Complete Tractor 1707-0507 Tachometer Compatible with/Replacement for Case International Tractor 706 806 Others-388588R91

What It Is

This is a replacement tachometer for vintage Case International and International Harvester tractors, designed to display engine RPM for proper throttle and PTO speed management. It fits models like the 706, 806, and others requiring OEM part 388588R91.

Fitment & Compatibility

• Direct fit for Case IH 706, 806, 856, 966, 1066, 1466, 1566, 4166, and similar models with the original tach drive and mounting hole pattern. Also replaces IH part 388588R91.
• Check your tractor’s model year and serial number – some early 706/806 units use a different cable drive angle or ratio. Measure the drive cable length (typically 36-48 inches) and verify it matches your existing cable.
• OEM vs. aftermarket: This Complete brand tach is a direct-replacement aftermarket unit, not a genuine IH/Case part. It uses the same 3-hole mounting pattern and 1/8-inch drive cable fitting, but may have slight gauge face differences.
• Measure the mounting hole spacing (center-to-center) – standard is 2.5 inches. If your tractor has a different pattern, you’ll need an adapter plate or a different tach.

Key Things to Know

• Quality: 4.6/5 rating from 4 reviews – generally reliable, but a few users report the needle can be slightly off at low RPM (idle). Calibrate against a known-good tach if possible.
• Installation difficulty: Moderate – you’ll need to remove the old tach, disconnect the drive cable (may be seized), and route the new cable. Expect 30-60 minutes if the cable is accessible.
• Common gotcha: The drive cable must be lubricated with a light grease or cable lube before installation to prevent premature wear and erratic readings. Dry cables cause needle bounce.
• Lighting: The tach has a built-in bulb for night use – check your tractor’s wiring connector (typically a single wire for 12V power). If your tractor uses a different bulb base, you may need a socket adapter.

Should You Buy It

If you own a Case IH or International 706/806-series tractor and need a functional, affordable tach replacement without paying OEM prices, this is a solid choice. It’s not perfect for precise engine tuning due to minor accuracy reports, but it’s more than adequate for daily operation and PTO speed monitoring. Skip it if you require exact OEM appearance or need a tach for high-RPM race/track use.