Clutch pressure plate testing

[Mertz]

I have a clutch out my 40 Plymouth that looks to be in very good condition. The disc doesn’t look bad either. I was tempted to use both but I think I will definitely replace the disc. The only way I would use the pressure plate if it can be tested for correct pressure but I can’t find anybody in Spokane who can test them. I don’t have a press. Can anybody suggest how I can test it or who might be able to test it for me?

[Los_Control]

I wonder what our mopar pressure plates look like .... I've never seen mine yet. I do have a 1951 Ford I have worked on .... I assume the technology & construction is similar?

What I learned from my experience might help you?

How I took mine apart without a press ......

 

I took mine apart, the spring height is important. The idea that they are all the same height and not collapsed or giving a uneven spring pressure.

Seems the springs are color coded. My red ones are considered to be a "Dump truck clutch"  This is a 11" clutch from a 1/2 ton truck.

I can buy some softer springs that might be blue then I think there is yellow .... you get my point, they are color coded for the stiffness of them. Again this is Ford but assume all pressure plates have same options.

 

No good photo of the fingers, but I was able to properly grease the pins that hold them in place. Inspect the holes the pin rode in was not wollered out from wear.

The fingers where they meet the throw out bearing is important to equally meet the bearing surface of the bearing. .... Mine are adjustable for fine tuning.

 

I'm only suggesting that the average Joe can go through a pressure plate & freshen it up, inspect it for wear, replace the springs if needed.

IMHO this pressure plate is ready for service, I just spent a afternoon on it before putting it on a shelf. .... Just a motor/trans I saved from the scrap yard that I may never use.

 

A modern pressure plate is a throw away or maybe a core .... older pressure plates were made to be serviceable.

I'm a little torn on the disk myself ..... something tells me to replace it .... something tells me to scuff it up with some sandpaper & run it.

[desoto1939]

Miller Factory Pressure plate rebuilding tool.  I currently owner this tool with the adapters. I have a spare PP but have not taken the time to take it apart

I found the complete tool on Ebay and decided to purchase it just because the history of the tool and is part of my 1930-50's Miller tool Collection.

 

When I sell my 39 Desoto the tools will all be up for sale.

Rich Hartung

Desoto1939@aol.com

 

 

 

[Mertz]

Mine looks a little different. The 3 fingers are stamped steel. It does have the ability to adjust the pressure. Your setup with the jack would work for me if I could get a pressure gauge in between the jack and the hitch. Mine is a 10” clutch. I believe the correct pressure is 155psi at 1.5” depression. 

[Los_Control]

1 hour ago, Mertz said:

Mine looks a little different. The 3 fingers are stamped steel. It does have the ability to adjust the pressure. Your setup with the jack would work for me if I could get a pressure gauge in between the jack and the hitch. Mine is a 10” clutch. I believe the correct pressure is 155psi at 1.5” depression. 

Sometimes I think we get a little carried away (with perfect)

I feel if the pp has been sitting for a long time, you have it out in front of you .... You can disassemble clean & inspect it, grease it properly where it is needed.

 

I'm only suggesting that maybe Drag Racers took the time to measure pp spring pressure. .... The farmers or kids never bothered with it & worked just fine for them.

 

What exactly would you do if your spring pressure was at 145..... instead of 155 .... would you replace your 70 year old springs for new ones?

 

We are talking about 70 year old equipment & a 90 hp engine. ..... what exactly would 155 spring pressure tell you?

[Mertz]

If the springs are at 145 I would use the pp. You are correct about it being old equipment. The truck was used on a Montana farm and only shows 26000 miles on the odometer which based on the internals of the non synchro 4 speed trans and rear end, which look like new, it appears an accurate reading. There is still good surface on the disc and the faces of the pp and flywheel just need resurfacing. I don’t know if springs weaken over time by non use or not. I bought the truck 30 years ago and it’s alway been stored undercover. 

 

Everyone knows that when working on a clutch always replace the throughout bearing.  While I have it apart and easy to get to, it makes sense to replace everything but with the pp looking good and being on a limited budget I would like to at least use the pp.  

 

I think I will put some pressure on it like pictured above and see what kind of resistance I get.  If it moves to easily it will be replaced, if it has good resistance regardless of actual psi I will probably use it. 

 

Thanks for all all the comments and help 

[Mertz]

I’m installing the old disc and pressure plate. I took the disc to a parts store and compared surface thickness with a new one and mine looked very good. When I laid the pp on I have about 1/8” of clearance between the pp and the flywheel before tightening the bolts. Does that sound right?

[Los_Control]

I do not know what the specs are, sure you can find them in a book somewhere.

 

I would think it would be fine, when you tighten it down it will be the pp springs compressed that distance applying the pressure.

Then if you removed aprox 1/8" from the disk, it would be worn out & close to the rivets .... destroying the surface of you pp & flywheel.

You have compared it to a new disk, you can see the new one would give you about the same distance.

 

I think that a clutch disk gets a lot less wear then a brake shoe. When in use we ride the brakes safely slowing to a stop, causing wear on the shoes.

Properly operated, a clutch is either engaged or disengaged. Normally you do not slip the clutch causing wear.

So 1/8" wear should give you many thousands of miles. Or years?

 

I almost question changing the throw out bearing. Only because it may be easier to physically check a bearing for condition.

A bearing needs to spin freely with zero roughness or noise. ..... If your existing bearing fits this description, it may be better quality then a new one you can replace it with.

 

Another thing to consider is your pilot shaft bushing. ..... With 26k miles on it, it may not be worn out .... something to think about though.

[Mertz]

I did visually compare the disc to a new one and it appears that the old one had just been replaced with very little wear showing. The through out bearing is being replaced because it is what normally fails first. I never replace a clutch without replacing the through out bearing. Having said that I will check the old one. The engine going in was used as a stationary engine I believe to pump water and it had a new pilot bushing installed when the engine was rebuilt so it is basically new. 

[Los_Control]

The pilot shaft bushing is recommended to pack it full of grease to create hydraulic pressure to remove it.

 

I read too much sometimes ..... Seems that applying grease to a bronze bushing may not be the best. Clogs the pores, the grease wears out & no further lubrication.

While I have read that applying a light oil to the bronze bushing, it will soak it up like a sponge & supply lubrication for years to come.

 

I'm only suggesting you do some research on it yourself.

I really would have to do the same the next time I'm faced with the issue.   ..... Only pointing out their is a conflicting opinion.

[kencombs]

1 hour ago, Los_Control said:

The pilot shaft bushing is recommended to pack it full of grease to create hydraulic pressure to remove it.

 

I read too much sometimes ..... Seems that applying grease to a bronze bushing may not be the best. Clogs the pores, the grease wears out & no further lubrication.

While I have read that applying a light oil to the bronze bushing, it will soak it up like a sponge & supply lubrication for years to come.

 

I'm only suggesting you do some research on it yourself.

I really would have to do the same the next time I'm faced with the issue.   ..... Only pointing out their is a conflicting opinion.

That's true if it is an Oilite bushing,  but not if it is just a plain bronze or brass part.  The Oilite has 'pores' that soak up oil.

[Eneto-55]

2 hours ago, Los_Control said:

The pilot shaft bushing is recommended to pack it full of grease to create hydraulic pressure to remove it.

 

I've also heard that you can use fresh white bread to force the bushing out.