Model L & C Gear Ratio Identification - - The Friendliest Tractor Forum and Best Place for Tractor Information
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post #1 of 1 Old 12-26-2011, 09:20 PM Thread Starter
RIP Chip, "Gravely Guru, Gone But Not Forgotten"
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Join Date: Jan 2011
Location: Maryland
Posts: 27
Re: Is it an Li?

Model L & C Gear Ratio Identification

Beginning in 1954 the Model L could be ordered with three different gear ratios, determined by the number of "leads" on the worm. A Model L's gearing is identified by the model shown on the large ID plate on top of the fuel tank. Model L is the fast speed model (8-lead worm), Model LI is the intermediate speed model (6-lead worm, and Model LS is the slow speed model (4-lead worm). Those model IDs were stamped on the plate at the end of the assembly line.

On the assembly line he following method was used to identify the gearing before the ID plate was stamped: Look at the right hand axle housing (right hand from the operator's position). When an LI went down the line it had a bolt and nut in one of the holes in the outer flange on the axle housing. An LS had a large washer under one of the six bolts that secure the axle housing to the transmission. A standard L had no bolt in the outer flange and no large washer.

The Model C (Convertible 7.6) was also available in the same ratios, but the small ID plate on the Advance Casting doesn't show whether it is a C, a CI or a CS. Look at the left hand axle housing. When it went down the assembly line an aluminum tag stamped "C", "CI" or "CS" was put under one of the six bolts that secure the axle housing to the transmission. It's possible that early examples of the Model C used the old Model L method described above, so check that too.

Problem is, after all these years the tractor's ID plate may be gone, and the bolt, washer, or tag may have been removed during repairs. In that case the following test can be used to determine the gearing:

- Jack up the tractor so one tire is off the ground. Make sure the other wheel remains on the ground so it can't rotate, or find another way to prevent it from rotating.
- Remove the spark plug, put the cable back on the plug, and ground the plug on the engine to prevent magneto damage.
- If electric start, remove the starter chain so the crankshaft can be rotated by hand.
- Lock the high/low clutch lever into low.
- Lock the forward/reverse clutch lever into forward.
- If it is a Swiftamatic, engage high range.
- Rotate the crankshaft and count how many crankshaft revolutions it takes to rotate the wheel 1/4 turn.

L or C (8-lead worm)
1/4 wheel rotation requires 6 crankshaft rotations.

LI or CI (6-lead worm)
1/4 wheel rotation requires 9 crankshaft rotations.

LS or CS (4-lead worm)
1/4 wheel rotation requires 12 crankshaft rotations.

Chip Old
Cub Hill, Maryland, US

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Last edited by DJ in WV; 12-26-2011 at 09:36 PM.
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