure 1, the oil drainback passage in the revised pump body connects with one of the core slots. This design change allows for more effective oil drainback, thereby relieving pressure under the oil seal assembly.
FIGURE 2 - CUT-AWAY VIEW OF DRAINBACK PASSAGE:
SERVICE INFORMATION
When servicing a THM 700-R4 built prior to this change which either: (1) pushes the oil seal assembly out of the oil pump body or (2) forces oil past the lip of the seal around the converter hub. Correct the drainback restriction as follows:
1. Following the service manual procedure, remove and disassemble the oil pump assembly.
2. Place the oil pump body on a cloth to protect the oil passage face. With a 6.0 mm (1/4") drill bit, enlarge the hole at point "A" to a depth of 12.9 mm (1/2") maximum (see Figure 2). Hole "A" must connect with the drainback passage (see Figure 2).
3. Turn the pump body over and inspect the drainback passage at point "B" (see Figure 2). If the drainback passage is restricted at point "B" (i.e. the two passages do not meet evenly), use a 8.0 mm (3/8") drill bit and enlarge the passage at point "C". Do not drill any deeper than necessary to remove the restriction.
4. Clean out any metal chips and reassemble the oil pump using the service manual procedure.