Monday, November 29, 2021


Be kind to your transmission for its long and happy life

By Greg Illes

Most of us check our transmission fluid now and then (don’t we?). Some of us even have it changed every once in awhile. But aside from that, what else is there to do with a typical automatic transmission other than drive it – and hope it keeps on working?

There are actually some very proactive things that can be done to give your transmission the best possible chance for a long and happy life.

Never forget that your transmission is not only a key link in your drive train, but one of the highest stressed as well. A typical motorhome, or trailer-hauling vehicle, works its transmission many times harder than any comparable street vehicle. And the single biggest enemy of your transmission is loss of lubrication. This can happen from something as simple as a leak (loss of lubricant) to something more insidious — the loss of the lubricity (capacity for reducing friction) of the oil in your transmission.

Fact is, transmission oils simply wear out. They work so hard that the long-chain molecules in the oil break up into shorter chains, with less lubricity. This happens largely due to only two factors: load and heat. The heavier the load and the higher the heat, the shorter the life of the transmission oil (and the transmission).

What can you do? It’s fairly simple:

Give your transmission the best possible lubricant money can buy. Cash spent on the excellent synthetic oils available will be more than paid back by extended transmission reliability and life span. Monitor the oil and change it at regular intervals, or when it shows any sign of wear (discoloration or burned smell).

Make sure you have a good transmission cooling system in place. This can be as little as a standard cooler in front of the engine radiator, or you can buy some more “temperature insurance” and install an aluminum oversize transmission sump. Both of these will drop transmission temperatures, increase fluid life and add to reliability and transmission life.

Lastly, it’s a good idea to monitor your transmission temperature, especially on hot days and steep climbs when it works the hardest. Many coaches and trucks have these gauges stock, or you can add one at a modest cost. Knowing when your transmission has undergone a long, hot spell can clue you in to managing your driving patterns, and changing that precious transmission fluid right after it’s been “cooked.”

photo: Hatsukari715 Wikipedia/public domain

Greg Illes is a retired systems engineer who loves thinking up RV upgrades and modifications. When he’s not working on his motorhome, he’s traveling in it. You can follow his blog at



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1 year ago

Please, won’t someone take The joke of the day to immediate care? It’s been limping for so long that it’s become lame. Poor thing.

1 year ago

From a 1995 article that I have, it states your tranny should be close to your coolant temp, ie: around 195ᴼ F as it’s cooled in the lower part of your radiator. It goes on to say GM recommends that the maximum transmission-fluid temperature (measured in the sump) for short durations shall be no greater than 285ᴼ F. At 300ᴼ F, research shows, metal parts inside the transmission begin to warp and distort, seals begin to melt, and fluid life is extremely short because of heavy oxidation. As well, in cold weather, excessive cooling can increase the fluid viscosity to a point where flow to vital transmission components is restricted. RVers who travel in both hot and cold weather may experience premature transmission trouble if they have installed a large auxiliary cooler. Some coolers have a by-pass which helps prevent overcooling. (Taken from Trailer Life magazine issue of July 1995). On my Ford F350 my transmission has never been over 214 degrees and my total weight is 25,200 lbs.

Dick and Sandy near Buffalo, NY
1 year ago

For those of us who have Diesel Pusher motor homes have mostly Allison transmissions that can hold from 12 to 48 quarts of fluid, depending on the model from a 2000 series to the huge 4000 series. Transmission repair can be a very expensive issue. HEAT is the major destroyer of transmissions, any transmission because of the friction involved. Always monitor your transmission fluid temperature and drive accordingly. There are basic instructions of how to drive while towing and/or driving in hilly or mountainous terrain.

Transmissions filters are usually easy to change out and are not overly expensive to be done at prescribed intervals.

There are tests for the quality of your trans fluid that will tell you the status and life expediency of your trans fluid. I highly recommend those tests be done at an authorized Allison dealer Changing out 48 quarts of trans fluid just because it has a lot of miles on it is not the way to go. Have it tested first.

Stay safe, Stay well.

1 year ago

How do I monitor the trans oil condition?
There is no dipstick, I can’t smell or see it!
What is too hot for a trans?

1 year ago
Reply to  Harry

you can by monitors which plug into the OBDII connector (bullydog is one). And they usually have warning points for overtemps on several sensors.

1 year ago

Thank you for the Excellent information. I do check the fluid level and never thought to also test for the lubricity!

1 year ago

THIS ARTICLE IS IMPORTANT! I volunteer as a Disaster Duty Officer for the Red Cross. I was on duty yesterday and received a call regarding a schoolie on WB I70 just inside the Utah state line. The RV was a total loss. The family of three was devastated that their life dream had gone up in flames before their eyes. The cause was an overheated transmission. They were notified and stopped before the smoke turned into flames and saw the smoke coming from the transmission and the gaskets dripping onto the asphalt. The best part is none were hurt. The worst part is they had picked it up from a transmission shop before setting out that day. The shop was supposed to change the transmission fluid and filter.

1 year ago

Few people even think about changing transmission fluid. I just checked Chevy’s interval for severe use like pulling a trailer and it says 45,000 miles. Another often neglected fluid change is the brakes. Brake fluid is hydroscopic, it absorbs moisture. That results in diminished braking power and corrosion in the braking system.

Daniel Bridger
1 year ago
Reply to  Bob

And where is it recommended to change brake fluid? It’s a sealed system, if there is moisture getting in, there is a leak and you would need more than a fluid change.

1 year ago
Reply to  Daniel Bridger

In doing some research, I’ve found that there is some disagreement about how well brake systems are sealed. I have read that small amounts of air can enter via the reservoir cap.

Even if the system is completely sealed, there is still the effects of heat to consider. the fluid in the lines entering the calipers or drums is being heated repeatedly as the vehicle is driven. This contributes to fluid breakdown and potential damage as well as diminished braking.