Questions on the 48RE & Programmers or Boxes.

[GaryCarter]

Hi all- a couple of questions about the transmission control.



Is the shifting in the 48RE all electrically controlled, or is it still basically hydro-mechanical? IIRC the 47 RE was all hydraulic except OD and TC lockup was electrical.



IF- the 48RE is electrically controlled, do any of the downloaders or boxes alter the transmission pressures or shifting characteristics?



Inquiring minds want to know. For instance I know with the 47 the throttle position cable determined pressures- thus the BD 'Pressure lock' to enhance pressures. Haven't seen this for the 48. How do they compensate for increased torque with less throttle?



TIA-

Gary

 

[ThomasLawrence]

Is the shifting in the 48RE all electrically controlled, or is it still basically hydro-mechanical?

Sorta-kinda-both. The shifts themselves are strictly hydraulic - however, the governor pressure is electronically-controlled, giving the PCM slight control over shift points. This is no different than any 4xRE, dating back to 96-97. The 48RE is essentially the same as a 47RE - just more clutches, beefier internals, maybe some slight valve body differences...



AFAIK, none of the downloaders alter the transmission behavior.

How do they compensate for increased torque with less throttle?

More clutches, with the majority of the re-work in the OD section.



-Tom

 

[lcaad1249]

I was told that the Juice Attitude changes the transmission slightly on the #2 "Towing" setting. SOTP I can notice a little difference, it seems to hold the gear longer, but that might have been all in my head.

 

[JCleary]

It sure would be nice if the shifts were electronically controlled.



I know with my BDDL you can change to one of three different shift strategies with the Ford Torqshift.



That is, as long as you can keep the motor together.

 

[GaryCarter]

Thomas, I'll have to disagree with respect to earlier models having electronically controlled governor pressures. My 2000 truck with the 47RE; that transmission used a cable from the TPS on the engine down to the transmission. This cable communicated throttle position down to the trans so increased pedal = increased pressure to the clutches.

I wonder does the 48RE have a similar function (variable clutch pressure), and if so how is it controlled. I expect it is likely all electronic since the CR is drive-by-wire.



Anyone?



Gary

 

[ThomasLawrence]

My 2000 truck with the 47RE; that transmission used a cable from the TPS on the engine down to the transmission.

That's for line pressure, not governor pressure, and exists on all transmissions up to the '05 model year, where an electronic actuator has replaced the throttle valve cable.



Governor pressure is the opposite of line pressure. With line pressure on one side of the valve, it's the governor pressure that opposes it. When line pressure overcomes governor pressure (plus the force of a mechanical spring - because since line pressure is used to develop governor pressure [they come from the same pump], it's impossible to have more governor pressure than line pressure), the valve moves, and the shift occurs.

I wonder does the 48RE have a similar function (variable clutch pressure)

The only thing that varies the amount of pressure exerted on the clutches (and servos, for that matter) is the line pressure. That's the pressure developed by the pump, and regulated by the throttle valve... it's been like that since the original 727, and it's that way on the most modern 48RE.



The governor pressure exists only within the valve body, and as I described, is used to control the action of the various valves, who's function it is to direct that line pressure to the various components, and apply clutches and bands as required.

I expect it is likely all electronic since the CR is drive-by-wire.

As I mentioned above, only the '05 and up are truly "drive-by-wire". While it's true that from '03 on up, throttle position is determined electronically with respect to engine operation and fuel delivery, it wasn't until '05 that the mechanical throttle valve cable was replaced.



-Tom

 

[GaryCarter]

Thanks for the clarification- sounds like you know your stuff!



Gary

 

[p-Bar]

The 2004. 5 trannys and beyond are engine controlled by the computer

 

[GaryCarter]

So I take it no one is (yet) making a box or programmer that increases line pressure for the electronically controlled trans?

That is what the pressure loc did for the previous trans- commanded maximum line pressure regardless of throttle position. This was to eliminate slip at lower throttle positions with a pumped up engine.



Gary

 

[p-Bar]

About all Iv'e seen are the commanders for locking the torque converter. Probably going to be a while.

 

[GaryCarter]

Well, I think I figured it out. Just got my hands on the '05 service manual this week. It describes procedures to be done after transmission repairs to let the transmission learn and adjust the shift parameters. Basically repeated accelerations at part throttle, and watching with the scan tool until reading stabilize.



This tells me the electronic 48RE has adaptive programming similar to what Ford uses on their Torqueshift transmission. It watches the trans and adjusts pressure and timing. I assume the ECM is monitoring shift times and other transmission sensor values to adjust its outputs to produce the desired shift quality. If this is true, then if the engine torque increases -from a box for instance- presumably the transmission management logic would respond by increasing line pressure.



Perhaps a trans tech will chime in here sooner or later and let us know what the scoop is.



Gary

 

[jcroman]

Well, I think I figured it out. Just got my hands on the '05 service manual this week. It describes procedures to be done after transmission repairs to let the transmission learn and adjust the shift parameters. Basically repeated accelerations at part throttle, and watching with the scan tool until reading stabilize.



This tells me the electronic 48RE has adaptive programming similar to what Ford uses on their Torqueshift transmission. It watches the trans and adjusts pressure and timing. I assume the ECM is monitoring shift times and other transmission sensor values to adjust its outputs to produce the desired shift quality. If this is true, then if the engine torque increases -from a box for instance- presumably the transmission management logic would respond by increasing line pressure.



Perhaps a trans tech will chime in here sooner or later and let us know what the scoop is.



Gary

The proceedure you are reading about pertains to the 5 speed not the 48re. the 48re has very limeted learning curve and does not change much. the only electronics for shifting gears 1-3 are the govenor. there is no way to electronicly raise the line pressures in a 48re. it is all mechanical. the throttle valve is controlled by a servo now and maybe someone could program that to raise pressure a little. but if its raised to much the truck would always hold gears to long even at light throttle. so there is really no way to get around modifing the mechanics of it. it sucks but thats the way it is until they make a 5 speed electonic shift transmission like there gassers have that can hold the torque.

Jamie