Axle Ratios and Valve Bodies?

[A. G. Olphart]

What differences may be found in valve bodies with a given trans ID (AA, CQ, KC etc.)?
Are VB's matched to axle ratio?
If so, what changes from a vehicle with a performance (3.42/ 3.73) axle ratio to a car with a ratio in the 2.75-3.05 range? (bogus? ratios used for example only)

Thanks... I get curious

 

[Alky V6]

Valve bodies, separator plates, band servo sizes, accumulator spring rates, pressure regulator spring rates, pressure regulator boost valve sizes, governor weights and springs, and in some model transmissions the clutch pack capacities (number of clutch plates) are matched to the car's engine torque curve, rear axle ratio, and tire size to arrive at the proper shift points and shift feel for that particular car model.

All these items are considered a package to arrive at the desired shift pattern/feel for the car.

I think I covered all the variables involved.

 

[bison]

What differences may be found in valve bodies with a given trans ID (AA, CQ, KC etc.)?
Are VB's matched to axle ratio?
If so, what changes from a vehicle with a performance (3.42/ 3.73) axle ratio to a car with a ratio in the 2.75-3.05 range? (bogus? ratios used for example only)

Thanks... I get curious

There are a lot of factors involved as Don stated. The shift springs, pressures, valve sizes, and governor calibration all have a huge effect on the shift timing. Its not just the axle ratio that is taken into consideration. Light throttle shift timing, kick downs, and WOT shift timing are all considered when the engineers designed the transmission. There has been a lot of discussion on the use of alternate vb's in TR's as a means of retaining or improving driveability and extending the WOT shift points and what it takes to get there.

 

[Alky V6]

I didn't even want to get into the different valve sizes and spring rates in the different valve bodies. It can turn into a real mess matching a different VB to a TR.

 

[bison]

I didn't even want to get into the different valve sizes and spring rates in the different valve bodies. It can turn into a real mess matching a different VB to a TR.

It sure can be. But when i find something that works i post it so other can benefit. The KC vb/BR or KZ governor combo works great for a low 10 second TR that revs to 5900.

 

[Alky V6]

It sure can be. But when i find something that works i post it so other can benefit. The KC vb/BR or KZ governor combo works great for a low 10 second TR that revs to 5900.

Bison. You should start a thread where VB/governor combinations can be listed. That would make a great reference.

 

[chris718]

Here is something that may extend ones perception of the combination.Lets say that we have an original BRF valve body and governor in your car with the original 3.42 axle ratio.Lets say the 1/2 upshift happens at 10 mphour and 2000 rpms with minimum throttle applied.Now you install a 3.08 ring and pinion .Now the 1/2 upshift happens at 18 mphour and 2000 rpms with minimum throttle applied.The reason for this is that the ROAD SPEED in mphour (not engine rpm)required for the 3.42 axle ratio to spin the governor fast enough to generate enough upshift oil pressure to cause a 1/2 upshift is a LOWER ROAD SPEED in mphour than what is required for the 3.08 axle ratio to spin the governor fast enough to generate enough upshift oil pressure to cause a 1/2 upshift.Anyone find this useful?

 

[bison]

Here is something that may extend ones perception of the combination.Lets say that we have an original BRF valve body and governor in your car with the original 3.42 axle ratio.Lets say the 1/2 upshift happens at 10 mphour and 2000 rpms with minimum throttle applied.Now you install a 3.08 ring and pinion .Now the 1/2 upshift happens at 18 mphour and 2000 rpms with minimum throttle applied.The reason for this is that the ROAD SPEED in mphour (not engine rpm)required for the 3.42 axle ratio to spin the governor fast enough to generate enough upshift oil pressure to cause a 1/2 upshift is a LOWER ROAD SPEED in mphour than what is required for the 3.08 axle ratio to spin the governor fast enough to generate enough upshift oil pressure to cause a 1/2 upshift.Anyone find this useful?

Chris, i wonder if its actually 100% linear for the same throttle position? Seems like it should be based on the % of change of rear gear. So about 11% in that instance (3.42 to 3.08). Probably not very noticeable on the 1-2. 2-3 and 3-4 would be more noticeable since the road speed would be higher for a given driveshaft rpm. Another thing to keep in mind is that going taller will load the engine a little more and can change the converter slip a little even at lower speeds. This would make it shift a little later engine speed wise. Some of hte calbrations the engineers came up with do baffle me a little. Like the light throttle 3-4 with a BR calibration. Its much later than most others.

 

[bison]

Bison. You should start a thread where VB/governor combinations can be listed. That would make a great reference.

