Hi all--

I have a 1984 F250, 460 big block, RWD, 8ft bed with super cab (two door, two bench seats).

It leaks oil pretty bad. Every 50-100 miles loses 1/4 quart of oil. The owner before me told me it needed a rear main seal. I haven't had time to actually check where exactly the oil is coming from, but until that time comes, I want to fill up on understanding anyhow. Assuming he is correct, is replacing one any different then on any vehicle?

Remove driveshaft, drop transmission and clutch, etc...?

There are very limited sources on the internet for replacing one-- all that I can find, the motor is pulled and on a stand. Moreover, when searching to buy a new seal, they seem to be in two pieces, not one full circular piece as I am used to.

Do you gentlemen have any advice? I don't have the ability to pull the motor, and I certainly don't have the cash (or desire) to pay someone to do it for me.

Thanks--

Mike

 

I don't know the 460 motor but if it does use a 2 part rear main seal then the motor should come out as I am sure you need to drop the oil pan to drop the rear main bearing to replace the seal.
When out and the oil pan is down replace the pan gasket and why not the front seal too.

Only other place the oil could be coming from is valve cover gaskets leaking down the back of the motor and at the rear of the intake manifold.
The intake manifold has a seal between it and the block that can dry out and start leaking.
Take a mirror & light to look at the rear of the intake if you can see oil leaking out.
Dave ----

 

I have never done it on a 460 in one of these trucks. But in some vehicles you can replace it with it in the engine. It's not much fun though. You have to jack the engine up after you take the motor mounts loose, and put blocks between the engine and the motor mounts to hold it up high enough to get the oil pan off. Then you take the rear main cap off, and half the seal comes out. You can loosen all the main caps some so the crank drops just a hair, and they used to make a tool or maybe you can find something on the web, to push the upper half of the seal around while you turn the crankshaft.

This is old school stuff, everything is one piece seal now and no one does this much anymore in the shops.

 

Here is a video of a guy changing one in a 4.0 jeep. Very much like you would do, except you will not have all that room he has to take the oil pan out.

 

Yup split rear main seal in these engines. The advantage is you do not have to pull the tranny. but you do need to drop the oil pan and remove the rear main cap. You may be able to replace it with out having to drop the crank/ loosen other main caps. I have never had to drop the crank when doing them. Just be sure not shave any rubber off the seal when dong this. A quick hit with a jewelers file to "just" knock the corners off the seal boss on block will insure you have no issues. Then put a very small smear of silicone around the protruding seal on the main cap to seal the chamfer.

 

Ya ignore the install on this video and the Fords the rubber seals seals should protrude about a 1/4" above the block and main cap

 

ive done a couple rear mains in the car, and was just thinking could I do this on a 300 I have (and I thought no, pans gotta be too long). I have only done it on small block V-8s. they make a tool called a "Sneaky Pete", which is sorta like a Chinese finger trap for the rear mains seal. I even took a 289 down to the car block once while it was in the car, and climbed in and wrestled the bare engine block out of the bay of my 67 fastback by myself back when I was 18 or 20. Lack of funds and plenty of want to and spare time used to exist when I was younger.

 

Sneaky Pete's are for installing rope seals. The rubber ones don't need them for installation.

 

The following infamous thread has all the gory details on how difficult the process was on the 460. It started out with a rear main seal replacement, but progressed to having to drop the oil pan. The thread included the infamous statement (gently paraphrased) "I will let the thing leak and start itself on fire before I ever attempt this again with the engine in the vehicle.". Although this job wasn't fun on my 351W, I can honestly say I never wished I'd purchased highway flares instead:

https://www.ford-trucks.com/forums/1...on-pulled.html

 

I do recall having to reach inside the dropped oil pan and unbolt oil pump or the extension (can't recall) and letting it drop into oil pan to get off. I also recall having to rotate crank several times to get pan out around crank throws. And I recall putting on same way, putting oil pump or extension in pan, getting in place and reinstalling while pan partially in the way. certainly no fun.

 

If you do attempt it, have lots of time available and a spare vehicle. I lacked both those things when I tried replacing the RMS on mine and it was likely the difference between the job being successful and not.

If you can possibly wait until you can pull the engine, I recommend it! The thread linked to above explains the abortion I went through in trying to do it underneath the truck. It's terribly difficult to get the upper halve of that seal out (I was never able to, but was short on time) and if you do get it out, I suspect it's an even bigger challenge to get the new one in CORRECTLY.

I never did get to replacing the RMS yet, but the oil leak has not gotten any worse. It still leaks a manageable amount about a quart every 1000 miles or so.