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1989 Ford F-150 Rear Main Seal Leak

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BIGO
  • MEMBER
  • 36 POSTS
I have a 89 f150 5.8,c6automatic with almost 200.000. Its got oil flowing out the rear main.which is easier drop the tranny or pull the motor,im leaning toward tranny drop, if I drop it would it hurt to replace the fluid and filter in it, as it has that many miles the trans shifts fine however. also since i noticed this leak the oil pressure goes to nothing at a stop in gear then after it blew naturally it was dropped at a idle think the seal will cure that,as its gushing now would a test be accurate or should i just put a new oil pump in while she is down? The motor runs like a champ dont burn oil plenty of pickup,no chatter when gauge dropped either. I just dont wanna keep tearing it apart all winter in the -5 wind chill weather is why ive got so many questions. thanks for any help
Feb 2, 2007 at 10:53 AM
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BOOTDOG
  • ✓Experienced Mechanic
  • 665 POSTS
i would drain the tranny first. removing the tranny will be a lot easier then removing the engine to replace the rear seal. replace the rear main and do a filter change on the tranny. if the oil pressure still drops, change out the oil sending unit (which is cheap) before dropping the oil pan to change the oil pump. i would make the oil pump my last resort. good luck :)
Feb 2, 2007 at 11:46 AM

Suggested Repair

Drain and drop the transmission rather than pulling the engine. Replace the rear main seal and change the transmission filter. If oil pressure still drops, replace the oil pressure sending unit before considering an oil pump as a last resort.

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Conversation Summary

The owner of a 1989 Ford F-150 5.8 with a C6 automatic and nearly 200,000 miles reports oil gushing from the rear main seal and oil pressure dropping to nothing at a stop in gear. The engine otherwise runs well and does not burn oil. The expert recommends draining and removing the transmission to replace the rear main seal and changing the transmission filter, then replacing the oil sending unit if pressure still drops, with an oil pump replacement as a last resort.

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