Ken Brubaker
Senior Editor, Four Wheeler
Photographers:
Courtesy the Manufacturers
Do you prefer a manual or automatic transmission? This question is akin to asking someone if they wear boxers or briefs-most have strong feelings one way or the other, and they'll passionately defend their choice.
However, in the 'wheeling world, the manual/automatic debate takes a back seat to durability. One thing we can all agree on is that a transmission must be stout. After all, it can have a low First gear that is the Mother of All First Gears, but if the trans leaves you stranded on the trail, what good is it?
Over the years, the manufacturers have trotted out a number of transmissions. Some were exceptional right out of the box, while others needed a bit of massaging to work to their full potential. Some were so weak and poorly designed that we wonder how the engineers who designed them can sleep at night.
We've selected a total of 10 of our favorite manual and automatic transmissions. Our selections are skewed towards units that are transplantable-thus valuable to 'wheelers. After all, 'wheelers are known to mix and match.
Model: Muncie SM465 four-speed
Short on length and long on durability.
Case material: Cast iron
Top cover material: Cast iron
Length (in): 12
Weight (lb): 175
Ratios: 1st 6.55:1, 2nd 3.58:1, 3rd 1.70:1, 4th 1.00:1
PTO port(s): Yes, both sides
The good: Simple, reliable, and parts are readily available. You can find them primarily in '68-'91 Chevy trucks.
The bad: They can develop a situation where they pop out of Third gear. Motive Gear offers a kit to fix this problem.
Model: New Venture Gear NV4500 five-speed
For those who need or want a five-speed, this is the Holy Grail.
Case material: Cast iron
Top cover material: Aluminum
Length (in): 18.9
Weight (lb): 195
Ratios: 1st 6.34:1, 2nd 3.44:1, 3rd 1.71:1, 4th 1.00:1, 5th 0.73:1
PTO port(s): Yes, both sides
The good: Even though it has been out of production for a few years, our sources tell us that all parts are available in the aftermarket. Try to find a unit from a '93 or '94 Chevy truck because it will have the 6.34:1 First Gear ratio.
The bad: Avoid the Dodge NV4500 because it had design differences from the Chevy NV4500 that resulted in a troublesome Fifth gear.
Model: Borg-Warner T-18 four-speed
Legendary and delightfully simple.
Case material: Cast iron
Top cover material: Cast iron
Length (in): 11.87
Weight (lb): 145
Ratios: 1st 6.32:1, 2nd 3.09:1, 3rd 1.69:1, 4th 1.00:1
PTO port(s): Yes, passenger side
The good: Parts are readily available. There are many different versions of the T-18 used in Ford, Jeep, and IH applications.
The bad: Non-synchronized First gear.
Model: Muncie SM420 four-speed
Short and light, with a crawly First gear ratio and legendary durability.
Case material: Cast iron
Top cover material: Cast iron
Length (in): 10.4
Weight (lb): 135
Ratios: 1st 7.00:1, 2nd 3.60:1, 3rd 1.70:1, 4th 1.00:1
PTO port(s): Yes, driver side
The good: Stout, short, and light. If you're salvage-yard shopping, look for '48-'67 GM trucks or '56-'68 Dodge trucks.
The bad: Getting rare in the salvage yard.
Model: New Process NP435 four-speed
This could quite well be the best four-speed ever made.
Case material: Cast iron
Top cover material: Cast aluminum
Length (in): 10.7
Weight (lb): 135
Ratios: 1st 6.68:1, 2nd 3.34:1, 3rd 1.66:1, 4th 1.74:1
PTO port(s): Yes, passenger side
The good: Very reliable and still used in some UPS trucks. They can also be found in '64-'85 Ford trucks and Broncos as well as '63-'93 Dodge trucks.
The bad: They don't give them away.
If you've found one of these bulletproof manual transmissions, but the poor thing needs a rebuild, the guys at Motive Gear can help you out because they stock almost all of the parts for these five manual transmissions. But that's not all. They also stock parts for hundreds of other manual transmissions as well as transfer cases. As their name implies, they're also a great parts source for axle gears too. If you don't want to mess with finding and rebuilding one of the five manual transmissions we've listed, you can simply call Novak Conversions because they offer the NP435, T-18, SM465, and even the hard-to-locate SM420 in complete, ready-to-bolt-in form. Advance Adapters offers complete ready-to-install NV4500s.
Want to replace that troublesome Getrag transmission in your Dodge with an NV4500? Do you want to fit your Ford with a GM 700R4 transmission? Well, the guys at Advance Adapters can help make this happen and more. They offer adapters not only to complete transmission swaps, they also offer adapters so you can fit a variety of transfer cases. Their online catalog makes for entertaining reading. If Jeeps are your thing, log onto Novak Conversions' Web site. They offer gobs of information and a variety of parts to help you upgrade your Jeep's running gear.
Model: Turbo-Hydramatic 350
Small, light, and easily adaptable.
Case material: Cast aluminum
Length (in): 21.75
Weight (lb): 120
Ratios: 1st 2.52:1, 2nd 1.52:1, 3rd 1.00:1
The good: Easy adaptability, strong front pump, input shaft, and drum
The bad: The intermediate sprag is weak, and when it fails, the transmission can lose Second gear
Model: Turbo-Hydramatic 400
Durable and rated at 450 lb-ft of input torque in stock form.
