Small Block V6/V8 Engine - Product Enhancements
File In Section: 6 - EngineBulletin No.: 87-61-32
Date: November, 1998
INFORMATION
Subject:
1999 GEN 1e Small Block V6/V8 New Product Service
Models:
1998-99 Chevrolet and GMC S/T, M/L, C/K, G, P Models
1998-99 Oldsmobile Bravada
with 4.3L, 5.0L, 5.7L Engine (VINs X, W, M, R - RPOs LF6, L35, L30, L31)
This bulletin addresses product enhancements made to small-block V6 and V8 (Gen 1e) engines used in the 1999 truck product line. Although these changes are few and may seem relatively minor, they could manifest into considerable service concerns to uninformed service technicians, PLEASE READ CAREFULLY.
New Features...1999 MY 4.3L V6, 5.0L and 5.7L V8
1. ALL
Engine Oil Pressure Switch now has a 1-pin connector. This was a mid-1998 Model Year (MY) running change that eliminated the redundant fuel pump power circuit. See the "Service Information" chart, below, for specific service information for each platform.
2. 4.3L V6 (VINs X, W - RPOs LF6, L35)
Notice:
Care must be taken to NOT cross-thread these locations. These locations on the engine block are NON-SERVICEABLE. ANY DAMAGE DONE TO THREADS IN THESE LOCATIONS WILL REQUIRE A SERVICE ENGINE BLOCK.
Metric Fasteners starting in 1999. The 4.3L engine block and oil pan will be machined with metric threads at the following locations.
a. L.H. Motor mount boss (M10 x 1.5), 3 locations
b. R.H. Motor mount boss (M10 x 1.5), 3 locations
c. Starter mounting pad (M10 x 1.5), 2 locations
d. Transmission mounting flange, rear engine block (M10 x 1.5), 6 locations
e. Transmission mounting Flange, Oil pan (M10 x 1.5), 3 or 4 locations
CRANKSHAFT, Flywheel mounting flange change. Starting in 1999, the crankshaft will have 3.0 mm (approx. 1/8 inch) of less material at the flywheel mounting flange. Referred to as "short crank", the overall length of the crankshaft has not changed, but the flywheel will now mount 3 mm closer to the rear of the engine block. This change required other specific changes listed below.
a. Revised crankshaft rear oil seal housing
b. Revised crankshaft rear oil seal
c. Revised crankshaft rear oil seal housing stud location
d. Application-specific flywheels
Kent-Moore tool J 35621-UPD2 (Rear Main Seal Installer Update Kit) is required to update Kent-Moore tool J 35621-A (Rear Main Seal Installer) for use on the 1999 4.3L V6. With the addition of this kit, the J 35621-B will service both 1999 4.3L V6, and 1999 (and previous) 5.0L V8/5.7L V8/1996 (and previous) 4.3L V6.
This change to the crankshaft was made to address a requirement for a "thicker" torque converter on new style C/K Pickup Truck applications. Other 4.3L V6 applications will have an offset stamped into the flex-plate, or material added to the flywheel, to retain proper alignment of components. THEREFORE, THESE COMPONENTS SHOULD NOT BE INTERCHANGED.
CRANKSHAFT, Manual Transmission Pilot Bearing. The 4.3L V6 will utilize a new ball bearing type pilot bearing for manual transmission applications. A new Kent-Moore tool J 43276 is required to remove this new 4.3L V6 bearing. The V8's will retain the current (1998) type needle bearing.
Product Availability
Due to marketing concerns, some models may have VIN badges to indicate one model year, but the engine content may actually be of a previous, or of a future year. This can cause confusion when trying to reference a Model Year (MY) for service concerns. To address this, two RPOs have been designated to indicate a MY "pull ahead" or "Push back". These RPOs (and an explanation) are as follows.
1. RPO "ZN4"
Which means a vehicle is badged for one model year while it is being manufactured into the next (pushed back). A specific case of this are some 1998 S/T pickup trucks which are VIN'd as 1998, but are manufactured after the traditional August changeover, and contain 1999 Powertrain components. These trucks would contain RPO "+ZN4".
2. RPO "ZK3"
This RPO indicated a vehicle with an indicated VIN MY that is "pulled ahead". A specific case would be the G Van which "started" 1999 MY production in May 1998, but included RPO "+ZK3", which indicated 1998 MY content. When the content switches to 1999 MY, the G Van will include RPO "-ZK3", designating 1999 MY content.
Service Information