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Backward Glances - An Experimental Military Amphibious Chevy Corvair

Posted in Features on January 18, 2016
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"Well, it seemed like a good idea at the time."

These words have been spoken by many engineers and executives as people scratched their heads and looked at what had just swallowed up a million bucks of development money. Sometimes those words were spoken by people on the way out the door escorted by security. We don't know if heads rolled after a very odd military prototype debuted from Chevrolet in 1963, but this rig quietly disappeared soon thereafter.

They called it TUFI, an acronym for Truck Utility Floatable Independent. As far as we can tell, it didn't come directly as a result of an Army request; rather it was an idea developed by Chevrolet to sell to the military. It was likely based on certain trends observed by the guys at the commercial and government sales offices at Chevrolet, or perhaps it came from an "unofficial" request. We do know that Jeep built an amphibious prototype at about the same time.

TUFI was designed to be light, compact, and simple. It was rated for a 3/4-ton payload off-highway and 1-ton on the highway. The prototype TUFI sat on an 88-inch wheelbase and could carry six troops in the 23 cubic feet of cargo space, plus the driver and one more up front. The body (or should we say hull) was made of five-ply Royalite, which was one of the earliest successful thermoplastics and was beginning to see use as automotive bodies in the early ’60s. It was lighter than fiberglass, structurally stronger, and a more impact resistant. It was easier to mass produce as well, but more expensive.

The heart of TUFI was none other than the air-cooled flat six of the Corvair. In its industrial form, it made 75 hp and 129 lb-ft from 164 cubic inches. It was mid-mounted, had two one-barrel carbs and used a waterproofed 24V electrical system. The spec books aren't clear exactly how the power was transmitted, but they do mention a special aluminum two-speed transaxle/transfer case that incorporated the two ranges and the front differential. An aluminum case Corvair truck four-speed transmission, with a First gear ratio of 3.65:1, was integrated into the unit. The axle ratios are not listed, nor is the transfer case low-range ratio. The independent suspension used Corvair diffs and since it's doubtful new ring-and-pinions were produced just for this project, they probably used the lowest ratio offered in the Corvair: 4.11:1. The spec sheet lists the Corvair version of the GM Posi limited slip was installed at both ends. Listed tires size was 9.00-16 (non-directional military tread), and those tires worked as paddles in the water, propelling TUFI at a screaming 2.5 mph. On land, top speed was listed at 60 mph.

The Army tested TUFI in 1963. Pictures of the tests exist in a couple of books, but we have not seen any test results to report upon. Obviously, TUFI was a no-go and the fate of the single prototype known to have been produced is unknown. The Jeep amphib also disappeared. TUFI is certainly one of those prototypes that makes a guy shrug his shoulders and wonder why. The name is kinda cool though. How ya doing TUFI?

The Details: ’63 Chevrolet TUFI
Engine: 164ci Chevrolet air-cooled flat six
Power(hp): 75 @ 3,500 rpm
Torque (lbs-ft): 129 @ 2,600 rpm
Bore & Stroke (in.): 3.44 x 2.94
Comp. Ratio: 8.0:1
Transmission: 4-spd manual (Saginaw)
Transfer Case: 2-spd, integrated
Front Axle: Independent suspension
Rear Axle: Independent suspension
Tires: 9.00-16 NDT
Wheelbase (in.): 88
L X W x H (in.): 156.5 x 87 x 74
Curb Weight (lbs.): 3,464
GVW: 4,969
Fuel Capacity (gal.): 45
Min, Grd. Clearance (in): 10.5
App. Angle (deg.): 34
Dep. Angle (deg): 44
Max Speed (mph): 60

The front winch was a Ramsey PTO, probably the same 6,000-pound unit used on military Jeeps of the day, driven off the transmission. The chassis was all aluminum, as were the bumpers and other parts of the framework. The 7-inch brakes had sintered metallic linings so as not to be affected by water, but they were power boosted. The suspension was the same as used with the standard Corvair pickup, but a special spindle in the front incorporated the four-wheel drive. And yeah, look at the Bowtie!

The Royalite used for the body was about 30 percent lighter than the same thickness of fiberglass and could be permanently color impregnated. Impact resistance was much better than aluminum, wood, or fiberglass. Royalite had been around since 1946 and had been improving ever since. The tailgate was waterproofed. The skirts in the wheel openings were found to improve the efficiency of the NDT tires as paddles.

Pretty much a Corvair, but with a huge, double-belted 24V generator and waterproof suppressed ignition. This pic, from the presentation booklet, shows what appears to be a power steering pump. Power steering isn't listed in the specs but seems likely.

Seating for eight, which was only two less than the Dodge 3/4-ton M-37, but the big Dodge didn't float.

We didn't have access to any images of TUFI afloat, but this drawing from Chevrolet shows how the tires were spun to achieve a whopping 2.5 mph top speed in the water.

The presentation booklet for TUFI from the Chevrolet Engineering Center doesn’t show images of the TUFI powertrain, only this line drawing. The transfer case unit was said to be aluminum, as was the transmission housing.

Interestingly, there is a possible Jeep connection in this. In April 1966, the engineering department at Kaiser Jeep presented a sleek 4x4 prototype that also used a Corvair engine, transmission, and axles in a 4x4 configuration. The layout looks similar but with no powertrain pics of either rig, only drawings, it isn't clear if the GM powertrain was recycled into the Jeep prototype. Certainly, the concept was just about the same.

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