Re: Hemi torqueflite valve body
[Re: 68jim]
#982205
04/29/11 05:14 PM
04/29/11 05:14 PM
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Joined: Jan 2003
Posts: 25,817 Rio Linda, CA
John_Kunkel
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In '68 the Hemi VB is identical to the 440 HP, even the same part number.
Even then, the only difference between them and any other BB 727 VB is the transfer plate. I don't have a sample of each to compare to see what the actual difference is but I'm sure it's minor.
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Re: Hemi torqueflite valve body
[Re: RAH]
#982207
04/30/11 05:02 PM
04/30/11 05:02 PM
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Joined: Jan 2003
Posts: 25,817 Rio Linda, CA
John_Kunkel
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Don't confuse the transfer plate (aluminum casting) with the separator plate (stamped steel sheet).
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Re: Hemi torqueflite valve body
[Re: RAH]
#982210
05/01/11 05:07 PM
05/01/11 05:07 PM
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Joined: Jan 2003
Posts: 25,817 Rio Linda, CA
John_Kunkel
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Quote:
If i remember the transfer plate is the same part number as a 383 torqueflite stock.
Nope, in '68 only the Hemi and the 440 used the same transfer plate. The Hemi and 440 use P/N 2466886; all others (yes even the 904) use P/N 2801295.
I dug around in my parts stash and found an example of each, the only difference I can see is the depth of the channel (second channel from the right) that feeds the rear servo. In pic below the plate on the right is the 886 and it has a noticeably deeper channel than the 295 on the right. I believe this is to allow a quicker apply/release of the rear servo...an advantage on a manual 1-2 shift.
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Re: Hemi torqueflite valve body
[Re: 68jim]
#982213
05/02/11 03:23 PM
05/02/11 03:23 PM
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Joined: Jan 2003
Posts: 25,817 Rio Linda, CA
John_Kunkel
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Since it's inception, the 727 has had a problem with rear servo and rear band breakage; this is due to the fact that line pressure is about 3 times higher (around 300 psi) in Reverse than in the forward gears. I believe that they purposely made the rear servo feed passage smaller on most units to limit the flow to the rear servo to help prevent problems. I also believe they made the passage deeper in HP versions to aid servo release.
In later years ('71-on) they did make the rear servo feed orifice in the steel separator plate smaller to limit flow and most kits instruct you to enlarge this orifice. The ideal setup was used for a few years when they used two orifices in the steel plate (one large, one small) to feed the rear servo, the large orifice was blocked with a check ball during apply that fell out of the way during release but they (unwisely IMHO) dropped this feature.
The deeper passage did carry on into later years due to the smaller feed orifice that serves the same purpose as the shallow passage.
Since the rear servo isn't applied in Drive the size of the passage/orifice has no effect on the 1-2 upshift in Drive.
The rear servo plays no part in 2-3 upshifts.
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