Is it worth going to the more robust belleville washer and matching piston used in the later 727 rear clutch drums? Is the earlier, thinner cross sectioned ones problematic? My trans is a '73 so it has the thinner belleville...Im just using a Cheetah reverse pattern valve body so no sky high line presures. 600 hp approx... This is my first transmission job, so im a little in the dark...(pic from another thread on here)

We've used the thinner, pre '74 washer in the trans with no issues. Usually lives behind a 655, or a 572 motor when the reserve motor steps in.
HTH's

Thanks Tig!

Same here. I use the early one behind my 572 and Dizusters turbo motor. Never had a problem. Just make sure which ever spring you use it matches the correct piston.
Doug

I would upgrade while you have it apart. There are a couple of factors at work. The wave spring allows fore and aft movement, which effectively increases piston travel irrespective of clutch retainer clearance. Not all piston retainer to clutch retainer fit, is the same. The looser the fit, the worse the problem of excessive piston travel and consequential over centering of the spring. If you have a good selection of oem, and aftermarket snap rings, you will find that a combination of 2, will replace the wave spring nicely.

The early Belleville works OK when it's new but will fatigue with use and weaken more than the later one. HP has nothing to do with failures, line pressure kills them. Even if they don't break, the early ones can flex enough to allow the piston to pop out of its bore...very common failure.

I've seen a bunch of the early ones fail but never the later one. A worthwhile upgrade IMO.

I have used both style Springs. The only one I have ever had break was the thin style.

Thanks a bunch guys. Sounds like with the line pressures Ill be running Id be fine. But with wanting to buy a new belleville anyway, Ill just get the new style with the newer piston. Cheap upgrade.

Good Info

Andrews racing transmission, forward clutch video:

https://www.youtube.com/watch?v=eJsRtPhlwoA&t=9s

The video claims the early piston isn't any different than the late; I've found, by actual measuring, the late piston is taller. The casting number 2124834 ('62-'73) is .783" thick and the 3743623 ('74-later) is .830".

Just picked one up. Casting number 3743623AB. Measures .782 thick. Maybe the "AB" is a revision?

Most anytime you have letters following the numbers its
been upgraded and on yours with a AB it was down a
couple times

👍

In looking at both the pre '74 and 74up I see no differences between THESE two. The only small difference is a .060ish chamfer on the bore of the newer one. That's it.

Lay each on a flat surface and measure up to the OD of the piston.

Or take a mic and measure the top of that OD to the backside of the piston - on the back you will see a machined ridge, measure to it.

The piston rests on this ridge when in the clutch retainer. The inner bore does nothing In regards to the Belleville spring.

Not sure what you mean Transman....heres a couple more comparason pics..

Unless you mean overall height..

I just saw your last photo. - yes - depending how you measure.
Thickness is different - as long as you measure correctly using the machined register on the bottom of the piston ( the machined radial ridge ) to the top of the outer rim of the piston. EDIT- The way you are measuring in the last photo should show the different thicknesses between the two p/n's.

part numbers 623 and 834