TH400 clutch Plates 5 or 6?

[gronlit]

I need some help...

 

I'm mid-rebuild on my TH400 (code CR) out of a 70' SS and have run into a problem...

 

Here's what I pulled out of the transmission:

Forward Clutch

-4 flat steel plates (~.090" thick)

-5 radially slotted clutch disks

-1 Wave Washer

 

Direct Clutch

-5 flat steel plates (~.090" thick)

-6 non-slotted clutch disks

-1 Wave Washer

 

Here's what the rebuild kit (from NAPA) has:

-5 Flat steel plates (~.065" thick)

-5 Flat steel plates (~.090" thick)

-10 non-slotted clutch disks

 

The rebuilt kit only has 10 clutch disks for these two clutches, but I pulled out 11 old clutch disks of this size. And the rebuild kit flat steel plates come in two sizes, but the ones I pulled out are all the same size. Anyone seen this before, do I have the wrong kit? I checked on O'Reilly autopart's website and their rebuild kit only shows 10 of these clutch disks as well.

 

My dad had an A/T rebuild book which covers the TH400 up to 69' which I’ve been using. The book lists 5 clutch disks for both the direct and forward clutches (which is what the kit has), but the transmission had 6 disks in the direct clutch. Was an extra clutch disk added in 70'? Also, the book doesn't show there being a wave disk in the direct clutch (only in the forward clutch), but the transmission had one in it...did this change in 70'?

 

Are radially slotted clutch disks needed for the Forward clutch, the kit only has non-slotted disks.

[overdrive]

I rebuilt the exact same trans in Sept. I think mine had 6 plates in the direct clutch, too.

 

Note, I'm no expert.

My book shows 70 has the wave plates and recommends replacing the waved steel plate in the forward clutch with a flat steel plate for firmer shifts. This also reduces friction plate [clutch] wear. You can do the same on the direct clutch stack. The book shows 5 steel plates and 5 friction plates in the direct clutch, but it doesn't specify the # in the forward clutch. You can use 5 in either, as long as the clutch-to-backing plate clearance is within specs. You can get 2 different thickness steel plates from GM to adjust the clearance of each clutch stack. The book also shows you can usually reuse your old steels. Just make sure they aren't warped. You should sand them or blast them to remove heat discoloration, minor scoring and glazing. It seems you have 5 wrong steels.

 

Be sure to soak the friction plates for at least 15 mins.

[gronlit]

Thanks for the reply, always nice to hear someone else has run into the same thing.

 

I think im leaning towards reusing the old clutch disks and plates. They don't look too bad. The reason im rebuilding is that it has been sitting for ~25year and i assumed the seals would be shot. I'm leary of reducing the number of clutch disks i use, i would think using 5/6 (83%) clutch plates would mean a the amount of torque that can be transmitted w/o slipping would reduce to 83%. I've looked a couple different rebuily kits and the ones i've seen all seem to be missing that 6th plate.

 

BTW, i like the pictures of your SS, looks like you're making good progress...hopefully i'll get there someday

 

Tim

[Ian]

You should be able to just buy a couple extra clutch discs and put them. If it is that far apart why not do it once?

[overdrive]

Quote:

BTW, i like the pictures of your SS, looks like you're making good progress...hopefully i'll get there someday

Thanks.

From the book: "It's pointless to reuse the frictions unless the transmission has very few miles on it- 10,000 miles or less. If you do reuse them, inspect carefully for burning, glazing, cracking, pitting, flaking, imbedded particles and warpage. Check for wear. New frictions are about 0.080 in. thick. Replace all frictions if any are worn to 0.070 in. or less."

I'd be leery of the old frictions because of the age, if nothing else. I'd call some kit manufacturers for help getting the correct # of parts.

I posted a question I had when I was working on mine on the Team Chevelle site and got a quick answer. You may want to try there, also.