A/T - Enhancement of Shift Smoothness
No.: REISSUE 86-190Section: 7A
Date: DEC., 1986
Subject: THM 440T4 TRANSMISSION ENHANCEMENT OF SHIFT SMOOTHNESS
Model and Year: 1984-86 CELEBRITY WITH 440T4 TRANSMISSIONS
TO: ALL CHEVROLET DEALERS
Bulletin 86-190 (Section 7A) dated Nov., 1986 is being reissued to correct the Service Package P/N listed for Harsh Upshifts At High Altitude. All copies of 86-190 should be destroyed.
HARSH UPSHIFTS AT HIGH ALTITUDE 1985-1986 MODELS
Harsh upshifts at high altitudes may be caused by high line pressure due to low engine vacuum and may be corrected on certain transaxle models by installing an aneroid modulator service package.
The service package includes a new vacuum modulator assembly, modulator valve, O-ring seal, and instruction sheet.
-THM 440-T4 TRANSAXLE I.D. NAMEPLATE:
SERVICE PACKAGE P/N TRANSAXLE MODEL IDENTIFICATION
(Refer to Figure 1)
1985 1986
5CM 6CFH
8646956 5CN 6CMH
5CP 6CNH
5CW 5HA
A new engine to modulator vacuum line P/N 14062624 must also be installed.
HARSH 3-2 DOWNSHIFT AT HIGH ALTITUDE 1984-1986 MODELS
A harsh 3-2 downshift at high altitude may be corrected by installing new spacer plate gaskets and a 3-2 control valve spring. These parts, including instructions are contained in a service package.
3-2 CONTROL VALVE TRANSAXLE MODEL IDENTIFICATION
SPRING PACKAGE P/N ( Refer to Figure 1)
1985 1986
5CM 6CMH
8646983 5CN 6CNH
6CFH
8646993 5CP
5CW
NOTE: Before installing a service replacement transmission assembly (SRTA) that will be used extensively at high altitude, install the new 3-2 control valve spring. (Designated high altitude counties listed on pages 3 and 4 of this bulletin.)
HARSH 3-2 SHIFT MANEUVER (17 TO 20 MPH) AT ANY ALTITUDE
Commencing with the start of production 1987, an orifice pipe has been added between the 1-2 servo release cover plate and the 3-2 coastdown valve to allow for a smoother second gear apply. The four new parts installed as a set will service certain past model transaxles and may correct a harsh 3-2 shift maneuver.
P/N DESCRIPTION TRANSAXLE MODEL IDENTIFICATION
(Refer to Figure 1)
1985 1986
8662322 Body Assembly
Oil Pump Complete 5CM 6CFH
5CN 6CMH
5CP 6CNH
5CW
P/N DESCRIPTION TRANSAXLE MODEL IDENTIFICATION
(Refer to Figure 1)
8662376 Gasket, Release
All Models Listed
Cover
8662377 Pipe, Plug and
All Models Listed
Release Cover Assembly
8662394 Clip, Conduit
All Models Listed
NOTE: If the new pump body assembly has a 1-pin 3rd clutch switch, remove it and replace with the 2-pin switch from the original pump body assembly.
DESIGNATED HIGH ALTITUDE COUNTIES*
STATE OF ARIZONA STATE OF NEVADA
Apache
Carson city Humboldt
Navajo Douglas
Lander
STATE OF COLORADO Elko Lyon
Esmeralda Mineral
Adams Jefferson
Eureka Storey
Alamosa Lake
White Pine
Arapahoe La Plata
Archuleta Larimer STATE OF NEW MEXICO
Boulder Las Animas
Bernalillo Mora
Chaffee Lincoln
Catron Rio Arriba
Clear Creek Mesa Colfax
Sandoval
Conejos Mineral
Curry San Juan
Costilla Moffat De Baca
San Miguel
Crowley Montezuma
Grant Santa Fe
Custer Montrose
Guadalupe Sierra
Dolores Morgan
Harding Socorro
Delta Ouray
Lincoln Taos
Denver Park
Los Alamos Torrance
Douglas Pitkin
Luna Union
Eagle Pueblo
McKinley Valencia
Elbert Rio Blanco
El Paso Rio Grand
STATE OF OREGON
Fremont Routt Lake
Garfield Saguache
Gilpin San Juan
(CO continued on page 4)
COLORADO (continued)
STATE OF UTAH
Grand San Miguel Beaver
Piute
Gunnison Summit Box Elder
Rich
Hinsdale Teller Cache
Salt Lake
Huerfano Washington Carbon
San Juan
Jackson Weld
Daggett Sanpete
Davis Sevier
STATE OF IDAHO Duchesne
Summit
Bannock Custer
Emery Tooele
Bear Lake Franklin
Grand Uintah
Bingham Fremont
Iron Utah
Blaine Jefferson
Juab Wasatch
Bonneville Madison
Kane Wayne
Butte Minidoka
Millard Weber
Camas Oneida
Morgan
Caribou Power
Cassia Teton
STATE OF WYOMING
Clark
Valley Albany
Natrona
STATE OF MONTANA Carbon Niobrara
Converse Park
Beaverhead Madison
Fremont Platte
Deer Lodge Meagher
Goshen
Gallatin Sublette
Park Hot Springs
Sweetwater
Jefferson Silver Bow
Johnson Teton
Laramie Uinta
STATE OF NEBRASKA Lincoln
Weston
Banner Sioux
Kimball
* Counties which have substantially all of their area above 4,000 ft. Ref. Federal Register, Vol. 42, No. 76, April 20, 1977, Pg. 20464