727 (340) TRANSMISSION REBUILD QUESTIONS THREAD

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CFD244

CFD244

"THE NEW OLDSMOBILES ARE IN EARLY THIS YEAR"
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Hi Folks

I am starting this thread in hopes to get some of our transmission guys/gals on board and willing to lend your expertise. I am sure that I will have several questions during my journey. Looking forward to much needed input. The transmission is a numbers matching 727 from a 1971 340 Demon. The build will be a typical OEM build going behind a mild 340. Thanks to all.

Question #1: When tearing it down, I found a 3 disc front clutch assembly? This seems odd for this transmission......Thoughts?

Question #2: The rear clutch clearance was .026 under a flat snap ring. Is this too tight?

Thanks
 
IMO, any non-pro should have Carl Monroe or Tom Hand's books on 727 (Torqueflite) trans rebuild and upgrade guides. So many questions are answered and an unbelievable amount of understanding will be at your fingertips.
Without looking it up, I do believe the answer to your questions is no and no.
 
Any chance Trans was rebuilt at some point in its life which would answer why trans isn't correct.
 
Rear clutch is engaged in forward gears only. So it can only drag at low speed in reverse. I shoot for .025". The front clutch likes .012"-.015" clearance per friction. I'd swap in a 4 clutch front drum. If it's the early small pin KD servo use the inner and outer springs. Raybestos or Borg Warner frictions will be fine. As many springs in the front clutch as it has provisions for 10-15. A TF2 shift kit is a nice addition. 3.8KD lever prefered. A deep 46rh pan from Ebay. With a quality front band this setup will easy handle 700hp for years.
Doug
 
Lefty71 said:
IMO, any non-pro should have Carl Monroe or Tom Hand's books on 727 (Torqueflite) trans rebuild and upgrade guides. So many questions are answered and an unbelievable amount of understanding will be at your fingertips.
Without looking it up, I do believe the answer to your questions is no and no.
Click to expand...
Forgot to mention, I am following Tom Hand's book.
 
dvw said:
Rear clutch is engaged in forward gears only. So it can only drag at low speed in reverse. I shoot for .025". The front clutch likes .012"-.015" clearance per friction. I'd swap in a 4 clutch front drum. If it's the early small pin KD servo use the inner and outer springs. Raybestos or Borg Warner frictions will be fine. As many springs in the front clutch as it has provisions for 10-15. A TF2 shift kit is a nice addition. 3.8KD lever prefered. A deep 46rh pan from Ebay. With a quality front band this setup will easy handle 700hp for years.
Doug
Click to expand...

which flavor do you cook up with the TF2 kit? the race or street rod?
 
CFD244 said:
Hi Folks

I am starting this thread in hopes to get some of our transmission guys/gals on board and willing to lend your expertise. I am sure that I will have several questions during my journey. Looking forward to much needed input. The transmission is a numbers matching 727 from a 1971 340 Demon. The build will be a typical OEM build going behind a mild 340. Thanks to all.

Question #1: When tearing it down, I found a 3 disc front clutch assembly? This seems odd for this transmission......Thoughts?

Question #2: The rear clutch clearance was .026 under a flat snap ring. Is this too tight?

Thanks
Click to expand...
From a 1971 fsm. ------ 727 w/340. front clutches = 3 clutch plates = 3 clutch discs = .035 to .088 clear.
rear clutches = 3 clutch plates = 4 clutch discs = .025 to .045 clear.
 
The factory is pretty sloppy on their clutch clearance. But there min of .035" is within my .012"-.015" per friction recomendation. 3 x .012"= .036". Same with the rear clutch at .025"
Doug
 
pt70 said:
From a 1971 fsm. ------ 727 w/340. front clutches = 3 clutch plates = 3 clutch discs = .035 to .088 clear.
rear clutches = 3 clutch plates = 4 clutch discs = .025 to .045 clear.
Click to expand...
This is where I am getting confused. I have an original OEM 1971 service manual, and it reads 4 front and 4 rear clutch discs for a 727 w/340.
 
