66RFE TROUBLE

[70UTE]

I’ve gone through this thing as best I can without a complete tear down and rebuild. The truck is a 2013 5.7 66rfe 4x4. I have now 100K on the clock. When I bought the truck I didn’t notice it right away because I don’t hammer on the gas. What I have issues with now is lag/slipping during hard acceleration/downshift. I replace the fluid and filters with OEM, and put in the sonnax valve body complete unit, changed both input and output speed sensors and transducer/pressure switch. The relearn was done correctly. I still have the same issue with no codes. All the parts were changed to fix/prevent a total failure. There’s absolutely no change with all the new parts and no codes/ check engine light. I’m at a total loss here. This maybe the end to my ram days and might be getting rid of the truck. It’s absolutely infuriating because these trucks are great but mopar continues to suffer with terrible transmissions. Wondering if anyone else has this issue that seems phantom.

 

[gtomike60]

It seems to me that with everything you've replaced,it pretty much leads to the conclusion that your clutches are slipping and you need a rebuild.
Went through pretty much the same thing a few years ago with mine at 123k

 

[crash68]

It’s absolutely infuriating because these trucks are great but mopar continues to suffer with terrible transmissions.

That came to an end when they moved away from the RFE transmissions and starting using the ZF 8HP line of transmissions.

 

[HEMIMANN]

That came to an end when they moved away from the RFE transmissions and starting using the ZF 8HP line of transmissions.

Except for the goofy Germanic perfectionist ethic that vehicle service is to be done only by professionals, therefore serviceability is made as cumbersome and difficult as possible, without any forethought for customer self-service.

Seriously. Working in and out of design engineering for 32 years (now retired), serviceability was a core requirement of new product design at our corporation in USA. Germans and Japanese culturally pay no attention to this. They make perfect components that are exceedingly difficult to service.

 

[gtomike60]

Except for the goofy Germanic perfectionist ethic that vehicle service is to be done only by professionals, therefore serviceability is made as cumbersome and difficult as possible, without any forethought for customer self-service.

Seriously. Working in and out of design engineering for 32 years (now retired), serviceability was a core requirement of new product design at our corporation in USA. Germans and Japanese culturally pay no attention to this. They make perfect components that are exceedingly difficult to service.

In my opinion,the 8HP trans isn't any more difficult to service other than having to fill it from underneath and raising the rear so that the trans is level
In fact,the 8HP has an actual drain plug in the pan vs none on the 66RFE,making it a bit easier and cleaner
Cost to service is much higher with the 8HP,though

 

[HEMIMANN]

In my opinion,the 8HP trans isn't any more difficult to service other than having to fill it from underneath and raising the rear so that the trans is level
In fact,the 8HP has an actual drain plug in the pan vs none on the 66RFE,making it a bit easier and cleaner
Cost to service is much higher with the 8HP,though

???

Jacking up your truck, leveling it, running the drivetrain while filling is no more difficult than a gravity drain from an RFE! Not to me.

 

[mtofell]

OP, is your fluid getting burnt? If so, I'd tend to agree with @gtomike60 in post #2. I've been through two rebuilds on my 66RFE (both warranty at the dealer due to valve-body issues related damage) and it still feels a bit like it slips during hard acceleration. I keep a close eye on the fluid and it's never burned so I've just chalked it up to how the tranny is. With hard acceleration it feels as though the engine overruns the tranny (for lack of a better description). Basically, the engine seems to be ahead of the tranny for a second after letting off the gas and the tranny has to catch up and find a gear.

I agree FCA trannys for the most part are crap. I'm glad to hear it might be better with some newer ones but that also could just be that most don't enough miles to be having widespread problems... yet.

 

[HEMIMANN]

If you haven't gotten rid of that stupid pencil thin themostat in the the trans oil cooler line, you'd better be changing your transmission oil every 20,000 miles due to excessive heat.

Think of it this way - your engine oil operates at 220 F, and you change it at 5,000 miles. I know it's not apples to apples because engine oil also holds combustion blowby contaminants, but you get my point.

Oil oxidizes and breaks down with temperature and stress. And it's not linear - it's exponential. For every 18 degrees F above 140 degress F, oil life is cut in half. Oil time trans oil changes @ 50,000 miles were designed for max. 160 F bulk oil temp - NOT what FCA called their new "normal".

