Re: 66 thru 71 727 Valve Body Questions
[Re: dragon slayer]
#2866574
12/30/20 04:15 PM
12/30/20 04:15 PM
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Joined: Jan 2003
Posts: 25,748 Rio Linda, CA
John_Kunkel
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Rio Linda, CA
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There were more changes from year-to-year than I can list. Some notable changes that I have observed:
'66 had an orifice restrictor in the rear servo feed channel, this delayed the manual 1-2 upshift.
'67-'68 the diameter of the throttle and kickdown valves changed. '67 was the introduction of PTK for the /6 and a sense port was added for it. VB casting appearance changed, more rounded corners.
'69-'70 the addition of a plastic shoe on the rooster comb for the new NSS and a pressure relief ball was added; both were late '68.
'71 was a complete redesign with PTK for the V8 and the addition of the 1-2 shift control valve with a new passage to feed the accumulator.
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Re: 66 thru 71 727 Valve Body Questions
[Re: dragon slayer]
#2866966
12/31/20 01:28 PM
12/31/20 01:28 PM
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Joined: Jan 2003
Posts: 25,748 Rio Linda, CA
John_Kunkel
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The only difference I have seen in transfer plates of the same year is the depth of the channel that feeds the rear servo. In the pic below you can see that the channel on the right is considerably deeper; this allows higher flow for a quicker release which is beneficial during a manual 1-2 upshift but risks servo damage during application.
The pressure relief ball is intended to relieve pressure over 300 psi which can occur when Reverse is selected when the trans is cold.
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Re: 66 thru 71 727 Valve Body Questions
[Re: dragon slayer]
#2867508
01/01/21 01:34 PM
01/01/21 01:34 PM
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Joined: Jan 2003
Posts: 25,748 Rio Linda, CA
John_Kunkel
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For the "why", you'll have to ask the guys who designed the trans...I can only speculate.
The deeper channel feeding the rear servo would make for both a quicker apply and a quicker release. This would seem to be beneficial but the downside is, when the rear band is applied in Reverse, the in rush of higher pressure fluid can cause band/piston breakage. Line pressure in Reverse is increased by a factor of about three and the cold pressure can exceed 300 psi.
In later years they addressed this problem by using a restrictor orifice and later yet a check ball to route the incoming fluid through a smaller orifice and outgoing fluid through a larger orifice.
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Re: 66 thru 71 727 Valve Body Questions
[Re: dragon slayer]
#2868092
01/02/21 01:37 PM
01/02/21 01:37 PM
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Joined: Jan 2003
Posts: 25,748 Rio Linda, CA
John_Kunkel
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The transfer plate is completely immersed (below the fluid level) so there's no place to drain to.
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Re: 66 thru 71 727 Valve Body Questions
[Re: John_Kunkel]
#2868362
01/03/21 06:58 AM
01/03/21 06:58 AM
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Joined: Nov 2020
Posts: 348 Isle of Sheeps
Gtxxjon
enthusiast
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enthusiast
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Posts: 348
Isle of Sheeps
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Happy New Year to everyone on Moparts. I think you guys have been reading my mind about Vb Separator Plates... I have several different ones here from early 60’s to 78. Some have a large hole above the channel orifice. Some have a small hole that B&M say drill to 3/16. Some have ‘No hole’ as per the B&M own plates. And to top it All, transgo says “fit a 1/4 ball in there”... I was always happy to follow B&M advice on all things VB, but. Now I have done a few Transgo VB’s, they are more ‘up to date methinks’? Best wishes from Limey
Last edited by Gtxxjon; 01/03/21 07:04 AM.
Carpe diem, quam minimum credula postero, thanx Horace!
There’s no point trying to fix stuff that ain’t broke,,, 'but if ain’t broke',,, you is not trying hard enough...
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Re: 66 thru 71 727 Valve Body Questions
[Re: Gtxxjon]
#2869238
01/05/21 10:47 AM
01/05/21 10:47 AM
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Joined: Jun 2014
Posts: 1,321 VA
dragon slayer
OP
pro stock
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Here are some of the interesting items about VB I found going through the Mopar parts manuals for 727s, service manuals and the Master tech lessons.
In 1966 all the VB were the same part number with same internals regardless of transmission model matched to engine. They used the same plate and aluminum transfer plate. The 2466886 deep channel version. In 1967 through 70 there are 2 basic VB. The version for LP engines and HP engines. The internals are again all the same inside a year. The only difference is the transfer plate. The HP get the deep channel 2466886, and the LP get the new 2801295 with narrow channel. The plate was the same. 67-68 VB did not have the plastic isolator for the neutral safety switch, the body changes number because a few valves changed. 69-70 VB have the isolator and added a pressure relief ball and spring, body changes again, because of the relief valve, but are otherwise the same as the 67-68 internally
So if the vb is original and has the 2466886 bottom plate it came out of an HP transmission 67-70.
71 is a revision and there is an extra valve, extra springs, and many differences depending on model, engine, transmission. Mix match of plates, and transfer plates. So now, there are several VB part numbers and while you can narrow down what you have by the transfer plate number, there are spring and plate differences that prevent you from knowing exactly what you have. The one thing I am not sure, is the later model 71? and up seem to have a stamped number punched through the plate. Is that meant to be an identifier of the plate? If so that might help narrow down what you have.
By the way, in 71 the accumulator operation seems to have changed. It get line pressure in a different way, has this new valve pressure applied on the side, and the spring location or no spring depending on LP, HP 440, or Hemi/6 pack. But that is another subject.
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Re: 66 thru 71 727 Valve Body Questions
[Re: dragon slayer]
#2869385
01/05/21 03:58 PM
01/05/21 03:58 PM
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Joined: Jan 2003
Posts: 25,748 Rio Linda, CA
John_Kunkel
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Joined: Jan 2003
Posts: 25,748
Rio Linda, CA
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The number punched in the steel separator plate is the last three digits of the plate's part number.
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