[desman]

Concerning a 1965 C4 transmission, can anyone tell me why some friction plates have grooves in them and others dont? I have the reverse-high clutch assembly apart and the old friction plates have a cross-hatch groove pattern on them while the new ones only have horizontal grooves on them. On the forward clutch assembly the old friction plates have concentric grooves and the new plates have no grooves. I'm wondering if this is just a manufacturing thing or if there a technical reason for it? More friction, less friction, some other reason? I'm rebuilding the tranny with a Transtar kit that has Raybestos friction plates. The kit doesn't specify which friction plates go in which clutch so I took some calipers and measured the new ones and old ones and made the assumption (uh-oh...) that the new thicker friction plates with horizontal grooves replace the old thicker ones with cross hatch grooves(all are in the reverse-high clutch) and the new thinner plates with no grooves replace the old thin plates with concentric grooves(all are in the forward clutch). Sound right? Thanks!

[scrot]

The grooves allow the trans fluid to escape as the discs are squeezed together. More grooves= quicker engagement. The flow of fluid also removes heat. Some of the clutches are shifting clutches, while some of the clutches are holding clutches meaning that once they are engaged, like the forward clutch, they don't do a lot of shifting. All that said, I couldn't tell you which ones to use where.

[desman]

That info about the fluid moving in & outmakes sense, thanks for that info. The snap ring clearances in the clutches are correct with the new plates in the clutches so I think everything is ok, but I'm heading to the trans. shop tomorrow to get some thrust bearings and will check with them about the thicker & thinner plates. Luckly the guys at the shop are great about helping backyard mechanics. Thanks again!