727 UPGRADES

[J10-401]

Has anyone put the "RV" gearset in their AMC/Mopar 727 TF trans? My stock low gear is 2.45:1. That's way too lazy for first gear. The RV gears bring 2.65:1 - much better! But can the RV gears work in the AMC TF housing?

Also, are any torque convertor stall speeds that are better than stock for our application - with a 401 V8.

[Heavy_Metal_Thunder_81]

I think all the internals of both 727's are the same. The gearset should work.

[Ristow]

jon's correct,internal parts all are the same.

i highly recommend carl munroes performance 727 handbook-lot's of ways to beef up that tranny.

[shimniok]

I'm running a lower stall converter in mine, not sure what rating it was custom made, but probably ~ 1000 rpm. The idea being that it helps a tiny bit controlling downhill speeds.

I never knew there was a lower 1st gearset you could get. Thanks for the tip!

Michael

[360]

i've heard talk of a lower 1st&2nd gears for the tf 727?
so where could i get in touch with this lower 1st gear your interested in?
cheers..dc..

[Rogue]

http://www.allpar.com/mopar/transmissions/torqueflite-tom-hand.html

all you ever wanted to know about the 727 and then some.

[Rogue]

Also, are any torque convertor stall speeds that are better than stock for our application - with a 401 V8.

define "better"

vehicle weight, tire size, rear end ratio and camshaft specs - give those to a custom convertor builder and tell him what you want for performance, anything other than that is a crapshoot - trial and error.

[J10-401]

Better meaning quicker accelertion from a stand still. But without too much loss of fuel economy. Maybe 2 MPG would be OK.

I don't want to raise the rpms much more at highway speeds either. A lockup convertor doesn't seem available for the 727.

So what's the stock stall speed? And do any of you out there have higher stall speeds?

[Rogue]

SUBJECT:
TRANSMISSION MATH FORMULAS (Your most valuable tool)
Transmission math formulas are not reserved exclusively for engineers. Understanding some basic mathematical formulas can be one of your most valuable tools.
The following information contained in this bulletin will discuss various basic formulas dealing with:
1. Shift Speed
2. Pressure
3. Speedometer ratios

Take the time, now, to understand these relatively simple concepts.
You will be saving yourself many problems, and considerable frustration, and also dollars, in the future.

Planetary Gear Sets:
Knowing the gear ratios of an automatic transmission can come in handy at times -- especially when you're swapping transmission types or differentials. The problem is in trying to find a manual with the ratios listed. What do you do?
BREAK OUT THE CALCULATOR, AND FIGURE IT OUT.
When you figure the gear ratios for planetary gear sets, it is just like any other gear set. You divide the output gear by the input. Also, don't count the idler gear; planetaries are considered idler gears. Set them aside, their tooth count doesn't matter.

[Rogue]

Now for the tricky part -- which gear do you consider the input, and which one the output? Figure 1 shows a planetary gear set with 34 teeth on the ring gear and 20 teeth on the Sun gear.
FOR GEAR REDUCTION, one of the gears is held stationary, and the other is used for the INPUT. THE TOOTH COUNT FOR THE OUTPUT GEAR IS THE SUM OF THE SUN GEAR AND THE RING GEAR, so if you are using the Sun gear for the input, then the ring gear + the Sun gear divided by the Sun gear = Ratio.

EXAMPLE: 34 + 20 divided by 20 = 2.7:1 This is how 1st gear on a THM 700 R4 is calculated. (See figure)
When the ring gear is used as the input, then the ring gear + the Sun gear divided by the ring gear = Ratio.

EXAMPLE: 34 + 20 divided by 34 = 1.58 This is now 2nd gear on a THM 350 is calculated. (See figure)
FOR OVERDRIVE, the sum of the ring gear + Sun gear is used for the input tooth count.
So, IF THE SUN GEAR IS HELD, then the ring gear divided by (ring gear + Sun gear) = Ratio
EXAMPLE: 34 divided by (34 + 20) = .63:1 Look familiar?

The A4LD, the THM 200-4R, the A-140E, the A-40D, the THM 325-4L are some of the units that use this method of getting overdrive. (See figure)
If the ring gear is held, then the Sun gear divided by (ring gear = Sun gear) = Ratio

EXAMPLE: 20 divided by (34 + 20) = .37:1 (See figure)
REVERSE IS THE EASIEST - THE PLANET IS HELD.
The Sun gear is the input, and the ring gear is the output. The formula for this is: The ring gear divided by the Sun gear = Ratio.

