545RFE Kick down gear sluggish

[Dennis Flannery]

I have an 06 5.7 hemi with a 545RFE tranny. It is very sluggish to kickdown when I depress the accelerator. When I depress enough to kick it in it kicks down too far, neck snapping. Anyone know where to start diagnosing? Is it vacuum operated?

 

[Fast69Mopar]

I have an 06 5.7 hemi with a 545RFE tranny. It is very sluggish to kickdown when I depress the accelerator. When I depress enough to kick it in it kicks down too far, neck snapping. Anyone know where to start diagnosing? Is it vacuum operated?

The 545RFE is a fully electronic control transmission. There are no vacuum lines on this transmission.

If you are experiencing issues with downshifts, can you take a video and post it? The easy way is to shoot a video and upload it to YouTube and then post the link here.

How many miles have you put on the truck since you bought it?

Have you serviced the transmission?

What does the fluid look like and smell like?

Is the check engine light on? Either way hit up the local auto parts store to connect a scan tool so you can see if there are any
1-Trip Failures stored or even a stored DTC.

Now, with that being said, how about some background on the truck. Is this the stock, original 15 year old transmission?

How far are you having to press the accelerator pedal to get the transmission to downshift? If you are cruising the highway in 5th gear it can take quite a bit of pedal input to get it to downshift from 5th to 3rd or even 2nd Prime. The 5-4 downshift should occur pretty easily because it only takes a few degrees of TPS input to downshift. The 5-3 downshift requires quite a bit of pedal because the software in the PCM/TCM is designed to keep the trans in high gear or the highest gear available based on engine load and throttle input for fuel economy and emissions purposes.

The 5-2 downshift is really rough on the RFE transmissions and I don't recommend trying to get it to downshift that far to accelerate to pass someone. Here is what I do. I tap the Tow/Haul button while cruising. When I do it will downshift from 5th to 3rd and engage the converter clutch. In Tow/Haul Mode 5th gear is locked out and the trans will only upshift to 4th gear. If you press the button again it will say O/D Off and the trans will only upshift to 3rd gear and engage the converter clutch with 4th and 5th being locked out.

This is the way I always recommend to downshift to a lower gear while driving, especially once you are in 5th gear.

The only real way to diagnose a concern like this is with a scan tool connected and driving the truck which only shops or mechanics like me can do. There may not be anything wrong with your transmission though.

I Think some further diagnostics is required with a scan tool and a mechanic who knows what they are looking at in the scan tool to determine if there is really a problem or not.

 

[Dennis Flannery]

Thank you for the fast reply. I’ll post a vid in the next few days. I’ve got 334,000 on the original drivetrain. Tranny has been serviced regularly. Fluid is pretty close to the color of new fluid. No engine check light and codes are clear. I run it in Tow mode because I have a bad MDS solenoid. I think I t’s the 3 - 2 downshift. It happens consistently at 30-35 going up a grade near my house, it bogs down and I have to put the pedal more than halfway down to get it to kick in. It used to kick in sooner and smoother. I have resorted to anticipating it and putting the shift selector to 2 before the engine starts bogging down.

 

[Fast69Mopar]

Thank you for the fast reply. I’ll post a vid in the next few days. I’ve got 334,000 on the original drivetrain. Tranny has been serviced regularly. Fluid is pretty close to the color of new fluid. No engine check light and codes are clear. I run it in Tow mode because I have a bad MDS solenoid. I think I t’s the 3 - 2 downshift. It happens consistently at 30-35 going up a grade near my house, it bogs down and I have to put the pedal more than halfway down to get it to kick in. It used to kick in sooner and smoother. I have resorted to anticipating it and putting the shift selector to 2 before the engine starts bogging down.

