Anyone ever come up with a manual shift mode?

crd260 · **Joined:** Mon Oct 29, 2012 2:28 pm **Posts:** 103

06' crd.
GDE hot
euro TC
aftermarket fan clutch.

When towing through the cascade mountains, I find the doo doo points are terrible.

Ideally, it would be nice to be at like 80% throttle and like 2,800 - 3,300 RPMS or so on some of those long, steep climbs.

problem is:

80% throttle makes it upshift, which bring the rpms down bellow 1,800 which causes you to lose speed, and foot to the floor causes it to downshift which brings your rpms too close to redline, which runs the motor too hard and too hot. I've tried the gear shifter (2) but it still doesn't solve the problem.

This inability to select the desired gear is having a huge negative effect on towing performance on big climbs.

I know with the Chrysler intrepid, you could swap out TCU's from one model to another, and add paddle-sifters. After the mod was done, you could select whatever gear you wanted and have the vehicle hold that gear.

Has anyone ever done something similar to this? Are there any other 545RFE vehicles out there with any kind of manual shift mode that we could borrow parts from? a 3rd party TCU? something like a megasquirt/megashift?

gmctd · **Posted:** Sun Nov 23, 2014 1:24 pm

Was a company PCS Powertrain Control Solutions had a manual\auto TCU and paddle-shifter called Shrifter available for all oem's auto transmissions - do a search and see if they're still around

I have seen several companies offering similar, but didn't register them because I got the $980 PCS models for the GM 4L80E and the big 6-spd version of the 545RFE in the Dodge Cummins Rams (BTW, your 545RFE 5-spd is actually a 6-spd, where 2nd (3rd?) spd is one ratio upshifting, a different ratio downshifting :seuss:

)

All their TCU's are identical, with a downloaded apgm and wiring harness specific to each oem hardware

crd260 · **Joined:** Mon Oct 29, 2012 2:28 pm **Posts:** 103

Did some looking, the same year WK's (grand cherekee's) had autostick available with the 545.

So I guess the way forward would be to look at the wiring harness pinouts of both vehicles, and seeing if our TCU's are capable of accepting autostick inputs, and if that doesn't work, physically swapping TCU's .

anyone every go down this road?

gmctd · **Posted:** Sun Nov 23, 2014 1:35 pm

Most GC's had the NGC New Generation Computer powertrain management computers, with TCM integrated onto ECM printed circuit assembly for the smaller transmissions - later and current versions got the 5.7L Hemi which required the 545RFE early-on, but switched to the newer (dayum!!!!! done fergot the terminology! AISIN??? NAG???) 5-and-6-spd transmissions

Possibility the early 5.7L Hemi version with 545RFE got the PCM with separate TCM, but dunno about the AUTOSTICK option, which had a shifter on the CAN communication bus for the integral PCM\TCM module................

Dennis MacGyver · **Posted:** Sun Nov 23, 2014 1:40 pm

Would be nice on the shift console if there was a position "3" in addition to the D, 2, 1.
Dropping the rig out of OD in 5th, it would be nice if it simply downshifted to 4th instead of going into 3rd.

gmctd · **Posted:** Sun Nov 23, 2014 1:45 pm

IIRC, GDE did offer a TCM with towing tune - check it out...........................

flash7210 · **Posted:** Sun Nov 23, 2014 1:59 pm

If you want to be towing uphill with engine at about 3000 rpm, you need to turn over-drive OFF.

papaindigo · **Posted:** Sun Nov 23, 2014 2:16 pm

Or you could look into one of GDE's tow tunes for the TCM

crd260 · **Joined:** Mon Oct 29, 2012 2:28 pm **Posts:** 103

apparently this subject's been around for a while (been reading through old posts)

here's a thought.

I *believe* this is how our system works, if I'm wrong, someone chime in.

There is a TPS signal coming from the accelerator (For arguments sake, let's call it 0-5 volts)

That signal runs to the ECU, which controls fueling (more throttle = more fuel)

That signal also runs to the TCU, which controls shifting (more throttle = lower gear)

I'm thinking of a simple electronic circuit you could use to fool the TCU:

the circuit starts with a 3 pin, 2 way switch. When the switch is in the "normal" position, that 0-5 volt TPS signal goes to the TCU as normal.