I will when i get enough feedback on several different combos. We have the KC vb/BR gov combo nailed down pretty good. But i dont have any feedback with that combo and a less efficient converter. 10% more slip at a given road speed means a lot when trying to spec a combo for a car. For a situation where the owner had a 10% more slip at a given shift road speed id spec a CZ vb/governor. With 14% slip it would probably act like the KC with 4% at WOT. Though they would more than likely be faster with a KC and a better converter. Some cant find it in their budget to spend $950+ on a good converter. 10 years ago this didnt mean much but now since we are making a lot more power and blowing through converters so easily it all has to be considered.

 

[A. G. Olphart]

Don- The Chrysler 727s of years gone by varied clutch disc count with engine power, but with the 200-4R don't only the builders do that?
I was hoping that an AA valve body was an AA and a CZ was a CZ regardless of build year.

Bison- CK's book explained the governor part to me:wink: . As to the various springs in the VB itself: I've no idea where to buy that sort of calibration spring even if I knew enough to play with them. That's a black art, and as a onesy twosey tranny guy... I'll buy CK's shift kits.

Chris- Increased road speed before shifts makes sense with a higher (lower numerical) diff ratio, but that would hold true only if the driven (by the output shaft) half of the speedo/governor driving gear isn't changed. Is that half of the speedo/governor driving gear the same for all colors? If it is, might it be varied for effect?

Bison- Slip percentages are far beyond where I'll get with my toys, but thanks, especially for the combinations that work.

Thanks to all!

 

[Alky V6]

Don- The Chrysler 727s of years gone by varied clutch disc count with engine power, but with the 200-4R don't only the builders do that?

I just included that variable to illustrate the extremes that the OE will go to, to get the desired shift feel. It also saves money for the OE to use a smaller pack if they can get away with it.

Other transmissions that use different plate counts per application,
TH350
TH400
TH200C
C6
C4
TF6
TF8
AOD
E4OD
700R-4
A500
A518 and later family
And many, many others.

 

[bison]

Don- The Chrysler 727s of years gone by varied clutch disc count with engine power, but with the 200-4R don't only the builders do that?
I was hoping that an AA valve body was an AA and a CZ was a CZ regardless of build year.

Bison- CK's book explained the governor part to me:wink: . As to the various springs in the VB itself: I've no idea where to buy that sort of calibration spring even if I knew enough to play with them. That's a black art, and as a onesy twosey tranny guy... I'll buy CK's shift kits.

Chris- Increased road speed before shifts makes sense with a higher (lower numerical) diff ratio, but that would hold true only if the driven (by the output shaft) half of the speedo/governor driving gear isn't changed. Is that half of the speedo/governor driving gear the same for all colors? If it is, might it be varied for effect?

Bison- Slip percentages are far beyond where I'll get with my toys, but thanks, especially for the combinations that work.

Thanks to all!

They vary over the years. CZ, CZ2, CZ3, etc. The higher the number the later the vb. There are slight differences between them and the seperator plates may vary. Not enough difference in driveability for most to notice.

The governor is driven by the output shaft and all have the same tooth count on the driven part of the gear that rides on the output shaft (which all have the same tooth count also) . So the color or speedo part of it has no effect at all on shift points.

Slip % is very important when selecting a vb. Its linear as far as driveshaft speed increase and earlier shifts for a more efficient converter.

 

[bison]

Don- The Chrysler 727s of years gone by varied clutch disc count with engine power, but with the 200-4R don't only the builders do that?
I was hoping that an AA valve body was an AA and a CZ was a CZ regardless of build year.

Bison- CK's book explained the governor part to me:wink: . As to the various springs in the VB itself: I've no idea where to buy that sort of calibration spring even if I knew enough to play with them. That's a black art, and as a onesy twosey tranny guy... I'll buy CK's shift kits.

Chris- Increased road speed before shifts makes sense with a higher (lower numerical) diff ratio, but that would hold true only if the driven (by the output shaft) half of the speedo/governor driving gear isn't changed. Is that half of the speedo/governor driving gear the same for all colors? If it is, might it be varied for effect?

Bison- Slip percentages are far beyond where I'll get with my toys, but thanks, especially for the combinations that work.

Thanks to all!

They vary over the years. CZ, CZ2, CZ3, etc. The higher the number the later the vb. There are slight differences between them and the seperator plates may vary. Not enough difference in driveability for most to notice.

The governor is driven by the output shaft and all have the same tooth count on the driven part of the gear that rides on the output shaft (which all have the same tooth count also) . So the color or speedo part of it has no effect at all on shift points.

Slip % is very important when selecting a vb that will be used ofr WOT auto shifting . Shift rpm linear as far as driveshaft speed increase and earlier shifts for a more efficient converter.