Lets talk about C6 Servos and Levers

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72HCODE

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Lets talk a little about the confusing world of the C6 transmission and what Servos and Levers mean:

I'm a transmission novice But i wanted to understand a little about why people want certain servos and levers inside their transmission.

the servo comes on at different pressures they have different piston diameters that customize how the transmission shifts gears, you can have a soft shift like in a

luxury car or a firm shift like in a race car.

the Levers multiply the force of the servo and hold the band clutch, the harder the band holds the less power slip you have.

From Softest to Most firm

CODE ON COVER, APPLY DIA, RELEASE DIA, SEAL TYPE

N 1.93 2.92 Molded piston

S 2.00 2.86 Molded piston

G 2.04 3.02 O-rings

J 2.07 2.69 O-rings

L 2.07 2.98 Molded piston

D 2.08 2.98 O-rings

P 2.10 2.86 Molded Piston

H 2.34 3.02 O-rings

R 2.48 3.50 O-rings

the levers...



A = 1.65:1

B = 1.73:1

D = 1.97:1

E = 1.85:1

H = 2.18:1

F = 2.30:1

FF = 2.82:1

Intermediate servo apply levers are identified by a large cast letter.

The ratio say an 'E' multiplies band apply force by 1.85 times.

The higher the ratio the the greater the band force(to keep it from slipping)

but the slower the actuation speed

What all this means is holding the 2nd gear Band with greater and great force which offers greater holding power, giving cleaner, firmer 1-2 and 2-3 shifts.

there is a limit as too much band force can crack or explode the side of the C6 aluminum case by the band adjuster stud and nut.

using the R code and a FF lever is not a good idea, F or H is much safer.

Now you can improve street performance by changing the Servo you have to a firmer one, a lever change requires the transmission come out of the car.

This is because the shaft for the lever has to come out from behind the torque converter along with the plug.

the servo is almost a hot swap option as you can access it on the car without taking too much apart, thus swapping to a firmer servo improves street performance.

All C6s were not the same:

Ford took advantage of the servos and levers in the C6 so when you ordered a higher HP engine you got a firmer servo and a lever that held more force.

all those Tags on the C6 transmission on the servo cover have some extra meaning as you want to try and find a transmission from a 4V verse a 2V

The big block cars had a different bolt pattern for the block, but the 302 and 351 had the same bolt pattern.

(the top 2 bolts on the trans were about 5" apart for small block. on a big block the bolt pattern is over 7" apart)

so as decode example:

PGA-AH 71 351-4v Mustang

PGA-AU 71 351CJ-4v Mustang

PGA-AU1 72 351CJ-4v Mustang

PGA-AU2 72 351CJ-4v Mustang

PGA-AV 71 351-2v Mustang

PGA-AV1 72 351-2v Mustang

PGA-AV2 73 351-2V Mustang EGR.

PJC-G 71 429 Mustang

PJC-G1 72 351-4v Mustang

in this case the PGA-AV2 Had a "N" servo and a "B" lever making it a very soft shifting transmission smooth slow shifts.

the PGA-AU2 Had a "J" servo and a "D" lever making it much have much firmer and harder shifts with more power transfer.

You can of course go nuts and build a C6 any way you want, there are tons of Aftermarket CNC machined "R" code and "RR" code servos that are even firmer then ford ever made

and "FF" levers that apply so much force you have to re-enforce the C6 case to use them.

you can also buy CNC machined Drums or certain Year C6 parts that allow more Clutches to be installed "4 verse 5" as well as planetary Gears from heavy trucks that have 4 gears instead of 3, which are

stronger and alter the final drive ratio to be lower. there are also after market gears with 5 gears that are even lower ratio and offer a low friction alternative.

you could spend 1000$+ of dollars in a C6 just trying to build the most insane one on the planet.

Anyway as a novice i found the whole thing interesting and answered some of my questions on why people wanted certain C6 parts.

since I'm a novice I'm sure I have missed something feel free to chime in and offer corrections or additional information.

For me I'm working on rebuilding a C6 transmission and I happen to have one transmission with damaged case and bad internals but with a better lever and servo combo, and another trans in good shape but with soft servo and lever combination.

So i plan to transfer the parts from one to the other and make a better overall C6.

Thanks for reading :D

 
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Great post, very informative.

I can attest to how hard a C6 can shift. I have to be careful to not over-apply the throttle when going around a corner and shifting from 1st to 2nd (the Detroit Locker doesn't help).

 

barnett468

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you want an r servo for most performance builds



Great post, very informative.

