545rfe shift point mods

[gusthewonderslug]

Gday all,
What's available to modify the shift points on my 2010 CRD, I'm pretty sure they had the Merc 545rfe box
Thanks

[MightyMouse]

Really doesn't matter all that much what box, its the ECU that needs to be flashed so other makes experiences / techniques are of little help.

There's also some mumbo / jumbo about programmers reprogramming the shift points.... most simply correct for ratio changes to stop the things having a hissy fit when the calculated engine rpm at a set speed doesn't match the actual. ( ie axle changes )

And......... Id be cautious.... they rely on the electronics for all the shift functions such as overlap / pressure modulation etc, its not just a one parameter mod so real expertise required.

The only serious reflash that I've heard of was on a 42RLE and that was a total disaster... the auto "expert" completely F'ed it up and destroyed the original and a second box trying to set it right again. Ended up having a third auto and a replacement ECU to get the programming correct again.

Good luck with your search...... but IMHO be very cautious about easy fixes and so called experts - modern autos are totally dependent on programming and the strategies involved are very complex. Like dyno tuning.... everyone's an expert when they want your $$ its only afterwards that you realize most of them are just winging it .

[samft]

I have tried setting lower axle ratios with the procal, hoping to get the gearbox to hold onto gears longer. I've also tried higher ratios to see if i can get it to lock the TC earlier.

I didn't get any errors, but I also couldn't notice a difference.

I have searched around and havent found much in the way of physical mods.

there is a clip on resistor made by sonnax that will boost pressure and firm up shifts by reducing slip between the clutches. apparently the computer eventually compensates however and pressure drops back to normal. i think it's best to clip this thing on when you drag race, and then take it off after (545rfe is in lots of cars the yanks use to race)

there is a shift kit made by transgo that i think speeds up the shift duration, but doesnt modify the shift points or firmness

there is also aftermarket torque converters available that could make a big difference...big job to change though

I have given up on changing anything, the esiest way to alter shift points is to hit the OD off button! I think that allows the box to use gear 2' on the way up as well as on the way down

i.e. 1,2,2'3 rather than 1,2,3,OD1,OD2

gears 4 and 5 are both overdrives so i think they are both disabled with OD off, 2' is another ratio that only gets used on down shifts under normal mode

[Cherokee30D]

I had my transmission fully rebuilt recently and paid extra to have a shift kit fitted. Made a difference at first, but gear changes have now gone back to normal.
Matt (a forum member) works at The Horsepower Factory. Apparently they do ECU tunes for the JK. I assume that they would be able to do something with the gear changes?

Cheers, Craig

[gusthewonderslug]

Is there a mod to turn off the Od, eg so we can run with the Od turned off instead of turning it off when we drive off via the console switch.

[samft]

Originally Posted by gusthewonderslug

Is there a mod to turn off the Od, eg so we can run with the Od turned off instead of turning it off when we drive off via the console switch.

let me know if u find one...
i would think a clever autoelec could splice in a relay that picks up the ignition signal and sends a signal to the OD button wiring loom

[chris0375]

The Mercedes box and 545rfe refer to different models. 545rfe in earlier jks. The Mercedes box in newer to current.