The Simple Guide to Maintaining and Upgrading Truck Transmissions

Learn warning signs of a bad truck transmission and find out how best to upgrade your rig.

Part 1, Hot Isn't Cool: "I think the vision an outdoorsman has of a hunting or fishing trip is a lake filled with jumping trout or a big deer stepping out into view at first light. I don't think it's peering under a truck, watching boiling transmission oil pour out onto the ground."

Those are the words of transmission specialist Brian Appelgate of B&M Racing and Performance Products. I've corralled him at a trade show to talk turkey: I want to know how hunters and fishermen can improve the performance of the automatic transmission in their 4x4.

His words surprise me. I was braced for an arcane discourse on clutch packs, control valve bodies, and vacuum modulators.

Appelgate looks at me, smiles, and says, "Now that I've got your attention...." This is a guy used to the thousand-yard stares that transmission talk normally induces. I realize I'm in for something special. So stay with me; you're about to get a painless lesson on how to keep your transmission out of trouble.

Cool Solutions: "Hunters and fishermen need to know that a transmission will last the life of vehicle--if it's cooled properly," Appelgate says. "Unfortunately, the way your guys use their trucks--grinding slowly over offroad trails, climbing steep hills, towing boats and trailers--places a great deal of stress on the transmission. Stress creates heat, and heat is the number one killer of automatic transmissions. That's the main reason why so many fail prematurely. But that can be prevented."

How?

"The primary way to control heat is with an auxiliary transmission oil cooler. Any good unit that can circulate transmission fluid efficiently will do the job. And when the fluid stays cool, the transmission enjoys a long life."

I interrupt. "All right. I hear you. But over the years I've talked to many outdoorsmen who believe such equipment really isn't necessary. They say, 'I don't stress the vehicle enough to need one. And besides, the truck comes with a cooler. The dealer's just trying to rip me off for another option.'"

"Yeah. Well, we at B&M for the most part disagree. First, just doing what you guys do--hunting and fishing--stresses the transmission in ways many outdoorsmen don't consider. For example, when you climb a steep offroad trail, you often get a lot of wheelspin, which generates extra heat in the transmission fluid. That's why even though original equipment transmission radiator technology has come a long way, we still recommend an auxiliary cooler.

"Still not convinced? Think of it this way. It's really no more than an inexpensive insurance policy. Our cooler costs about $60 retail. Compare that to as much as $2,000 for a rebuilt transmission."

Appelgate's eyes have lit up. He's in his element. "In addition, there are a few other things--besides ongoing maintenance, such as changing the fluid and making sure the filter is clean, which many people ignore completely--that anyone can do to increase the life of the transmission.

"Next on the list is to install a deep transmission oil pan. A deep pan allows the transmission to benefit from another 3 to 4 quarts of fluid. If you can circulate a larger quantity of transmission fluid, you greatly increase the ability of the transmission to stay cool."

Though a deeper pan means a small loss in ground clearance, most 4x4s are high enough so the loss doesn't affect offroad performance. It's a worthwhile compromise.

Slipping Into Trouble: Appelgate moves over to a cut-away transmission display in the booth. His fingers run over the polished metal surface as if it were the Rosetta Stone. "Heat can also be caused by how the transmission operates internally. Most late-model transmissions are built to be comfortable to the driver even though the shifts may not be most efficient for the transmission. What I mean by this is that some shift overlap and slippage is built in for smooth operation. What we've found, and this is based on years of high-performance transmission experience, is that by improving the quickness and the firmness of the shift just slightly--not enough to be uncomfortable--we can reduce the slippage considerably in the transmission and thereby reduce the heat."

How do you do that?

"The simplest way is to use our do-it-yourself Shift Improver or Transpak valve body recalibration kit. A few simple hand tools and a three hours of time allow you to modify the hydraulic circuit of the valve body."

None of this alters the status quo of computer controls, so engine performance isn't affected.

I ask Appelgate one last question before I leave: "Brian, B&M is really known as a racing company. What have you learned from racing that translates to guys who hunt and fish?"