What are the numbers on the side of the case, at the drivers side pan rail?? Usually start with "PK"...

Be wary anyway, hard parts like that could have been changed out during a trans rebuild eons ago....unless you know the cars entire history.
 
Lefty71 said:
What are the numbers on the side of the case, at the drivers side pan rail?? Usually start with "PK"...

Be wary anyway, hard parts like that could have been changed out during a trans rebuild eons ago....unless you know the cars entire history.
Click to expand...
The transmission has the VIN stamped on the ID plate, and the number 3515843 on the pan rail. Tom's book confirms this is an HP 340 transmission. But like you say, after 50 years, who knows what they put in. 75 k on the clock......Can't tell if it's been rebuilt prior or not. Then again, Ma Mopar was known to mix and match based on parts supply etc.
 
CFD244 said:
This is where I am getting confused. I have an original OEM 1971 service manual, and it reads 4 front and 4 rear clutch discs for a 727 w/340.
Click to expand...
That page is a little hard to read. I find it interesting that a 904 front clutch [for a 318] takes 4 discs and 4 plates. And how many years did your trans last behind a 340? Run it.
 
just a driver/cruiser I wouldn’t worry about the 3 disc direct clutch.
….and i always check input shaft end play prior to tear down. Can give you insight to wear or how far off it was in the first place.
 
A body said:
just a driver/cruiser I wouldn’t worry about the 3 disc direct clutch.
….and i always check input shaft end play prior to tear down. Can give you insight to wear or how far off it was in the first place.
Click to expand...
.049 input shaft end-play. Figured while it was apart, I'd get it to 4 clutches. If I can find a 4 clutch drum, or machine the retaining plate......Still tossing those ideas around.
 
Is it a factory wide bushing drum or narrow bushing? If its a factory 1971 it will be a wide bushing. I have a few narrow bushing 4 plate drums if someone swapped out the parts to 1970 or earlier. A machine shop can cut a second snap ring groove in a 3 plate drum for 4 clutches. I can give you the dimensions. Or you can use a Turbo 400 pressure plate and shim it to get 4 plates in there.
Doug
 
I've got the wide bushing drum. Those dimensions for the extra snap ring would be handy......

I have a line on a Cummins 47RE core (???) for $150. Hoping to get a 4 clutch drum, 3.8 lever (I have a 3.2) and deep pan from it. Those parts should work in my 727 I believe.
 
Bobzilla said:
Aren’t the friction plates splined differently from the 727 to the overdrive transmissions?
Click to expand...
Some parts are interchangeable from what I read. A part number look-up at a supplier shows the same number for the direct drum between the 2. Pans are the same, and hopefully the band apply lever.
 
I install 5 .061 Red Eagles in every 727 I build; makes no difference if it's a 3 plate or 4 plate drum because if it's a 3 plate I just use a forward clutch bottom pressure plate on top, and of course five thins will fit into a four plate drum easily since the oem direct frictions are a lot thicker. Nothing to it.
 
CFD244 said:
I've got the wide bushing drum. Those dimensions for the extra snap ring would be handy......

I have a line on a Cummins 47RE core (???) for $150. Hoping to get a 4 clutch drum, 3.8 lever (I have a 3.2) and deep pan from it. Those parts should work in my 727 I believe.
Click to expand...
You can buy a drum for less than $150. I'll measure one up tommorow.

Doug
 
CudaFactHackJob said:
A forward lower pressure plate is $6..
Click to expand...
I'm almost $800 CDN in for parts with OEM frictions and steels here in Canada. Heck, they want $250 for a Trans go TF-1 (glad we have Rock Auto). If I shop at a US Transmission supply chain, we get hammered for shipping and brokerage pretty heavily. If we US Postal service anything of value (over around $100) they hold it up at the border to tax asses it for who knows how long......almost ready to pull the pin on this restoration.
 
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