EXAMPLE: 34 divided by 20 = 1.7 (See figure)
Occasionally, the ring gear is used as the input, and the Sun gear as the output.
The formula for this is: The Sun gear divided by the ring gear = Ratio.

[Rogue]

EXAMPLE: 20 divided by 34 = .59
(See figure)
Notice that the output is overdriven.
A transmission using this method must use another planetary gear set to reduce the output. The Mercedes W3A-040 is a good example of this
To get more than one gear forward and a reverse, requires multiple, or compound planetary gear sets.
Two of the most common of these are the SIMPSON GEAR SET, used in transmissions like the THM 350, the Ford C-4, and the TF 6 & 8, and the RAVIGNEAUX GEAR SET, found in transmissions such as the FMX, the AOD, and the T-35.
Figuring out all the ratios for these transmissions is a little tricky, so I'll give you the formulas, and let you figure out how these formulas were derived.
THE SIMPSON GEAR SET:
For this example I'll use a THM 200, which has 74 TEETH ON THE FRONT RING GEAR, 42 TEETH ON THE FRONT SUN GEAR, 30 TEETH ON THE REAR SUN GEAR, AND 62 TEETH ON THE REAR RING GEAR.
The formula for 1ST GEAR is: rear ring divided by rear Sun x front Sun plus front Sun + front ring divided by front ring.
EXAMPLE: On the THM 200, it would be:
62 divided by 30 x 42 + 42 + 74 divided by 74 = 2.74:1
SECOND GEAR is easy: Front Sun + front ring divided by front ring.
EXAMPLE: 42 + 74 divided by 74 = 1.57:1
THIRD GEAR is Direct Drive, or 1:1
REVERSE is rear ring divided by rear Sun
EXAMPLE: 62 divided by 30 = 2.06
THM 440-T4 (BACKWARDS SIMPSON):
The THM 440 T4 is sort of a backwards version of a Simpson gear set, and although it looks complicated, it really is very simple.
The front Sun gear has 26 teeth, while the rear Sun gear has 42. The front ring gear has 62 teeth, but keep in mind that it is part of the rear carrier, just as the rear ring gear is part of the front carrier, with a tooth count of 74.
As I said earlier, the THM 440 T4 is sort of a backwards version of a Simpson gear set, so in figuring the ratio for 1ST GEAR -- it is identical, except you substitute the words "front" and "rear" in the appropriate places. Front ring divided by front sun x rear Sun + rear Sun + rear ring divided by rear ring = Ratio
EXAMPLE: 62 divided by 26 x 42 + 42 + 74 divided by 74 = 2.92:1
2ND GEAR: Rear Sun + rear ring divided by rear ring
Example: 42 + 74 divided by 74 = 1.57:1
3RD GEAR: Direct Drive, or 1:1
4TH GEAR: Front ring divided by (front Sun + front ring = Ratio
EXAMPLE: 62 divided by (26 + 62) = .74:1
RAVIGNEAUX GEAR SET:
This is considered a compound gear set, and for this example I'll use an AOD, which has:
36 teeth on the front Sun gear
30 teeth on the rear Sun gear, and
72 teeth on the ring gear
The formula for first gear is: Ring gear divided by rear Sun gear = Ratio
EXAMPLE: 72 divided by 30 = 2.4:1
SECOND GEAR formula is: Rear Sun + front Sun divided by rear Sun x Ring divided by (Ring + front Sun)
EXAMPLE: (30 + 36) divided by 30 x 72 divided by (72 + 36) = Ratio 66 divided by 30 x 72 divided by 108 = 1.47
THIRD GEAR is Direct, or 1:1
FOURTH GEAR is: Ring gear divided by (ring gear + front Sun gear) = Ratio
EXAMPLE: 72 divided by (72 + 36) = .67:1
REVERSE on a Ford AOD is: Ring gear divided by front Sun gear.
EXAMPLE: 72 divided by 36 = 2:1

[Rogue]