"Well, actually, it directly relates. By building transmissions for more than forty years for racing applications, we've found out what all the weak points are. And that helps us improve the breed. Obviously, we don't try to apply everything we learn in racing to a light truck or a hunting and fishing application; nonetheless, a lot of it still applies. It has allowed us to find the most efficient and least expensive ways to cool the transmission."

"Most efficient and least expensive." Now those are words that anyone can understand.

The Big Five: B&M offers a full line of transmission performance accessories, but five are of particular interest to hunters and fishermen. All are designed for easy do-it-yourself installation.

1) Auxiliary transmission oil cooler. If you want more than 100,000 miles out of your transmission, get one of these. For what it does, it just may be the most inexpensive performance product on the market. ($60.)

2) Deep oil pan. In a nutshell--more oil, better cooling. This is a must for 4x4 owners who tow. B&M deep pans also offer a drain plug that allows easier service of the transmission. The pan has a filter extension, which places the filter down toward the bottom of the pan where it can draw in the coolest oil. ($45-$125)

3) Remote Transmission Filter. The other transmission killer is contamination of the fluid. A remote filter makes it easier to access and change the filter. ($30)

4) Temperature Gauge. The optimum operating range of the transmission fluid is between 160° and 200° F. Above that, the fluid starts to lose its lubrication qualities. The B&M gauge is an analog model that displays temperatures from 100° to 350° F. ($45)

5) Valve Body Recalibration Kit. Improves shifts. More important, it helps reduce slippage, which reduces heat. (Shift Improver Kit: $30; Transpak: $55.)

Part 2, King of the Grapevine: As you drive along at 65 mph, bass boat in tow, the Lyons Ave. Exit on California's Interstate 5 looks like any other freeway interchange. It's home to the usual cookie-cutter cluster of service stations, fast-food restaurants, and convenience stores. You stop, refuel, grab a cup of coffee and maybe a pack or two of Nabs or Devil Dogs. Just like you would any place else.

But Lyons Avenue is different, for just off the freeway you'll find The King of The Grapevine. This monarch doesn't stroll around in a royal purple robe. You'll find him in more common fare, which suits him just fine. This "king" is George Mayer, owner of Mayer's Freeway Shell.

Mayer's kingdom is just down the road from The Grapevine, an infamous stretch of highway that leads to a pair of popular fishing destinations: Castaic and Pyramid lakes. The Grapevine is a torture test supreme for vehicles--36 miles of steep, twisting, mountain grades. Vehicle and towing component manufacturers have learned the hard way that it's a route of no mercy; the notorious gauntlet quickly reveals any flaws in a product's design or execution.

For the past thirty years, tow vehicles stressed to the breaking point by The Grapevine have landed in one of Mayer's service bays, and this hands-on experience has made him a leading expert on towing. During a recent towing test, I stopped at Mayer's station to refuel. While the dual tanks on my diesel tow vehicle drank their fill, Mayer and I talked.

His observations are worth noting by anyone who uses a truck or sport utility to tow or haul heavy loads.

Weighty Matters: "I think heat is the biggest factor in towing," Mayer tells me. "The vehicle runs too hot."

How do you handle the heat?

"First thing, make sure you have adequate vehicle. Size the vehicle to the load that you're pulling."

In other words, don't try to pull 5,000 pounds with a vehicle rated only for 2,000 pounds. That's a recipe for disaster.

"Next, give yourself a good margin for loading camping, hunting, or fishing gear. The weight of your family or a couple of buddies also needs to be figured in. You have to compensate for the additional load. Most people don't realize how much weight they're adding to the vehicle because they're packing it in a little bit at a time."

Good point. Weight can build up unexpectedly in several ways. Let's take the boat, for example. How did you determine its weight? In all probability, you simply noted a figure in the manufacturer's sales brochure--say 400 pounds.

But that may reflect only the weight of the hull. By the time you add the engine and other accessories, such as the trailer, you could be dealing with as much as 1,000 pounds.

