2012 Grand Cherokee 645RFE Trans Parameter Help file attached

[topher455]

Hi Guys! Ive been tuning the wifes 2012 Grand Cherokee with the 5.7 since I first got the beta 2.25 and now that the 645RFE trans has support Id like to tune it as well. I do tons of gm cars and trucks as well as the new direct injected stuff and lots of Moprs with the WA580 so Im pretty good at figuring things out but some of the settings in this rfe trans are puzzling and very unlike what im used to. So Ill attach my stock and current file and below ill list what I am most puzzled by and you guys can help me understand them.

Acceleration limits A and B: Use an rpm/sec value that is negative in all the tables with sets of tables for A or B which Im assuming are shift modes

Desired Acceleration Offset and Desired Acceleration Offset WOT: one set has positive rpm/sec values and the other negative

Ramp Rate of Acceleration: Does not list what unit of measurement the value is and I don't see any real pattern to it. A appears to have lower values for all shifts except the 2-3 for some reason. I thought maybe these are shift times??

A and B: must be different shift patterns but I don't see anywhere this is broken out

Shift pressure adjustments: Not sure wether to adjust the clamps and then the gain per gear or do that and the duty cycle changes

Torque management adjustments: I tried maxxing the values out with no change so I am wondering if these values need to be lowered? Again its tough to decipher these adjustments since there seems to be no real pattern.

Any help would be appreciated!!

[Monzsta]

Your transmission is a 65RFE. Might make a difference to someone trying to help.

This transmission is completely non-sequential and has no bands. All shifts are clutch -to- clutch, meaning that one clutch begins applying then the holding clutch begins releasing in sequence to smoothly "hand off" the torque from one clutch to another. Also the valve body has a solenoid pack with direct acting solenoids that control the apply to the clutches. Shift timing is crucial in these transmissions.

I can't help you with your questions but I would lurk on the Ram truck forums. They have been going fast on this transmission since the early 2000's and they know what makes it work.

[topher455]

Thanks for the reply. That's odd. They Called the 5 speed version the 545rfe so I guess I may have just assumed. This trans had just come out when I stopped working for Chrysler so I don't know a ton about it except its almost identical to the 45rfe they have been using for years with an extra 2 prime gears that were a result of calibration changes. Im familiar with it being clutch on clutch which is why Im trying to figure out the parameters before I bind something up and cause damage trying to test. Good Idea on the ram forums Ill try looking there. Thanks!

[Monzsta]

The 45, 545, 65, 66 and 68RFE all have the same architecture. The 66 and 68 have different gear ratios and the 68 has different clutch packs in most of the elements for more holding power but most parts swap between transmissions. I agree the 545 should have been named the 55RFE to keep continuity. It's neat the transmission began as a 4 speed but grew two gears with nothing other than software changes.

[topher455]

Yes! When I was a Jeep service tech I bought a 2001 Jeep Grand Cherokee with the 4.7 V8 and there was a flash for the pcm that changed it from a 4 to a 5 speed Trans!

I really wish I could find more info about these parameters somewhere. Everywhere I have asked I have come up with nothing!!

[raceplayhavefun]

Did you ever find answers to your questions? I'm just trying to learn as well.

[jfreemanak]

Me too. I have been slowly tuning my 68RFE, but I really have no idea what most of the values mean.

[jfreemanak]

Just going to bump this thread to the top. Anyone have knowledge to share?