Transmission Refill and Initial Run Instructions
Once the transmission is installed back into the chassis, a refill and initial run procedure is required:
Flushing Transmission Cooler and Lines
The transmission cooling system is comprised of a small radiator inside the engine cooling system radiator. The transmission cooler transfers heat to the engine radiator as the transmission fluid travels from the transmission convertor, to the transmission cooler, and then returns to the transmission and feeds the transmission lubrication system thus lubricating the bearings, thrust washers, clutch discs and gears.
If the engine radiator is in “questionable” condition, it is recommended that you replace the engine radiator which will in turn also replace the transmission cooler. Here are reasons to flush or replace the transmission cooler:
When flushing a transmission cooler, always use ultra-low pressure fluid or air pressure. The cooler is easily damaged by high pressure shop air or high pressure fluid flushing procedures.
To flush a cooler, use a low air pressure (no more than 5-8 PSI) to first purge all old fluid from the lines and cooler. Once purged, flush the lines and cooler with suitable cleaning fluid (connect the Safety Clean tank to one end of the line and connect a return line to the tank basin. Flush until clear then dry with low pressure shop air. If you do not have a cleaning tank, spray Brake Cleaner into the line at cooler top and capture the return flow into a container at the other line exit point. Follow up this cleaning process with low pressure air to purge and dry the system of cleaner. NOTE: Be sure that you do not detect any flow restrictions while cleaning / purging. When in doubt, replace the radiator and flush the lines. A plugged or restricted cooler will damage the transmission.
Metal Cooler Line Repair
Metal transmission cooler lines move transmission fluid from the transmission convertor to the transmission cooler inside the radiator and back the transmission where the oil lubricates the bearings, gears, clutch packs, and thrust washers. The cooler line system must be leak free and allow fluid free-flow. Sometimes you may have noted that repairs of cooler lines may use a rubber or neoprene hose slipped over the two metal lines and secured with a worm clamp. This is a suitable temporary repair, but not a recommended long-term repair.
To correctly repair a section of damaged line, use the appropriate sized metal tubing bent to the correct configuration, and secured at appropriate retention locations. Splice metal lines to each other using brass double compression fittings. Be sure to securely tighten the compression fitting to ensure a leak free connection that will not come apart over time. Use the compression fittings over clean rust free metal lines. In some cases it may be better to simply remake a new metal line that will be connected to the transmission and cooler. This is easily accomplished by using the original line as a “bend guide” and adding the flare nuts and flares to each end.
Be sure the cooler line does not contact any frame members, engine or transmission housing, and related. The line should be securely fastened at the OEM recommended locations using the appropriate OEM style bracket. If line contact does occur, you may hear a “buzzing sound” in the passenger compartment while driving or idling. Plus, a line that contacts will eventually rub through and create a leak.