And don't forget the weight of the fuel (boat and vehicle) or water (in recreational vehicles). Figure about 6 pounds per gallon of gasoline, 8 pounds per gallon of water.

"The best--and easiest--way to determine whether your tow vehicle can handle the load," says Mayer, "is to look up the gross vehicle weight (GVW) in the owner's manual. Hitch up the boat or camping trailer, fill the fuel tanks (on the boat as well as the truck), and load up all the additional gear and people. Then take it to a sand and gravel pit, grain elevator, building and supply company, county waste disposal site, or moving company. These facilities have large drive-on scales, and for a nominal fee you'll get an accurate read on your truck's total weight.

"You do that, you'll know exactly what you're dealing with. I think many people will find that they're overloaded--and that extra weight will kill a vehicle."

Why? Because weight creates heat. And the component that is most vulnerable to heat is the automatic transmission.

Hot Stuff: "Many people don't fully understand how heat fries a transmission," Mayer says. "The transmission will heat up fast while you're towing because the automatic transmission fluid [ATF] is moving very quickly through it. Heat breaks down ATF, and that leads to premature transmission failure."

Under normal operating conditions, the temperature of the ATF is about 170° F. Stop-and-go traffic can raise the temperature to 250° F--and that's without a towing load.

In towing conditions, it's not unusual to get 270° F.

"If the temperature gets up to 300° F," Mayer tells me, "you better stop at the next gas station, because you're not going to go much farther than that. You've lost it all."

The easiest and cheapest way to solve this problem is to install an auxiliary transmission oil cooler, which helps ensure that the temperature of the ATF stays in the best operating range. For some reason, many tow vehicle owners resist this option, even though the cost is miniscule ($60 to $120) compared to a rebuilt transmission (as much as $2,000).

Another inexpensive transmission-saver is a temperature gauge so you can see when the transmission is headed for trouble.

"I definitely recommend an auxiliary transmission oil cooler," says Mayer. "Remember, the cooler the transmission oil runs, the better. You're definitely going to hit yourself in the wallet if you don't have it.

"I also strongly recommend a drain plug on the automatic transmission--if you can find one. We've learned this from vehicles that get heavy usage. When the transmission oil is drained between filter changes, the transmission is a lot less prone to breakdown and failure."

Gearing Down: Mayer also believes that The Grapevine claims many vehicles "that are inadequately geared." By this he means that vehicle owners are running the wrong size differential gears.

Let's say the truck is fitted with a rear axle ratio of 3.08:1, which is fairly common. This gear ratio ensures good fuel economy, but may not deliver enough power to the rear wheels for optimum towing performance. The end result is a lagging engine and a hot transmission--a deadly combination.

But a truck equipped with a lower axle ratio (4.10:1, for example) can pull a load more easily with less heat buildup. This is especially important if your truck pulls heavier loads such as big bass boats. The tradeoff is higher fuel consumption, which is still cheaper than a transmission rebuild (see Chapter 6).

Simple Formula: The tanks are full. I'm ready to head up to Castaic to chase bass, but The King is still holding court. So I ask, "George, other than transmission work, what's the most common repair you see here?"

"The most common repair we see now is usually related to maintenance. For example, lately we've been seeing a tremendous number of people with pre-1990 carbureted vehicles that are hauling pretty good loads. These vehicles aren't set up for the newer fuels, some of which act as cleaning agents in the fuel tanks. And that can result in plugged fuel filters.

"It's actually pretty preventable if you do regular maintenance. If the filters were changed before the trip...."

"They wouldn't have to make a stop here, would they?" I say.

George smiles. He's seen it all up along The Grapevine.

The intricacies of towing can fill an engineer's notebook with fine print, but for most of us it boils down to a simple formula. If you want maximum towing or load-hauling performance, match the vehicle to the weight, keep the transmission cool, and perform regular routine maintenance. Basic advice. For my money, it's worth a king's ransom.