68rfe

Hemi395 said:

FWIW my 1500 came from the factory without the TBV. I'm in New England and we get temps from -10F to 95F+. I've never had an issue with my trans shifting in the cold but I also run Redline C+ in it.

This winter I'll pay attention to what gear it in when it's cold out but I don't remember it not going into 5th until the fluid temp hit 55...

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I’m not sure what trans you have, but this is specifically for the 66 and 68. It’s not a matter of the type of fluid, but the way they are programmed to function. It even explains this in the diesel supplement manual.

Jimmy07 said:

Y

Just a note on removing the thermal bypass and running open, for others that might come along and think “running cooler fluid must be a good thing”- This should ONLY be considered for those in consistent hot climates. The trans won’t shift past fourth and there will be no torque converter lockup until the fluid reaches about 55f. Without a bypass, this would take considerably longer in extremely cold temps.

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Yeah I would not recommend the thermal bypass valve for people in constant extreme cold temps. The TBV is easy enough to swap out every summer for those who want to run the stock unit during the winter and the open one during the summer. It takes less than 10 minutes and you only loose about a half a quart which is easy to refill.

Where I really noticed the difference is in stop and go traffic on a hot day. Since the stock unit has a restriction, there is not as much fluid recalculation even with the internal thermostat open as you can see in the pics. Before installing the Revmax TBV, my temps would climb past 200F in traffic and would never get past 185F afterward. Ironically, the week I installed the Revmax TBV, I had the longest time sitting at iddle that I have ever had that weekend. I was waiting in line for the ferry to go to Port Aransas. Sat in line for over an hour in 100F+ heat. That would have easily put me past 210F with the stock one, but I never got past 185F.

Unloaded and light towing, my temps are between 150-170F. Stock they were 170-175F in the same scenario depending on the outside temp. Towing heavy, temps are between 170-175F, and stock they were between 180-195F.


This is the hot side(with the thermostat) going from the trans to the cooler. Even if completely open, there is still a restriction compared to the Revmax TBV.




This is the cool side coming from the cooler to the trans.




I wish I would have taken a picture of the Revmax TBV. It is open on both sides just like stock cold side is on the stock TBV, but with larger ports for more flow.

I will also add that the location of the temp sensor on the 66/68RFE is not the hottest part of the transmission. The temp sensor is on the sump side of the valve body so it is reading sump temps. The hottest part of the trans is coming from the torque converter and is generally 30-40F hotter than sump temps. If you have a laser thermal gun, take the reading of the hot side line coming from the trans right before it goes into the TBV. This will be a closer representation of the hottest temp in the trans.

It is also possible for the thermostat in the TBV to fail over time just as with any other thermostat would. My trans rebuilder said that this is somewhat common and why burnt overdrive clutches is a common failure for those who don't change their fluid sooner than what the manual states.

Jimmy07 said:

Yes, 66 also uses a TBV


Just a note on removing the thermal bypass and running open, for others that might come along and think “running cooler fluid must be a good thing”- This should ONLY be considered for those in consistent hot climates. The trans won’t shift past fourth and there will be no torque converter lockup until the fluid reaches about 55f. Without a bypass, this would take considerably longer in extremely cold temps.

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This is very good advise. Another item often overlooked when looking to reduce temperatures is the lubricant and what temperatures the lubricant is designed to best operate and lubricate.

Changing the operating temperature, in this case, the transmission isn't a good idea.

From what transengineer, an actual Chrylser engineer who worked on the 68RFE, stated in turbodiesel register and other forums, the TBV's main purpose it to get the fluid up to operating temps quickly to aid fuel economy. The temps will eventually get up operating temp like many other transmission that have oil coolers with no TBV, but it will take a lot longer in colder climates.

I not only had it removed to keep the fluid cool in the hot climates I tow in, but I also didn't want it to fail like it did to my brothers 2500. The thermostat in the valve was stuck closed. This seems to be somewhat common.

Have there actually been trans failures in the 545/65/66/68 trans (or other transmissions for that matter) due to fluid temps being too low?

Pretty sure there have been failures due to the fluid temp being too high.

Hemi395 said:

Have there actually been trans failures in the 545/65/66/68 trans (or other transmissions for that matter) due to fluid temps being too low?

Pretty sure there have been failures due to the fluid temp being too high.

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Bingo.




Sent while firmly grasping my redline lubed RAM [emoji231]

Get that **** off your truck is what I'd say. If it was a problem all of us pre 2012 who didnt get that wonderful tech in our transmsions would have exploded by now? The only reason it exists is for fuel economy goals, it drives everything when you had a president who weaponized CAFE to hurt manu's who don't do as they are told. Also gave birth to widespread emmisions scandals. Think, what year did this **** start? Right after mr obama got re-elected and weaponized the epa, coincidence? Yeah sure, ********. I'm glad my 2010 didnt have this garbage hanging off it.

lpfm1990 said:

66rfe and the 68rfe are the same trans, just different bell housing to fit the Cummins or hemi. So to be short. Yes


Sent from my iPhone using Tapatalk

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This is true on the inside the 66 has the 545 case . The 68 does not have pto like the aisin.https://www.allpar.com/mopar/transmissions/68RFE.html good read here

Fuel economy, yes, but only because the 66 and 68 are programmed not to shift past 4th with no converter lockup until 55* trans temp. The TBV helps achieve this quicker. Sure, this may not have been the case on pre 2010 trucks, but it is for the current ones, and needs to be taken into account when deciding to remove it in cold temps. Here’s were TransEngineer (mentioned above) explains another drawback in cold temps-



Also, the valve opens at 170*, so there’s no benefit having it removed above those temps, anyway, because the fluid is already moving through the cooler as if there were no valve. Of all the posts about the 68rfe on cumminsforum, temp issues and TBV delete just isn’t really discussed as being a problem. BUT, as with all aftermarket companies, there is a solution to every problem that doesn’t exist.

