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Old 08-24-2014, 11:22 AM   #263 (permalink)
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Location: Oklahoma City, OK
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ECONORAM - '07 Dodge RAM 1500 QC SLT flex-fuel
90 day: 18.16 mpg (US)

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Originally Posted by taredog View Post
I have been doing some research on an on demand TC lockup for my Dakota. I'm not quite there yet but have learned some interesting facts.

It appears that if I can find the right wire from the TCM that it applies B+ to the L/R-CC solenoid. I haven't figured out yet if the battery voltage is on the solenoid and the TCM gives it a ground or the TCM actually applies voltage. It does use PWM for partial lockup but PWM is just the amount of time battery voltage is on or off.

It also appears that the 45RFE transmission I have is mechanically the same as the 545RFE, but with a different TCM program. What the 545 program does is provide an additional OD ratio of .67:1 in addition to the current .75:1 ratio.

Yeah, I know, I called BS on this until I researched it a lot. It is a matter of which clutch is engaged in which of the three planetary gear sets. Turns out Jeep has been doing this since late 01 and Dakotas since late 02 or 03. The problem with Dakotas is that the TCM was combined in to the PCM for the 545 so you can't upgrade. The solution, allegedly, is to get a TCM from a late 01 to 04 Grand Cherokee. I have found a couple in salvage (junk to me) yards for less than $100 and am looking in to getting one.

Of course this will only help highway FE. The quest for the on demand TC lock up and eventually controlling the gear selection continues.

If any of you have any info on the 45RFE about TC lockup on demand or controlling the gear selection, please let me know. I have found a lot of data and it's just a matter of analyzing it all.
I realize this thread is older, but regardless I am still interested. I have been scouring the DR wiring diagrams, for the 545RFE and various connections. I believe the L/R solenoid is the one responsible for activating the lockup, but what I am not sure of is if I splice into that wire and put 12v on it, will the computer kick a code and then go into limp mode because it doesn't like the signal it's getting.

My first thought is to take the signal from the PCM and run it through a resistor to ground. Then provide 12v to the solenoid when I want (probably upshifting or steady state 2nd-5th, if the clutch will lock in all 4 gears). Any ideas?

[edit] just found this: looks like the solenoid needs a ground signal.
Originally Posted by orange4boy View Post
All I can say is WOW!

Latest mixed tank fill netted 30.2mpg up from an average of 24. I can hardly believe it but there it is. Also got a record tank distance of 818km/508mi.

That's almost a 26% improvement. It may settle down a bit on the next tank but we will see. I doubt most people would get the same improvement because I live in a very hilly area where the slushbox was labouring up these hills at low speed, high RPM and I could never get into OD. Now I cruise the flats at 30-35 locked up in OD and do most of those hills locked up in 3rd or OD.

30mpg combined! So happy!
This is good return on investment!! Really makes me want to do this.
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Last edited by ECONORAM; 08-24-2014 at 11:39 AM.. Reason: found more info
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