 

[70UTE]

OP, is your fluid getting burnt? If so, I'd tend to agree with @gtomike60 in post #2. I've been through two rebuilds on my 66RFE (both warranty at the dealer due to valve-body issues related damage) and it still feels a bit like it slips during hard acceleration. I keep a close eye on the fluid and it's never burned so I've just chalked it up to how the tranny is. With hard acceleration it feels as though the engine overruns the tranny (for lack of a better description). Basically, the engine seems to be ahead of the tranny for a second after letting off the gas and the tranny has to catch up and find a gear.

I agree FCA trannys for the most part are crap. I'm glad to hear it might be better with some newer ones but that also could just be that most don't enough miles to be having widespread problems... yet.

No burnt fluid and the filters and pan magnet look good without much buildup. I grew up in a transmission shop, my old man built everything from powerglides to 68rfe and everything in between. I’m not big on modifying outside of OE unless it’s a true problem solver. I’ve monitored this thing as best I can looking at line pressures and temp during daily, highway and towing. I never see temps over 175. Mind you I don’t haul a huge trailer but it is used as intended. I need to take a video of acceleration to show the actual rpm vs output. I lose rpm under light acceleration in what it seems only one gear, during downshift it falls on its face and then hits hard as if a trans brake is applied. It’s borderline death when trying to pass someone on the highway as the truck won’t get out of its own way. Using manual shift on the column toggle I can hold second gear and fell as well as see the rpm drop as I’m accelerating. It’s an absolute mind F**k. I’ve never in all my days had a trans act like this.

 

[70UTE]

If you haven't gotten rid of that stupid pencil thin themostat in the the trans oil cooler line, you'd better be changing your transmission oil every 20,000 miles due to excessive heat.

Think of it this way - your engine oil operates at 220 F, and you change it at 5,000 miles. I know it's not apples to apples because engine oil also holds combustion blowby contaminants, but you get my point.

Oil oxidizes and breaks down with temperature and stress. And it's not linear - it's exponential. For every 18 degrees F above 140 degress F, oil life is cut in half. Oil time trans oil changes @ 50,000 miles were designed for max. 160 F bulk oil temp - NOT what FCA called their new "normal".

I tend to be on the proactive side of fluid changes. Oil is done at 4500 no questions. Trans is between 20 and 30K. Agreed that there are many differences between the two but I’m over particular about scheduled maintenance.

 

[70UTE]

It seems to me that with everything you've replaced,it pretty much leads to the conclusion that your clutches are slipping and you need a rebuild.
Went through pretty much the same thing a few years ago with mine at 123k

Unfortunately I have to agree. I think it’s time to do it before it grenades and turns into hard parts replacement. Until I make a decision it’s back to the Tacoma for daily use.

 

[gtomike60]

???

Jacking up your truck, leveling it, running the drivetrain while filling is no more difficult than a gravity drain from an RFE! Not to me.

I'll admit the filling from underneath versus a dipstick tube is a pain in the butt,but realistically,it's not difficult.
And you run the 66RFE and run it through the gears and recheck the level don't you?
Both transmissions drain by gravity,so your point there is moot
I have a jack that gets the trans level at full extension

And the 8HP has a higher horsepower/torque rating than the 66RFE,so it's not operating at max capacity,or close to it, most of it's life
The RFE has always had issues since it was introduced,and continues to be troublesome to this day,so for me,the swap is worth it

I hope your RFE has a long life

 

[mtofell]

No burnt fluid and the filters and pan magnet look good without much buildup. I grew up in a transmission shop, my old man built everything from powerglides to 68rfe and everything in between. I’m not big on modifying outside of OE unless it’s a true problem solver. I’ve monitored this thing as best I can looking at line pressures and temp during daily, highway and towing. I never see temps over 175. Mind you I don’t haul a huge trailer but it is used as intended. I need to take a video of acceleration to show the actual rpm vs output. I lose rpm under light acceleration in what it seems only one gear, during downshift it falls on its face and then hits hard as if a trans brake is applied. It’s borderline death when trying to pass someone on the highway as the truck won’t get out of its own way. Using manual shift on the column toggle I can hold second gear and fell as well as see the rpm drop as I’m accelerating. It’s an absolute mind F**k. I’ve never in all my days had a trans act like this.

Yeah, it sounds like there's definitely something wrong. It's strange it isn't falling into limp mode with what you describe. Even thought FCA built a pretty crappy tranny they did put in a sensitive safety protection system. My first failure (38K) was strange in that it just blew pretty much instantly when sitting in traffic. I hit the gas to go and the truck essentially went nowhere. I was able to get it off the highway but that was about it. The second failure was much more gradual and started with some bad shifts but mainly it just kept getting stuck in limp mode so only gears one and four.