I can attest to how hard a C6 can shift. I have to be careful to not over-apply the throttle when going around a corner and shifting from 1st to 2nd (the Detroit Locker doesn't help).
a c4 can shift so hard it can almost break the mounts on a trans or engine . . any trans can be made to shift excessively hard.

 
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barnett468

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So how does a shift kit fit into all of this? Does it just apply more hydraulic pressure to these levers and in turn the bands?

the shift kit delays the shift so it shifts at a later rpm plus it increases the speed of the shift which is one of the things that makes it shift firmer.

the kit can provide a soft shift at lower speed so ones coffee doesnt spill but the faster you accelerate, the firmer it shifts . . this is how i prefer them.

one thing it does not do is change the distance from 1st to 2nd at low speed. . in other words, it will still almost immediately shift from 1st to 2nd at low speed . . this is especially prevelant on the c4 trannies and very annoyoing, lol.



I put a Sonnax "R" code servo in mine and I like it.
the r servo applies a lot of pressure to the band but its claim to fame is that it releases quickly which greatly reduces that annoying slow shift or spin up/flare feeling from 2nd to 3rd.

i think sonnax changed the ratios a bit so im not sure what they did but if the ratios of any servo are changed, it is no longer that particular servo and it then becomes a custom servo.

.

 
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72HCODE

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"the r servo applies a lot of pressure to the band but its claim to fame is that it releases quickly"

what i learned was this has more to do with the lever arm choice.

the lever applies more force but the rate of engagement is slower. so you can take a lower applied force arm combined with a R servo and reap the benefit of it engaging faster on the 2nd gear band. you can see you have a huge amount of adjustment possible, plus there are also different clutch materials that have more or less grab for the band. there are also older drums that are deeper and you can pack 5 clutch bands inside instead of 4 for even more engagement. pretty crazy world in the automatics.

 

barnett468

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pretty crazy world in the automatics.
yes it is, therefore, i am smart enough to take mine to my tranny guy and just have him fix them, lol.

 
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the r servo applies a lot of pressure to the band but its claim to fame is that it releases quickly which greatly reduces that annoying slow shift or spin up/flare feeling from 2nd to 3rd.
That's the main reason I did it... This C6 had a nice 1-2 shift, with a 2-3 flair under less than hard throttle. Now it bangs 2nd, and has a nice solid/firm 2-3. (I also put a B&M transpack in the valve body at "stage 2." )

 
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barnett468

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the r servo applies a lot of pressure to the band but its claim to fame is that it releases quickly which greatly reduces that annoying slow shift or spin up/flare feeling from 2nd to 3rd.
That's the main reason I did it... This C6 had a nice 1-2 shift, with a 2-3 flair under less than hard throttle. Now it bangs 2nd, and has a nice solid/firm 2-3. (I also put a B&M transpack in the valve body at "stage 2." )
did you do the valve body at the same time you installed the r servo?

shift kits and performance valve bodies can reduce 2 - 3 flare also.

 
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Yeah I did. But the trans already had a "shift kit" in it. I did the transpack mainly for manual control, so I could put it into first gear at more than 10-15 mph. 4V cleve gotta rev, ya know. :D

 
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barnett468

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Yeah I did. But the trans already had a "shift kit" in it. I did the transpack mainly for manual control, so I could put it into first gear at more than 10-15 mph. 4V cleve gotta rev, ya know. :D
ok, thanks . . i was just trying to determine if in your particular case it definitely was the servo alone that reduced flare which sounds like part of the reduction in flare could have come from the addition of the new parts.

do you know what lever you had?

did you have to modify your trans case for the new servo?

whose servo did you use?

thanks

 

72HCODE

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better then a shift kit is a manual valve body replacement but those are going to cost you big bucks.

The C6 manual valve body is harder to find usually you see C4 versions.

last i checked a shift kit was around 60$ and the manual valve body replacement was around 350-400$ the problem is also finding a valve body that fits your C6 ford changed the machining of the C6 and moved a part from the Case to the valve body (i forgot what it was called)

most valve body replacements only fit late very late 70s-80-90s C6 leaving out the early 68-75 transmissions.

manual valve bodies basically turn your automatic C6 in a Manual C6 transmission you have to make all the shifts yourself.

there are also different stage shift kits, usually everyone gets a stage one kit, which is springs and seals, there are stage 2 and 3 kits with machined piston changes that give you more performance, you go too crazy and you could snap your neck doing gear changes :).

the cool thing about swapping the servo is you can make an improvement without worrying about the lever inside. usually you have a N servo so swapping to a R servo improves the firmness of the shift anyway. you many not have the best transmission in the world but you improved it as far as performance of shifts. if you want to go more or have a choice of levers then you go for the change with the lever since the trans will be apart anyway.

 
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