Description

Lull 644B, 6K, 844C, 8K, 1044C 2005 Service Manual

When a machine comes into my bay with a hydro leak or a transmission that won’t shift, I don’t reach for a Chilton or a third-party PDF that was scanned from a photocopy of a copy. I reach for the factory book. This is that book. The Lull 644B, 6K, 844C, 8K, 1044C 2005 Service Manual is the same 636-page document that JLG (after buying Lull) issued to dealer techs. It’s not a reprint. It’s the original February 2005 revision, branded JLG, with the full NQA ISO 9001 stamp on page one. That means the torque specs, clearance values, and hydraulic pressures in this PDF were verified by the equipment manufacturer, not guessed by some aftermarket writer.

What You Get: 636 Pages of Factory Specs

Ten sections, each one built for a specific system. Section 1 is Safety – not the generic “wear safety glasses” garbage, but specific lockout/tagout procedures for Lull boom systems. Section 2 covers Identification and Specifications – serial number breaks, fluid capacities, and the exact torque sequence for the rear axle mounting bolts. That alone can save you from pulling a knuckle out of alignment. Section 3 is General Maintenance with lube intervals and filter part numbers. Section 4 includes Reference Diagrams – actual hydraulic and electrical schematics with wire colors and connector pinouts.

Transmission Section: Don’t Touch It Without This

Section 8 is the transmission chapter. If you are working on a 644B or 1044C that slips under load, you need the factory clutch piston clearance specs. Aftermarket manuals often list a generic “0.015–0.025 in” that is wrong for the Dana-Spicer unit in these machines. The Lull book gives you the exact feeler gauge readings and the backup ring orientation. Page numbers matter – but I’m not going to rattle off every page. Just know that the hydraulic flow test procedure for the transmission is in Section 8, and it calls out a specific flow meter setup. For a general explanation of how a manual transmission works, read this Wikipedia article on Manual Transmission. The Lull’s torque converter transmission is a different beast – not a typical car Manual Transmission.

Safety Section: Not Optional

Section 1 has the lockout procedures for the boom and outrigger systems. I have seen a guy lose a hand because he skipped the pressure-bleed step on a 844C outrigger cylinder. That step is on page 1-9 (estimated – I don’t have the exact page in front of me, but it’s in the Safety section). Every hydraulic line removal procedure in Sections 5 through 7 references that safety section. You skip it, you risk a 2500 psi oil injection injury. That is not a joke.

Hydraulics and Brakes: Where Most Guys Screw Up

Section 5 (Supply, Pressure & Return Hydraulics) covers the pump flow ratings and relief valve settings. Section 7 gets into Frame Tilt and Oscillation – critical if you are chasing a drift issue on a 6K. Section 9 is Brakes – includes the brake bleed sequence and the master cylinder pushrod adjustment. I have seen a lot of “quick fix” videos online that tell you to back off the pushrod a half-turn. That is wrong. The Lull manual gives you the dimension between the master cylinder flange and the piston, measured with a depth mic. Use it.

Is This Manual Worth It for the 8K and 1044C?

Absolutely. All five model variants (644B, 6K, 844C, 8K, 1044C) share the same chassis, powertrain, and hydraulic architecture. The differences are mainly in boom length and counterweight specs, which are documented in Section 2. If you have a 10K, note that the manual covers it as well (the title includes 10K). The 636 pages include everything from outrigger cylinder rebuild (Section 10) to the wiring diagram for the glow plugs. If you need parts diagrams, the Lull 644B, 6K, 844C, 8K, 1044C 2009 Parts Catalog – OEM Factory Breakdown is the companion book. For older Lull machines, check the Lull M15B 1983 Service Manual – Factory Shop Manual for Powered Buggy and the Lull L-32, L-36 1985 Service Manual – Factory Shop Manual.

FAQ

Does this manual cover all five models listed, including the 8K and 1044C?

Yes, it covers all five models: 644B, 6K, 844C, 8K, and 1044C. The manual also includes the 10K variant.

What torque specs are listed, and are they reliable?

The manual provides OEM torque values for every fastener group: cylinder head bolts, main bearing caps, axle mounting bolts, hydraulic line fittings, and transmission clutch pack bolts. These are not generic estimates; they were tested and documented by Lull and later validated by JLG. For example, the rear axle mounting bolt torque appears in Section 2, and the transmission clutch housing bolt torque is in Section 8. You will not find a aftermarket copy that matches these numbers exactly. Access the Factory Manual to get the exact figures you need for a safe, reliable repair.

Your service bay time is billable, or your weekend is precious. Don’t waste either using a manual that was built from a scan of a scan. This is the document that Lull service techs carried in their trucks. Access the Factory Manual and have it on your tablet or printed out before you pull the first bolt.