'34 Plymouth Rear Main Seal

[Crazyred]

So since I'm replacing the clutch, I will replace my leaking rear main seal as well.  As I have never replaced one of these before and the repair manuals that I have do not explain this area, i'm asking the experts. 

 

I pulled the lower half of the seal off to see what I had and it is the rope type seal installed.  On the 1934, are there any seals under the rear main cap that need replacing?  I have not taken the cap off and do not plan on it unless needed.

 

I looked up the replacement seals and for the '34 it appears that either the best gasket 4162 (rope type) or 4164 (rubber type) can be used.  Are there any advantages using one over the other?

[keithb7]

It appears not too many of us have worked on a 1934 rear seal. It is the type that you take the rear main cap off and 1/2 of the seal tucks up into a groove in the rear main?

Edited December 6, 2021 by keithb7

[TodFitch]

1 hour ago, keithb7 said:

It appears not too many of us have worked on a 1934 rear seal. It is the type that you take the rear main cap off and 1/2 of the seal tucks up into a groove in the rear main?

No. There are two sheet metal holders (top & bottom) that bolt to the back of the rear main.

 

Been decades since I did it on my '33 (which I believe is identical in this respect). If you simply bolt on the replacement then there is not a good enough seal on the crankshaft so you end up doing it again. At least that was my experience. So, the second time, I removed the rear main bearing cap to install the lower half of the seal properly.

 

For the upper half, I just worked it as tight as I could against the crankshaft. Hard to do with the limited clearance, etc. I do not have fond memories of the whole operation (done in the parking lot of the apartment complex I lived in at the time).

 

When I was done I got the leakage down to about 1 qt every 2000 miles which happened to be the oil change interval I use for that car. So I called it "good enough".

 

This was all with the original style rope seal. It is possible that with the replacement rubber seals you may not need the seal against the crankshaft quite as tight. In which case removing the rear main bearing cap may not be needed.

[Crazyred]

@keithb7 the rear seal is a split half similar to the one you have posted in your videos and as @TodFitch mentioned.  Below is the picture of the bottom half that I removed and that has the rope type seal on it. 

 

I am curious to know if there are any other gaskets under the bearing cap itself?  I have seen that some have a 4 shaped rubber piece that goes under the cap but not sure if the 33 and 34 have that.  @TodFitch I believe you are correct that the 33 and 34 are the same, do you know if these small 4 shaped gaskets go under the bearing cap on our engines?  Did you have to replace anything on yours?  I was trying to avoid removing the cap if I didn't have to but if no one knows then I can remove to get the answer.  The best kit is below with the rubber gasket that replaces the rope type and the small 4 shaped gaskets that I am referring to.  

 

 

 

Does anyone know if the rope style or the rubber type is better than the other or is this a preference thing?

[TodFitch]

I recall the rope seal I put in way back when as coming with those rubber pieces. And I recall not seeing how/where they installed even after I pulled the rear main bearing cap.

 

Were I to do it today, I'd give the neoprene seal a try. Seems like it would be easier to get it to seal than the old rope style and probably wouldn’t have to muck about trying to get it as tight against the crankshaft to do its thing.

[keithb7]

The "4" or "H" seals are important. They do go under the main cap. I just installed that same seal in my 1954 flathead. I thought I featured it in my engine assembly video. I'll go take a look. There was no other seal circular seal under the main cap.  Just the 2 halves shown. plus the two "4" shaped seals.

[keithb7]

Got to the 5:56 mark in this video:

 

https://youtu.be/kv7mH8i2hm4

[Dodgeb4ya]

It would be very difficult to pack the rope seals and trim them properly with the engine in the car.

It's tedious even when doing it on a stand.

The rope has to be packed/ rolled tight to the diameter of the crank.

The ends of the rope need to be cut .010"-.020" above the mating line so the ends crush tight. And a perfectly straight strand free cut too.

How ya going to do all this right with the crank in place and on your back ??

I did one recently on a rebuild with the same open difficult back retainer plates.

I did what I had to to be sure of no leakage.

[kencombs]

12 hours ago, Dodgeb4ya said:

It would be very difficult to pack the rope seals and trim them properly with the engine in the car.

It's tedious even when doing it on a stand.

The rope has to be packed/ rolled tight to the diameter of the crank.

The ends of the rope need to be cut .010"-.020" above the mating line so the ends crush tight. And a perfectly straight strand free cut too.

How ya going to do all this right with the crank in place and on your back ??

I did one recently on a rebuild with the same open difficult back retainer plates.

I did what I had to to be sure of no leakage.

 

Amen brother!  One of my first jobs when I went to work as a mechanic (at 17YO!) in a Chevy dealership was replacing that part of a Ford Y block.   Real common issue on that engine.   OJT of the highest order.   Drive it out with a brass punch until it could be grabbed with pliers, then pull and roll it out.  Then the old Chinese finger-cuff tool to pull and roll  the new one in.   Tamp it tight with brass punch and trim.  

 

The tool kit, pick, punch and steel finger-cuff, was common in parts stores at the time.

 

Then  do the magic on the bottom half.

 

Then pray it didn't leak, that one didn't.  I've done several since but, hope I never have to do one in chassis ever again!