727 shifting pattern help
#1273455
07/25/12 03:44 AM
07/25/12 03:44 AM
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Joined: Jan 2009
Posts: 106 Poland
willard
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Poland
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70 challenger, mild 383, stock 11" tc, 3.23 rear 26,5" tires, new cheetach standard automatic VB, 5400 rpm governor, proper throttle linkage, set as per FSM, holley carb with dedicated bracket, billet rear servo, 4.2 KD lever,
Symptoms: - WOT shifts at 3000 rpm and 3300 rpm - 3-2 downshift only below 40 mph, no manual downshift either! - 2-1 only below 10 mph, no manual downshift either - should be 1 at any speedwith this valve body. - governor pressure verified and ok. - line pressure 55-60 at 1000rpm in 3rd (measured at front servo), when throttle lever pushed climbs to 70 and then downshifts to 2nd and pressure drops to 0psi. - when operated manually acts ok, shifts are firm but wont downshift manually to 2nd above 40mph and to 1st above 10mph. closed throttle upshifts are like with stock VB.
I guess line pressure should be higher with that valve body? What part aside VB produces the line pressure?
Over last year I replaced the VB (before had a stock with TF2) and governor, and performance changes are very small. Before, WOT upshifts were even lower at 2500 rpm and no 2-1 kickdown until car stopped.
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Re: 727 shifting pattern help
[Re: willard]
#1273456
07/25/12 04:22 AM
07/25/12 04:22 AM
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Joined: Aug 2003
Posts: 12,291 Kent, Wa
340SHORTY
Truck Nut
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Truck Nut
Joined: Aug 2003
Posts: 12,291
Kent, Wa
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The pump makes the pressuse.. The pressure is adjusted by a screw in the valve body..
I am truckless..
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Re: 727 shifting pattern help
[Re: willard]
#1273458
07/25/12 03:09 PM
07/25/12 03:09 PM
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Joined: Jan 2003
Posts: 75,042 U.S.S.A.
JohnRR
I Win
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I Win
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Quote:
Damn... pulling the tranny out is not my favourite job ;/ I guess you're right... Is replacing the pump rotors enough? Or there is something else in the pump body?
I would swap the valvebody first to see if the line pressure problem is your new valvebody .
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Re: 727 shifting pattern help
[Re: John_Kunkel]
#1273462
07/26/12 02:09 PM
07/26/12 02:09 PM
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Joined: Jan 2009
Posts: 106 Poland
willard
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Quote:
Quote:
Sounds like the kickdown lever needs to adjusted farther back!
My thought too.
I appreciate your help but how can I adjust it further back (lenghten the rod with a slot) if now at WOT the stud a the carb pushes it to its limits?
John is my line pressure ok for cheetach VB (55 psi @1000rpm in 3rd) ?
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Re: 727 shifting pattern help
[Re: willard]
#1273465
07/29/12 06:27 PM
07/29/12 06:27 PM
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Joined: Jan 2003
Posts: 25,842 Rio Linda, CA
John_Kunkel
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There is no way to check the actual throttle pressure; for later shifts just adjust the linkage so that the transmission lever is further back for any given throttle setting (lengthen the linkage). BTW, line presure is measured at the accumulator (center tap) not the front servo which is servo release pressure.
Also, be sure that WOT under the hood is the same as WOT at the pedal. Misadjusted throttle cable will prevent the carb from going WO when the pedal is matted.
The INTERNET, the MISinformation superhighway
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Re: 727 shifting pattern help
[Re: willard]
#1273467
08/01/12 02:11 AM
08/01/12 02:11 AM
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Joined: Sep 2006
Posts: 150 Illinois
fishy68
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Pressure is definetly quite a bit low. I generally see close to (sometimes over) 100 psi. with a valve body like that or a stock vb with a trans-go kit. The sealing rings on the pump stator won't affect pressure in 1st or 2nd as their job is to seal oil pressure going to the front clutch pack. They'd affect it in 3rd gear or reverse only. Since it did this with 2 different valve bodies my guess is the pump is worn out.
68 Cuda 408/904/8-3/4 02 Dakota 4.7 auto
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