Now that you have explained it this way I think I know what is happening. When you are driving in Tow/Haul Mode at slower speeds like 30-35mph the transmission is in 3rd gear with the converter clutch engaged. With the stock TCM calibration your converter clutch will begin to engage at 36mph and be fully engaged at 39mph. When you start to accelerate like this with the transmission in 3rd gear and the converter clutch engaged it will take quite a bit of pedal to force a downshift. The reason for this is partly because of fuel economy and emissions but vastly towards vehicle performance. 3rd gear in the 545RFE is a 1:1 ratio which means all shafts are spinning at the same RPM which includes the crankshaft, input shaft, intermediate shaft, output shaft and the driveshaft. When a transmission is in a gear with a 1:1 ratio you can put the most power to the rear wheels hence why dyno pulls are almost always performed in a 1:1 gear.

The TCM software is designed to hold the transmission in 3rd gear with the converter clutch engaged as long as possible which is why it takes so much pedal to force a 3-2 downshift.

If you drive the truck with Tow/Haul turned off and let it shift normally you will notice the 4-3 and the 3-2 occurs much quicker because you are not holding the trans against the converter clutch. Give it a test drive and you will see what I mean.

All of my RFE transmissions perform exactly like yours does on the 3-2 downshift when in Tow/Haul Mode.

 

[Dennis Flannery]

wow, awesome info, thank you!

 

[Fast69Mopar]

wow, awesome info, thank you!

hope i explained it okay. im almost certain what you are experiencing is totally normal based on your driving conditions.

 

[sparkybg]

I have (i think) similar issue with my 545RFE - when it is in 5th and I depress pedal slightly in order to downshift to 4-th, it first disengages the lockup and then there's a second or two before shifting to 4-th. While this 1-2 second period happens, there are some small vibrations present and I am not sure is the trensmission generates then or they are motor vibrations due to harder throttle. Also, during this 1-2 second time, if I scan the transmission parameters with JScan or similar tool, the "present gear" parameter stays on 5th, and the "target gear" is 4th.

The transmission is doing this only on 5-4 shift. All other shifts are perfect, including 5-3 shift if I press it harder.

Is this really a problem, or is it just normal 545rfe behaviour?

 

[sparkybg]

Anyone?

 

[Fast69Mopar]

Anyone?

I believe what you are experiencing is normal RFE operation. Do you have access to another scan tool so you can see live data in the TCM. I think what you are seeing with J-Scan is not a fast enough refresh rate for live data to see the target gear. When I am using the Wi-Tech and driving with my laptop I can see target gear changes almost instantly. With my Snap On Zeus it is a little bit slower.

When I am driving my 2004 Ram 1500 5.7 545RFE in 5th gear at highway speeds I have the same small vibration when the TCM unlocks the converter clutch right before the 5-4 downshift occurs. I have tried multiple torque converters and different driveshafts and the little vibration that occurs has never changed. I have been inside this transmission a few times making changes and updating parts and I have found zero wear on anything that would cause the vibration. I will say that once the converter clutch is disengaged right before the 5-4 downshift and I feel the slight vibration it goes away as soon as the 5-4 downshift has been completed.

 

[sparkybg]

Yes, this is exactly what happens on mine. It is with new converter, new Sonax valve body, new OEM solenoid pack, remanufactured pump and upgraded clutches (OD+UD = like on 68RFE Raybestos GPZ , 4C upgraded Raybestos GPZ, 2C Kolene+Red Eagle with additional friction and steel) I bought a car with totally fried transmission (black fluid with pieces, absolutely destroyed OD and badly burnt UD clutches), so I had to make all this myself. It was fun, actually.

I have access to CDA, AlfaOBD (both Android and PC), DiagFCA. I am tuning it now - I decompiled the code and now I am looking inside how it works, searching how to resolve this single issue. There must be a time limit or something else, but I am yet to find it. I found many interesting things so far.

Even if this behaviour is normal, and even if I don't succeed resolving it (excuse my english ) the process is absolute fun to me, so I won't regret doing it anyway.

 

[mrack]

Normal crummy old 545rfe behavior, that’s why I haven’t bothered to do any power mods to my 2009. Not unless I come across the means to do an 8spd swap.