As the popularity of the 6.7-liter Cummins-equipped Rams increase, the number of owners looking to modify them do as well. Unfortunately, some of the truck owners find the weak link of the entire truck/drivetrain combination. The 68RFE, a six-speed automatic transmission, hasn’t started its journey of life as a dependable option. With very little power added, like custom tuning, you can experience a transmission failure due to burned up overdrive clutches.
If more power than just a programmer is added, it can cause more damage than just compromising the clutches. Although it’s uncommon and they rarely see a failure from one, but you could observe a torque converter failure. By modifying a late model Cummins and driving it with a factory transmission, it’s nearly a guarantee that it will fail. Our friends at BD Diesel Performance have the explanation and the fix to reviving the 68RFE transmissions.
Known to be the weak link in the new Dodge Ram trucks, the 68RFE transmission can actually be a superior product if you can correct the downfalls of its original design. For starters, BD has found that the cross leaks in the valve body have been a serious problem. We caught up with Jeffery Harris of BD Diesel Performance to get the scoop on the fix.
“It’s be known among the country’s top transmission builders that the valve bores need to be inspected, vacuum checked, and repaired and that the flat surfaces need flat sanding to reduce cross leaks,” said Harris. “This old wisdom doesn’t always result in a fix for newer transmissions.”
“The most common cross leak observed with 68RFE transmissions is leakage into the overdrive (OD) hydraulic circuit. This, in fact, is the only chronic cross leak,” said Harris. “We, like most others, increase line pressure in our transmissions to increase clutch holding capability. The forewarning of increased line pressure is elevated cross leaks, so it is important for them to correct these leaks when making a performance transmission.
The commonly observed P0871 Date Trouble Code (DTC) is generated because of leaks into the overdrive circuit but are still, in some measure, responsible for the burnt overdrive clutches BD see’s on a daily basis. “The code is triggered when the pressure switch in the solenoid pack detects pressure in the circuit when it shouldn’t,” said Harris. “Our experimentation shows this switch triggers at 16-psi, this just so happens to be right around the pressure required to apply the overdrive clutches.”
This means by the time you’re setting P0871 codes, you’ve already been damaging overdrive clutches. More than likely, there are minor leaks from different areas, but after comprehensive testing, there are only two areas they need to concentrate on to correct this leak. The Solenoid Shift Valve (SSV) and the Valve Body Separator Plate.
“The existence of this valve is a ridiculous and it should’ve been done away with decades ago. The SSV is an assembly of valves that direct the output of the LR/TCC solenoid to the torque converter clutch and direct fluid flow to the low/reverse clutch,” said Harris. “ This was done to use two solenoids for one and it originated at a time when Chrysler transmissions only used 4 solenoids. After years of repairs, one would think the design would’ve been replaced, but here we are in 2017, and parts are backward compatible with 1989 Caravans.”
The issue with the SSV is the valves aren’t supported axially which causes uneven wear. Also, since the transmission solenoids are pulsed on, these valves can fluctuate rapidly during the clutch apply which will lead to increased wear. “This allows fluid from other clutches to leak into each other,” said Harris. “It is perhaps no surprise that the overdrive circuit is between the other two, so it’s the most susceptible to leaks.”
The familiar fix for many years was to ream this valve out and install the oversized valves. While working great, BD tests the 68RFE valve bodies on their custom tester equipped with a digital overdrive circuit pressure readout. “After further review, the “fix” wasn’t working. The problem with the fix is that the surface finish from reaming the bore isn’t near as smooth as factory, which led to accelerated wear; faster than the original time around,” said Harris. “After one to two years of heavy use, the leakage in a repaired valve bore was right back to where it was when we started which means this wasn’t a permanent fix.”
The early models of the 68RFE had a normal cast aluminum valve bodies without any coating on them. The later models ranging from 2010 and later, came outfitted with a hard anodized coating on them. They are identifiable by the darker color of the part. This hard coating substantially reduces wear on the valves and makes a remarkable difference in life for the SSV valve bore.
BD Diesel Performance and their 68RFE development program have found that hardly any of the core transmissions are sporting the anodized coatings. “Knowing now that the coating has made all of the difference, all of the BD 68RFE transmissions now come equipped with the hard anodized valve bodies,” said Harris. “Don’t fall for the ‘fix,’ reaming is a cheaper option but for this valve, it is not the right one.”
Stay tuned for more information on common issues and fixes for the late-model Ram truck transmissions. Be sure and check out the BD Diesel Performance website. What are your thoughts on this particular fix? Let us know in the comments below.