Rear main seal replacement
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Mountain Pass
Joined: Apr 2023
Posts: 137
Likes: 31
Rear main seal replacement
I am doing a zf5 swap on a 1994 460 fwd. when I got in there, I noticed my rear main seal is leaking pretty bad. I wasn’t expecting it to be a bad replacement, until I found out it is a 2 piece design. I have absolutely no experience with this style, and I’m scared to tackle it to be honest. I figure now that I have the trans out is the time to do it.
could anyone get me step by step instructions on how to replace the rear main seal? And how do I know for sure it is the seal? I have been losing oil, and when the trans is out I had a puddle behind the rear of the motor right under it. Too far back to be from drain plug I think.
could anyone get me step by step instructions on how to replace the rear main seal? And how do I know for sure it is the seal? I have been losing oil, and when the trans is out I had a puddle behind the rear of the motor right under it. Too far back to be from drain plug I think.
Hotshot
Joined: Jul 2020
Posts: 10,453
Likes: 2,630
From: Near Salt Lake City
Well, with the trans out, you'll be surprised how much easier it is to get the oil pan off.
You still need to drop the oil pump and pickup tube down into the pan in most cases, to remove the pan (4x4).
Once you get the pan off.
Remove the 2 rear main cap bolts and wiggle the cap beck and forth using the bolts to get the cap off.
Then changing the lower portion of the rear main is easy just use your fingers to press the new one into the cap.
The upper half is more difficult.
I usually carefully push it up into the groove with a small punch a quarter inch or so.
Then grab the protruding part on the other side with some dykes or something and work it out using the side of the block as a fulcrum.
You need to be damn careful not to nick the crank with your punch or dykes
You need to verify and re verify the bigger lip of the seal goes towards the oil
You'd be surprised how many people install them backwards
Good luck
007
You still need to drop the oil pump and pickup tube down into the pan in most cases, to remove the pan (4x4).
Once you get the pan off.
Remove the 2 rear main cap bolts and wiggle the cap beck and forth using the bolts to get the cap off.
Then changing the lower portion of the rear main is easy just use your fingers to press the new one into the cap.
The upper half is more difficult.
I usually carefully push it up into the groove with a small punch a quarter inch or so.
Then grab the protruding part on the other side with some dykes or something and work it out using the side of the block as a fulcrum.
You need to be damn careful not to nick the crank with your punch or dykes
You need to verify and re verify the bigger lip of the seal goes towards the oil
You'd be surprised how many people install them backwards
Good luck
007
Tuned
Joined: Dec 2005
Posts: 400
Likes: 57
From: Saskatchewan
Make sure the oil is not coming from higher up. I've read the some people have been fooled by a leak and the rear of the intake manifold. Make sure things are dry above the bell housing to confirm it is the crank main seal.
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nflfreak43
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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