• JP Magazine
  • Dirt Sports + Off-Road
  • 4-Wheel & Off-Road
  • Four Wheeler

Gearboxing - The Transmission Debate

Posted in How To: Transmission Drivetrain on June 24, 2013 Comment (0)
Share this
Editor Cappa has a BorgWarner T-18 four-speed manual transmission in his ‘73 Jeep J2000. He seems to do well with it, but would he do better if he swapped it out for an automatic?

The automatic versus manual transmission battle is one of the oldest on record. Manual transmissions were standard equipment on early 4x4s, but automatic transmissions eventually burst on the scene and today the automatic dominates 4x4 sales. As a matter of fact, there are no new ½- or ¾-ton 4x4 pickups (with the exception of the ¾-ton Cummins-powered Ram) available with a manual transmission. Is this an indicator that the automatic transmission is superior to the manual? Four Wheeler Tech Editor Mansour says yes, Senior Editor Brubaker says no.

Allison 1000 six-speed automatic

Automatic: Drivers Have Spoken
There used to be a perception that a manual transmission was far superior to an automatic. We also used to think gas tanks under the seat and inside of the cab were a good idea- suffice to say that automotive engineers don’t always have the right formula the first time out. The fact of the matter is if more people wanted manual transmission 4x4s, they would buy them. There is a reason why so few companies don’t offer a stick shift 4x4—the take rate is dismal compared to the automatic. Some say it’s the result of the lazy modern American. I say the most developed nation is simply keeping up with the times.

The future of the 4x4 will probably have only two pedals.

Modern automatics are amazing. Sure, they are a bit heavier and more complex, but they make life easier on you and the vehicle on- and off-road. There are so many modern fail-safe’s built into the automatic transmission that destroying or rapidly overheating one to the point of failure takes more effort than not. If you are concerned about overheating your tranny, buy a temp gauge and use it. The same wheeler who overheats his auto tranny on the trail is just as likely to be the clutch cowboy that smokes his manual the first time out.

Let’s look at the Allison 1000 for a moment. It’s designed to easily handle 400hp and 800 lb-ft of torque in stock form. It has an excellent gear ratio selection, and similar to most electronically controlled automatic transmissions, the Allison 1000 can be manually shifted with a simple push of a button. This is a tow rig’s dream and used behind some of the most powerful diesel trucks in America.

Off-road is another spot where the auto shines. Again, with most automatics you can pick a gear and leave it. So when you are rockcrawling or doing any type of precision wheeling where throttle input and control is important, the auto delivers. Look at virtually any competition 4x4 and you won’t find a clutch pedal under the dash. Yes, autos can be power-robbing bandits that can make an already unpowered rig feel slower, but your real problem is your tiny engine, not the transmission!

The aftermarket is full of parts specifically designed to keep your automatic transmission alive and allow them to hold crazy amounts of power. Worried about heat? Get a deep pan and an auxiliary cooler with a fan. Want a lower stall? Have a custom torque converter built. Automatic transmissions are by design meant to make your life easier and allow you to focus more on driving duties. This means the automatic transmission is safer. It’s even been said that in most panic situations that people tend to lose motor skills. So if you are being attacked by zombies or hanging from the edge of a cliff, will you find the right gear and not stall out before it’s too late? Will you?

Summary: The limited availability of manual transmissions in the 4x4 market is all but putting a stake in the heart of the classic gearbox. Look, I don’t want to see the manual disappear, but if you don’t let the dealers know that they are important (by buying one!) then they have no reason to keep making them. Modern technology has gifted us with paddle shifters, eight-speed close ratios, and an overall stronger and lighter automatic that is allowing us to increase the performance potential and efficiency of our rigs. If you want to row gears, get a sports car. The future of the 4x4 will probably have only two pedals.
–Ali Mansour

Muncie SM465 four-speed manual

Manual: Simple, Inexpensive, Rugged
Clearly, automatic transmissions make driving on- and off-road easier. This point-and-punch simplicity gives you the ability to concentrate on other things, which is nice. However, in the off-road world there are many other factors to consider in transmission selection.

Let’s start with simplicity. If you take a gander at the guts of an automatic transmission you’ll see a zillion parts. If a part in the automatic transmission fails, the transmission may cease to function and leave you dead in the water. Thanks to the simplicity of the manual transmission, chances are that even with an internal failure you’ll be able to select a gear and keep moving. And if the starting system stops working on your rig, a manual transmission gives you the ability to pop-start the vehicle. Try that with your automatic.

In the end, the simple and tough manual transmission is the perfect transission for modern and classic 4x4s.

Speaking of water, this is another area where the manual transmission has the edge. Off-road travel often includes water crossings and sometimes a transmission can become submerged. If an automatic transmission ingests water it often becomes inoperable. On the other hand, a manual transmission can continue to operate.

A manual transmission also has the edge in size and weight. A manual is typically smaller and lighter than an automatic, which means it’s easier to install and remove and it helps to decrease your rigs overall weight. This helps to improve your rigs power-to-weight ratio and fuel economy. Even if a manual transmission only improves your mileage by 1 mpg, you’ll get another 30 miles of travel out of a 30-gallon tank of fuel. Multiply that by several tanks of fuel and the savings adds up fast.

And speaking of economy, some new 4x4s still come with a standard manual transmission (though the list seems to be getting smaller each year), which means you can skip the optional expensive automatic transmission and keep more of your hard earned cash.

When working an automatic transmission hard, like when crawling obstacles on a trail, plowing through mud, towing a heavy trailer, or plowing snow, it’ll build up heat. This heat is the sworn enemy of an automatic transmission and can contribute to transmission failure. The fix is to spend even more money to add an aftermarket cooler to keep the fluid temperature in its happy place. Not only does this add cost, it adds a potential leak or damage point. And do you really want to have to stop driving and wait for your tranny to cool? Conversely, with a manual transmission you won’t have to worry about overheating and/or auxiliary coolers.

Another benefit of a manual transmission is that many have a lower First gear ratio than an automatic transmission. For example, the SM465 four-speed has a First gear ratio of 6:55:1 and the six-speed manual overdrive found in the ’06 Ford Super Duty has a 5.79:1 First gear ratio. This low gearing is great for getting heavy loads rolling and helps create a better crawl ratio.

Summary: It takes a lot of gizmos and technology for an automatic transmission to do the same job as a good ol’ manual transmission. The newer, electronically-controlled heavy-duty transmissions do an amazing job, but they’re big, heavy, complex, and reliant on computers. Do you really want that weight and complexity in your work or play 4x4? In the end, the simple and tough manual transmission is perfect for modern and classic 4x4s.
–Ken Brubaker

Comments

Connect With Us

Newsletter Sign Up

Subscribe to the Magazine

Sponsored Links