66rfe Limp Mode - Stuck in 4th Gear

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mtofell

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Yes.
The valve body takes the inputs from the solenoid and applies it. It's basically the brains of the transmission so it tells what pressures it wants when and where. Mopar OEM quality is bad on their VBs AND there are lots of areas in the VB where the quality affects the pressure. These losses of pressure cause clutch packs to not lock up when they're supposed to be locked up. When this happens it's just wearing away the clutches and cause excessive heat build up, both of which can destroy the transmission.

Due to these reasons a VB upgrade was one of the first things I did upon purchase of my 2500. It's a crap shoot, some are better than others but unless you constantly monitor your CVIs you'll never know unless there's a change in operation and then it's most likely too late.

Great explanation and all makes sense but one question - if the clutches are burning up how come the fluid still looks okay basically right up until it fails? After my first failure I kept a pretty close eye on the fluid and it was bright purple right up until it blew up.
 

6.4LMegaMan

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With an episode that violent I'd say there is a pretty good chance it is going to fail very soon. This is the kind of thing mine did 3X and it was failure each time. The best case is that it's just the valve body.
I sure hope not. I'm out of warranty and just don't want to deal with the hassle. I know I won't be having the dealer do the work if it needs a new transmission. I wonder if there are any shops building better 66RFEs? I'd rather buy a good one and do the swap myself. I really like this truck and want to keep it. Darn near paid off, too.

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The valve body takes the inputs from the solenoid and applies it. It's basically the brains of the transmission so it tells what pressures it wants when and where. Mopar OEM quality is bad on their VBs AND there are lots of areas in the VB where the quality affects the pressure. These losses of pressure cause clutch packs to not lock up when they're supposed to be locked up. When this happens it's just wearing away the clutches and cause excessive heat build up, both of which can destroy the transmission.

Due to these reasons a VB upgrade was one of the first things I did upon purchase of my 2500. It's a crap shoot, some are better than others but unless you constantly monitor your CVIs you'll never know unless there's a change in operation and then it's most likely too late.
Do you have recommendation on manufacturer for a replacement valve body?

'16 Wagon Greene tune feed'n & fire'n 6.4L with 6spd 5.13 AAM, 37" KM3, -12mm Fuels Thuren Overland, DOR, Purple Cranium CAI, ARH, Solo Mach44 z36, EBC Custom vinyl AVS, 4% tint Morimoto, Rigid, Diode Dynamics AlfaOBD, Diablo, Nanny Kill, Locker bypass .................
 

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I sure hope not. I'm out of warranty and just don't want to deal with the hassle. I know I won't be having the dealer do the work if it needs a new transmission. I wonder if there are any shops building better 66RFEs? I'd rather buy a good one and do the swap myself. I really like this truck and want to keep it. Darn near paid off, too.

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I'm with OP on the expectation and proceeding with extreme caution, I'd maybe take the trailer on a test tow before throwing the family in and heading out for time in the wilderness. It would be such a disappointment on many levels to have your trans puke at that particular time.

It would be interesting to know how far the truck could limp mode tow. :l

You can take look at ATS Diesel, they show a 545RFE for Hemi 2500 and Ive read them doing 66RFE. They handle lots of 68RFE hardware, they are on the upper end of product and probably cost but not much more then the dealer got me for mine and its just another 66. Dealer was $5500 ish included install (with a new toraue converter), ATS shows $4400 for a 68, a bad ass 68 I think, I would also think a 66 to be less, never know.

They also have a couple youtube videos that explain the 68RFE sub-par valve body in very interesting detail. I assume 66RFE is fairly synonymous with 68RFE as far as valve body quality and crappy manufacturing goes. Maybe much worse failure rate on the 68 with that high torque its dealing with, just guessing tho. Any way ATS does Hemi trans also, would be a top choice especially if you can put it in.

Keep us posted on what happens and what you learn, always I interested, cause I'm keeping mine! (Truck, not RFE)lol

'16 Wagon Greene tune feed'n & fire'n 6.4L with 6spd 5.13 AAM, 37" KM3, -12mm Fuels Thuren Overland, DOR, Purple Cranium CAI, ARH, Solo Mach44 z36, EBC Custom vinyl AVS, 4% tint Morimoto, Rigid, Diode Dynamics AlfaOBD, Diablo, Nanny Kill, Locker bypass .................
 
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6.4LMegaMan

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Well the service manager basically said since it's operating normally and it didn't store any codes there's nothing they can really do. He recommended driving it and seeing if it happens again. Sounds to me if it doesn't trip a light or grenade there's not much they can (or know how to) do. In the meantime, I pushed our camping trip to next weekend so I can do some test driving this weekend.
Is it bad that I took a peak online at new trucks? And my goodness, NADA and KBB have crazy high trade in prices for this thing. Both are saying around $40k?!

