NO 3RD GEAR AND/OR NO DRIVE OR REVERSE
SUBJECT: NO 3RD GEAR, AND/OR NO DRIVE OR REVERSE - CENTER GEARBOX DISTRESS DIAGNOSTIC TIPS
MODELS AFFECTED: 1984-91 CENTURY WITH 4T60 (440T4) TRANSAXLE 1985-90 ELECTRA/PARK AVENUE 1986-91 LESABRE 1986-90 RIVIERA 1988-91 REGAL 1988-90 REATTA
BULLETIN COVERS:
Center gearbox distress diagnostic tips - all 1984-91 Hydra-Matic 4T60 transaxles. Center gearbox distress in a Hydra-Matic 4T60 transaxle may result in one of the following conditions:
1. No 3rd gear or slips in 3rd gear due to a distressed 3rd roller clutch cage.
2. No drive or reverse due to a distressed input sprag.
3. Distressed 3rd and input clutch fiber and reaction (steel) plates.
Many changes were implemented to help reduce center gearbox distress. This bulletin will discuss them and refer to service bulletins already published on previous changes and what components should be inspected during an overhaul. Also, some other helpful tips and information about lubrication flow have been added. Reference Figures 1 and 2.
Several aftermarket publications have been written concerning different ways to modify the center gear box. Some of the modifications include grinding slots, lining up the lube holes differently, and greatly increasing the fluid level. DO NOT ATTEMPT THESE PROCEDURES! These publications were written to supposedly improve the performance of the center gear box, but instead the modifications can cause durability concerns.
1. Changes have been made to the 3rd roller clutch which will improve its durability. Revisions have been made to the lube holes on the outside race. Four of the lube holes have been eliminated. When the lube holes are eliminated, the rollers are less likely to cock or skew when overrunning. When the rollers cock or skew, excessive heat is created. Refer to Service Bulletin 90-7440-10.
1A. To increase the lubrication to the 3rd roller clutch assembly, a 3rd roller clutch dam was added and the input housing shaft I.D. 4th clutch shaft seal was eliminated. This change occurred for the 1985-1/2 model year.
2. New Output Shaft With A Single Path Bearing: The new output shaft and bearing allows more lubrication fluid to flow to the center of the gearbox. Refer to Service Bulletin 90-7440-10.
3. New 10 Plate 3rd Clutch Assembly For SOP 1989: The 10 plate clutch assembly, compared to the previous 8 plate clutch assembly, is for higher torque engine applications and also helps eliminate heat build-up due to numerous repeat manual Lo engagements at speeds around 35 MPH. Refer to Service Bulletin 89-7440-2.
4. End Play: If the final drive has too much clearance, this will allow the final drive sun gear to move away from the thrust bearing in the final drive. This will allow too much lube fluid to leak out from the final drive sun gear shaft. With the correct final drive end play, the sun gear would block most of the lube fluid from escaping from the sun gear shaft. If the input housing has too much clearance, this would allow too much lubrication fluid to leak out between the input housing thrust bearing and 3rd roller clutch cam. Some leakage is designed in, but too much leakage, due to worn, damaged or missing bushings, too much end play or incorrectly installed parts could cause a durability concern. Refer to the lubrication circuit fluid flow description, Figure 1.
5. The final drive sun gear lube groove must face towards the parking gear to allow adequate lubrication flow to the final drive pinions. The final drive sun gear shaft has lubrication holes in the shaft that feed fluid into the step in the sun gear, then through the two slots in the parking gear to the final drive pinions - if the final drive sun gear was installed backwards, the holes in the final drive sun gear shaft would be blocked, not allowing fluid to lubricate the final drive pinions.
6. Check lube pipes for correct installation and any damage (plastic cracked, pipes bent, etc.). Ensure the lube pipe retainer is in the proper position. A mispositioned or damaged component will leak lubrication fluid into the bottom pan instead of directing the fluid to the center of the gearbox. While bolting down the accumulator cover, inspect the position of the lube oil pipe retainer - reposition if cocked.
7. Fluid Foaming Due To Overfilling Or Incorrect Thermo Element Height: If the fluid level is too high, the moving parts will churn the fluid, causing the oil to foam. This will cause many durability concerns including damage to the center of the gearbox. An incorrect thermo element height will cause the fluid level to be inaccurate (either too low or too high) when the fluid is up to operating temperatures. Too low a fluid level will cause air to be pulled into the filter, and too high a level will cause fluid foaming due to churning. Check the height with thermo element height setting tool, J 34094-A.
8. 4th clutch hub and shaft assembly should have one needle missing from the inside of the bearing cage for oil flow to the 4th clutch fiber and reaction plates.
9. Transaxle Oil Cooler Flow Test: Correct flow is two quarts of fluid per 30 seconds. Also, it must be flushed after certain repairs are performed; refer to the Labor Time Guide for labor operations that require transaxle oil cooler flushing. For flushing instructions, refer to Service Bulletin 87-7-3.
10. Input Housing To 3rd Roller Cam Thrust Washer Replaced With A Needle Bearing: Refer to Service Bulletin 89-7440-6 for details about past model service.
