Explain to me how the 47re shifts

[Me78569]

Alright,

 

I am trying to work through an idea of mine in regards to lockup.  What I am trying to do is figure out how to predict the 1-2 shift and predict the 2-3 shift.  So the question I have is what happens to make the VB decide, Time to shift into 2nd. and what happens in the vb to shift from 2-3.  

 

Is it a pressure difference between the tv and vb pressure?  I don't really understand what happens in the rats nest of a VB.  

 

So is there something I can watch VIA a pressure switch or whatever to show that the trans is going to shift?  Can someone smarter than me explain the magic of how a 47re shifts in low gears?  

Reason I am thinking of this is the advent of the Firepunk anteater tranny controller.

 

How is it that they can control all shifting 1-4 without needing a special VB?   http://www.firepunk.com/anteater/

[CTcummins24V]

ohh this good. Does fluid coupling and stall speed of the converter play a role too? My low stall shifts way too soon if if this controller can hang the gears a little longer this would be great!

[Me78569]

The anteater looks like a great product. 

 

My thought process is small at this point, I only want to disable lockup for the 2-3 shift automatically.

[Dynamic]

You basically have two different pressures at work in the VB when determining upshift and downshift points.

First, there is governor pressure, which is determined by road speed. Early transmissions (46RH, 47RH) used a mechanical governor on the output shaft, and the newer RE transmissions replaced the mechanical governor with the governor pressure solenoid/transducer setup that we all know and love. The PCM generates the governor pressure electrically via the solenoid, and monitors the governor pressure via the transducer. Either way, the faster you are driving, the more governor pressure...

Second, you have throttle valve, or TV pressure. This pressure is determined by throttle position. When you press on the throttle, the TV cable pulls on the lever at the transmission, which rotates the TV lever shaft, which then presses on the end of the TV plunger in the VB. The plunger then loads the TV pressure regulator spring more heavily which, in turn, increases TV pressure; the more throttle, the more TV pressure...

There are two shift valves in the VB that use governor and TV pressure to determine shift points; the 1-2, and the 2-3 shift valves. (The 3-4 shift valve and TCC lockup valve are controlled separately by the PCM via solenoids and do not use governor or TV pressure to determine their shift points.) At each shift valve, governor pressure acts on one end of the valve, constantly trying to stroke the valve to the "upshifted" position. At the other end, there is a spring holding the valve in the "downshifted" position. In addition to the spring, TV pressure also acts on that same end of the valve, assisting the spring in holding the valve in the "downshifted" position.

When you are at a standstill, governor pressure is at a minimum (basically zero psi) and the shift springs hold their valves in the "downshifted" position - first gear. As you take off from a stop, governor pressure begins to rise, acting on the end of the shift valves. If you are light on the throttle, TV pressure is very low and governor pressure quickly rises to the point that the force of the 1-2 shift spring at the other end of the valve is overcome and the 1-2 shift valve strokes, commanding a 1-2 upshift. The transmission is now in 2nd gear...

If you are heavier into the throttle, TV pressure assists the spring with greater force, making it necessary for governor pressure to build to a higher level before the force of the spring AND the hydraulic force of the TV pressure acting on the end of the valve to be overcome. This is how the transmission holds each gear for longer when you are heavier into the throttle.

As you continue to accelerate, governor pressure continues to rise until the 2-3 spring force (and whatever level of TV pressure that is acting on the 2-3 shift valve) is overcome and the 2-3 shift valve strokes, commanding a 2-3 upshift - 3rd gear...

When commanding a downshift, you press on the throttle harder and TV pressure rises. When TV pressure rises to the point that (with the spring's help) governor pressure can be overcome, the valve will stroke back to the "downshifted" position and either a 3-2 or 2-1 downshift is commanded, depending upon which gear you were in. If the throttle application is abrupt enough, and TV pressure rises quickly enough, both valves will be stroked to the "downshifted" position nearly simultaneously, and a 3-1 downshift will occur.

