Which Transmission is Right for Me?

By Jim McNeily

It was running great, never had a problem with it before, and then all of a sudden it started to smoke and puttered out. After limping off the road, from what my customer could see, all of the automatic transmission fluid was gone. Transmissions can't smoke like an engine, but when a transmission leaks three or four quarts of fluid on the red hot exhaust pipe, it smokes and can even catch fire. It also spreads all over the bottom and back of the vehicle. With that in mind, it is time to call AAA or a tow truck and have your vehicle towed to a reliable transmission shop for a diagnosis.

Let's say it is a 1999 Ford F-350 pick up truck with the 7.3L diesel engine and a 4R100 automatic transmission that you were using. The 4R100 is a Ford transmission and is known for puking automatic transmission fluid out the front pump seal when it's working hard in the hot weather. Simply put, the cooling system is the enemy in this situation. This article is not about cooling system repairs or updates, though, which is the remedy for the front pump leakage problem, but it is about choices.

When a transmission dumps the fluid in an unceremonious manner all over the road, it means that the front pump seal went south and no longer is 'holding fluid'. This is because the transmission loses most of its cooling ability under heavy loads and eventually, usually at the wrong time, the seal starts to leak transmission fluid just like a screen-door in a submarine would leak water. The problem is fixable with a good update kit and some added cooling.

The transmission has to be removed to fix a front pump leak and then the transmission shop must remove the transmission to fix the leak as well as inspect the transmission for damage. There is a good chance that the transmission has some significant wear in it, or enough wear to justify a remanufactured transmission. With that in mind, depending on how much wear and what is worn, a choice has to be made on how you want to fix your truck. You can fix the current transmission, buy a used transmission or have a rebuilt transmission installed in the vehicle. Everything depends on what your plans for the vehicle are. My advice is don't cheapen out here by buying the cheapest transmission available.

My recommendation will revolve around the fact that most of the time this happens when: A) It is a work truck carrying lots of weight B) The fluid is damaged from getting too hot all the time, taking the elasticity out of the front seal C) The pump failed. It is made of aluminum, which is a soft metal.The bottom line is that, if you do nothing other than regular errands and drive in a normal manner, at least make sure you buy a rebuilt transmission that is updated not to overheat under heavy load conditions. If this is a commercial vehicle, which is usually overloaded with just the tools and equipment on the truck, it is time to get serious. Also, the pumps we use in our shop were rebuilt with a metal sleeve where the gears wear the aluminum pump body, thus preventing a repeat problem.

Getting serious involves purchasing a rebuilt transmission with the most effective update kit installed and add a couple of external auxiliary transmission coolers to the transmission cooling system. Finally, request full synthetic automatic transmission fluid as a refill. Synthetic transmission fluid is like an added plus. It allows your rebuilt transmission to last its longest and function at its best. Don't forget to ask about the warranty because it is usually a good indicator of how much confidence the transmission supplier has in his merchandise. Meaning, a short-term one year warranty does not mean much when you can get a long- term three or five year guarantee on it. - 29952

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