11. The lube dam must be installed on most 1986 and newer models between the input and reaction carriers. Leaving a worn, damaged or missing lube dam will allow too much fluid to leak into the bottom pan. Refer to Service Bulletin 86-7440-9.
IMPORTANT: --------- When reassembling a 3rd roller clutch, ensure that the lube dam is pressed to the proper depth. If the 3rd roller clutch is mated to the thrust needle bearing instead of the washer, then:
- press the dam to a depth of 20.72/20.92mm (0.816/0.824") as measured from the bottom side (sprag side) of the outside race to the wide flat edge of the dam as shown in Figure 3.
If using the thrust washer, press the dam (on models so equipped) to a depth of 20.04/20.12mm (0.789/0.792") as measured from the bottom side (sprag side) of the outside race to the wide flat edge of the dam as shown in Figure 3.
NOTICE:
Measure the press in depth for the dam as shown in Figure 3. Measuring from the top of the 3rd roller clutch race to the dam will be inaccurate because all the machining of the 3rd roller clutch race is based on the opposite side (side that mates to the input sprag). If the dam is pressed in too far or not far enough, it could rub on the 3rd roller clutch cage or the snap ring that retains the 3rd clutch return spring and create excess heat to distress the cage of the 3rd roller clutch.
12. Line Pressure: Lubrication fluid is proportional to line pressure. If the line pressure is below specification, then lubrication fluid flow could be inadequate. Check the line pressure as outlined in the service manual.
13. Check the converter clutch regulator valve for proper operation, binding, sediment or damage. This valve controls the flow of lubrication - when the torque converter clutch (TCC) is applied, lubrication fluid from the pump pressure regulator is routed past the torque converter directly to the cooler; when TCC is not applied, the fluid is routed through the converter, then to the cooler.
- If the valve is damaged, included in service package 8646934 a new valve isuse only the convertor clutch regulator valve from this package.
SERVICE PARTS INFORMATION:
Part Number Description Usage ------ ----------- ----- 8646934 Package, Valve Body Spacer Plate Convertor All 1984-1991 4T60 Clutch Regulator Valve and Spring (THM 440T4) Models
IMPORTANT: USE ONLY THE CONVERTOR CLUTCH REGULATOR VALVE FROM THE PACKAGE.
Parts are currently available from GMSPO.
THE TWO HOLES IN THE INPUT SUN GEAR LINE UP WITH THE LUBE DAM IN THE SPRAG INNER RACE. THE DAM PROVIDES THE THREE LUBE GROOVES WITH LUBE. LUBE THEN GOES THROUGH THE THREE LUBE HOLES TO THE SPRAG ELEMENTS.
LUBE FLOWS DOWN THE OUTPUT SHAFT ON THE I.D. OF THE FINAL DRIVE SUN GEAR SHAFT THROUGH THE LUBE HOLE INTO A STEP ON THE FINAL DRIVE SUN GEAR THROUGH TWO SLOTS IN THE PARK GEAR TO THE FINAL DRIVE PINIONS.
NOT ALL THE LUBE GOES TO THE INPUT SPRAG. SOME GOES INTO THE TWO LUBE HOLES IN THE INPUT SUN GEAR (HOLES NEXT TO THE GEAR). LUBE ALSO COMES FROM THE FINAL DRIVE SUN GEAR SHAFT THROUGH THE TWO LUBE HOLES TO THE LUBE GROOVE IN THE INPUT SUN GEAR SPACER.
THE THRUST BEARING ALLOWS SOME LEAKAGE OF LUBE FROM THE OUTPUT SHAFT, SUN GEAR, AND INSIDE POCKET OF THE FINAL DRIVE CARRIER.
SOME OF THE LUBE GOES THROUGH THE TWO HOLES IN THE SPACER TO LUBRICATE THE BUSHING BETWEEN THE SPACER AND THE INPUT CARRIER; THE REST GOES ONTO THE SUN GEAR FROM THE INPUT CARRIER THROUGH THE LUBE GROOVE IN THE SPACER ONTO THE GEAR TEETH.
THE FINAL DRIVE SIDE GEARS, GOVERNOR DRIVE AND DRIVEN GEARS, GOVERNOR TO SPEED SENSOR HOUSING BEARING, AND FINAL DRIVE TO CASE BEARING ARE LUBED BY TRANSMISSION FLUID RELEASED BY THE GOVERNOR BALLS.
INSTALLING THE SPACER BACKWARDS WOULD BLOCK LUBE FLOW TO THE INPUT CARRIER GEARS
LUBE OIL COMES FROM THE COOLER THROUGH THE CHECK BALL COOLER LINE FITTING THROUGH A CASE PASSAGE INTO THE ACCUMULATOR COVER. THERE THE FLOW IS DIVIDED UP INTO TWO BRANCHES.
SOME LUBE COMES OUT OF THE OTHER SIDE OF THE SPACER FROM THE DIAGONAL CUTS ACROSS THE SPLINES OF THE INPUT SUN GEAR.
ONE BRANCH TO THE FINAL DRIVE INTERNAL GEAR, THE OTHER TO THE DRIVEN SPROCKET SUPPORT.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
