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; "Piston And Piston Ring Reference Chart For 3500 And 3500B Engines". Service Magazine; This issue; "Causes Of Worn And Broken Piston Rings".

Description of Change: The 3500B engines and 3500 engines with two piece pistons used in these machines now use new piston rings.

Illustration 1. Top Ring Wear. (A) Ring Face Wear. (B) Top Flank Wear. (C) Piston Ring. (D) Bottom Flank Wear. (E) Piston Crown. (F) Liner Bore Wear. (G) Cylinder Liner.

Illustration 2. Top Ring Face Change. (X) Former 8N-1233 Top Ring with Symmetrical Barrel Face. (Y) New 144-5694 Top Ring With Asymmetrical Barrel Face.

The new top ring improvements include:

* A new denser face coating.

* A new asymemetrical face.

* A different keystone angle.

* A smaller end gap.

The new denser face coating decreases ring face wear [see Illustration 1, Item (A)]. This new denser face coating does not increase liner bore wear. The new asymmetrical face proiveds lower brake specifice oil consumption (see Illustration 2). The new keystone angle of the top ring provides better contact between the top ring and the piston top ring groove. This results in decreased bottom flank wear [see Illustration 1, Item (D)].

The new intermediate ring has a smaller end gap. When used together, the smaller end gap in the top and intermediate rings result in less blowby, lower crankcase pressure, and a decrease in top flank wear [see Illustration 1, Item (B)].

The new oil ring exerts 17 percent more force against the liner bore than the former oil ring. This results in slightly reduced oil consumption.

The new piston rings provide lower ring wear and lower piston ring groove wear. This will result in increased service life and help prevent broken top rings.

Adaptable To: The new 144-5694 Top Ring replaces the former 122-5956 Top Ring in 3500B engines. The new 144-5694 Top Ring replaces the 8N-1233 Top Ring in 3500 engines with two piece pistons. The 8N-1233 Top Ring is still used in 3500 engines with one piece pistons.

The new 144-5695 Intermedate Ring replaces the former 123-8216 Intermediate Ring in 3500B engines. The new 144-5695 Intermedate Ring replaces the 8N-7810 Intermediate Ring in 3500 engines with two piece pistons. The 8N-7810 Intermediate Ring is still used in 3500 engines with one piece pistons.

The 123-4268 oil ring continues to be used in all 3500B engines and in 3500 engines with two piece pistons. The 7W-2221 Oil ring continues to be used in 3500 engines with one piece pistons.

NOTE: The previous style piston rings (122-5956 Top Ring, 123-8216 Intermediate Ring, and 123-4268 Oil Ring began usage in 3500 engines with two piece pistons with the 133-8383 Piston Crown. See the Reference Article "Improved Piston Crown Assembly Used In The Rod And Piston Group"

The new piston rings are in effect with machine engines and remanufactured machine engines as listed in Chart A. The new piston rings are in effect with Caterpillar machines powered by 3500B and 3500 engines as listed in Chart B.

NOTE: Even though the new piston rings will produce the best results with the latest style piston crowns, the new piston rings can be used with earlier style two piece piston crowns. See the Reference Article, "Piston And Piston Ring Reference Chart For 3500 And 3500B Engines" in this issue for details.

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.