Description

Michigan 55 IIIA GRR 1973 Parts Catalog – Factory OEM Parts Breakdown

I’m Mike Callahan, 28-year ASE Master. Over the years, I’ve seen more than one $2,000 repair go sideways because a guy ordered the wrong part number from a generic aftermarket site. That mistake is why I keep a factory Michigan 55 IIIA GRR 1973 Parts Catalog at every bench. You don’t guess on part numbers—not on a 50-year-old articulated tractor shovel. This is the original OEM document, 170 pages, printed by Clark Equipment in 1973. It’s the only source that matches every casting, bearing, and O-ring to the serial number stamped on your machine.

Page 3 of the manual spells it out: “Always furnish the distributor with the machine serial number when ordering parts.” That’s not a suggestion—it’s the difference between getting a front axle shaft that fits or a 3-week return hassle. The alphabetical index starts on page 1, so you can jump straight to “Axle Assembly — Front Drive A3, A5” or “Converter Assembly C9–>C13” without flipping through general sections. Every part group is lettered: A for axles, B for boom and brakes, C for converter and cylinders, and so on through Z for optional equipment.

Axle Assembly Breakdown – Front and Rear Drive Systems

The A-group sections cover everything from axle housing (A3-0-A9) to the planet carrier assembly (A14). If you’re rebuilding the front differential carrier, the catalog lists bearing part numbers for both the front drive and rear drive carriers. Page numbers are prefixed: A11 for front carrier, A13 for rear. No aftermarket drawing has the correct bearing cross-reference for a 1973 Michigan—the OEM index does. Look under “Differential Assembly All, A13” for the exact components.

Converter and Hydraulic System Coverage

The converter assembly section (C9–>C13) breaks down the charging pump, impeller, and pressure regulating valve. The hydraulic system is split into main (H9, H11), steering (H13, H15), and transmission/torque converter (H17, H19). Want the main pump part number? Go to P3. Steering cylinder? C16. This catalog gives you the factory part number, not a “cross reference” that might match only 80% of the dimensions. I’ve had apprentices try to order a pump seal from a generic listing—ended up with a 0.020” undersized ring. OEM data eliminates that gamble.

3 Reasons to Stick with Factory Parts Documentation

First, aftermarket catalogs for these old Michigan machines are usually scanned copies of copies—blurry, missing revision notes, and often include parts for later serial numbers that don’t fit your machine. This is a direct OEM scan, 1973 original. Second, the electrical section (E-group) includes the wiring color code (E13) and harness layouts (E11). When you’re tracing a short on a 50-year-old tractor shovel, guessing which wire is “brown with white stripe” vs “brown with yellow” can cause a fire. The factory code is printed here, page E13. Third, the brake system (B-group) shows both front and rear brake air lines (B7, B9), parking brake assembly (B10), and the power cluster (B16). Part numbers for linings and head assemblies are on page B13, B14.

Electrical System Layout – Wiring Color Codes and Harnesses

The E-group sections cover the instrument panel (L.H. and R.H.), headlight harness, main wiring harness, and the color code. If you need the neutral start switch or the voltage regulator, look under “Electrical System E7, E9”. The catalog even lists the hourmeter, back-up light, and horn. Again, no guesswork—factory part numbers for every switch and sender. The alternator and air compressor are under “Engine Accessories E14”. I don’t touch an electrical problem on this machine without page E13 open on the bench.

Use the Alphabetical Index to Find Parts Fast

Turn to the index at the front. Find “Boom Assembly” – that’s B4. “Bucket Cylinder Assembly” – C15. “Steering Control Valve” – V15. All page numbers are prefixed with the group letter and a dash, like A3-0. The index also flags items that are “NOT ILLUSTRATED” or “NOT SOLD SEPARATELY” with symbols. That saves you from ordering a bolt that’s only sold as part of a subassembly. If you’re looking for a seat belt assembly, it’s under Z4—optional equipment. The 170-page count means you can rebuild this machine from the ground up with correct part numbers for every nut, clip, and gasket.

Does this catalog include torque specifications?

No. This is a parts catalog—it lists part numbers, not torque values. You’ll need the factory service manual for assembly specs.

How do I find a part if I don’t know the exact name?

Use the alphabetical index starting on page 1. Let’s say you need the main hydraulic pump – look under “Pump Assembly, Main & Steer P3”. If the part is related to the transmission dipstick, go to “Dipstick, Transmission H17”. The index covers every assembly from A (Axle) to Z (optional equipment). For example, “Frame, Front & Rear F3, F5” lists all frame sections and their part numbers. If you can’t find it in the index, check the engine section under “Engine & Transmission Mounts F3” or “Engine Controls E17”. The catalog is organized by function, so once you know the system (brakes, converter, electrical), you flip directly to that alphabetical letter group. Page numbers are always prefixed with the letter, so “Hydraulic Oil Reservoir Suction Filter H7” is clearly under H group.

If you’re maintaining or restoring a 1973 Michigan 55 IIIA GRR, this is the only parts list you should trust. Don’t rely on aftermarket reproductions that miss revision histories or use generic illustrations. The OEM Clark catalog has every original part number, every change letter, and every exploded view as drawn in 1973. Related manuals you might need include the Volvo BM Michigan 125C 1988 Parts Catalog – Factory OEM Parts Manual, the Michigan 851 Parts Catalog – 72-Page Factory Parts Manual, and the Michigan 85III 1965 Parts Catalog – Factory OEM Parts Breakdown. For a broader look at how these machines fit into the Automotive Industry Overview, check the history of heavy equipment manufacturing. Otherwise, stop wasting time with cross-reference websites and get the actual factory data in your hands. Access the Factory Manual now.