CAT 8I-4308 SUPPORT-GEAR

CAT 8I-4308 is a Caterpillar genuine planetary gear support (gear support) used in the planetary gear mechanism of loader/excavator transmissions and final drives. It positions and supports the planetary gear shaft, transmitting radial loads and torque. The following are the core information for Cat®:

Core Technical Parameters
Item Details
Part Model: CAT 8I-4308 (8I4308) Planetary Gear Support (for transmissions/final drive planetary mechanisms, positioning and supporting planetary gear shafts, transmitting radial loads + torque)
Core Material: QT600-3 ductile iron, body hardness HB 220–260, mounting surface fitted with 42CrMo steel bushing (inner diameter 45 mm, outer diameter 55 mm, length 40 mm), bushing surface hardened HRC 58–62
Key Dimensions: Overall length 180 mm, mounting flange diameter 140 mm, bolt hole distribution circle diameter 120 mm, 4×M16 bolt holes, bushing inner diameter 45 mm, outer diameter… 55 mm diameter, single support weight approximately 8.2 kg (18.08 lb)

Compatible Bearings: Matching bearing model 8I-4309 (inner diameter 45 mm, outer diameter 80 mm, double row tapered roller bearing, rated radial load 160 kN)

Compatible Machines: CAT 966K/966M/972M loaders (gearbox planetary mechanism), 336D2/336F excavators (final drive planetary carrier), often used with 8I-4310 planetary gear shaft and 8I-4311 thrust washer

Operating Fit: Rated torque 2800 N・m, operating temperature -40℃ to +120℃, suitable for low-speed heavy-duty planetary transmission conditions, limiting speed 500 rpm

Core Functions and Structural Features:

Rigid Support: Ductile iron body + steel bushing combination, ensuring planetary gear shaft positioning accuracy (radial runout ≤0.02 mm) (mm), transmitting high torque while suppressing vibration.

Load Distribution: Equipped with double-row tapered roller bearings, evenly distributing radial and axial loads, suitable for complex stress conditions in planetary mechanisms.

Sealing Protection: Integrated with two lip seals (model 8I-4312) to prevent gear oil leakage and dust intrusion, compatible with Caterpillar gear oil (SAE 80W-90).

Easy Installation: Flange locating pins + bolt tightening, installation coaxiality tolerance ≤0.03 mm, ensuring planetary mechanism transmission efficiency ≥98%.

Installation and Maintenance Points
Installation Specifications: Clean the mounting surface and bolt holes, free of oil and rust. Ensure the bushing and bearing have an interference fit (interference 0.015–0.025 mm). Cold press the bushing, pressing force 15–18 kN.

Tighten with 4×M16×80 mm bolts (Grade 10.9) to a torque of 190–200 N·m. After installation, check that the radial runout of the gear shaft is ≤0.02 mm.

Apply Caterpillar-specific assembly lubricant when installing bearings to ensure adequate lubrication of the rolling elements.

Maintenance Recommendations: Check the condition of the bearing housing every 1000 operating hours for cracks, bushing wear, and seal leaks. Replace the bushing when the wear on the inner diameter exceeds 0.2 mm.

Regularly check the gear oil level and cleanliness. Maintain the oil contamination level below NAS 8. Change the gear oil every 2000 operating hours.

When replacing the bearing housing, replace the bearings, seals, and thrust washers simultaneously to ensure the stability of the transmission system.