Connecting Rod Fasteners - New Torque To Yield Design
Article No.96-25-24
12/02/96
ENGINE - 4.0L - NEW TORQUE-TO-YIELD CONNECTING ROD FASTENERS
LIGHT TRUCK:
1996 AEROSTAR, EXPLORER, RANGER
ISSUE:
New Torque-To-Yield (TTY) connecting rod fasteners have been introduced to replace the controlled torque fasteners for the 4.0L engine. Beginning 5/13/96, all connecting rod assemblies have been redesigned for TTY method of bolt tensioning.
ACTION:
Whenever a connecting rod is serviced, it must be examined to determine whether it is a TTY or Non-TTY rod. A determination will then be made as to whether the original nuts and bolts can be reused or if they must be replaced, and if replaced, what nuts and bolts must be used as replacements. Refer to the following Service Procedure for details.
SERVICE PROCEDURE
Engines with old tag numbers (refer to following Reference Chart) do not have the new TTY connecting rod assemblies, and the existing reassembly method, to a torque figure, is to be used. However, if one or more connecting rods have to be replaced due to damage and the old connecting rod assembly is no longer available, all six (6) connecting rods must be replaced by new TTY connecting rod assemblies.
Engines with new tag numbers (refer to Reference Chart) do have the new TTY connecting rod assemblies and are to be reassembled or serviced by following Service Procedures 1 and 2 in this TSB article (see the following NOTE for EXCEPTION).
The new TTY connecting rod can also be identified by the part number code stamped on the shaft of the connecting rod (Figure 1). Part number code "7AE" stands for TTY connecting rod (7AE derived from Connecting Rod Assembly 97JM-6200-AE). Part number code "7AC" also stands for TTY connecting rod and these rods carry a white color dot on the connecting rod cap for ease in identification (Figure 2).
NOTE:
IF A CONNECTING ROD WITH A "7AD" CODE APPEARS, THIS IS AN INTERIM ROD USED DURING TRANSITION FROM TORQUE CONTROLLED TIGHTENING TO TTY TIGHTENING. THESE RODS HAVE A NON-TTY BOLT WITH A TTY NUT AND ARE TIGHTENED USING THE EXISTING CONTROLLED TORQUE REASSEMBLY METHOD (30 N.m), EVEN THOUGH THE ENGINE TAG NUMBER MAY BE THAT OF THE NEW PART/TAG NUMBER TTY SHOWN IN THE REFERENCE CHART. THIS IS AN EXCEPTION TO THE INSTRUCTIONS ABOVE. IT IS IMPORTANT THAT THE TTY NUT BE USED ON THIS ROD ASSEMBLY TO INSURE ROD NUT CLEARANCE TO CYLINDER BLOCK DURING CRANK ROTATION.
NOTE:
THE EXISTING TTY BOLTS IN AN ENGINE MAY NOT BE RETORQUED AND USED AGAIN. IN THE EVENT THAT A CONNECTING ROD ASSEMBLY IS DISMANTLED IN SERVICE, NEW TTY BOLTS AND NUTS MUST BE USED (CONNECTING ROD BOLTS BECOME PERMANENTLY ELONGATED BY USING THE NEW TIGHTENING PROCEDURE: 20 +/- 2 N.m (15 +/- 1.5 LB-FT), THEN ROTATE A FURTHER 90 DEGREES +/- 5 DEGREES). DO NOT USE BOLTS AND NUTS FROM PREVIOUS NON-TTY ASSEMBLIES.
1. CONNECTING ROD INSTALLED ON THE ENGINE WITH LOOSENED CONNECTING ROD NUTS
a. Set the crankcase in a vertical stance.
b. Turn the crankshaft until the piston of the desired connecting rod is at bottom dead center.
NOTE:
FOR CYLINDERS 1, 2, AND 3, REMOVE THE CONNECTING ROD NUT AT THE OIL SQUIRT HOLE SIDE FIRST. FOR CYLINDERS 4, 5, AND 6, REMOVE THE OPPOSITE CONNECTING ROD NUT FIRST.
c. Loosen the connecting rod nuts (finger tight against the face of the cap).
d. Loosen the first connecting rod nut until the face is approximately 2 mm over the end of the bolt.
e. Tap the connecting rod bolt on the nut, with a copper hammer, until it is able to be removed by hand.
f. Remove the nut and bolt by hand or with a needle nose plier.
g. Insert the new connecting rod bolt and make sure the bolt head seats flush on the broached surface of the connecting rod.
NOTE:
BE SURE TO USE NEW CONNECTING ROD NUTS.
h. Tighten the connecting rod nut until the bolt head contacts the connecting rod surface. The torque must not exceed 20 N.m (15 lb-ft) to seat the bolt.
i. Exchange the second connecting rod bolt using the steps 1d-1g.
j. Loosen both connecting rod nuts.
k. Tighten the connecting rod nuts alternately to a snug torque of 20 +/- 2 N-m (15 +/- 1.5 lb-ft), then rotate a further 90 degrees +/- 5 degrees.
2. CONNECTING ROD REMOVED FROM ENGINE - PLASTIGAGE BEARING CLEARANCE PERFORMED ON REASSEMBLY
a. Reassemble the connecting rod and piston assembly to the engine with the old connecting rod nuts and bolts in place. Use the 1995 Aerostar, Ranger, Explorer Powertrain/Drivetrain Service Manual, Pages 03-010-42/80/81. Perform Plastigage bearing clearance check using the 1995 Aerostar, Ranger, Explorer Powertrain/Drivetrain Service Manual, Page 03-00-27.
NOTE:
USE GENERAL SPECIFICATION TABLE FROM THE 1996 AEROSTAR, RANGER, EXPLORER SUPPLEMENT, PAGE 03-01C-12.
b. Replace the connecting rod nuts and b6lts with new TTY Nuts (F77Z-6212-AA) and Bolts (F7TZ-621 4-AB). Refer to procedure 1a-1k details.
PART NUMBER PART NAME
F7TZ-6214-AB Connecting Rod Bolt
F77Z-6212-AA Connecting Rod Nut
OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS: INFORMATION ONLY
OASIS CODES: 490000, 499000