Description

Skytrak 3606 1999 Service Manual – What You Get on the Workbench

If you’re cracking open a Skytrak 3606 1999 Service Manual because the boom won’t lift or the Clark-Hurth T12000 transmission is grinding, you don’t need fluff – you need the exact procedure, the right torque, and the correct part number. This isn’t a reprint or a third-party summary. This is the original factory document Trak International published in October 1999, 412 pages thick, covering everything from the Perkins 1004 and Cummins 4BT3.9 engines to the 4-speed powershift transmission, the hydraulic system, and the electrical schematics. Let’s get into what matters.

Clark-Hurth T12000 Transmission – Tear-Down and Rebuild Data

The Transmission section (Section 7) covers the Clark-Hurth T 12000 powershift transmission. You get clutch clearance specs, shift linkage adjustment procedures, and the full overhaul sequence. Need the charge pressure? Page 73. That page gives you the test port location and the acceptable pressure range at operating temperature. If you skip that step and throw a rebuilt unit in blind, you’re asking for a comebacker. The manual even lists the special tools required – part numbers and all – so you’re not guessing which puller fits the input shaft.

Engine Overhaul: Perkins 1004 and Cummins 4BT3.9

Two separate engine sections (8A and 8B) give you the factory procedure for each. The Perkins 1004 Series section includes cylinder head bolt torque sequence in inch-pounds, then foot-pounds. The Cummins 4BT3.9 section covers injection pump timing and valve adjustment. Both sections have exploded-view diagrams that show every gasket, seal, and O-ring with OEM part numbers. You don’t need to cross-reference aftermarket catalogs – the manual gives you the original numbers. If you’re pulling a head in a dusty yard, this is the reference that keeps you from overtightening and cracking the casting.

Electrical System: Section 10 – Wiring That Actually Matches

The Electrical System section (Section 10) contains the full wiring diagrams for the 3606. Color codes, connector pinouts, and the start circuit path. This isn’t a generic schematic – it’s the exact harness layout that came from the factory. I’ve seen too many guys chase a no-start condition with a multi-meter while guessing which wire goes where. The manual shows the ground locations and the fusible link ratings. You’ll also find the diagnostic flow chart for the instrument cluster. If the alternator isn’t charging, the voltage regulator test procedure is laid out step-by-step.

7 Systems Covered – From Boom to Axles

Here’s what’s inside: Section 1 Safety (lockout/tagout and cribbing procedures), Section 2 General Information & Maintenance (fluid capacities, lube intervals, tire pressures), Section 3 Boom (cylinder removal, pin bore tolerances), Section 4 Cab & Covers, Section 5 Axles, Wheels & Tires (hub removal and wheel bearing preload), Section 6 Transfer Case & Drive Shafts (U-joint replacement and shaft phasing). Every section has its own table of contents, so you can flip directly to the job without scanning pages.

Source Validity – OEM Print, Not a Generic Copy

This manual is the original 1999 service manual from Trak International (now JLG). The barcode on the cover reads 8990300. I’ve worked with aftermarket manuals that substitute generic torque values – that’s how you snap a bolt in a cast-iron housing. This one uses factory-specified foot-pounds and inch-pounds. The safety warnings in Section 1 are not CYA boilerplate; they reference specific lockout points on the 3606 frame. If you’re a shop owner, having the OEM document on hand protects you from liability when a tech does a repair using published specs.

Who Needs This Manual?

DIY mechanics who own a 3606 and want to replace the boom cylinder seals without taking the machine to a dealer. Home garage enthusiasts rebuilding a Skytrak that sat in a field for ten years. Shop foremen training a junior tech on the transmission rebuild – you can hand them the manual and say read steps 1-18 before touching a wrench. Professionals who need the OEM torque table for the axle flange bolts. Anyone who has ever been halfway through a job and realized the manual they obtained from a forum has wrong page numbers – that won’t happen here.

Frequently Asked Questions

Does this manual cover the fuel system for both engines?

Yes. The Perkins 1004 Series section includes the fuel injection pump removal and timing procedure. The Cummins 4BT3.9 section covers the injector replacement and fuel line routing. Both sections list the OEM injection pump part numbers.

Can I use this on a later model 3606, like a 2005?

This manual is for the 1999 model year. Later machines may have updated electrical circuits or a different transmission control valve. For a 2005, you need a later revision. Check the SKYTRAK 3606 Operators and Safety Manual for operational differences, but for service specs, stick with the year-matched book.

Are torque values given in foot-pounds only, or also inch-pounds?

Both. The Engine sections list small fastener torque in inch-pounds (e.g., valve cover bolts at 10–12 in-lb) and large fasteners in foot-pounds (e.g., main bearing caps at 100–110 ft-lb). The hydraulic section also includes metric-to-imperial conversions.

What about the boom drift procedure – is that in here?

Section 3 (Boom) includes the cylinder drift test procedure and the relief valve adjustment steps. You’ll need a pressure gauge with a 5000 PSI rating – the manual specifies the required tool by part number.

Related Manuals You Might Need

• Skytrak 3606 2007 Parts Catalog – OEM Illustrated Manual
• SKYTRAK 5030/6034 Maintenance Manual

If you’re working on the transmission or the drivetrain, also check the external reference for Manual Transmission fundamentals – but always come back to the factory specs for the T12000. I’ve rebuilt more Clark-Hurth units than I can count, and the only way to get the clutch pack clearances right is to follow the OEM numbers. Don’t guess. Access the Factory Manual and keep it next to your torque wrench.

Access the Factory Manual – no reprints, no copies, just the original 1999 service book that Trak International printed for the 3606.