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Iron Outlaw

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I just joined the club today with mine. 66,750 miles on it. Cruising along at 60mph and went partial throttle to accelerate up a hill and the truck shifted to first, hit redline then banged into 4th where it locked out. Pulled off the exit and it shifted to first fine. Upon pulling out it went from 1st directly banging into 4th. I immediately pulled over and disconnected the battery. Hooked it back up and restarted and it's been fine since. I've never had a single issue with this truck and it's been good since disconnecting the battery. Going to call the dealer tomorrow to get their opinion. I'm going camping next weekend and need to haul the camper so I'm pretty nervous at this point.

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Did your truck have the solenoid recall? Mine did and I waited too long to get it done and I think its what caused my transmission to fail. I has my 66rfe built by a local shop for $4500.

Mine did that multiple times and started slipping between the 6th to 5th downshift and then it just kept getting worse in each gear.
 

6.4LMegaMan

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Did your truck have the solenoid recall? Mine did and I waited too long to get it done and I think its what caused my transmission to fail. I has my 66rfe built by a local shop for $4500.

Mine did that multiple times and started slipping between the 6th to 5th downshift and then it just kept getting worse in each gear.
Yes, my truck has had the U30 transmission solenoid pack campaign accomplished.

Since having the issue I've put about 50 miles on it and have not had any problems yet. I'm hoping it was just a fluke. Not betting on it but hoping...

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mtofell

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Well the service manager basically said since it's operating normally and it didn't store any codes there's nothing they can really do. He recommended driving it and seeing if it happens again. Sounds to me if it doesn't trip a light or grenade there's not much they can (or know how to) do. In the meantime, I pushed our camping trip to next weekend so I can do some test driving this weekend.
Is it bad that I took a peak online at new trucks? And my goodness, NADA and KBB have crazy high trade in prices for this thing. Both are saying around $40k?!

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When mine was going out it would usually go into limp mode after a hard acceleration when holding 2nd for a long time. This may have just been the weakness in my truck but it's worth a shot. To really test it I'd be rolling at 35 or so and then just hammer it to the floor so it drops down to second and holds it up until 60 or so.

It would really have harsh shifts as I let off and it found the right gear. The best way I can describe is it felt like the engine was spooled up and over ran the tranny. Meaning the engine was running/churning away and the tranny couldn't figure out what gear to settle into. There would often be a big clunk or two as I was coasting and waiting and it would end up in limp mode.

I hear you about the towing thing and being stuck. I finished my annual, out in the middle of nowhere camping trip with my 11K 5th wheel and made it. Sucks to pay all this money and not be able to rely on these things.

I suppose it's partially my fault. Dodge/Ram has been churning out crappy trannys since I was a kid 40 years ago.
 

michaelrc51

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Great explanation and all makes sense but one question - if the clutches are burning up how come the fluid still looks okay basically right up until it fails? After my first failure I kept a pretty close eye on the fluid and it was bright purple right up until it blew up.

I'm not sure, I would think it would show some signs of wear and also some discoloration of the fluid.

Did they tell you what the cause of the failure was?
 

michaelrc51

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Do you have recommendation on manufacturer for a replacement valve body?

'16 Wagon Greene tune feed'n & fire'n 6.4L with 6spd 5.13 AAM, 37" KM3, -12mm Fuels Thuren Overland, DOR, Purple Cranium CAI, ARH, Solo Mach44 z36, EBC Custom vinyl AVS, 4% tint Morimoto, Rigid, Diode Dynamics AlfaOBD, Diablo, Nanny Kill, Locker bypass .................

I used Revmax. I think the leaders are Revmax and Suncoast. That's just my opinion based on research I have done, but there are people who are against these companies as well.

The issue is that once you replace the VB you will get a higher pressure to where it needs to be. This will find other week links or if there is wear this may accelerate it. I put the Revmax VB/ pan/ thermostat delete in my truck at 40k miles, I'm just hoping it was early enough.
 

michaelrc51

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I'm with OP on the expectation and proceeding with extreme caution, I'd maybe take the trailer on a test tow before throwing the family in and heading out for time in the wilderness. It would be such a disappointment on many levels to have your trans puke at that particular time.

It would be interesting to know how far the truck could limp mode tow. :l

You can take look at ATS Diesel, they show a 545RFE for Hemi 2500 and Ive read them doing 66RFE. They handle lots of 68RFE hardware, they are on the upper end of product and probably cost but not much more then the dealer got me for mine and its just another 66. Dealer was $5500 ish included install (with a new toraue converter), ATS shows $4400 for a 68, a bad ass 68 I think, I would also think a 66 to be less, never know.