SHIFT SPEED AND PRESSURE
To figure the area of a circle (valve or servo):
Radius (which is 1/2 the diameter) x Radius x 3.14159 = Area
EXAMPLE: A 1" diameter circle has a radius of 0.5"
0.5 x 0.5 x 3.14159 = 0.785
Therefore a 1" diameter circle has an Area of 0.785 sq. inches
Pressure x Area = Force
EXAMPLE: 100 psi line pressure, on a servo with an area of 2 square inches = force
So, 100 psi line pressure x 2 sq in = 200 pounds of force.
Force divided by Area = Pressure
EXAMPLE: 200 lbs divided by 2" = 100 psi
Force divided by Pressure = Area
EXAMPLE: 200 lbs divided by 100 psi = 2 inches
THINGS WE CAN DO WITH THESE FORMULAS:
EXAMPLE: A 700 R4 has 62 psi of line pressure at Idle.
The PR spring weighs 6.5 lbs
The tip (reaction end) of the PR valve has a diameter of 0.365" (0.365 divided by 2 = 0.1825 radius) 0.1825 x 0.1825 x 3.14159 = 0.1046" area
We want 75 psi of line pressure at Idle
First, let's see if those numbers add up, using: Pressure x Area = Force
62 psi x 0.1046 = 6.48, or 6 1/2 lb PR Spring
We want 75 psi:
Pressure x Area = Force (Spring) 75 psi x 0.1046 = 7.85 lb spring
What if we put in an 8 lb Spring? Force divided by Area = Pressure
8 lbs divided by 0.1046 = 76.48 or 76 1/2 line pressure
Now, let's look at RATIO.
Ratio is the relationship in quantity, amount or size, between two or more things.
In our example ratio is: How many psi each pound of spring will add.
Pressure divided by Force = Ratio
EXAMPLE: 62 psi divided by 6.5 lbs = 9.5 ratio Each pound of spring will increase pressure 9.5 psi
Force x Ratio = Pressure
EXAMPLE: 6.5 lbs x 9.5 = 61.75 or 62 psi
(Let's add 1 lb of spring, and see if we get 9.5 more psi.)
Force x Ratio = Pressure
EXAMPLE: 7.5 lbs x 9.5 = 71.25
New pressure Old pressure = Pressure difference
71.25 minus 61.75 = 9.5 psi change (by adding 1 lb of spring)
Once you know the ratio, a lot can be determined. Pressure divided by Ratio = Force
62 psi (actually 61.75) divided by 9.5 = 6.5 lb spring

[Rogue]

The ratio never changes. This means that if I know that line pressure is 55 psi at idle, in a 700 R4, the the PR spring must be 5.78 lbs.
Pressure divided by Ratio = Force
So, 55 psi divided by 9.5 = 5.78 lbs.
Now, let's look at a math formula for shift speeds.
Suppose we had shift speeds of 15 mph and 20 mph, for the 1-2 & 2-3 shifts on a transmission. 20 mph may be too early for the 2-3 shift. If we adjust TV modulator, we will move both shifts. We don't want to do that because the 1-2 shift is fine, so let's work with just the 2-3 shift spring.
EXAMPLE: Original spring divided by Original MPH = Ratio
As, 4 lbs divided by 25mph = 0.2
Ratio x Desired MPH = New Spring
0.2 x 25 mph = 5 lb spring
A 5 lb spring will raise the shift on this transmission to 25 mph.
All you need to know is -- Where is it shifting now (at MINIMUM throttle) and what does the spring weigh.
This formula will get you very close, but may be a "tad" off, because we are not accounting for TV pressure helping the spring. This is why you want to check it at minimum throttle, so TV has the least effect.
Finally, let's look at speedometer ratios.
Suppose we put an exchange transmission in a car, and now the speedometer is off, because the speedometer drive gear has a different tooth count. What do we have to do to the driven gear to correct it?
Let's say the old drive gear had 7 teeth and the old driven gear had 21 teeth. The exchange unit had 8 teeth on the drive gear.
Old Drive Gear divided by the New Drive Gear = Ratio
7 teeth divided by 8 teeth = 0.875
Old Driven Gear divided by Ratio = New Driven Gear
21 teeth divided by 0.875 = 24 teeth
A 24 tooth driven gear will correct the speedometer error.
Let's do one more speedometer change. This time the old drive is 9, and the new drive is 10. The old driven gear is still 21.
Old Drive Gear divided by New Drive Gear = Ratio
9 tooth divided by 10 tooth = 0.9
Old Driven Gear divided by Ratio = New Driven Gear
21 tooth divided by 0.9 = 23.33 teeth
We can't get a 23.3 tooth count so we round it off to 23 teeth. Now the speedometer will be close, but not exact, because we had to round off the number.

[Rogue]

To test the stall on your current torque converter: With the engine running and the brake pedal held firmly with your left foot put the selector in drive and depress the accelerator fully to the floor with your right foot for two to three seconds. Your stall speed will be the maximum RPM shown on the tach.

[BlackBart]

Hey, Rogue, Thanks for the data and info, I hadnt quite figured out how to calculate planet gear ratios. This is some cool stuff... Why cant they teach this kind of stuff in high school math classes? I might have actually paid attention.