This is kind of a simplified explanation of what goes on in the Dodge valve body for 1st - 3rd gear. As I stated earlier, 4th gear (OverDrive) and TCC are controlled directly by the PCM via their respective solenoids.

[JOHNFAK]

Best explanation I've heard ^^^^^ 

thankyou sir 

[Me78569]

That's why we have been trying to bribe him to come over to the good side.

 

Dynamic,

 

So in theory you could control the shifting using the governor solenoid to increase / decrease pressure one way or another at a given speed and TPS input?  I am assuming that is how the anteater controller from Firepunk works?

 

So then does governor pressure increase all the way from 1-3 shifts?  I am assuming pressure does not drop when the trans shifts?   

 

 

I am going to read your post a few more times to ensure I am reading everything correctly.

 

Another question for you.  Is there a test port in the trans that I can watch for pressure at for the 2-3 shift and log shift points at given speed and TPS values?  

[Dynamic]

12 hours ago, Me78569 said:

So in theory you could control the shifting using the governor solenoid to increase / decrease pressure one way or another at a given speed and TPS input?  I am assuming that is how the anteater controller from Firepunk works?

Yes, you could do that. In fact, if you were to graph the governor pressure curve (ie. governor pressure psi vs. road speed) of some of the newer trucks, particularly the newer TTVA controlled 48RE's, you would find that the curve is more "stair-stepped" than linear.

12 hours ago, Me78569 said:

So then does governor pressure increase all the way from 1-3 shifts?  I am assuming pressure does not drop when the trans shifts?   

The valve body cannot perform a direct 1-3 upshift due to the fact that there is no apply oil available at the 2-3 shift valve until the 1-2 shift is completed. In other words, 2-3 apply oil is downstream of the 1-2 shift valve. You can easily get a scenario where the shifts are stacked one on top of another (ie.very light throttle, TV cable broken or unhooked, etc.), but the second shift is dependent upon the first one.

Going the other direction (downshifting), all the transmission is doing is releasing elements, so that can happen independent of one another.

12 hours ago, Me78569 said:

Another question for you.  Is there a test port in the trans that I can watch for pressure at for the 2-3 shift and log shift points at given speed and TPS values?  

There is no test port that directly reads 2-3 oil. You could add a port to the intermediate servo area, I suppose. Or you could just watch main line pressure for the pressure fluctuation when the 2-3 shift is commanded. There will be slight drop in line pressure as the intermediate servo and direct clutch piston stroke, followed by restoration of full line pressure when they're fully released/applied...

The description I gave above is very simplified, rudimentary explanation of what takes place hydraulically to determine shift points. There are several other things that are at work to smooth things out. Things such as once an upshift has taken place, it now will require a greater amount of TV pressure to command a downshift than was overcome to allow the upshift. In other words, once a shift valve has stroked to the "upshifted" position, it is held in place hydraulically so that it doesn't simply shuttle back and forth between the "upshifted" and "downshifted" positions with the slightest pressure variations. Try this: take off in your truck with light throttle and wait for the 2-3 shift. Once you feel the 2-3 shift, squeeze into the throttle a small amount. Unless you gave it too much throttle for our little object lesson, it stays in 3nd gear, right? Why didn't it immediately downshift back to 2nd? I mean, TV pressure increased, didn't it? Yes, it did, but the 2-3 shift valve is being held in the "upshifted" position by a hydraulic signal that will require a bit more TV pressure to overcome to push it back to the "downshifted" position.

There are also other things that come into play such as what happens hydraulically in manual 1st and manual 2nd to hold the shift valves and prevent upshifts altogether, what happens when OD is engaged to prevent any downshifts at the 1-2 or 2-3 shift valves, TCC lockup signals, etc. It is a fairly hydraulically complex environment, but none of it is magic or voodoo...!