Case material: Cast aluminum
Length (in): 24.37
Weight (lb): 135
Ratios: 1st 2.48:1, 2nd 1.48:1, 3rd 1.00:1
The good: Like the TH350, the TH400 is easily adaptable to a number of engine/transfer-case combinations; it has a strong front pump, input shaft, and drum.
The bad: Like the TH350, the intermediate sprag is weak and can cause the trans to lose Second gear, and even Reverse when it fails.
Model: Turbo-Hydramatic 700R4
Could be the finest automatic overdrive trans ever produced.
Case material: Cast aluminum
Length (in): 23.4
Weight (lb): 155
Ratios: 1st 3.06:1, 2nd 1.63:1, 3rd 1.00:1, 4th 0.70:1
The good: The input shaft was especially stout. The pros say to purchase a later-model 700R4 because many internal parts were improved from their predecessors.
The bad: If the throttle cable isn't set up right, it can alter the transmission line pressure, which will result in an overall transmission failure.
Model: TorqueFlite 727
Plentiful and extremely durable (but Mopar and some Scout folks already knew that).
Case material: Cast aluminum
Length (in): 34
Weight (lb): 145
Ratios: 1st gear 2.45:1, 2nd gear 1.45:1, 3rd gear 1.00:1
The good: Transmission builders generally agree that the 727 is a tough trans overall. Back in the day, it was used in funny cars.
The bad: In stock form, the rear sprag can fail. When it does, the trans can literally grenade, causing catastrophic damage.
Model: Ford C6
Ford's durable success story.
Case material: Cast aluminum
Length (in): 33
Weight (lb): 160
Ratios: 1st gear 2.46:1, 2nd gear 1.46:1, 3rd gear 1.00:1
The good: High-horsepower capable-an overall workhorse.
The bad: A little porky weight-wise, and in stock form it robbed a lot of horsepower from the engine due to its thrust washers and overall heavy parts.
Everybody has an opinion. Especially when it comes to transmissions. We polled a few folks in the off-highway world to see what transmissions trip their trigger. Here's what they said.
Eric Forsberg, Vice President, Novak Conversions: "The SM465 took what GM had learned about transmission design over its previous six decades and rolled it into an extremely strong, compact, and easily serviceable design. It is rare to see gearbox engineering with such polish. The 465's compatibility with essentially all GM engines (and some others) and their relative abundance make them easy to find, adapt, and use in many applications. I consider GM's 4L60-E Hydramatic to be the greatest automatic transmission in history. The 4L60-E's excellence of engineering and craft has yielded unusual strength, refinement, and elegant simplicity. Additionally, the 4L60-E's compatibility and integration with GM's Generation III powerplants are further compelling reasons to consider them in the very best factory and conversion vehicles."
Gary Heusted, professional mud racer, owner/driver of Rapid Transit and Da Judge: "In Class 3, automatic transmissions are the choice of most racers. My first choice would be a well-built Powerglide. In Classes 4-6, automatic transmissions are still the choice of some, but I believe the slipper-clutch with either an SCS, B&J, Lenco, or a reverser and a Pro Fab transfer case would be my choice and would be the toughest and most reliable."
Joey Leone, owner of Leone Off Road Racing, home of the Tropical Depression and Tropical Storm Pro Stadium trucks: "My pick for the manual transmission would have to be the Borg-Warner T-10 four-speed. It came with a yoke that carried the 1350-series U-joints and it's able to handle plenty of performance. You can also get kits that rollerize the trans, making it even better. For an automatic, I have to go with the TH350. It's an all-around great transmission and parts are plentiful and inexpensive. When built right, they can handle plenty of power. The one I use is TCI-prepped with a TCI manual valve body. I usually run First or Second gear, but on a long track, Third gear is no match for a two-speed Powerglide."
Fred Perry, experienced trail rider and owner of Clemson 4-Wheel Center: "Most of the old standby four- and five-speed transmissions are drying up or just plain worn out, but the NV3550 is becoming more and more plentiful. Parts are really available, they have a good 4.01:1 First gear ratio and a good 0.78:1 Fifth gear overdrive for the highway. They're tough enough for most V-8s too. There are many good automatic transmissions out there, but I chose to run a 545RFE from an '02 Grand Cherokee. It has a great gear-ratio spread for on- and off-pavement with a 3.00:1 First gear and a 0.67:1 Fifth gear; it's tough and fits behind most Chrysler V-8s; and it's easy to find. The electronics can be a bit of a challenge, but the end result is worth it."
John Peterson, Bigfoot Racing transmission technician: "My favorite transmission is Ford's C6. It's a very durable unit from the factory, and with a few modifications, we routinely put 1,500 hp through it."
If you're tired of getting stung by wasps while lying on the glass- and metal-covered ground of a salvage yard while trying to ogle your project transmission, take a look at TCI Automotive. The folks at TCI offer all of these automatic transmissions, plus a whole bunch more. Best of all, they've improved on them in such a way that their inherent weak points have been eliminated. Take the Ford C6, for example. The stock trans robbed horsepower due to its design, so TCI made a number of internal changes that actually cause it to use 11 less horsepower than the stock unit. All of these transmissions can be purchased with Sizzler, StreetFighter, or Super StreetFighter modifications. B&M Racing & Performance Products is also a good source for these automatics. Best of all, they're ready to bolt in your rig.
A big thanks goes out to Bryan Krystulovich at Motive Gear and Stanley Poff and Riley Jeter at TCI Automotive for their help with the technical aspects of this story.
