Standard practice says you should change a vehicle's transmission oil every 60,000 miles unless it has been used heavily, in which case you'd want to change it more frequently. The transmission oil or fluid is what helps to keep the metal parts of your transmission cool enough that they do not begin to break down while you are driving. For an older "Class C" motor home, this is a very important aspect of your maintenance. Fortunately, it is easy to change the transmission oil in a 1978 Ford motor home. Marketed primarily under the name "Midas," these motor homes are easy to maintain.
Tools Used: Drain pan, Socket set, Engine cleaner/degreaser, Water, Rags, Paint scraper, New transmission pan gasket, Transmission oil, Funnel
Change Transmission Oil
Park your 1978 Ford motor home on a level surface and engage the parking brake. Wait for the engine to completely cool down before moving to Step 2.
Slide a drain pan under the transmission oil pan, which is located under the motor home on the transmission and almost directly in line with the cab doors. The transmission oil pan looks very similar to the engine oil pan: It has a flat surface, measures about 1 square foot, and has a series of bolts around the edges attaching it to the transmission.
Loosen and remove the drain plug to allow the transmission fluid to drain. The drain plug will be located on the side of the pan or in the bottom of the pan (1978 Ford motor home transmissions have two different types of pan, depending on where they were manufactured). Use a socket wrench to loosen and remove it. When the used fluid stops dripping, replace the plug in the pan.
Loosen the bolts attaching the pan to the transmission. Don't loosen each one in order around the pan rim; instead, work from one side to the other, slightly loosening one bolt and then doing the same for the bolt that is opposite it. Do this until all the bolts are loose enough that you can turn them by hand.
Press up against the bottom of the pan to hold it in place with one hand and remove all of the bolts with the other. When all the bolts are removed, pull the pan from the transmission.
Remove the old gasket. Use a paint scraper to remove any gasket material that is stuck to either the pan or the mating surface on the transmission. Scrape very gently so as not to score (damage) the metal of the pan or the transmission.
Clean the inside of a pan with an engine cleaner/degreaser. You can purchase this at any auto supply store. Spray the cleaner into the pan, wait five minutes, then rinse the pan with water and wipe dry.
Lay your new transmission pan gasket into place on the lip of the pan. Make sure the bolt holes in the gasket line up with the bolt holes in the pan.
Lift the pan back into position and reinstall the bolts by hand to hold it in place. Hand-spin the bolts in all the way, then, using a socket wrench and working from one bolt to its opposite, tighten the bolts into place.
Refill the transmission with new fluid. On a 1978 Ford motor home you will need a long spout funnel to reach the fill spout located in the engine compartment. Add half of the amount specified in your owner's manual. Turn the engine on and shift through all of the gears. Turn the engine off and check the level of the transmission oil. Continue to add small amounts of oil, then run the engine and move through the gears. Repeat this process until the level reads 'full.'
Tips & Warnings
It's a good idea to change your transmission fluid after any major trip (15,000 miles). The transmission and engine of an RV work harder then a car due to its weight and the stress of moving all that weight. It's better to play it safe and change your fluid more frequently then wait 60,000 miles for a change.
Do not install the transmission pan without thoroughly cleaning it first. Small bits of debris can remain in the pan and contaminate the new transmission oil and cause damage to the transmission.
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