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Manual and Automatic Trail Transmission - Off Road Gear Box Groupies

Muncie Sm465 Four Speed
Ken Brubaker
| Senior Editor, Four Wheeler
Posted August 1, 2006
Photographers: Courtesy the Manufacturers

Our Top 10 Favorite Trail Transmissions

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.

Sources

TCI Automotive
Ashland, MS 38603
888-776-9824
www.tciauto.com
Advance Adapters
Paso Robles, CA 93446
800-350-2223
www.advanceadapters.com
Motive Gear
Chicago, IL 60609
800-934-2727
www.motivegear.com
Novak Conversions
Logan, UT 84321
435-753-2513
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