5-101.bk Page 7 Friday, March 17, 2006 11:05 AM Special Tools Required During initial production, part numbers were stamped onto the through hole of the connecting rod bearing cap. In later production, the part number was forged into the I-beam of the rod. Piston Pin Bushing Remover/Installer J 37717 Piston Pin Burnishing Broach J 37718 Connecting Rod Fixture 945-6041 Inspection Old-style connecting rods (without alignment sleeves) and new-style connecting rods (with alignment sleeves) may be intermixed in an engine. However, the capscrews and alignment sleeves are not interchangeable between the two rod assemblies.
The alignment sleeves will physically fit into either of the connecting rod assemblies, but the sleeve must be used in the new-style 367GC4267M or M2 connecting rods ONLY. The capscrews cannot be mixed. The difference in the thread size between the two rod assemblies is significant enough that the 14-mm threaded capscrews will not even engage the 16-mm tapped hole in the old-style (367GC4255M or M2) rod assemblies. The 16-mm threaded capscrew cannot be assembled into the 14-mm tapped hole of the new-style (367GC4267M or M2) connecting rod assemblies. Inspect connecting rods for nicks, cracks, signs of overheating, bends or twisting that can cause rod failure.
Inspect bolt holes for elongation or pulled threads. Check mating surfaces between rod and cap for correct fit. Inspect the crankshaft journal bearing surface and wrist pin bushing. If any of the above parts are suspected of being faulty, replace the connecting rod. If it is determined that the condition of any part or component is questionable or is at the limit of tolerance, throw it out; it may fail or become out of tolerance after a short time in operation. It is cost- efficient to replace components when rebuilding. It is essential to closely control the weight of reciprocating parts. MACK E7 connecting rods fall into two weight classes.
Prior to mid-1996 production, the weight classes are identified by an “M” number (M1 or M2) stamped onto the connecting rod bearing cap. Effective with mid- 1996 production, the M2 connecting rod is no longer stamped with this weight designation. The M1 weight class rod will continue to be stamped on the rod cap. When installing a single rod, or less than a full set, examine removed rod for part number and M number. Installing parts with the same weight class is preferred. Always use genuine MACK replacement parts. Wrist Pin Repair WRIST PIN BUSHING REMOVAL If the wrist pin bushing is found to be out of tolerance, it should be replaced. Refer to Figure 5-4.
Connecting rods can be weighed to ensure using proper weight class. Connecting rod weights for each engine, within each weight class, should not vary by more than 0.46 ounce (13.04 grams). The maximum weight difference between the heaviest possible M2 rod and the lightest possible M1 rod is 0.83 ounce (23.53 grams). To replace bushing: 1. Position rod in a press with piston pin bushing remover/installer J 37717 inserted into wrist pin bushing. 2. Press bushing out of rod. Page 5-7 200 BENCH PROCEDURES