727 clutch pack clearance

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Mojack

Mojack

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The main question is the clearance
on the front clutch pack. This is an unknown big block RV trans. The FSM calls for .082-.151. The original pack clearance measures in at .045..?.. BTW the original frictions look really good, wish I hadn't opened this unit up, eh too late now. The new frictions are thinner than the original (.062 vs. orig. .096). The same number (3) of the new, have a clearance of .140, if I sneak another friction and steel in it's .013 clearance. The manual "says" you can get thinner retaining snap rings to adjust the clearance. With the original clearance being so far from the FSM I'm a little unsure.
One more detail, the thickness of the original frictions in the rear clutch are the same as in the rebuild kit (.062) whereas like I described above, the original frictions in the front clutch are .092. The kit has all at .062...

1. Just reinstall the originals.
2. Leave the new larger clearance. (.140)
3. Chase down a thinner retaining ring to get back to the original .045 clearance and have 4 frictions.
 
#3, additional friction plates are the way to go. 65'
 
Be sure to pay attention to wavy versus flat snap ring use and the difference in clearances with them.
 
The wavy retaining ring that goes on the front clutch pack is thinner than the rear drum retainer but it takes up more room . It is MEASURED from the top pressure plate to the top inside of the snap ring at its highest point. You can install a rear clutch lower plate on the top of the front clutch to gain one extra plate. You have to twist the retainer to install it. I use .061 red eagle smooths in the front clutch to install even one more.
 
I have not built a lot of TFs but my rule of thumb has always been minimum .010 per friction. More is ok, but I have never installed looser than .015 per friction.

As for me, I would hunt up different frictions to better get into the ball-park. I have mixed and matched with no issues.
And I have also reused many many good frictions.

My test to proove the frictions is to push a small screwdriver along the surface (about a tip size of 1/8, and on the flat), slightly tipped up to attempt to dig a groove.. If carbon material chips off leaving a groove, it has been baked and is junk. If it leaves a trail of dry still-bonded material behind it, and only oil ahead of it, then it is reuseable. There is no in-between.
If you suspect your test is lying, then dig a corner in and drag backwards; if it leaves chipped up carbon material and a groove, it's junk.
You don't have to be rough, and if you do and it still passes, don't worry about a mild groove as long as NO carbon chipped up.
 
CudaFactHackJob said:
The wavy retaining ring that goes on the front clutch pack is thinner than the rear drum retainer but it takes up more room . It is MEASURED from the top pressure plate to the top inside of the snap ring at its highest point. You can install a rear clutch lower plate on the top of the front clutch to gain one extra plate. You have to twist the retainer to install it. I use .061 red eagle smooths in the front clutch to install even one more.
Click to expand...

Thanks, I understand how to measure the wavy ring for the clearance. So I can substitute the wavy ring for the solid ring without any other problems? That would get me the clearance I need.
 
AJ/FormS said:
I have not built a lot of TFs but my rule of thumb has always been minimum .010 per friction. More is ok, but I have never installed looser than .015 per friction.

As for me, I would hunt up different frictions to better get into the ball-park. I have mixed and matched with no issues.
And I have also reused many many good frictions.

My test to proove the frictions is to push a small screwdriver along the surface (about a tip size of 1/8, and on the flat), slightly tipped up to attempt to dig a groove.. If carbon material chips off leaving a groove, it has been baked and is junk. If it leaves a trail of dry still-bonded material behind it, and only oil ahead of it, then it is reuseable. There is no in-between.
If you suspect your test is lying, then dig a corner in and drag backwards; if it leaves chipped up carbon material and a groove, it's junk.
You don't have to be rough, and if you do and it still passes, don't worry about a mild groove as long as NO carbon chipped up.
Click to expand...

That's good to know, that gives me a good tolerance no matter how many discs I use. And to tell if the frictions are useable again.
 
How thick is the snap ring now. Thinnest Mopar 1 is about .062 thou. U can get a thinner 1 from General Motors for a TH 400 that is .040. U could also put an extra steel in there to take up some space, or use ur old clutches. Kim
 
Last edited:
CudaFactHackJob said:
You can install a rear clutch lower plate on the top of the front clutch to gain one extra plate. You have to twist the retainer to install it. I use .061 red eagle smooths in the front clutch to install even one more.
Click to expand...
I thought the rear clutch lower plate was super thick with a ring protruding to push on the diaphragm/ spring...
 
Mojack said:
I thought the rear clutch lower plate was super thick with a ring protruding to push on the diaphragm/ spring...
Click to expand...
Flip it over. The edge is half the thickness of the direct pressure plate, allowing for an extra fiber and steel.
 
If it's just the three friction drum, and you have it apart, I'd just find a four disc drum.
 
It's easier and cheaper to just use the forward plate to make it a four plate drum; it's just harder to check the clearance. I always use air anyway and watch the clearance open and close to check it.
 
67Dart273 said:
How do you identify one from the other after they are apart? Is there a depth measurement, etc?
Click to expand...
From the snap ring groove down, you can see the difference. Once you see them side by side.
 
The four plate drum measures 9/16" or .55 from the top of the snap ring groove to the top of the drum. The three plate is about an eighth inch more.
 
You see, even the fancy dancy tech. manuals don't have this kind of good info!
 
CudaFactHackJob said:
Ya might have to twist the waved retaining ring back and forth to get it in the groove.
Click to expand...
That part does look a little difficult.
Now, you've solved the front clutch question, but does anything need to be done to the rear clutch to even out things, does it help any? If so, just the same tricks?
 
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