BD Diesel: Fixing The 68RFE Transmission Cross-Leaks

As you may know, we have already dipped into the brains of the experts at BD Diesel Performance regarding their 68RFE Transmission problems. Today, we’re going to dive into what exactly is wrong with these transmissions and what BD does to keep you and your truck running on the road.

To begin with, there are oftentimes cross leaks into the Overdrive Hydraulic circuit; but the leaking doesn’t stop there. The 68RFE has a known side-effect of failures starting with the valve body separator plate. The valve body separator plate is a simple stamped or laser cut sheet of steel that is sandwiched between the two halves of the valve body. What the separator plate does is directs the fluid flow into both castings and acts as a seal between the two halves.

Due to their design, it is inevitable that the valve bodies are going to cross leak. Yes, it is normal, but the problem with this transmission is that the leakage at the surface is not a minimal amount. As a matter of fact, it’s enough leakage to generate fault codes and lower the performance of the truck, or even put the truck into limp mode.

The 68RFE transmission comes in most of the 6.7-Liter equipped Ram trucks.

 

The BD team spent many hours looking into these issues and found more than expected. We spoke with BD’s Jeff Harris to see about their testing. “By using a scan tool, we have found that the pressure switch rising, followed by more elevated numbers. If the truck reaches a certain pressure, the truck will set a fault code,” said Harris. “The data logs showed that in this particular scenario, the pressure was elevated, but not enough to trigger a fault code. However, just because there isn’t a code doesn’t mean there isn’t a problem.”

The BD R&D team has manufactured their own gizmos and gadgets to figure out issues with factory parts.

Separator plate leakage is not something that you can physically mimic on the valve body tester, nor can you do it on a transmission dyno. “The only way we have been able to observe real-world results is by installing a battery of sensors into the transmission hydraulic circuits and strapping the truck down on the dyno,” said Harris. “Using our modified transmission oil pan, we wired our sensors into a high-speed data logger that is connected to the engine and TCM sensors.”

“To best replicate the fault, we observed the conditions that caused a P0871 in a late model truck (that already had the anodized valve body) and recreated those on the dyno. To keep it all equal, we held the truck at 2,000 RPM, third gear, put between 200-240 wheel horsepower of load on it, and held that for one-minute intervals, with brief cooldown periods in between,” said Harris. “Each time, the transmission temperature would climb somewhat, and we would continue repeating the tests until it was at least 200 degrees Fahrenheit in the transmission.”

To their surprise, it wasn’t until the fourth test that the problem began rearing its head. It was then possible to replicate every run after that while the transmission was hot. What happens when it’s hanging out at 15 psi continuously and lightly dragging the clutches without setting a fault?

After testing, you can see the parts of the gaskets that are doing better and sealing correctly now.

As you can see above, in this before and after picture, the pressure sensitive film is sandwiched between the plate and valve body casting. On the left, the factory valve body with the separator shows gaps between some of the fluid runways. The right, with the valve body gaskets installed, there are no longer gaps and it looks to seal much better than before.

“We tried fourteen different tests to work at eliminating and reducing this leakage. These tests included overriding solenoid control to eliminate the periodic pulse tests, staking check ball seats, flat sanding various pieces, changing separator plate surface finish, changing fastener torque values, and combinations of the above,” said Harris. “Finally, we made a set of one-off paper gaskets cut with our laser etch machine for the separator plate.”

“Once we aired out the smoky new gaskets, pressure sensitive film was used to check clamping force on the sealing surfaces. The gaskets provided a much more even sealing surface and gave us a strong indication that they would be an improvement,” said Harris.

“After dyno testing, the results showed that we were able to get our overdrive leakage pressures down from 16 psi all the way to a measly 5 psi,” said Harris. “Remember, this is 5 psi at high temperature, high load, and high line pressure. This is well within the realm of normal cross-leaks from valves and other areas of the valve body and well within our comfort zone.”

As you can see, after the BD fixes on the valve bodies, they are actually safer and performing better than the factory units.

Given this news, it followed that all of the BD Diesel 68RFE transmissions come with these special gaskets and separator plates. With this combination, the transmissions will withstand a lot more stress levels, including higher line pressures. “Our transmissions are intended for 250-260 psi at full load,” said Harris. “These gasket and plate kits are also available separately from the complete trans kit, but keep in mind, if you use these we strongly recommend you upgrade the valve body to the late model anodized unit. It will eliminate the previously found SSV leakage issue.”

After speaking with the specialists at BD Diesel Performance, we now hold a comfortable peace of mind knowing that these 68RFE transmissions really aren’t as bad as it may seem. For a simple weekend project, BD now offers a fix if you’re experiencing these problems or want the insurance against it happening in the future. For more information and to buy your next transmission and valve body, check out their website.

Article Sources

About the author

Artie Maupin

Artie Maupin is from Southeast Missouri and has an extreme passion for anything diesel. He loves drag racing of all kinds, as well as sled pulling competitions.
Read My Articles