I recently took a road trip through Nevada and was on a lot of two-lane highways passing and she'll get up and go when needed for sure so, again, you are right that something's not right. Keep us posted.

 

[70UTE]

Dropped it off with the local Ram service center. Explained the entire dialog with them. They completed a relearn and “software update”. Completed a test drive and was able to repeat the rpm loss while accelerating and driving under load. Interesting that they could not find a single thing wrong, all line pressures are fine, all solenoids are fine. Nothing alarming in their diagnostic testing. The service manager was nice enough not to charge me because they couldn’t find anything wrong and had the truck all day with a total of 75 drive miles during testing. Back to the drawing board for me as I make a decision on replacing the entire unit with a built one from a supplier or just rebuild it myself.

 

[mtofell]

Interesting that they could not find a single thing wrong

Not that it's any help but it's got to make you feel better about your own skills if the pros can't figure it out.

 

[70UTE]

Not that it's any help but it's got to make you feel better about your own skills if the pros can't figure it out.

It is a decent feeling knowing I’m not crazy lol.

 

[70UTE]

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I don’t know how well this is going to work but here is one example of the issue I’m dealing with. Only giving it part throttle, rpm loss but continue gaining speed.

 

[iammattjones]

Dropped it off with the local Ram service center. Explained the entire dialog with them. They completed a relearn and “software update”. Completed a test drive and was able to repeat the rpm loss while accelerating and driving under load. Interesting that they could not find a single thing wrong, all line pressures are fine, all solenoids are fine. Nothing alarming in their diagnostic testing. The service manager was nice enough not to charge me because they couldn’t find anything wrong and had the truck all day with a total of 75 drive miles during testing. Back to the drawing board for me as I make a decision on replacing the entire unit with a built one from a supplier or just rebuild it myself.

Mine is doing the exact same thing. At the exact same mileage. I've had 3 shops look at it, one agreed the trans needed to be replaced but Mopar declined my claim due to lift and larger tires. I'm going to go with an ATSDeisel.com 66RFE. They have stages all the way up to 500hp. So the transmission shouldn't be overworked ever with a stock motor. I swear sometimes this transmission thinks it's a breadbox then suddenly decides to identify as a transmission, then clunkily shifts where it *thinks* it needs to be. Which is never where I want it to be.

 

[theviking]

Having just gone through a trans rebuild I think there are reasonably priced upgrades which address most of the common issues. I see a lot of big dollar 68RFE trans builds available but seems like the diesel guys blow those up just as easily. In my case I wore out the overdrive cluches and 5th/6th started slipping.

Personally, I would upgrade the valve body (accumulator pistons, springs, seals, etc) and channel plate to handle increased line pressure. Sonnax and other companies make a variety of components to handle this. Overdrive clutches are the primary weak link for sure, but there are a number of upgraded friction plates available. My shop added an extra clutch without having to purchase an aftermarket housing kit. I purchased a Mag-Hytec pan since it holds extra fluid and has a drain plug.

IMO the stock converter is junk, at least as far as drivability is concerned. I purchased a 2600 stall Edge converter from Moe's and it's been one of my favorite upgrades. Night and day over the stock converter.

 

[buckeyexx]

Having just gone through a trans rebuild I think there are reasonably priced upgrades which address most of the common issues. I see a lot of big dollar 68RFE trans builds available but seems like the diesel guys blow those up just as easily. In my case I wore out the overdrive cluches and 5th/6th started slipping.

Personally, I would upgrade the valve body (accumulator pistons, springs, seals, etc) and channel plate to handle increased line pressure. Sonnax and other companies make a variety of components to handle this. Overdrive clutches are the primary weak for sure, but there are a number of upgraded friction plates available. My shop added an extra clutch without having to purchase an aftermarket housing kit. I purchased a Mag-Hytec pan since it holds extra fluid and has a drain plug.

IMO the stock converter is junk, at least as far as drivability is concerned. I purchased a 2600 stall Edge converter from Moe's and it's been one of my favorite upgrades. Night and day over the stock converter.

What difference do you notice with the new upgraded torque converter? Was there something that you noticed wrong with the oem that made you feel the difference? I’m getting ready to upgrade my valvebody and solenoid pack and just curious about the torque converter.