Brake - Slight Lead/Pull to the Right During Application
File In Section: 5 - BrakesBulletin No.: 86-50-25
Date: February, 1999
Subject:
Brake Lead/Pull to the Right
(Replace Front Leaf Springs and Rear Brake Chamber)
Models:
1998 Chevrolet and GMC Medium Duty C Series Models
with 157 Inch Wheelbase, 8,100 # Front Axle, 50 Gallon LH Fuel Tank,
Air Brakes, 19,000 Rear Multi-Leaf Suspension, and 8,100 # Front Tapered Leaf Suspension (RPOs EG4, FL1, ND5, JE4, GNO, F14)
Condition
Some owners may comment about a slight brake lead to the right while applying the brakes. This condition may be more prevalent when applying the brakes between 72-105 km/h (45-65 mph) and with the vehicle carrying a light payload.
Cause
The condition may be caused by steering geometry, a short wheelbase, or weight distribution. This applies to vehicles that were built with ALL of the above listed RPO content and also exhibit at least a 500 lb COMBINED front/rear weight imbalance on the left side of the vehicle.
Correction
An alternate taper leaf spring and brake chamber have been recommended to correct this condition. Replace both of the front taper leaf springs and the right rear brake chamber. Use the part numbers listed below and the following Service Procedure.
The vehicle should be properly weighed in order to determine if a weight imbalance exists on the left side. Measure the vehicle weight at each tire. The fuel tank should be full.
Spring Replacement
1. Replace both of the front taper leaf springs using P/N 15574818. When replacing the left front spring, remove the 20 mm (0.8 in.) spacer between the axle and the shock absorber bracket. Discard the spacer. Refer to Section 3C of the appropriate Medium Duty Service Manual.
2. Remove and discard the 10 mm (0.4 in.) spacer from the RH spring pack. Also remove the locating pin extension from the lower shock bracket of the RH spring pack.
3. Remove and discard the spacer (U shaped) from the LH and RH spring packs.
4. Replace the spring U-bolts with P/N 15983090 and washers, P/N 15650968. Replace the U-bolts nuts with P/N 11516202.
5. Tighten the U-bolt nuts, in a criss-cross pattern, to 100 N.m (75 Ib ft) then to 250 N.m (185 Ib ft), and then to 340-360 N.m (250-256 Ib ft).
Rear Brake Chamber
Replace the right rear brake chamber with P/N 15637587. Refer to Section 51 of the appropriate Medium Duty Service Manual.
Steering Wheel
Center the steering wheel. Refer to Section 3F of the appropriate Medium Duty Service Manual.
Alterer's Label
Because part of this modification requires a change to the rear axle brake chamber, the rear axle rating, as recommended, will be changed from 19,000# to 17,500#. As required by FMVSR 567.7, an alterer's label will also be required to state this revised rating.
An alterer's label can be obtained by contacting Technical Assistance at (888) 461-9903.
Parts Information
P/N Description Qty
15574818 Spring, Taper Leaf 2
RPO F26
15983090 U-bolts, Spring 4
11516202 Nut, U-bolt 8
15650968 Washer, U-bolt 8
15637587 Brake Chamber RH 1
Parts are currently available from GMSPO.
Warranty Information
For vehicles repaired under warranty, use the table.