Here we go. 84 f150 4.9l has an oil leak it's not the valve cover I've checked from underneath and the oil is not coming from the top. I'm pretty sure it's not the oil pan, I just did that gasket and the oil seems to be coming from in front of the pan. I think it's the rear main seal. I have oil coming out of both sides of the bell housing. Up by the starter and everything. Now if it is the rear seal when I was looking there was one that said "rubber" is there two? And is it easier to pull the engine to do the clutch then it is to drop the tranny? It sure looks like it would be easier.

 

First is to find where the oil is coming from.
Nothing like ding the rear seal only to have it still leak

Get some de-greaser and carb or brake clean.
Use the de-greaser first to get most of the oil & dirt off the motor & transmission.
Also see the 2 bolts at the bottom of the bell housing, remove them and pry the plate away from the bell housing a little and try and clean that area the best you can.

Now any oil / grease that is left use the carb / brake clean to get it clean.
Again pry that plate away and clean it better with the spray cleaner.

I would keep that plate pried away and start the truck and let it idle.
Try not to bring the RPM up as that may blow the oil all over and not be able to tell where it is coming from.
Check to see if you can now pin point where the leak is coming from.
Check and re-check the valve cover at the rear to make sure it is not leaking and running down the bell housing and making it look like the rear seal. Use a mirror and light to check back there.

If it is running at idle and not leaking after say 5 min. bring the RPM up a little and check everything again.
I cant see the rear main seal leaking oil up on to the starter and why rechecking the valve cover.
Also with the plate away from the bell housing if the rear seal was leaking it should now drip out as the plate is not holding it back.

I had a oil leak at the front and at first thinking front seal.
Oil pan, side cover & valve cover gaskets were all changed before motor went back in.
After cleaning it for the 100th time I put some time into finding the leak.
I de-greased the motor and used a pressure washer to get it really clean.
I started the motor and could not pin point the leak so out came the carb cleaner.
It also did not really leak at idle so the RPM had to be up a little and the fan would then blow the oil all over.
Spray cleaner again, removing the fresh paint on the motor but I was then able to find it.\

Turned out to be the timing cover gasket at the top and only spit out when the RPM was above idle and the fan blowing it all over.
Year ago new years eve I pulled the cover and replace the gasket and no more oil leak from the motor.
I have a PS fitting now leaking and maybe the trans?
Dave ----

BTW It looks like you have a heavy T18 or NP435 from the PTO plate.
If it is the rear seal it is a 50 / 50 on what to pull.
Being the trans is not flat on the bottom using a floor jack to pull it is not fun and you will be fighting to keep it on the jack.
I bought a HF trans jack when I had to swap transmissions and even with it it was a little better.
Think I would pull the motor.

 

If you are setup to pull a engine, with a crane and everything, rather than working underneath the truck, then it probably would be easier. It certainly would be easier to change the rear main seal with the engine out. Oil leaks are hard to find sometimes.

 

And to add to that, if one is going to go through the effort of pulling the engine, it's not much extra work and expense to install a new oil pan gasket at the same time. I'd swap in a later 1 piece rubber gasket at the same time and get rid of the multi-piece cork affair.

 

Have you checked out some of the "related threads" below, may be some help there.

 

Pulled the motor oil all over the clutch and lots of hair I wanna say. The valve cover seems fine I'm putting the motor on a stand and cleaning it all up today and I'm doing new oil pan and valve cover gaskets. Looks like the front crank seal is leaking also so that's getting fixed also. Is there a seal on the transmission there that could be leaking?

 

I would do the trans front seal as well while you're in there.

 

IS it the same type of seal as the crank seals? Do I just remove the bolts and take that cover off swap the seal and bolt the cover back on or do I need to tear the tranny apart?

 

Here's the info on the NP435. It shows the seal and describes out to replace it down in the text. https://www.garysgaragemahal.com/np435.html

 

Over the years I have been plagued by many oil leaks in different places .I came across a product that was rated high .Tried this product and it has worked in both of my older trucks .Recently my power steering leak returned (seals).used it there and after a few months I am not seeing any leaks from both trucks .I do not work or am a paid advertiser for them .

Works for me

 

Looks like it's just a little felt gasket. I'll probably make one if I can't find one at the parts store.

 

https://ford.oempartsonline.com/oem-...hfordparts.com

That appears to be the correct OEM part . I googled the 7051 p/n from Gary's page, and looked down the page a bit and found that link.

Dave F is the best...along with Dave G and Karl...not in any order...

 

I did not look close at the link but I thought the transmission seal was a rubber seal like the rear & front seals on the motor?
I dont remember, been a few years now, when I had the front bearing retainer off my NP435 to cut it shorter for the over drive unit what seal it had sorry.

I will tell you the paper gasket around the bolts is how they adjust the pre-load on the main shaft.
So be careful when you remove the retainer and if it dose rip use vary little / thin layer of sealer with what is left of the paper gasket as you dont want to change the pre-load.
Dave ----

 

That little paper gasket was shredded I believe it was the cause of the leak as well since the splines we're dry and even a little rusty, the rubber seal seals the shaft and the paper gasket seals the housing. I'm glad you said something about the gasket I had just made one I was going to use. I'll buy the Ford replacement. I think that was my whole leak judging from the condition of the gasket, the color of the oil, the way the oil flung around it was mostly the transmission side. I'm going to put a drill on the oil pump and spin it to schedule for leaks but the rear main appears to be in really good condition and not leaking. I'll change it anyway but it looks like you either have to open the block or lunch a couple holes in the gasket to work it out. Is that the way or am I missing something.

 

I did not change the rear main on my 300 just the oil pan and the motor was on a stand.
ATT I did not know of the 1 part pan gasket and went with the 4 part but after some driving and tracking down leaks found some of the pan bolts loose but been dry since.

On that paper gasket it may come as a few gaskets to set the pre-load so you will need to find what that pre-load isbefore putting the gasket back on.
Dave ----