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I continue with the rebuild of my '99 transmission but need some help understanding something.
I installed a new bonded piston and on that a TH400 waved plate and then 5 steels '090 thick and 5 clutches 0.080 thick. When I measure like in Nicks transmission video's on YouTube I measure 0.045 - 0.050 between the ledge and the top of the clutch plate. When I add the backing plate and the snap ring and measure when applying air I get 0.041 play. So total 0.090 about which is way off. How is this possible ? I did not see any wear on the direct drum so I don't get it that there is so much clearance ...
UPDATE
I Got rid of the wave plate and installed 5 steels of .077 and one of .090 and 6 clutches.
Now when I measure the distance from the ledge to the to of the clutches like Photo below I get around .025
When I measure together with the backing plate and original spring I get .040 clearance.
So if I add the 2 together I should have 0.065 clearance. Should I look for a thicker snap ring or is this good ?
Last edited by stingraymax; Jan 25, 2026 at 03:53 AM.
Just a hair on the high side for my taste but workable . Some would say fine. I always try and stay about .030-,040 . But have seen many a working unit with much higher.
__________________ Frank formerly of Performabuilt, Now just me, What can I build for you today? Call or message me. Click sig pic for my facebook
OK, went back in and tried some more different combinations. I came to the conclusion that my direct drum is haunted...
So tried TH400 wave plate, 5 steels .090 and 5 clutches and got about .075 clearance when air testing. As I couldn't find thicker steels my only option is dumping wave and go 6 clutches. Or can I put 2 thinner steels together on each other ? So Wave, 6 steels and 5 clutches ?
So dumped the wave and tried 6 steels 6 clutches with different thicknesses, got it to 0.070 now.
But every time I want to change the clearance and change for example a .080 steel for a .078 steel the clearance when I air test it jumps like .010. Each time I adjust it with a small difference in 1 steel plate the difference is way more when air testing .
How is this possible ??
Last edited by stingraymax; Jan 28, 2026 at 02:05 PM.
The apply compressed the friction material. This is why I tell people and I do the same. Whatever I measure in a loose pack I add .010 to that number . or instance if i get .025 loose I assume .035.
I have had units down that I built and set the clearance at .025 . Little to tight, run on dyno and tear down for some other issue or to check something and note it now .035 to as much as .045
Get close to the ball park you want to be and you will be fine.
__________________ Frank formerly of Performabuilt, Now just me, What can I build for you today? Call or message me. Click sig pic for my facebook
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Direct drum clearance 4l80e problem. 
