Description

Koehring 6620-7, 6620LC Parts Catalog – Factory OEM Parts Reference

I’ve seen too many guys order the wrong part because they trusted an aftermarket parts listing. Then the machine sits, the customer fumes, and you eat the cost. That’s why I only reach for factory documentation when I’m hunting parts for a Koehring 6620-7, 6620LC Parts Catalog job. This isn’t a reprint or a scanned substitute – it’s the original OEM parts catalog, 105 pages, straight from Koehring’s Cranes & Excavators division. If you’re tearing down a hydraulic excavator built after serial number 1177001, this book is your only reliable source for part numbers, group indexes, and interchange notes.

Crawler & Carbody: Getting the Undercarriage Right

Group 0 covers the crawler and carbody – tracks, rollers, idlers, sprockets. Page 2 shows the parts groups index, which tells you that Group 0 is the starting block. Each exploded view illustration pairs with a parts list that includes the exact Koehring part number. You don’t guess. You look up the serial number of your machine (it’s stamped on the frame, right?), then cross-reference the group number printed on the page. If you’ve ever swapped a track chain using an aftermarket seller’s “universal” number, you know how fast that leads to a mismatch. This catalog kills that headache.

Upper Engine Group: Not Just a Parts List

Group 4 – Upper Engine – shows every component from the air cleaner to the flywheel housing. But here’s the difference between this catalog and a generic diagram: the part numbers are tied to production changes. The manual says “Serial numbers are used to identify parts when a product improvement is made.” That means if your 6620LC has a later engine variant, the catalog lists the correct updated part, not the one that fit the prototype. Fuel system parts, engine mounts, coolant lines – they’re all in this section. Don’t order a fuel filter head without checking the block number; you’ll waste half a day.

Hydraulic System: Group 00 – The Heart of the Machine

Group 00 is always the hydraulic system in Koehring parts books. The pump drive case, swing system, and hydraulic lines all get their own groups, but Group 00 ties them together. The exploded views break down the main control valve, cylinder seals, and hose routings. If you’re chasing a drift in the boom, you need the exact seal kit number – not a kit labeled “fits Koehring 6620.” That’s a bet I don’t take. This catalog gives you the group number with a letter suffix for optional or variable parts. Page 3 explains how to read the part number sequence: 1.1, 1.2, 1.2A, 1.2B. Miss the suffix and you’ll get the wrong revision.

Electrical System: Tracing Circuits with Factory Diagrams

Group 30 – Electrical System – covers the wiring, switches, sensors, and control modules. The catalog doesn’t include wiring diagrams (those are in the service manual), but it lists every electrical component by its factory part number. That includes connectors, relays, and the entire harness assembly. When you’re diagnosing a no-crank condition, you need to know that the start relay part number changed at serial break 1177001. This catalog tells you. Without it, you’re flipping through aftermarket cross-references that are often wrong for Koehring machines.

Why This Parts Catalog Beats Aftermarket Lists

Aftermarket parts websites love to claim “OEM replacement.” But they don’t have access to Koehring’s engineering changes. This catalog was printed for the 6620-7 and 6620LC models specifically. It includes the Excavator Attachment group (Group 40), the Operator’s Cab & Machinery Housing (Group 10), and even Tools, Paint, Lubricants (Group 35). The numerical parts list at the front of the manual (page 3) cross-references every part number in the book to the page where it appears. That’s how you check if a part is still valid or if there’s a supersession. No third-party catalog offers that.

Using the Numerical Parts List and Serial Number Cross-Reference

Flip to the inside front cover. Page 1 has a blank for your serial number – write it there. Then use the Parts Group Index (page 2) to find which groups apply to your machine. The manual warns: “Know the serial number of your machine before searching for replacement parts.” Follow that rule. The numerical parts list at the front lets you look up any part number you find on an old component and see if it’s still current. I’ve saved hours this way when a customer brings in a 6620-7 that’s been rebuilt with random parts.

FAQ

Does this catalog include torque specs?

No, this is a parts catalog – torque specs are in the service manual.

How do I find the correct part if my machine has a serial number after 1177001?

Start with the serial number stamped on your machine’s frame. Write it on page 1 of the catalog. Then go to the Parts Group Index on page 2 – it lists every group number from 0 (Crawler & Carbody) through 40 (Excavator Attachment). Each group has its own page numbering system (e.g., group 4, page 4.10). The page headers include a block number that corresponds to the group. When you find the component on the exploded view, note the part number. Then check the Numerical Parts List at the front of the manual. That list tells you if the part number is active or if there’s a newer replacement. If Koehring made a product improvement after serial 1177001, the catalog includes a note or a letter suffix. Always verify the group number suffix (like 125A) – it indicates an optional or variable parts group for your specific serial range.

If you’re working on a Koehring 6620-7 or 6620LC, having the factory parts catalog on your bench stops the guesswork. Order the wrong part once and you’ll swear by OEM documentation. Related manuals you might need: Koehring T-S44, 644 1974 Parts Catalog – Factory OEM Parts Reference, Koehring S-155 1977 Parts Catalog – Factory OEM Parts Reference, Koehring 366 Hydraulic Hoe Parts Catalog – OEM Factory Specs. For background on why factory specs matter, see Automotive Industry Overview. The same principle applies to heavy equipment parts – OEM documentation is the only reliable path. Automotive Industry Overview Don’t gamble your machine’s uptime on aftermarket catalogs. Access the Factory Manual.