Strange RPM Pulsing Behavior 1500 45RFE

[Korishan]

Any suggestions as to why a dodge ram 1500 w/ 45rfe would rhythmically pulse rpms?

I notice it a lot more while pulling a trailer, but can tell when not. As accelerating gently, enough to keep in current gear w/o downshifting (usually 4th, but happens in 3rd as well if slow enough), the engine will pulse, like it was on a pwm controller. As long as i keep my foot steady on the throttle, it'll do it. If i push harder, it may downshift, if I let up, it'll stop or be unnoticeable.

it feels/sounds like a permanent magnet motor that is cogging when turned manually

could this be the trans slipping?

on another note (possibly related), I have replaced the filter and the drain back canister. But, after starting up, and putting it into gear, it's sluggish to engage. Once engaged, it'll move just fine, regardless if i put it back in P, or N, then back to D. However, almost always, dropping into R there'll be a several second delay before it engages

 

[Fast69Mopar]

Any suggestions as to why a dodge ram 1500 w/ 45rfe would rhythmically pulse rpms?

I notice it a lot more while pulling a trailer, but can tell when not. As accelerating gently, enough to keep in current gear w/o downshifting (usually 4th, but happens in 3rd as well if slow enough), the engine will pulse, like it was on a pwm controller. As long as i keep my foot steady on the throttle, it'll do it. If i push harder, it may downshift, if I let up, it'll stop or be unnoticeable.

it feels/sounds like a permanent magnet motor that is cogging when turned manually

could this be the trans slipping?

on another note (possibly related), I have replaced the filter and the drain back canister. But, after starting up, and putting it into gear, it's sluggish to engage. Once engaged, it'll move just fine, regardless if i put it back in P, or N, then back to D. However, almost always, dropping into R there'll be a several second delay before it engages

Can you record a video of this happening? I'd like to see and hear what you are talking about. If I can see it I can probably help. I've been building and repairing the RFE since they were introduced in 1999.

 

[Korishan]

Can you record a video of this happening? I'd like to see and hear what you are talking about. If I can see it I can probably help. I've been building and repairing the RFE since they were introduced in 1999.

Not sure if my phone will pick up the sound. My tach is slightly busted. It's only somewhat accurate when it closes in on 5k. When the engine is around 1k, it reads about 450. I've verified this with an OBD scanner. Problem is, the scanner doesn't report fast enough to show the pulsing. Unless it's the app I'm using, Torque Lite. I do have another scanner called Zus. I'll see if it'll show the updates faster.
I also have a condenser mic with a long cable on it, so maybe I can put it in different spots and record under the hood and maybe next to the transmission.

 

[Fast69Mopar]

Not sure if my phone will pick up the sound. My tach is slightly busted. It's only somewhat accurate when it closes in on 5k. When the engine is around 1k, it reads about 450. I've verified this with an OBD scanner. Problem is, the scanner doesn't report fast enough to show the pulsing. Unless it's the app I'm using, Torque Lite. I do have another scanner called Zus. I'll see if it'll show the updates faster.
I also have a condenser mic with a long cable on it, so maybe I can put it in different spots and record under the hood and maybe next to the transmission.

Okay cool. The Torque Lite app is not the fastest in the universe. I don't know if Zus is faster but maybe give it a try.

Another thing, using the Torque app or Zus, see if you can view the transmission CVI's and record their values. Then perform a Quick Learn. Test drive the truck again and see how it shifts and feels and see if the engine rpm fluctuates.

 

[SYKRAMMAN]

Any suggestions as to why a dodge ram 1500 w/ 45rfe would rhythmically pulse rpms?

I notice it a lot more while pulling a trailer, but can tell when not. As accelerating gently, enough to keep in current gear w/o downshifting (usually 4th, but happens in 3rd as well if slow enough), the engine will pulse, like it was on a pwm controller. As long as i keep my foot steady on the throttle, it'll do it. If i push harder, it may downshift, if I let up, it'll stop or be unnoticeable.

it feels/sounds like a permanent magnet motor that is cogging when turned manually

could this be the trans slipping?

on another note (possibly related), I have replaced the filter and the drain back canister. But, after starting up, and putting it into gear, it's sluggish to engage. Once engaged, it'll move just fine, regardless if i put it back in P, or N, then back to D. However, almost always, dropping into R there'll be a several second delay before it engages

Mine does the same thing since I bought it two years ago, I took it back to dealer but they just used their canned excuse "That's normal". It really feels like slippage but if it was slipping, I think it would have died already, truck runs great otherwise.

