When it comes to diesel-engine maintenance, there are always varying opinions about oil changes and when they should be done. While the mileage at which people feel it should be changed can vary from person to person, there is no denying that proper oil maintenance is a requirement. That said, when was the last time you changed the other fluids in your truck? You know, the stuff lubricating the transmission, differential(s), and transfer case?
While engine oils seem to get the required attention, how many actually maintain the rest of the drivetrain? In the case of Project WorkHorse, my 2019 Ram, the owner’s manual calls for a transmission fluid and filter change somewhere between 60,000 and 120,000 miles. That’s a large disparity so I am comfortable doing it now, at 69,000 miles. As far as the differentials, 20,000 to 30,000 miles is the suggested fluid lifespan. I missed the boat on that one. Since I knew it was time to give WorkHorse some new fluids, I also felt it was time to make a few easy 68RFE upgrades to help the transmission avoid any issues.
To accomplish this, I decided to add an aFe POWER deep transmission pan (P/N: 46-71160B), a larger-capacity rear differential cover (P/N: 46-71150B), and BD Diesel Performance‘s Cooler Bypass Delete (P/N: 1061527). While I was at it, I saw no reason to reuse the seasoned fluids, so I placed an order with AMSOIL for a few gallons of automatic transmission fluid for the transmission and transfer case, and a few jugs of 75W-90 gear lube for the differentials. Although this article is showing a Ram getting worked on, the maintenance intervals for the fluids are fairly common for you Ford and Chevy owners as well.
68RFE Upgrades For Keeping Heat Away
The reason for upgrading the transmission pan and differential covers is simple, heat reduction. Heated transmission fluid is the number cause of failures in almost every situation, and while the 68RFE transmission in WorkHorse has never experienced any issues or alarming operating temperatures, I am being proactive. Let’s face it, the 68RFE has a bad reputation in stock form and I am not taking any chances.
It is no secret that excessive heat is a huge contributing factor to many unexpected transmission failures. This is especially true when talking about trucks that see duty towing and hauling. Frequent exposure to temperatures in excess of 200 degrees will exponentially reduce a transmission’s lifespan. In fact, the optimal temperature range for transmission fluid is roughly 180 to 195 degrees. For every 20 degrees above 200, bad things happen. For instance, varnish will start to form at 240 degrees, followed by the hardening of seals, plates slipping, seals and clutches burning out, and ultimately, failure.
There are various 68RFE upgrades you can use to improve the cooling system of an automatic transmission. While the addition of an auxiliary fluid cooler is a great option, in the case of the Ram, the OE cooler is of sufficient size, so adding an additional cooler will net minimal results.
Panning For More
That said, adding fluid capacity is a good way to help. Utilizing a deeper-than-stock transmission pan will accomplish this and be very beneficial. The larger aFePOWER pan carries an extra two quarts of oil, and although that might not seem like much at first, those two extra quarts can actually help a lot in the long run. Something else to consider is, having the added capacity is highly recommended for larger vehicles or when towing and hauling. Besides allowing more time between transmission services, the extra transmission fluid affords the fluid cooler more time to cool ATF even better.
Also, the aluminum construction of the pan delivers other benefits as well. First, a larger-capacity aluminum transmission pan is highly regarded as the quintessential piece of the 68RFE upgrades plan. An aluminum pan not only holds more fluid, but the aluminum is sturdier than a stock-stamped-steel pan and adds rigidity to the transmission case. Finally, aluminum also helps to dissipate heat better, which ultimately cools ATF better than steel.
No More Switch
Now, let’s talk about the thermal bypass valve that is found in the transmission cooling system as part of the fluid lines. The OE thermal valve is designed to direct fluid to either the cooler so it can then flow back to the transmission, or keep fluid from entering the cooler in cold situations. to allow the fluid temperature to get to an acceptable operating temperature quicker. How it works is like a thermostat. A heat-sensitive stopper and spring are actuated within the valve block. When the fluid is cold, the valve is closed, causing the transmission fluid to not flow to the transmission cooler. When a certain fluid temperature is achieved (around 170 degrees), the valve opens, and fluid can then flow to the cooler.
In theory, replacing the thermal valve is a good idea to include in any 68RFE upgrades plan. Why, you ask? Unfortunately, the valve can malfunction, resulting in transmission fluid never getting to the cooler. If the thermostat gets stuck closed, overheating of the transmission fluid is inevitable, and as previously mentioned, hot transmission fluid is bad.
To remove any possibility of the thermal valve sticking closed and causing issues, I ordered the thermal switch bypass (Cooler Bypass Delete) from BD Diesel. This bypass block ensures that 100-percent of the transmission fluid always flows to the transmission cooler, no matter what the fluid temperature. There is no valve that can stick closed.
There is a myriad of transmission and differential fluids on the market and choosing the correct fluids — especially for a transmission — can be confusing. In the case of my 68RFE, Ram calls for transmission fluid meeting ATF+4 specifications. The AMSOIL OE Transmission Fluid I chose to use does that, and resists wear and varnish. What’s more, if, for whatever reason, the transmission in WorkHorse would ever see elevated temperatures, AMSOIL’s thermally stable formulation guards against thermal breakdown. It also resists the formation of varnish that can cause internal valves to stick.
I do need to let you know, AMSOIL warrants the use of this product for Chrysler ATF+4 applications above -38 degrees. The product does not meet the cold temperature requirement of ATF+4 at -40 degrees. If it gets that cold where you live, my condolences. However, Amsoil recommends those in cold climates to step up to their best product that covers the spec, Signature Series Multi-Vehicle Synthetic Automatic Transmission Fluid | ATF – AMSOIL
Finally, the differentials each received AMSOIL’s 75w-90 Severe Gear fluid. Severe Gear is specifically engineered for use in vehicles that see more than just daily driving. Diesel trucks tow and haul things, so this will be the perfect fluid. Severe Gear maintains a stable viscosity and proprietary additives form an iron-sulfide barrier that coats gear surfaces, providing the ultimate line of defense against wear, pitting, and scoring.
The Severe Gear lube excels in extreme temperatures (I live in Florida), helps maintain efficiency, and outperforms conventional gear oil. It is an excellent choice for all cars and trucks, but especially well-suited for towing, hauling, racing, commercial use, or other severe duty. Don’t forget, I call the truck WorkHorse for a reason. I used the quart bottles, but I hear quarts are old news when it comes to filling differentials. When you order your Severe Gear, might I suggest you order the Easy Packs? These make it so much easier for DIY’er to pour into the differentials.
Our 68RFE Upgrades Did Make A Difference
While it is nearly impossible to quantify if any temperature change occurred within the differentials without expensive monitoring devices, I can say that I noticed a drastic change in transmission temps as monitored by the Bully Dog GT device mounted in the truck. In fact, I noticed the fluid temps dropped from 190 to 200 to between 160 and 175 degrees with the loaded gooseneck behind me. This was on level roads and the ambient temperature was 83 degrees on the day I did the testing.
These simple 68RFE upgrades are something that all diesel truck owners need to consider as they will surely increase the life of your truck which is always a good thing. And if your fluids have been flowing for more than 60,000 miles, what are you waiting for, something to break? All told, it only took the better part of an afternoon to complete the tasks and it was definitely worth the time investment.