They also have a couple youtube videos that explain the 68RFE sub-par valve body in very interesting detail. I assume 66RFE is fairly synonymous with 68RFE as far as valve body quality and crappy manufacturing goes. Maybe much worse failure rate on the 68 with that high torque its dealing with, just guessing tho. Any way ATS does Hemi trans also, would be a top choice especially if you can put it in.

Keep us posted on what happens and what you learn, always I interested, cause I'm keeping mine! (Truck, not RFE)lol

'16 Wagon Greene tune feed'n & fire'n 6.4L with 6spd 5.13 AAM, 37" KM3, -12mm Fuels Thuren Overland, DOR, Purple Cranium CAI, ARH, Solo Mach44 z36, EBC Custom vinyl AVS, 4% tint Morimoto, Rigid, Diode Dynamics AlfaOBD, Diablo, Nanny Kill, Locker bypass .................

I had a built ATS 545RFE in my 1500 before I sold it and went to 2500. I can't complain about it. The fluid did get a bit dirty in the first 3k miles which was a surprise to me. My only complaints were with the shop I had do the work and the refund of my funds for the ATS pan/girdle.

I had one issue with ATS. I had a Mag-Hytec pan on the original transmission and unfortunately I couldn't use the ATS pan/girdle that came on the new one, which disappointed me. I was hoping not to touch anything with the new trans as to avoid any possible warranty issues, if necessary. But of course, the ATS pan wouldn't work with the exhaust where it is on the 1500 so we had to swap pans. I talked to ATS and they said they would credit me once they got it back, so I put it on the old transmission as was discussed and sent it back. I confirmed that the trans was received by ATS and contacted them the same day to make sure they were aware of the "new pan" on the returned core. Long story short, after a bunch of emails and calls I was told I hadn't done the right things and that the pan was lost somewhere in the mix so I was out of luck.
In the end I received the refund for the pan a few months later, so it worked it's way out and they ended up coming through.

There are lots of videos on the internals of the 68RFE and it's weak points. The VB issues are glaring and you really don't know if your trans has one of the good or bad ones in it unless you remove it and analyze it.
But, any of these aftermarket ones are way better than an OEM one......just look at the piston to bore issues. They are so bad, anything is an improvement. To be fair, lots of transmissions have some of these issues.

I bet if you contact Revmax they would help you out or point you in the right direction. When I spoke to them before ordering my parts they were very helpful and informative.
One thing that helped me decide to make the purchase is that they'll refurbish their parts and put them in a new transmission if I ever blow this one up and have to get one of their built transmission. This Means it will be cheaper if/when I have to get a built transmission.
 

michaelrc51

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When mine was going out it would usually go into limp mode after a hard acceleration when holding 2nd for a long time. This may have just been the weakness in my truck but it's worth a shot. To really test it I'd be rolling at 35 or so and then just hammer it to the floor so it drops down to second and holds it up until 60 or so.

It would really have harsh shifts as I let off and it found the right gear. The best way I can describe is it felt like the engine was spooled up and over ran the tranny. Meaning the engine was running/churning away and the tranny couldn't figure out what gear to settle into. There would often be a big clunk or two as I was coasting and waiting and it would end up in limp mode.

I hear you about the towing thing and being stuck. I finished my annual, out in the middle of nowhere camping trip with my 11K 5th wheel and made it. Sucks to pay all this money and not be able to rely on these things.

I suppose it's partially my fault. Dodge/Ram has been churning out crappy trannys since I was a kid 40 years ago.

Interesting. With my truck I also notice a pretty hard shift once in a while when I am on the gas and then it shifts into the next gear. Once I let off it shifts kind of hard for basically being in a spot the engine isn't accelerating. It should just shift and pretty much lightly shift into the higher gear and be smooth.
Of course, this is with my 14k-ish 5th wheel attached.

I do get a bit nervous towing the trailer knowing of all the issues with our trans'
 
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mtofell

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Once I let off it shifts kind of hard for basically being in a spot the engine isn't accelerating. It should just shift and pretty much lightly shift into the higher gear and be smooth.
Of course, this is with my 14k-ish 5th wheel attached.

I do get a bit nervous towing the trailer knowing of all the issues with our trans'

Yeah, that's exactly what mine does... but even without the 5th wheel. Like the tranny hasn't got the message that the engine is revving anymore. I've also noticed and occasional clunky shift when coasting up to a light.

