727 shift point question, automatic valve body

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4mulas

4mulas

Fixem'up
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Here’s a question for you ‘in the know’ transmission guys - What is to cause a 727 trans to BLOW through all the gears really fast (1-2 shift at about 9mph, then 2-3 shift immediately after that) under light acceleration? (Even under light to medium acceleration)

If from off idle you floor it AND can prevent the tires from blowing off it will upshift from 1 to 2 at about 4000 rpm and then the 2-3 shift at about 4400 RPM.

I doesn’t like to downshift into first ever once rolling, and also is lazy downshifting into 2nd from 3rd as well (higher the speed less likely to downshift) when rolling down the road

It is a rebuilt transmission and my transmission builder says he knows what to check and has few ideas to remedy all of this and is going to tackle it for me soon I would just like to have a better understanding of all this myself

I have just been shifting manually with the TF2 kit installed and getting firm crisp shifts and it performs well when used like this.

Some info:
3300 pound A body
It’s a 727 (out of an early 70’s c body I think),
Rebuilt, with a TF2 transgo kit.
Billet 2800 ish stall (foot brakes to 2400 before it pushes)
Lokar kick down with shorter Dakota lever. Works in complete unison with throttle. I get both full throttle and full deflection on kick down lever.
Behind small block 408 magnum
Currently 3.23 gears -(also did all of this with 4.30 gears too)
 
1. You need to install a lighter governor out of a 340 or Max wedge trans this will hold second gear longer. light weight on the right standard on the left
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2. Install a Part Throttle valve on the Valve body. Most all 71 up 904 and 727 are the same valve. most 904 cars had them. This will make the car down shift at low speeds with partial throttle application. Its is only three screws that hold it on Both of these modifications can be done with the trans in the car.

1734451110074.png

1734451370744.png
 
I was reading about the part throttle valve before and was under the assumption that both 904 and 727 after about 1970 ish got this? Is that wrong? Thanks for the governor input. If this thing came from a c body with highway gears initially maybe that’s what dictated the heavier governor?

Just learning here

A&A seems to have governor kits, but which one would I need?
 
See if the kickdown is actually moving on the valve body. Drop the pan and have someone move the throttle and check it out.
 
LO23M8B said:
See if the kickdown is actually moving on the valve body. Drop the pan and have someone move the throttle and check it out.
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It’s working against the spring detente. ? Being freshly rebuild by a known good rebuilder wouldn’t think that is assembled incorrectly?
 
Well with the normal up shift at 9 mph and then 2nd right after that it would be the aera I would double check, the entire kickdown system to start.
 
Murray said:
There is a line pressure problem.
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Would line pressure affect shifting manually? The trans when shifted manually works perfectly. Rubber in between gears.

The builder did mention checking pressure quickly before removing the pan and checking things out in the valve body. He also mentioned governor as a possible cause. Again I’m trying to be more well versed in this topic so I understand what he’s doing.

Again, automatic transmissions are like unicorns to me. This is my first automatic car in about the last ten cars.
 
The kickdown only controls shift pressure not shift point. Until you are flat out into the detent for passing gear then that second to drive is controlled by the governor.

One other thing to know is when ever manually shifting a mopar trans always start off in drive. Once the car is rolling then pull it back to low. The shift will be much crisper from 1st to second rather low to second while flat out.. No overlap due to band apply low gear. You want to launch in 1st not in low.. Once it leaves in 1st it will not go to low while moving. Try it and you'll see
 
Read it a coupla times.
Does it "kickdown" if you're cruising in high and punch it ?
The early shifts kinda reminds me of the valve body
spool not positioned on the lever correctly inside the trans.
 
Inertia said:
Read it a coupla times.
Does it "kickdown" if you're cruising in high and punch it ?
The early shifts kinda reminds me of the valve body
spool not positioned on the lever correctly inside the trans.
Click to expand...
Only at lower speeds. Let’s say once above 40 mph oh it stays in drive no matter how hard you punch. (Currently 3.23 with 27" tire)

It should kick down at that point based on my foggy memory of auto’s I’ve had in the past for a decade or 2 ago…
 
Oldmanmopar said:
The kickdown only controls shift pressure not shift point. Until you are flat out into the detent for passing gear then that second to drive is controlled by the governor.

One other thing to know is when ever manually shifting a mopar trans always start off in drive. Once the car is rolling then pull it back to low. The shift will be much crisper from 1st to second rather low to second while flat out.. No overlap due to band apply low gear. You want to launch in 1st not in low.. Once it leaves in 1st it will not go to low while moving. Try it and you'll see
Click to expand...
Not sure if I’m understanding the low vs 1st and what exactly you are saying here. I’m kind of with you but not 100% here… ?

Once the car is rolling and I pull it back to 1rst it WILL downshift to 1rst no matter what speed your doing, this is a function of the tf2 shift kit from what I understand? (is this the ‘low’ you are referring to?)

If I start in first and shift to second myself at higher rpm it’s fast and firm. Same as second to 3rd (drive) also, crisp, fast, and firm.

I do launch in first. Again not sure what you mean by low?
 
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I would start with a teardown and very thorough inspection of the governor and valve body (look for sticky parts), then build the unit accordingly to match your desired specs.
 
4mulas said:
Not sure if I’m understanding the low vs 1st and what exactly you are saying here. I’m kind of with you but not 100% here… ?

Once the car is rolling and I pull it back to 1rst it WILL downshift to 1rst no matter what speed your doing, this is a function of the tf2 shift kit from what I understand? (is this the ‘low’ you are referring to?)

If I start in first and shift to second myself at higher rpm it’s fast and firm. Same as second to 3rd (drive) also, crisp, fast, and firm.

I do launch in first. Again not sure what you mean by low?
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For anyone shifting their car manually with a full auto trans. Leave it in drive to launch the car. As soon as it leaves pull it into low before it shifts. You will not have the overlap on the shift to second gear. There is a big difference on the shift without low band apply. To achieve this you must launch in drive and then pull it to low before it shifts then shift second manually

In a 727 transmission, when in "drive," low gear is achieved using a roller clutch (also called a "sprag") rather than applying the low/reverse band, which is only engaged when manually selecting "low" on the shifter; essentially, "low gear band apply" refers to the dedicated low gear function accessed through the manual low selection, while "1st gear in drive" utilizes the roller clutch to provide a low gear ratio without directly applying the band.
 
4mulas said:
Only at lower speeds. Let’s say once above 40 mph oh it stays in drive no matter how hard you punch. (Currently 3.23 with 27" tire)

It should kick down at that point based on my foggy memory of auto’s I’ve had in the past for a decade or 2 ago…
Click to expand...
With a part throttle valve on the valve body. If you are cruising in drive at any speed when you depress the throttle just a tad to accelerate it will down shift. Once it shifts and you want to accelerate again it will again downshift to accelerate.

Another wards step on the throttle it down shifts hold a steady throttle it shifts to the next gear. Give it a little more and it will keep down shifting as it needs to. You don't have to keep kicking it into passing gear. It will work hydraulically the same as a new trans does electrically. I thought this was common knowledge on this site.
 
To much line pressure will give it a hard shift. but could break parts. I did it on a truck. Turned the allen screwed in 1 turn. worked great for a week and it destroyed itself plowing.
 
I never saw a performance factory big block 727 with a PT valve, Put one in and what a difference with a big block. Night and day. Have new tires on hand. LOL
 
As well as shift control valves that shift the gears, these valves in auto mode are getting inputs from the KD valve & governor, combined with 1-2 & 2-3 shift springs. If these springs have been changed, are broken or lost tension, I would think the shift speed would be affected.
 
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