Ribtipram said:

This is true on the inside the 66 has the 545 case . The 68 does not have pto like the aisin.https://www.allpar.com/mopar/transmissions/68RFE.html good read here

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They also have different torque converter’s so they’re not really all the same but there are some similarities


Sent while firmly grasping my redline lubed RAM [emoji231]

What about when the TBV fails and fluid never gets to the cooler? I mean the bypass valve seems like a good solution to a problem that does exist....

My trans temps before the TBV delete would push 220 degrees in suburban traffic around Chicago in 80-85 degree weather, post delete it has a hard time reaching 150 in the same route.

I drove from Chicago to Kalamazoo 2 weeks ago, temps were in the 60’s, even after 2 hrs on the highway at 70mph, it never reached 140.

Here’s what I would do to help the trans live a long life.
TBV delete
Metal **** for the spin on filter
Bonded separator plate
Deep pan
Sonnax accumulator pistons & plate

If you want to get crazy, a DNJ billet valvebody channel plate

Hemi395 said:

What about when the TBV fails and fluid never gets to the cooler? I mean the bypass valve seems like a good solution to a problem that does exist....

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Then replace it. Pretty simple stuff. Just like we replace thermostats when they fail, but we don’t go around deleting those? Don’t get me wrong, anyone can do what they feel is best, but me? I’d rather replace a TBV than a TC due to not enough fluid not returning back to it in extreme cold temps.

Jimmy07 said:

Then replace it. Pretty simple stuff. Just like we replace thermostats when they fail, but we don’t go around deleting those? Don’t get me wrong, anyone can do what they feel is best, but me? I’d rather replace a TBV than a TC due to not enough fluid not returning back to it in extreme cold temps.

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The pour point for ATF+4 is -48*C.

https://sharena21.springcm.com/Publ...2d889bd3/2623ada3-92bb-e711-9c12-ac162d889bd1

If you live where it actually gets colder than that so the fluid gels, then yes you probably should leave the TBV on. But then it would be gelled in the trans as well...

Or, just run Redline C+ that has a pour point of -76*. Personally I'd just delete the TBV and run C+.

https://www.redlineoil.com/c-atf

But seeing as -48* is pretty damn cold and only people way far north would see those kind of temps, I say delete the TBV.

Want to know how to solve the problem in cold weather?

Put the cold weather cover on the grill and don’t let airflow over the cooler, that will help it warm up.

Personally I don’t care about the MPG increase, I can buy a **** ton of gas for what a new 66RFE costs. So I’ll deleted the thermostat on the trans, that and we have DECADES of real data on transmissions without thermostats to help get the fluid up to temp, and absolutely ZERO fails due to fluid being too cool.


2018 2500 6.4 4x4 4.10 Amsoil SS 0w-40, Softopper
Black Rhino Arsenal 18x9 +12mm
Cooper St MAXX LT295/70R18

2016 Durango 5.7 AWD 3.07 Redline 5W-30 RP 10-48
1996 Nissan Altima 2.4 Amsoil SS 5W-30

Jimmy07 said:

Fuel economy, yes, but only because the 66 and 68 are programmed not to shift past 4th with no converter lockup until 55* trans temp. The TBV helps achieve this quicker. Sure, this may not have been the case on pre 2010 trucks, but it is for the current ones, and needs to be taken into account when deciding to remove it in cold temps. Here’s were TransEngineer (mentioned above) explains another drawback in cold temps-



Also, the valve opens at 170*, so there’s no benefit having it removed above those temps, anyway, because the fluid is already moving through the cooler as if there were no valve. Of all the posts about the 68rfe on cumminsforum, temp issues and TBV delete just isn’t really discussed as being a problem. BUT, as with all aftermarket companies, there is a solution to every problem that doesn’t exist.

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Saying someone is a transengineer for fca is supposed to give hin credibilty? Do you know how bad these things are built? Ask him why he built this **** so badly would be what I would want to know before anything else. Automatic transmisions have been working great without this tech for generations, but future transmisons may not. It is this tech and similar that likely a culprit in many failures.

Have you watched the transmision video posted in the forum that goes into fine detail these rfe's were built? If not would you like too? I'll be happy to post it.

Burla said:

Saying someone is a transengineer for fca is supposed to give hin credibilty? Do you know how bad these things are built? Ask him why he built this **** so badly would be what I would want to know before anything else. Automatic transmisions have been working great without this tech for generations, but future transmisons may not. It is this tech and similar that likely a culprit in many failures.

Have you watched the transmision video posted in the forum that goes into fine detail these rfe's were built? If not would you like too? I'll be happy to post it.

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Please do[emoji106]

I’m just glad my install video is getting around! Maybe YouTube will send me some cash to be able to pay for the valve! [emoji1787][emoji23][emoji1787][emoji23]


2018 2500 6.4 4x4 4.10 Amsoil SS 0w-40, Softopper
Black Rhino Arsenal 18x9 +12mm
Cooper St MAXX LT295/70R18

2016 Durango 5.7 AWD 3.07 Redline 5W-30 RP 10-48
1996 Nissan Altima 2.4 Amsoil SS 5W-30

And this is a healthy discusion, I'm not trying to blow up your spot, I keep an open mind. But this is what we all bought, every guy with a rfe should watch that, and the valve body video.