1998/08/10 Caterpillar

777B (4YC),
777C (4XJ),
777D (3PR),
783B (8YM),
785 (8GB),
785B (6HK),
787B (9TM),
789 (9ZC),
789B (7EK),
793 (3SJ),
793B (1HL),
793C (4AR) Off-Highway Trucks;
776B (6JC),
776C (2TK),
776D (5ER),
784B (5RK) Off-Highway Tractors;
854G (1JW) Wheel Tractors;
D11N (74Z, 4HK),
D11R (8ZR, 9TR, 9XR) Tractors;
992G (7HR),
994 (9YF) Wheel Loaders;
5130 (7TJ, 5ZL),
5130B (4CS),
5230 (7LL) Excavators

Reference: Service Magazine; September 22, 1997; Page 38; "Improved Piston Crown Assembly Used In The Rod And Piston Group". Service Magazine; September 22, 1997; Page 39; "New Piston Crown Improves Service Life". Service Magazine; April 28, 1997; Page 27; "Improved Cylinder Liner Has Longer Service Life". Service Magazine; July 28, 1996; Page 19; "New Oil Jet Tube Assemblies Replace Oil Cooling Jet Assemblies". Service Magazine; This Issue; "New Piston Rings Provide Increased Service Life". Service Magazine; This Issue; "Causes Of Worn And Broken Piston Rings".

The following chart provides a description of the different piston types used in the 3500 and 3500B engines in Caterpillar machines. Below is additional information to determine which serviceable parts to use with each piston style.

Group One

Group One components include the various one piece pistons for 3500 Series engines. The 7C-2431 and 9Y-4124 Pistons are not suitable for use in machine engines. Only use the 9Y-2100 Piston in machine engines. Because the piston rings have not changed for 3500 engines with one piece pistons, always use the rings as shown.

Group Two

Group Two components include cast steel piston crowns. Do not use a cast steel piston crown in a 3500 machine engines. This piston uses the rectangular 8N-1234 Intermediate Ring. Because the 7C-6146 Crown and 7C-1645 Skirt are no longer available, use replacement components from Group Seven. See the Reference Article on Piston Cooling Jets.

Group Three

Group Three components include the original forged steel two piece piston crown. If a piston skirts needs to be replaced, use the 4P-1658 Piston Skirt. This piston uses the rectangular 8N-1234 Intermediate Ring. If a piston crown needs to be replaced, use components from Group Seven.

Group Four

Group Four and above components include the 8N-7810 Keystone Intermediate Ring. If a piston skirt needs to be replaced, use the 4P-1658 Piston Skirt. If a piston crown needs to be replaced, use components from Group Seven.

Group Five

Group Five components were used very little in production. If a piston skirt needs to be replaced, use the 6I-3018 Skirt. If a piston crown needs to be replaced, use components from Group Seven.

Group Six

Group Six components have been used a great deal in production. If a piston skirt needs to be replaced, either a 6I-2863 Skirt or the new 125-2782 Skirt can be used. The new 125-2782 Skirt can be used on any 3500 two piece crown with the top ring position at 19 mm or any 3500B piston crown. If a piston crown needs to be replaced, use components from Group Seven.

Group Seven

Group Seven components represent current production for 3500 engines. The main difference between Group Seven components and Group One through Group Six components is the piston crown. The 133-8383 Piston Crown is a 3500 crown designed to work best with 3500B rings.

Group Eight

Group Eight components are for 3500B engines. Only use 3500B rings on 3500B piston crowns. All 3500B crowns can be mixed and matched in the same 3500B engine.

NOTE: To maintain acceptable engine balance for engines in Group Two through Group Four, if one cylinder needs to be replaced with Group Seven components, replace all cylinders at the same time with Group Seven components.

NOTE: The lube oil requirements for 3500B engines and 3500 engines with two piece pistons is as follows:

* Use Caterpillar Diesel Engine Oil (DEO) CG-4.

* When Caterpillar DEO is not used, a multigrade API CG-4 is preferred. A multigrade API CF-4 is acceptable.

* The obsolete API classifications CC, CD, CD-2, and CE are not acceptable. The current API classifications CF and CF-2 are not acceptable.

NOTE: An effort should be made to NOT mix 3500 rings on 3500B pistons or 3500B rings on 3500 pistons. The one exception is the Group Seven 3500 piston crown is designed to maximize the value of 3500B rings. If a 3500 or 3500B piston is assembled into an engine with the wrong rings, there should be NO significant problem, but the best value only occurs when piston rings are only used as per the chart.