PIN ASSEM. 4Y7089 - Caterpillar

Use Correct Piston Rings
Three different top piston rings are available for the above engines. See Service Magazine, May 6, 1985, Page 14, "Be Sure Correct Piston Rings Are Used On 3400 Series Engines" to make sure you are using the correct piston rings. If a 3.05 mm (.120") thick top ring is installed on a piston designed for a 3.84 mm (.151") thick top ring, the ring can break within a few hours. A chrome plated 3.84 mm (.151") thick ring is for use in engines with lower power ratings. Chrome plated rings may scuff or wear out early if installed in an engine that has a higher power rating.
Check Clearance Between Pistons And Piston Cooling Tubes
Several hundred 3400 Series Engines were built with pistons that had thicker skirts which required special 7W7496 Cooling Tubes. If these pistons are used along with the standard 4N9881 Cooling Tubes, interference could occur between pistons and the cooling tubes.
Whenever pistons are installed, check the clearance between the pistons and the piston cooling tubes with a 0.64 mm (.025") diameter wire after the internal engine work has been completed. If the clearance is less than 0.64 mm (.025"), install a new cooling tube at this location. The cooling tube may have been bent during piston installation. If a cooling tube is bent, replace it with a new one.
A broken cooling tube will cause piston seizure and engine failure. If you have a piston seizure resulting from a broken cooling tube, measure the piston-to-tube clearance on all pistons before they are removed to help determine the cause of the failure.
Use Correct Idler Gear With Single Gear Crankshaft
When rebuilding a 3406 Engine using a newer, single gear crankshaft, remember to update the idler gear also. See Service Magazine, October 11, 1982, Page 12, "Wider Crankshaft Gear Used" and Special Instruction, SMHS8542-01, "Installation Of Short Blocks and Crankshafts" for more information.