 

[Korishan]

Mine does the same thing since I bought it two years ago, I took it back to dealer but they just used their canned excuse "That's normal". It really feels like slippage but if it was slipping, I think it would have died already, truck runs great otherwise.

I bought mine at 24000 miles. It didn't do it back then. It has gotten worse over the past year. I'm guessing (not certain) is because I'm pulling a trailer now. Or it could be that the trailer, being heavy load, causes the issue to be more pronounced.

Okay cool. The Torque Lite app is not the fastest in the universe. I don't know if Zus is faster but maybe give it a try.

Another thing, using the Torque app or Zus, see if you can view the transmission CVI's and record their values. Then perform a Quick Learn. Test drive the truck again and see how it shifts and feels and see if the engine rpm fluctuates.

I know Torque app can't read the transmission. Maybe the Pro version can. I haven't tested the Zus one yet, so not sure. I didn't know about the Quick Learn option. I can give that a try.
I have thought about replacing the control valve assembly as I've read in a few other posts that that 'could' be an issue. But I'd like to narrow down the issue before I go that route.

Is there a way to do the Quick Learn without going to a dealership? I did a quick search and several threads show going to the dealership or buying a $2k piece of equipment, DRBII.

As a side note, about 6 months ago I did change the plugs. I replaced the Copper stocks with Iridium plugs. According to specs, the Iridiums are supposed to be gapped at 44, whereas the coppers are 40. Could this make a difference? Oddly, the plugs I got from the parts store where all pre-gapped at 40, and I had to regap to 44. Should I have them re-regapped to 40?

 

[Fast69Mopar]

I bought mine at 24000 miles. It didn't do it back then. It has gotten worse over the past year. I'm guessing (not certain) is because I'm pulling a trailer now. Or it could be that the trailer, being heavy load, causes the issue to be more pronounced.



I know Torque app can't read the transmission. Maybe the Pro version can. I haven't tested the Zus one yet, so not sure. I didn't know about the Quick Learn option. I can give that a try.
I have thought about replacing the control valve assembly as I've read in a few other posts that that 'could' be an issue. But I'd like to narrow down the issue before I go that route.

Is there a way to do the Quick Learn without going to a dealership? I did a quick search and several threads show going to the dealership or buying a $2k piece of equipment, DRBII.

As a side note, about 6 months ago I did change the plugs. I replaced the Copper stocks with Iridium plugs. According to specs, the Iridiums are supposed to be gapped at 44, whereas the coppers are 40. Could this make a difference? Oddly, the plugs I got from the parts store where all pre-gapped at 40, and I had to regap to 44. Should I have them re-regapped to 40?

Just to make sure, is your truck a 2006 Ram with a 4.7?

The one thing I can think of that may be causing your issue is the torque converter. Have you verified that the torque converter clutch is staying engaged while driving? If you press the Tow/Haul button and start driving the transmission will shift 1-2-3 and then engage the converter clutch. Watch the tach and see if the RPM drops during converter clutch engagement.

Also, there are a few ways to do a quick learn without going to the dealership. Many independent shops have scan tools that are capable of doing a quick learn. Call your local Firestone or independent shop and ask them how much they will charge to do a quick learn. It shouldn't cost more than a half hour of labor.

When you do the quick learn make sure you have them look at the transmission CVI's before they do it and record the values so you can compare them after the quick learn.

 

[Fast69Mopar]

I bought mine at 24000 miles. It didn't do it back then. It has gotten worse over the past year. I'm guessing (not certain) is because I'm pulling a trailer now. Or it could be that the trailer, being heavy load, causes the issue to be more pronounced.