But when the switch is in the "other" position, you can use a potentiamteter to "trick" the TCU into thinking your "flooring it" when your really not.

55 MPH on the floor would be... what..... 3rd gear? 4th gear?

if this idea holds water, you would be able to force 3rd/4th gear, and have your throttle at less than 100%.

basically giving a separate TPS signal to the ECU and TCU. It would take some trial and error, but I bet we could come up with some simple resistor values that would make a reliable solution that works that we could all use.

We would basically end up with a secondary over-drive button.

the stock OD button disables 5th gear: this OD button / switch would disable 4th gear.

So basically, your towing up a big hill with a lot of weight:

Right now your choices are:

Foot to the floor, 70 MPH, 3,700, too much rpm, too much heat.
80% throttle, 37 MPH, 1,900 RPM, *&^^&* I hate my shift points.

IF you could fool the TCU to thinking you're on the floor, when your really not, on the same hill, you could have:

80% throttle, 57 MPH, 2,900 RPM, perfect.

dirtmover · **Posted:** Sun Nov 23, 2014 3:18 pm

crd260 wrote:

I *believe* this is how our system works, if I'm wrong, someone chime in.

There is a TPS signal coming from the accelerator (For arguments sake, let's call it 0-5 volts)

As far as I can see there's only crankshaft position sensor, transmission input/output sensors, vehicle speed, torque management request and O/D off going into that connector. There may be other info coming over the comms bus from the ECU but I've only just started digging around.

crd260 · **Joined:** Mon Oct 29, 2012 2:28 pm **Posts:** 103

dirtmover wrote:

As far as I can see there's only crankshaft position sensor, transmission input/output sensors, vehicle speed, torque management request and O/D off going into that connector. There may be other info coming over the comms bus from the ECU but I've only just started digging around.

Torque management request may well work the same way.

Do you have a link to a pdf?

Are we talking digital or analogue here? Are these coper wires in the harness?

gmctd · **Posted:** Sun Nov 23, 2014 6:39 pm

TCM sends TMR torque management request to convince ECM to reduce engine power output under several scenarios - not owner useable - owner is usually trying to get more power outta the li'l Diesel..................

Again, have a look at GDE's TCM towing programs, tomorrow

DOC4444 · **Posted:** Sun Nov 23, 2014 7:14 pm

Keith spent a lot of time and effort trying to come up with a way to manually select whatever gear you want, when you want it, but finally gave up. Best he could do was the "tow tune". However, he is willing to custom program to your preferred shift points, but after about 70K of experience, his standard ones seem best for a mix of heavy towing and commuting.

DOC

gmctd · **Posted:** Sun Nov 23, 2014 8:17 pm

Then there's the 'idiot factor', or plausibility clause, in the programming code that allows ECM to over-ride any input that is outside established limits for that input during acceptible normal operating conditions - not to worry, tho, 'cause limp-back mode can get you home

mustang_gt_350 · **Joined:** Tue Jun 01, 2010 8:47 am **Posts:** 191

Is there anyway to run the solenoids on the trans manually with switches like the XJ guys do the aw4s? It would be ugly with switches but with some time a circuit could be build that when turned on would give you up and down arrows and maybe a T/C lock button as well.

I have a converter lock switch on my powerstroke (7.3) all you needed to do with it was find the lock signal wire that ran to the trans and ground it. It would override the PCM and keep it locked. With that on a toggle switch and the tunes i wrote for my 6 pos chip i can "shift" gears by swapping chip positions while driving along with controlling the T/C lockup. Way easier on the trans since i let off the throttle when i flip into the next chip position and then after the shift roll back into the throttle.

gmctd · **Posted:** Tue Nov 25, 2014 6:21 pm

All the required signals are not simply switchable on\off conditions - they are on\off conditions up to 20000 times per second - 'nuther words, pulsed signals, maybe some with PWM - might converse with Green Diesel Engineering - they're the only ones I know of that have done any EATX TCM reprogramming, offering several towing upgrades

Anyone ever come up with a manual shift mode?

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