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Performing a bench teardown, auxiliary section overhaul, or timing alignment on an Eaton Fuller heavy-duty transmission? Attempting to hold auxiliary countershafts in place using improvised C-clamps, wooden blocks, or pry bars creates severe assembly hazards. Unsecured auxiliary countershafts swing off-center, binding mainshaft drive gears, damaging precision taper roller bearings, and destroying gear timing during auxiliary case reinstallation. Engineered for heavy diesel rebuild bays and transmission service stalls, the M40080 Fuller Auxiliary Countershaft Retaining Tool Kit provides rigid structural locking plates supplied in both .100" and .125" precision thicknesses to clamp auxiliary countershafts dead-straight and perfectly parallel during reassembly.

The Critical Physics of Eaton Fuller Auxiliary Gear Timing & Countershaft Support

Heavy-duty Eaton Fuller twin-countershaft transmissions—powering Class 8 vocational trucks, highway tractors, and dump trucks—rely on exact dual-countershaft gear synchronization to split engine torque evenly across the mainshaft. When servicing the auxiliary section (range/splitter section), the auxiliary countershaft bearings must be supported firmly while the auxiliary housing is slid onto the main transmission case. Without dedicated retaining straps, the heavy auxiliary countershafts tilt under gravitational force. When a tilted countershaft strikes the main drive gear during casing mating, the precision gear teeth bind and chip. Even worse, off-center loading crushes taper roller bearing cages and misaligns timing tooth index marks. A mis-timed auxiliary section causes catastrophic gear clash, howling gear noise, and immediate transmission failure within miles of service. The M40080 Auxiliary Countershaft Retaining Kit completely eliminates these transmission overhaul hazards. Machined from high-strength structural tool steel, this 8.00-pound service kit includes precision-machined retaining plates supplied in both **.100"** and **.125"** thicknesses to fit various Eaton Fuller transmission housing tolerances. The plates bolt directly into the rear housing face, rigidly clamping both auxiliary countershafts in fixed parallel alignment so the auxiliary housing glides on smoothly without gear binding or timing loss.

• Broad Eaton Fuller Platform Fitment – Purpose-built specifically for auxiliary section overhaul and countershaft locking on Eaton Fuller heavy-duty twin-countershaft manual and automated transmissions.
• Dual Thickness Precision Plate Set – Includes both **.100"** and **.125"** thick precision steel retaining plates to accommodate specific housing series tolerances and end-play specifications.
• Enforces Rigid Parallel Shaft Alignment – Clamps auxiliary countershafts dead-straight during housing assembly to ensure perfect gear tooth timing engagement and prevent bearing pinch.
• Protects Precision Gears & Taper Bearings – Eliminates gear tooth binding, tooth chipping, and roller bearing cage crushing during auxiliary section reinstallation.
• Heavy-Duty Commercial Grade Construction – Substantial 8.00 lbs solid precision-machined tool steel build engineered for daily continuous use in transmission rebuild shops and commercial fleet stalls.

Stop Juggling Auxiliary Countershafts. Command Total Transmission Service Precision.

The M40080 Fuller Auxiliary Countershaft Retaining Tool Kit is an essential capital asset for commercial truck transmission rebuilders, fleet maintenance facilities, heavy equipment service bays, and mobile diesel technicians. Prevent gear timing misalignment, protect expensive gear sets, and rebuild Eaton Fuller transmissions with complete mechanical authority using Apex tools.

Technical Specifications

Technical Metric	Value / Fitment Reference Guidelines
Target Transmission Platforms	Eaton Fuller Twin-Countershaft Heavy-Duty Transmissions
Primary Operational Function	Rigid locking and parallel retention of auxiliary countershafts during section service
Included Plate Thicknesses	.100" Plate & .125" Plate (Precision Ground Steel)
Part / Model Reference Number	M40080 (40080)
Construction Metallurgy	High-tensile precision-machined structural tool steel
Total Package Shipping Weight	8.00 lbs (Substantial, professional heavy-duty shop service kit)

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