A Chevrolet Impala equipped with the 5.3 Liter V8 and a 4T65E transmission comes back with a serious leak coming from the front of the transmission. When the transmission is removed the front seal is found to have moved out of the seal pocket in the case.
The transmission was checked for drainback hole problems as well as checking the torque converter for leaks and the converter neck for true center position. The case bushing and stator support shaft were also verified good. A new seal, when installed, fit tightly in the case seal pocket.
The transmission alignment dowel pins as well as the dowel pinholes were also checked and were verified to be good. The flywheel showed no signs of damage.
At this point in time the technician thought to see how the torque converter pilot fit the crankshaft pilot hole, this was found to have an excessive amount of clearance.

The Impala with a transversely mounted 5.3 Liter engine and a 4T65E transmission is equipped with a torque converter with a pilot hub that measures .824” in diameter (Figure 1) which requires a pilot bushing (figures 2 and 3).

Without the pilot bushing the con-verter would spin off center and “walk” the front seal out of the seal pocket in the case.
A general repair shop had changed the engine in this vehicle that did not have this bushing causing the front seal to walk out. This can happen without the engine being replaced as the bushing could seize onto the converter hub. Always inspect and lubricate the converter hub and crank shaft bushing to avoid this from occurring in most all applications.

Install a pilot bushing into the crankshaft pilot hole.

Crankshaft Pilot Bushing ……………………..12571220

A vehicle equipped with a 6T30/40/45/50 transmission may have a complaint of no third, fifth of reverse gears. Upon disassembly of the transmission, the 3-5-Reverse retaining ring is broken into pieces (Figure 4).
The transmission may have also had a complaint of harsh shifts with a P0776 for “Pressure Control Solenoid B Stuck OFF.” The 3-5-Reverse “waved” plate was found to be broken (Figure 4).

The 3-5-R/4-5-6 clutch housing has a 3-5-R retaining ring groove that is not machined deep enough. The 3-5-R retaining ring is not made thick enough. The 3-5-R backing plate needed a higher step for better retaining ring retention (Figure 5).
The 3-5-Reverse clutch apply piston with the three (3) notch early design did not contact the wave plate evenly during clutch application which would eventually cause it to break (Figure 5).

Replace 3-5-R/4-5-6 clutch housing, retaining snap ring and backing plate with the updated second design level parts which comes in a kit (Figure 6).
Replace the 3-5-Reverse clutch apply piston that has no notches and the updated 3-5-Reverse waved plate that is stress relieved; it is darker in color than the first design waved plate (Figure 6). Updated parts are shown in figures 7 and 8.

Updated 3-5-Reverse Clutch Housing,
Backing Plate & Retaining Snap Ring Kit………………..………….24255922
Updated 3-5-Reverse Clutch Apply Piston (No Notches)………24259061
Updated 3-5-Reverse Waved Plate …………………………………….24230757

Some 2015 to 2016 Chevrolet/GMC Suburban, Tahoe, Sierra, Yukon and Yukon XL models equipped with the 6L80 (RPO MYC) may have a complaint of no fourth, fifth or sixth gears. DTC P0796 (Pressure Control Solenoid 3 – Stuck Off) may be set and the Malfunction Indicator Lamp will be illuminated.
An inspection of the transmission oil pan show little or no debris and the fluid appears to be in good condition.

The above-mentioned complaint is caused by a broken 4-5-6 Clutch Hub Assembly as seen in Figure 9 below. This complaint is not caused by the transmission control module or faulty solenoids therefore these components should not be replaced at this time.

Replace the 4-5-6 clutch hub assembly. Be sure the replacement clutch hub contains a new friction dampener as shown in Figure 10. The 4-5-6 Clutch Hub Assembly indexes into the 4-5-6 friction plates as seen in Figure 11.

5-6 Clutch Hub Assembly (6L80 RPO MYC) ……………….24230368
5-6 Clutch Hub Friction Dampener …………………………..24238004

During the rebuild process the technician searches for clutch clearance specifications but none are found. It is a common practice for General Motors to not publish these specifications.

General Motors is of the opinion that if original GM parts are used in all clutch packs, the clearance will be correct.

Figures 12 to 16 show clutch clearance specifications. Also shown are all available selective snap rings to adjust clutch clearance to the correct specification. Take notice that the clutch clearance specifications for the 6L80 are different than those for the 6L90.

3-5-Reverse Clutch Pack:
1.88 – 1.98MM (.074” – .078”) – Light Green…..24240195
2.15 – 2.25MM (.085” – .089”) – Yellow……….…24240196
2.42 – 2.52MM (.095” – .099”) – No Color ………24240197
2.69 – 2.79MM (.106” – .110”) – Purple …..….…24240198

1-2-3-4 Clutch Pack:
2.42 – 2.52MM (.095” – .099”) – No Color ….24240197
2.69 – 2.79MM (.106” – .110”) – Purple ….…24240198
2.96 – 3.06MM (.117” – .120”) – Light Blue .24240199
3.23 – 3.33MM (.127” – .131”) – Orange ..….24240200
3.50 – 3.60MM (.138” – .142”) – White …..…24240201

4-5-6 Clutch Pack:
1.60 – 1.70MM (.063” – .067”) – Yellow………24233407
2.02 – 2.12MM (.080” – .083”) – No Color …24233408
2.44 – 2.54MM (.096” – .100”) – Purple ……24233406

Low – Reverse Clutch Pack:
1.85 – 1.95MM (.073” – .077”) – Yellow…..…24245063
2.26 – 2.36MM (.089” – .093”) – No Color …24224737
2.67 – 2.77MM (.105” – .109”) – Purple ……24245064

2-6 Clutch Pack:
1.88 – 1.98MM (.074” – .078”) – Light Green ..24240195
2.15 – 2.25MM (.085” – .089”) – Yellow …….…24240196
2.42 – 2.52MM (.095” – .099”) – No Color …….24240197
2.69 – 2.79MM (.106” – .110”) – Purple …….…24240198

Note: Some snap ring part numbers are duplicated,
the same part number represents the same snap ring
thickness.

March 2019 Issue
Volume 36, No. 3

• GM 4T65E: Front Seal “Walk Out”
• GM 6T40 Series Transmissions: No Third, Fifth or Reverse Gears
• GM 6L80/90: No Fourth, Fifth or Sixth Gears
• GM 6L80/90: Clutch Clearance Specifications