Cummins development progresses

[JoshH]

I know the DODGE 4 speed trans is actually a fairly wierd control pattern as it uses an electrocic governor control to shift. Basically they took the old fashioned governor assembly off the rear and put in an electronic control for it to make it shift. It is a wierd control system by all acounts as the pressure control actually controls the shifts and not line pressure per say so much.

Yep, all shifts, with the exception of overdrive, are controlled with governor pressure. There is a shift solenoid for overdrive, and there is also the converter lockup solenoid.

[THEFERMANATOR]

Yep, all shifts, with the exception of overdrive, are controlled with governor pressure. There is a shift solenoid for overdrive, and there is also the converter lockup solenoid.

I remember having a hard time wrapping my head around this idea when I first heard about when I was working for DODGE. It made no sense to me to do it this way when a shift solonoid is so much more precise and controllable.

[L31Sleeper]

Nick, one of the Dodge experts might correct me on this, but the 4-speed 48RE doesn't have much in the way of electronic control, from what I can see on the wiring diagrams you only have, Pressure solenoid, 3-4 Solenoid & TCC, nothing like the Allison (or GM's 4 speed transmissions). Those 48RE solenoids are controlled from the ECM
The 6.7L went to a more complex full separate ECM & TCM system with the 6-speed 68RFE.

Yep, all shifts, with the exception of overdrive, are controlled with governor pressure. There is a shift solenoid for overdrive, and there is also the converter lockup solenoid.

So if the pressure solenoid controls the governor pressure and the governor pressure controls shifts then the PCM can control shifts.

[GMPX]

So shift points (as in MPH) via pressure control? What about shift firmness?

[L31Sleeper]

Pressure controls both in a Turbo 350 transmission right ?

Seems like a LAZY way of adding computer controls.

[2007 5.9]

Lazy but cost effective.

Most VB guys can tailor shift firmness and points based upon your requirements.
To me I'd rather have hard parts fail then chasing electrical gremlins.

[THEFERMANATOR]

So shift points (as in MPH) via pressure control? What about shift firmness?

In the 47Re it was done via the throttle pressure cable, on the 48RE it is done via a force motor that is mounted externally of the trans.

[JoshH]

The shifts are also controlled by the throttle valve. I totally forgot that the newer trucks have an electronic motor that controls it (I think it's called a TTVA?). The older trucks use a cable. I can never remember what year they switched.

Really, the shifts are controlled by both throttle valve and governor pressure. Governor pressure has to overcome throttle valve pressure to move the shift valves. Higher throttle valve pressure will generally create later and firmer shifts.

[joecar]

So if the pressure solenoid controls the governor pressure and the governor pressure controls shifts then the PCM can control shifts.

So shift points (as in MPH) via pressure control? What about shift firmness?

Generically (most transmissions):
- pump fluid is regulated into line pressure (by the pressure solenoid in this case),
- line pressure feeds the governor,
- the governor regulates line pressure into governor pressure according to how fast the governor is spinning (spring loaded weights flying outward)...

i.e. governor pressure is "vehicle speed signal" pressure...

i.e. line pressure does not control governor pressure, but rather it simply provides fluid pressure which the governor regulates into the vehicle speed signal pressure...

i.e. shift firmness is still controlled by line pressure, but the side effect is that with higher line pressure, governor pressure will be higher, so the upshifts will come sooner, it will hold higher gears longer, and it downshifts later... however most governors are designed to have a reduced sensitivity to line pressure being high or fluctuating by having cleverly calculated areas on both sides of the governor valves that line pressure acts on so that governor pressure relies mainly on how far the spring loaded weights move... i.e. if line pressure is high, the valves do not move as easily.

So the PCM is not controlling the VSS-vs-TP shift schedule.

Then, at each shift valve, governor pressure opposes throttle pressure (they act in opposite directions on the shift valve)...
if governor pressure wins, then the shift valve moves to the upshift position,
if throttle pressure wins, then the shift valve moves to the downshift position.

Throttle pressure is also used to assist line pressure to increase shift firmness at high engine torque (by having cleverly calculated areas on the line pressure regulator valve).

[Blacky]

Joe, you've got to get out more
Paul