I've done it on a 360 2WD and it wasn't too bad. Not a lot of fun but I think less work than pulling the engine.

 

Some more POR is supposed to show up today, so I plan on finishing that tonight.

In the mean time I'll drain the tranny and fix the leak in the bolt hole, Permatex 2 is the stuff to use? I can't remember what thread I was reading on the the replacement of the rear main, but it was said to use Permatex 2 also. I have mixed feelings about that stuff, I haven't found out the source of the main/oil pan leak, but the only thing I can think of is the Permatex 2 I used for the seal didn't work. Do you use Permatex 2 when replacing rear main seals?

As far as the exhaust leak goes, there's no donut gaskets being used, but from what I've heard they weren't used stock. Plus, the studs are not long enough to use them. The exhaust didn't fit perfect, but went together ok. I figured that May be the cause of the leak, but didn't feel any leaks when I put my hand around that area. It seemed there was a previous leak before breaking down everything and from what I hear there was no manifold gaskets used on these motors stock, it's a wonder how any of these exhaust systems were sealed leaving the factory. I decided to use manifold gaskets and that might of changed the way the exhaust mated up to the manifolds. Wonder if I should go for a dual setup and see if a new fitment of the pipes will help?

 

I wouldn't use #2 Permatex on the rear seal.
If the rear main turns out to be the source of the leak. Pull the rear main cap. Clean off the mating surfaces, be sure to clean off any sealer residue and oil from the surfaces.
Remove the seal from the main cap. Next take a flat nosed punch small enough to fit in the channel that holds the seal in the block. Push the end of the seal to get it started out of the block.
Once the seal half is out, it's time to start working the the new seal in.
I put some oil on the new seal. Be sure the seal is facing the correct way. Then, and here's the tricky part, start working the new seal into the grove. The tricky part is to get the seal to go in without "skinning" the back side of the seal against the sharp machined edge as it rotates into the groove. If it looks like its going to be questionable, I'll take a thin piece of plastic and trim it so it'll fit into the groove to protect the seal. It's only the edge that causes the problem, Once the seal is past the edge its okay.
Once the seal is in, offset the ends do they are not flush with the main cap mating surface. Leave one end of the seal sticking out about ¼".
Place a bead of high temp silicone from the seal to the edge of the main cap. The bead needs to run side to side, not for and aft.
Offset the seal in the cap the same amount on the opposite side.
Coat the main bearing half with some oil and install the cap and torque to specs.

 

I haven't given up, but I haven't got around to addressing the leak. My 7 year old son loves these old trucks and since the truck has been down for a little over a month we're going to a local parts store this weekend where they're having a customer appreciation day and people show up with their classic rides. So, I don't want to tear it apart just yet.

Do I have to loosen any of the other main caps?

Seeing how I used Permatex 2 on the rear main previously, do you think that's the source of the problem? If so, do you think I have to change the seal again or just reseal the cap with the correct RTV? Prolly just suck it up and buy a new seal, huh?

Also I'm having some clunking noise when I step on the gas quickly and let off quickly. I thought this was a loose engine or transmission mount, so I double checked the mounts and bellhousing bolts and everything is torqued to the correct specs. I don't know if the whole drive shaft setup is the culprit

https://www.ford-trucks.com/forums/1...ft-angles.html

 

No, you don't need to loosen the other main caps.
Yes, I would suck it up and buy a new seal.
Check the U joints and, if your truck has one, the center support bearing (2 piece driveshaft only)

 

Hey Mike, forgive me if I'm asking dumb questions, but should I be alright using the same pan gasket? If it comes off ok and doesn't rip.

Just asking because if I need a new gasket, I have to wait a day or two for the parts store to get it.

 

My personal preference would be to replace the gasket but if it comes off clean with no damage, I really don't see anything wrong with reusing the old one. I would clean the mating surfaces and apply a thin coating of RTV to the block and oil pan flange and then bolt everything together.

 

Yeah, it's probably better to just replace it. I don't know for sure that it's not the pan gasket itself i just got off the phone with Federated and they can have a pan gasket there by 3:00 so looks like I'll start on it.

 

From what I'm looking at, I put the seal in backwards the first time. Every pic I pull up online shows the lip toward the front of the motor, but you would think that the seal would ride on the smooth part not the part that has grooves in it.
Why are those grooves there?

 

To be honest, that doesn't look right. I'm foggy on this one and hope someone more familiar with the engine will chime in.
It looks like the crank is one for a rope style rear seal, but everything I find says the 351M-400 only came with the neoprene seal.
Regardless though, the seal in the picture is backwards, the lip goes to the front.

Those grooves act like an oil pump to force any oil that gets to the seal area back towards the crankcase.
I remember back in the late 60's Ford had a recall because some of the 428 crankshafts were made with the grooves machined backwards and caused a huge rear main leak problem.

 

That's funny! I was thinking that, but, then I said to myself "noooooo"

 

I've spent the last couple of hours looking at pictures of the 351M-400 rear main (I really need to get a life ) and all the ones I see have a smooth rear journal.
I'm lost on this one.

 

The only pic I pulled up is this one ,and it's of a 69 351w.



Now, a W and M have the same size main journals 3" and the same stroke of 3.5" and from what I've read this morning it has the same size rod journals of 2.13. I know the M crank will not fit in a W because of the counterweights not having enough clearance, but a W crank should fit in a M block without clearance issues. So I wonder if the PO swapped in a W crank for some reason. I'm heading out to the garage in a little bit and I'm going to look at the casting # on the crank. The M rod is thicker at the big end and needs to be machined down to fit the W crank and a few other things that have to do with pin size. With the way some of the other things on the truck were done previously, I don't think that the PO spent the money needed to swap the crank. And why would you? It doesn't seem to me like you would gain anything by doing so. I guess some people swap M connecting rods into W's for more torque at a lower RPM range than stock W's, but that's another topic.

EDIT: plus I don't know if the flywheel and vibration damper would still work with that setup

 

Is your engine a "W"? I was thinking it's an "M".

 

It's a M, but seeing the photo of 69 W, I was wondering if it was possible that the PO swapped out the M crank for an older W crank.