MTFCA Forum

Looking at what I presume is a "Jackrabbit" replacement, in time, the friction linings fail. According to hearsay, this clutch pack has probably over 20,000 miles. I wonder where the lost clutch facing went ?

The lugs on the driven (?) plates wore to less than 2/3 their original width. I wonder why the notch ?

I believe those are Turbo 400 discs.

They're notched because they started out in life looking like this...

Comparing an original steel clutch pack, this set has seen a lot of miles, no doubt, but there is no appreciable wear. Bluing indicates overheated stress, possibly from running out of adjustment ?

What are the earmarks of an original clutch pack that should be replaced ?

Jerry, parts catalogues show the clutch you illustrate as the "Turbo" clutch, which requires its own splined inner drum to replace the original Ford part.

"Jackrabbit" is just a modified turbo disc - you know you need clutch replacement when you have no more adjustment at the 3 fingers and the T clutch slips constantly ! Notice how thin the turbo disc tab is compared to the Ford disc, thus the wear pattern. What do the drum lugs look like ?

Rich P. Bingham wrote: ↑

Fri Sep 08, 2023 12:00 pm

What are the earmarks of an original clutch pack that should be replaced ?

Heavy warpage.
Cracks.
Galling.
Worn down lugs.

The disc you show looks reusable to me. I usually blast them with glass bead before re-installing.

Rich P. Bingham wrote: ↑

Fri Sep 08, 2023 12:03 pm

Jerry, parts catalogues show the clutch you illustrate as the "Turbo" clutch, which requires its own splined inner drum to replace the original Ford part.

Yes, the special inner drum is the right way to do it. However, before those were available, many folks just snipped/ground off the spline teeth that were "not needed" and used the stock T inner drum. That's what you've got.

That first disk looks badly burnt from slipping. The lower disks dont look as bad. Poorly adjusted clutch linkage, notched clutch lugs, a weak spring & poor pedal engagement habits can all contribute.

I tore down a motor with over 10K miles that had no measurable wear. I reused them.
That worn down lug is interesting. I have not seen one that bad.
Your original disks were likely not prepared. I also bead blast & recommend that or light sanding. Had they been blasted, that blue would have been removed as evidence. The polished condition of your original disks probably also contributed to the slippage.

Just a comment on blasting clutch discs- its very easy to warp clutch discs if they get blasted with coarse media or high pressure. Contrary to the beliefs of some folks, clutch discs need to be dead flat in order to function properly. Some may disagree with that statement, and that's ok as well.............

Dan McEachern wrote: ↑

Fri Sep 08, 2023 2:47 pm

Just a comment on blasting clutch discs- its very easy to warp clutch discs if they get blasted with coarse media or high pressure. Contrary to the beliefs of some folks, clutch discs need to be dead flat in order to function properly. Some may disagree with that statement, and that's ok as well.............

Good point. Why I use glass bead and a light pass. Thanks!

Rich P. Bingham wrote: ↑

Fri Sep 08, 2023 11:47 am

Looking at what I presume is a "Jackrabbit" replacement, in time, the friction linings fail. According to hearsay, this clutch pack has probably over 20,000 miles. I wonder where the lost clutch facing went ?

Appears in the photo that that set of worn modified Turbo 400 discs are the lower performance type (i.e. lower cost discs) because they show a "in - line' groove facing, friction material. Think perhaps the liner steel for the circular tabs could have been poor heat treat or something to wear that way?

The better or Jackrabbit style uses high performance friction lining, these have a 'waffle' pattern on the friction surface. Have used this style always in my T's and never any trouble with wear.

Here's a question on the pressure ring : this obviously genuine Ford part is kinda ugly where it interfaces with the clutch pack. I wonder if the contact it applies at the dowel pins is conducive to a smoother release into direct drive ?

By comparison, here's a clutch rung that has seen service. The contact face is dead flat and smooth. Would it be "grabbier" than the one previously shown ?

Another interesting point, the first ring measures 1.075" from the top of the dowel pins to the contact surface. The worn ring measures 1.010". Might we assume .065" of wear on the smooth faced ring ? I'm presuming a range of .065" or more isn't an issue when adjusting spring tension with the clutch "fingers" ?

The ring doesnt rub/wear in a proper clutch pack. The last disk is a large. Keyed to the drum.
The ring only pushes against the large disk.
A nicely machined flat ring does provide even pressure.

What John said above is true, but only if the last disc to be installed is a large disc. The last disc in needs to rotate with the brake drum/ driven plate assembly. It is a common mistake to over look this detail if you don't fully understand how the clutch pack should be installed. All those drive plates with the push ring holes worn out is the result of the push ring having to act as that last large clutch plate. The early production push rings were machined on the clutch pack side but later rings are not.