Here is a photo of the 1-2 and 2-3 shift valves, their governor pressure plugs (the mushroom shaped things on the right), and shift springs out of a 47RE. The 1-2 is on the top, and the 2-3 on the bottom. Their is one additional piece that is not shown, and that is the 2-3 TV plug, which is in the part-throttle body that bolts to the side of the main upper valve body. It's function is a whole separate discussion...

[Russ Roth]

Jon, I swear I am going to have to start calling you Tony.      This kind of stuff is exactly what he would say on numerous occasions and at times would even trace it out in the colored hydraulic section of the FSM.  Even though I understand about hydraulics due to my work, most of it was still was over my head although I did learn some.    Thanks for going above and beyond. Wish mine was still functional.

RR

[The_Hammer]

@Dynamic

Very nice explanation! 

I didn't know there were controllers for the 47RE transmission that didn't require a new valve body. Learn something new everyday. 

[Me78569]

11 hours ago, Dynamic said:

The valve body cannot perform a direct 1-3 upshift due to the fact that there is no apply oil available at the 2-3 shift valve until the 1-2 shift is completed. In other words, 2-3 apply oil is downstream of the 1-2 shift valve. You can easily get a scenario where the shifts are stacked one on top of another (ie.very light throttle, TV cable broken or unhooked, etc.), but the second shift is dependent upon the first one.

Sorry I meant, does governor pressure increase from 1sts, to 2nd, then for the 3rd shift?  governor pressure doesn't drop off or jump back to low after each shift does it?  IE: Random Numbers, 1st 1000 rpm 5psi, 2000 10psi, 3000, 15psi, 2nd shift 1000 rpm 5psi, 2000 10psi, etc etc etc

[Dynamic]

Ahhhh... I understand your question now. No, governor pressure continues to rise with road speed.

Also, FWIW, engine rpm has no bearing on either governor or TV pressure. Only road speed and throttle position, respectively.

11 hours ago, Russ Roth said:

Jon, I swear I am going to have to start calling you Tony.   

I've certainly been called worse...! I'll take a Tony Garcin reference any day! Thanks, Russ...

[Russ Roth]

2 hours ago, Dynamic said:

I've certainly been called worse...! I'll take a Tony Garcin reference any day! Thanks, Russ...

 

    

[Staying broke]

SoSo I realise that is been a while since anyone talked on this thread, but got some questions if any body is listening. 

I have the 47re in my 2000, 2500. I would really like to shift it my self. and from what I've read here it looks like if I give the right wire, varied voltage I can tell the governor how much pressure to give the valve body and make out shift.

  Just a poor kid that likes to turn wrenches and don't have much mony. 

 

[Mopar1973Man]

Dynamic is your man you might send him a quick PM and tell him of your posting here.

[Me78569]

unless you are jonesen for a project I would either go with a manual VB or the anteater setup.  I promise you it will cost less time and money in the long run haha.  

 

 

[Staying broke]

Well I hear you but i kinda like reinventing the wheel at this point thoughi think I'm just going to convert the valve body to full manual. Between me and a buddie we can't think of any reason that we can't convert the 47re valve body to full manual just as easily as converting a rh valve body. Thanks for the input though.

[donaldlrow515]

So did you ends up converting your factory valve body to a manual shift? I'm very curious how this is done a lot of point I really would like to try that. and I'm definitely the type that likes to do things on my own and figure out a way to do it. Anybody can just go buy things, but I like to know how they work oh, and add my own little spin to it.

[Cowboy]

The easy way is to buy a manual valve body kit from Transco, it’s gonna include the new valves and springs you need to both convert your trans to full manual as well as bump your pressures up to help your trans hold power.

[Dieselfuture]

On 6/6/2020 at 6:40 PM, donaldlrow515 said:

So did you ends up converting your factory valve body to a manual shift?

He converted his truck to a 4th gen instead 

[Evan]

Bumping a great read with tons of information