Hey guys, I'm a newbie here and have my first classic. It's a 65 F100 with the original 240 and 4sp manual in it. I got it apparently in good working order with no worries. While driving it the 350 miles home it developed an oil leak. Not life threatening but concerning none the less. I have done my best to trace it to the back of the oil pan and mostly at the bottom of the engine rear plate. I noticed that it is missing 3 bolts that hold the plate to the trans/bell housing. It doesn't really leak that bad while sitting but was a steady drip while running. I was hoping to try replacing those 3 bolts at the bottom of the plate and see if that sorted my problem before going after the pan gasket. So my questions are...

Does anyone know the size of the 3 bolts at the bottom of the rear main plate that tread into the trans/bell housing?

Do you think that could be the cause of my leak or am I dreaming and should get a new pan gasket?

I tried searching the threads for a while and have tried general internet searches to no avail. I have ordered shop manuals but am waiting on delivery and want to get going sooner if possible. I have pics in my album of the site if you want to check it out.

Cheers
Charles

 

Not sure on the bolt sizes, but i can say that that isn't the cause of the oil leak. The leak is either going to be the oil pan gasket, rear main seal, or possibly the side cover or valve cover gasket.
If the oil is coming from inside the bellhousing, most likely the rear main seal.
Not sure about the early models, but later model 300's use a one piece rear main seal that is replaced by dropping the trans and flywheel.
If the oil is running down the outside of this plate, then it's most likely a gasket. Oil pan gets a bad rap for being the cause, but either the side or valve cover gaskets can leak, causing oil to run down the engine and drip from this area.

 

Thanks for the reply. I have checked around the valve covers and can't see any signs of oil. There also doesn't seem to be any staining above the pan. It really seems to be coming a little from the back of the pan, the front of the plate is stained and then the gap in the plate. I was worried that there shouldn't be engine oil behind that plate so it had to be the rear main seal. From what I've read I think I have a two part seal but I will check to be sure. How hard is it to replace? I don't have an engine hoist only basic jacks/stands.

thanks again
Charles

 

Welcome abroad.

This web site describes it as a 1 pc. rear main...

Fel-Pro Rear Main Seals Rear Main Seal - 1-Piece - Rubber - DeTomaso - Ford - Mercury - 240 - 300 - L6 - 351W. Fits many Fords, Mercurys, and more ranging from 1965 to 2006. |...

As far as I know all 240/300/4.9l I6's are 1 pc. You will need to drop the trans to get to it. Then you need to get it out. Punch small holes in the metal, screw in some dry wall screws... grab em and tap it out...it's just that easy . Be very careful and tap evenly. As stated above make sure it is not the oil pan/lifter/valve cover first. Spray them down with starting fluid. That will dry it out so you will see any new oil. The bolts may be 3/8's x 1/2 x 24

HTH
Jim

 

Thanks again. I will try to clean it all down again and see if I can tell if it's in front or behind the plate. I would really like to not have to replace that seal. It sounds like it will be a fair piece of work by myself. I have the Haynes book and shop manuals on order and am just waiting for them to arrive, is that going to be enough in terms of diagrams to get this done? It will be the first transmission that I have to drop.
I guess one other question I have is the transmission is rather sloppy and very difficult to find gears and occasionally I need to double clutch to find 3rd going up and 1st going down. I had attributed that to just being "an old truck" would it be worth having the trans rebuilt while I have it out? what is the price like for something like that? Is that something I can do?

This forum is a life saver, cheers guys

Charles

 

As for the trans, a 4 speed doesn't have a syncro'd 1st (low) gear. So if that's the one you are having the most trouble with, it's normal.
On the other hand, having trouble getting it into other gears could be from a misadjusted clutch, or worn syncros in the trans. Another item that can cause hard shifting, is trans lube that hasn't been changed recently. This stuff is rather thick to start with, and left in a trans too long, it can get really thick.
You might want to change the trans fluid before going much further on diagnosing transmission issues, along with checking/adjusting the clutch linkage.
Those older 4 speeds are rather stout, and there's not much that fails inside them, unless the fluid changes are neglected or the trans is abused heavily.

For a trans that isn't going to see heavy work, I recomend draining out the old lube, and using a 50/50 mix of new gear oil and ATF. The ATF will help clean it up inside, and keep it clean, as well as make the lube flow faster, particularly when cold.
Some people will try saying that ATF isn't designed to be used in this manner, but since around 87/88 all factory manual tranmissions have used ATF as their only source of lube.

You may need to look into the shifter itself. There is a pin (or pins) that keep the stick from turning side to side. These pins and the slots they go into can both wear, allowing the shifter to get a bit sloppy.

 

allowing the shifter to get a bit sloppy
REAL sloppy, like spinnin around 3/4 of the way +, no?

If the leak is only while runnin is that more helpful in diagnosin?

 

You might consider installing a speedy sleeve on the crankshaft oil seal journal as well, since there is probably a groove in it where the seal contacts it. jem is right- your engine has a one piece seal, and once you get the tranny out, it'll be easy to replace. While you're in it, replace the tranny front seal- it's the next one to cause you trouble, and it's easy to change while the tranny is out.