QUESTION: What is the difference between a Transmission Fluid Exchange and a Transmission Oil Cooler (TOC) Flush? Are they not the same thing?

ANSWER: No, they are not the same thing; but they are each equally important and necessary services. According to the Automatic Transmission Rebuilders Association (ATRA) fluid breakdown is the number one cause of transmission failure.

Friction modifiers are chemical additives in ATF that affect how smoothly the transmission shifts gears. Over time, heat and constant shearing break down the ATF. The friction modifiers lose their ability to lubricate and protect moving parts, shifts become hesitant and rough, and lubrication-related failures begin to occur.

Transmission Fluid Exchange is commonly used as a routine transmission maintenance service. It is recommended when the existing transmission fluid has been in the vehicle so long that the additives that protect the fluid from thermal breakdown are themselves depleted. Always follow the vehicle manufacturer’s recommended service interval for transmission fluid replacement.

The traditional transmission fluid drain and fill (by dropping the pan) only replaces about ½ (maybe a little more) of the fluid in the entire system. Most fluid exchange equipment available today will connect directly to the TOC line and uses the transmission oil pump to move fluid. Old fluid is pumped out while new fluid is drawn into the transmission. This method actually replaces almost all of the fluid, including that in the torque converter.

Fluid exchange equipment does wonders for replenishing transmission fluid additive strength. However, it does little to remove any debris or sludge that has settled in the bottom of the system, or accumulated in the TOC.

TOC Flushing is used to remove metal shavings, debris or excessive sludge that is in the TOC. When you overhaul or replace a transmission, TOC flushing is mandatory to ensure that oil flow is adequate to maintain cooling.

After flushing, install a TransGuard transmission filter. TransGuard installs where the Transmission Return Line connects at the TOC outlet and protects your transmission repair from any debris that may still be circulating in the system.
 
The in-radiator TOC circuit in most vehicles uses water temperature to help maintain optimum transmission oil temperature. Replacing the TOC can require a complete new radiator, and late model installation can often include disassembly of the entire heat exchanger stack, A/C system service and more. Although replacement may at times be necessary, such as if the TOC is leaking, it can be a very expensive solution.

Computer monitoring of minimum and maximum oil temperatures is common in today’s vehicles. For that reason, bypassing a failing OE TOC and hanging an economical auxiliary cooler is no longer an effective alternative to flushing. Flow rates and cooling outside of the established OE computer monitoring parameters will confuse the computer, possibly set trouble codes, and send the technician down an unnecessary and costly troubleshooting path.

Small passageways in modern TOCs act like a filter and capture large metallic and clutch particles. It only takes a metal shaving or hard particle the size of a human hair (30 microns) to plug a transmission valve.

Constant heating and cooling of the fluid also strips varnish and wax from the lubricant, making a sludge that slows fluid flow. Over time enough debris and sludge accumulates to reduce or completely block TOC passageways.

The most cost effective solution is to back flush (remember fluid exchange is done in the normal flow path) the TOC with an effective chemical cleaner using equipment that features adequate volume, velocity, and powerful agitation. Significant velocity and agitation are required to dissolve sludge and to dislodge and back out any restrictive debris from the TOC.
 
Using effective TOC flushing equipment (such as HECAT’s pulsing technology) will usually take no more than 10-15 minutes to accomplish the cleaning and flow verification process. In addition, the use of an environmentally friendly cleaning chemical (HECAT Safe-Flush) and recycling (a feature of some HECAT models) will keep the cleaner costs around $5 per TOC. Used cleaner can be disposed of with waste oil products.

Add a reasonable TOC flushing labor charge to your transmission R&R fee. You will produce a rapid ROI on the equipment investment, produce more profit dollars for the shop and provide better protection for the new or overhauled transmission. You will also offer the most effective and reasonable cost solution for the customer. Everybody wins!

Poor performing equipment and chemicals can leave debris and sludge loosened but not fully removed. This spells disaster for the new or overhauled transmission. Enough debris or sludge can break loose during the first 100 miles after the repair to enter and damage the transmission.

Install a TransGuard Filter after cleaning (or replacing) the TOC and verifying that fluid is flowing. TransGuard will protect the new or overhauled transmission from any small metal particulates that may pass through the TOC, thus further guaranteeing the quality of your work and the cleanliness of the fluid in the lubrication circuit.