Something my truck has done from the start that I swear is bad and I just gave up fighting the dealer about is the behavior when using the downshift feature (can't remember what it's called but it's in the manual). Basically, when coming off the freeway or wherever, hold the manual shift arrow on the column shifter down for a couple seconds and it will auto-select the best gear to target to slow you down (basically 1 or 2). When exiting the interstate at 60 it always picks 2 and all is well. This is actually a pretty cool feature. The problem comes in when I'm going a bit slower.... usually under 45, it picks 1. As it's downshifting it seems to hang around 3/2 and then absolutely SLAMS down into 1. It's so violent that it actually causes the rear wheels to grab and skid momentarily. Post-rebuild #1 I fought with my dealer and they first said they couldn't replicate it. Then when I made them come out on the road with me they just said it was normal... LOL. It's really not a big deal and I just don't ever let use that feature when starting to slow at a speed under about 50. Anyway, I'd be curious if anyone else's trucks do this too. Again, it's ONLY if it pre-selects "1".

Dealer never really told me how/why my tranny failed the second time. I asked if it was related to the first failure and they kind of shrugged their shoulders and said maybe.
 

6.4LMegaMan

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Live action here... had camper loaded and heading into the mountains and the truck hit limp mode again. No lights on dash and transmission temp was low. I was able to pull a code though. P0871 Transmission Fluid Pressure Sensor/Switch “C” Circuit Range. Code reader says not to drive it and from the fast research I did on the side of the road I decided to turn around and head home. Not worth getting stranded with 2 babies and a wife with no cell service. Now I'm draining my fresh water tank drinking the beer I brought for the camp fire. So disgusted right now. Going to call the dealer in the morning and see what they say. I absolutely love this truck but I can't have any chance of unreliability with a young family going on long distance camping trips. Might be time to hang it up for something with an Aisin. I say that very reluctantly. Maybe after sleeping on it and getting this thing diagnosed I'll change my mind. Just keeping you all updated. 94bc166cca2bc12be047f5d6f523d959.jpg

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mtofell

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Live action here... had camper loaded and heading into the mountains and the truck hit limp mode again. No lights on dash and transmission temp was low. I was able to pull a code though. P0871 Transmission Fluid Pressure Sensor/Switch “C” Circuit Range. Code reader says not to drive it and from the fast research I did on the side of the road I decided to turn around and head home. Not worth getting stranded with 2 babies and a wife with no cell service. Now I'm draining my fresh water tank drinking the beer I brought for the camp fire. So disgusted right now. Going to call the dealer in the morning and see what they say. I absolutely love this truck but I can't have any chance of unreliability with a young family going on long distance camping trips. Might be time to hang it up for something with an Aisin. I say that very reluctantly. Maybe after sleeping on it and getting this thing diagnosed I'll change my mind. Just keeping you all updated. 94bc166cca2bc12be047f5d6f523d959.jpg

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Ugh.... man, that sucks (at least there is beer involved :)) I hope your dealer will do something for you. Ram really likes to kick the can down the road on these things. Keep us posted....
 

6.4LMegaMan

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Just talked to the dealer and they advised it needs a new valve body. I do trust the service manager at this dealership and he definitely knows the lingo and they have mechanics there with big diesel trucks that are tuned and all that so I feel like they know what they're doing. He said it's not exactly a common problem that they see but they have done plenty of valve bodies on the 66RFE and 68RFE with good success. I told him to go for it and replace the filters and fluid while he's at it. Should be done tomorrow. Here's hoping! Maybe we can get another camping trip in before the freeze hits!

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6.4LMegaMan

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Just to wrap things up...I picked up the truck last night. $1450 roughly for the fix. I'll load up the camper and see what it does.

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mtofell

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Just to wrap things up...I picked up the truck last night. $1450 roughly for the fix. I'll load up the camper and see what it does.

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About a week after my 2nd rebuild it failed again - slipping/banging, etc. I limped it into the dealer and they said valve body was bad. For some reason that completely escapes me, they didn't replace it. So, new valve body and it's been working ever since. Point being, it's possible for the valve body to cause total havoc with the tranny so hopefully that is all you needed!!
 

Nobody38

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I've got a 2014 2500 6.4 . mine just ovetheated and left me on the side of the road. Mine hit limp mode the first time pulling a 28' gooseneck with a car on it, that was about a month or so back.Today it hit limp mode twice before overheating and shutting the whole truck down. I wasn't pulling or hauling anything either.

Oh Dodge you still have the finest transmission in the world LOL.
Glad I got that lifetime powertrain.
 

buckeyexx

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I have a 2015 2500 6.4 with 66rfe. I get a hard downshift from 6-5 and 5-4. I will usually just manually shift into 4th as long as I’m not on highway. Keeps the mds from kicking in and it keeps the rpms up a little but the trucks feels much better not going into 5th or 6th. A little sluggish to me. What I do notice is that when I am pulling any weight or some weight in the bed it seems to shift great. But when empty it a harsh downshift.
 
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