Bonneville V8-350 5.7L DSL (1984)
Output Shaft: All Technical Service Bulletins
A/T - 3T40 Center Gearbox Distress, Diagnosis Tips
Bulletin Number:
91-7-13
Reference Number:
077140
Publish Date:
10/90
Subject:
NO 3RD GEAR, AND/OR NO DRIVE OR REVERSE CENTER GEARBOX DISTRESS DIAGNOSIS TIPS
Models
Affected:
1984-91 6000, BONNEVILLE, GRAND PRIX MODELS WITH 4T60 TRANSMISSIONS
BULLETIN COVERS:
Center gearbox distress diagnosis 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 due to a distressed 3rd roller clutch cage. Also, slips in 3rd gear or no 3rd gear.
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 reference 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 or the procedures are
not necessary.
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 the rollers are less likely to cock or skew when overrunning.
When the rollers cock or skew, excessive heat is created. Reference Pontiac Service Bulletin 90-7-35 issued 4/90.
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.
Reference pages 1-7 and 1-8 in the Hydramatic 440-T4 Product Update book.
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. Reference Pontiac Service Bulletin 90-7-35 issued 4/90.
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.
Reference Pontiac Service Bulletin 89-7-2 issued 10/88.
4.
End Plays: 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 bousing thrust bearing and 3rd roller clutch cam. Some leakage is designed in, but too much due to worn,
damaged, missing bushings, too much end play or incorrectly installed parts could cause a durability concern.
