Usage:
768C, 772B Tractors;
769C, 773B Trucks
- SUPPLEMENT: 01/10/83
SERVICE MAGAZINE, SEPTEMBER 13, 1982, PAGE 2. In the article, "Different Nuts And Washers, Increased Torque Prevent Loose Pistons, Broken Bolts In Suspension Cylinders," another suspension group number must be added to the chart. Add "3G681" to "Changes To 3G684, 3G685 Suspension Groups (Front)" in the chart. Also, remove the asterisk (*) from "*Changes to 3G680, 1U4031 Suspension Group (Front)."
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Description of Change: Different nuts and washers and higher torque values are used in the front and rear suspension groups for the above machines. See the illustration.
New heat-treated nuts are used to fasten the pistons to the rod assemblies. The new nuts permit use of increased torque, 90 ± 14 N·m (65 ± 10 lb ft). The former nuts, tightened to a lower torque, some times loosened during machine operation. The result, in time, was internal damage to the cylinders.
Hardened washers are now used in place of the lockwashers in the suspension groups. Also, a higher torque and a different sequence are used to tighten the head bolts, under which some of the hardened washers are used, on the front suspension groups. The new sequence and the higher torque, together, will possibly prevent broken head bolts.
Adaptable As: The new parts are direct replacements for the former parts as shown in the chart.
Sequence To Tighten Head Bolts On Front Suspension Cylinders
1. Tighten four equally-spaced head bolts in an "X" pattern to a torque of 50 N·m (37 lb ft).
2. Tighten all the head bolts around the circle to a torque of 100 ± 15 N·m (75 ± 11 lb ft).
3. Use the same rotation as in Step 2 and tighten the bolts, again, to a torque of 100 N·m (75 lb ft). Tighten the bolts several times, if necessary, until there is no change in the torque.
Locations of the heat treated locknuts which hold the pistons to the rod on the front suspension cylinders and the hardened washers which are now used with the head bolts.