I know Torque app can't read the transmission. Maybe the Pro version can. I haven't tested the Zus one yet, so not sure. I didn't know about the Quick Learn option. I can give that a try.
I have thought about replacing the control valve assembly as I've read in a few other posts that that 'could' be an issue. But I'd like to narrow down the issue before I go that route.

Is there a way to do the Quick Learn without going to a dealership? I did a quick search and several threads show going to the dealership or buying a $2k piece of equipment, DRBII.

As a side note, about 6 months ago I did change the plugs. I replaced the Copper stocks with Iridium plugs. According to specs, the Iridiums are supposed to be gapped at 44, whereas the coppers are 40. Could this make a difference? Oddly, the plugs I got from the parts store where all pre-gapped at 40, and I had to regap to 44. Should I have them re-regapped to 40?

Also, another thing I would do is take the Iridium plugs out and go back to a copper spark plug. The 2006 4.7's are designed to run on a copper plug. I have had to repair too many trucks over the years that have the wrong spark plugs installed.

 

[Korishan]

Just to make sure, is your truck a 2006 Ram with a 4.7?

The one thing I can think of that may be causing your issue is the torque converter. Have you verified that the torque converter clutch is staying engaged while driving? If you press the Tow/Haul button and start driving the transmission will shift 1-2-3 and then engage the converter clutch. Watch the tach and see if the RPM drops during converter clutch engagement.

Yes, 2006 w/ 4.7
The converter clutch is engaging. It does it with and w/o the tow/haul mode engaged. Does the converter clutch "only" engage as the upper most shifting? Ie, after it's gone through all gears

I think it does engage with tow/haul, at least. When I'm about 55mph and either drafting, going slightly downhill, or have a good tailwind, it'll shift into a final rpm drop (this is with pulling the trailer). I 'think' the rpms at that point are around 2k. But I will need to use the obd tool to verify that, as my tach doesn't display accurately at low rpm.

Also, another thing I would do is take the Iridium plugs out and go back to a copper spark plug. The 2006 4.7's are designed to run on a copper plug. I have had to repair too many trucks over the years that have the wrong spark plugs installed.

I have been highly considering going back to copper plugs, tbh. I will say that I had OE plugs all the way to about 110k miles. You could tell they were worn, but they still had the electrodes in tact.


btw, I appreciate the quick and detailed responses.

 

[Fast69Mopar]

Yes, 2006 w/ 4.7
The converter clutch is engaging. It does it with and w/o the tow/haul mode engaged. Does the converter clutch "only" engage as the upper most shifting? Ie, after it's gone through all gears

I think it does engage with tow/haul, at least. When I'm about 55mph and either drafting, going slightly downhill, or have a good tailwind, it'll shift into a final rpm drop (this is with pulling the trailer). I 'think' the rpms at that point are around 2k. But I will need to use the obd tool to verify that, as my tach doesn't display accurately at low rpm.



I have been highly considering going back to copper plugs, tbh. I will say that I had OE plugs all the way to about 110k miles. You could tell they were worn, but they still had the electrodes in tact.


btw, I appreciate the quick and detailed responses.

The converter clutch will engage after the upshift into 3rd gear, then after the upshift into 4th gear and will apply after the upshift into 5th.

I highly recommend switching back to the stock style copper plugs. This engine is designed for the copper plugs.

 

[Korishan]

Just a quick update, I haven't been able to get the testing done to record the sounds or the app.
As a side note, Zus ODB Scanner/App sux! You can't even get any data off of it w/o having 'active' account and logged in and have an 'active' internet connection. It absolutely won't work w/o internet. Piece of junk.

I hope to get the recordings done either Fri or Sat. Been a busy week.

 

[Korishan]

Another update. I haven't been able to do any testing or get readings. Been way too busy, and fighting the weather and free time alignment issues.

However, I did go ahead and switch out the plugs from the Iridiums back to Copper. The Iridium plugs didn't look so good, at least to me.
Here's what the plugs look like. I think I got them in the right order.





These plugs have less than 30k miles on them. I think less than 20k actually. They look a little rough to me for such short life. Plug 2 & 8 look like they have melted spots on them. I haven't been able to tell if the pulsing has stopped yet. I'll have more time to do that tomorrow, I hope.