The bore plug in GM 4L60-E, 4L65-E and 4L70-E units is held loosely in place with a coiled spring pin, allowing the opposing spring and oil pressure forces to stroke it within the bore.
This constant oscillation causes the plug to wear and allows PR oil at the low overrun valve and 3-4 clutch oil at the 3-2 downshift valve to exhaust at the abuse valves. This excessive oil loss can result in delayed apply of the Low/Reverse clutch and a tie-up of the 3-4 clutch and 2-4 band. Sonnax Forward and Reverse abuse bore plug 77754-21 resolves these problems.
This plug is used in two locations in the valve body: to separate the forward abuse and low overrun valves, and to separate the reverse abuse and 3-2 downshift valves.

The Sonnax plug has an increased diameter to restore proper valve body clearance in the circuits
The plug has a smaller retaining pin hole to reduce plug movement that results in wear
No tooling is required for this bore plug
Drop-in Zip Valve™ parts install quickly and easily

Learn More About Zip Valve™ Drop-In Repairs

More From This Category

PHC Clutch Bearing, Release, For Porsche 911 2.2 Ltr Turbo, 92kw 1/70-8/71 1970-1971, Each

PHC Clutch Bearing, Release, For Porsche 911 2.2 Ltr Turbo, 92kw 1/70-8/71 1970-1971, Each

$634.07

Sonnax Oversized Tcc Modulator Plunger Valve Kit, 5R55W/S O/S Sleeve, Each

Sonnax Oversized Tcc Modulator Plunger Valve Kit, 5R55W/S O/S Sleeve, Each

$44.69

TCI Automatic Transmission Rebuild Kit, Master Racing, For Ford, For Lincoln, For Mercury, C-4, Kit

TCI Automatic Transmission Rebuild Kit, Master Racing, For Ford, For Lincoln, For Mercury, C-4, Kit

$409.03

RTS Performance Transmission Duluxe Rebuild Kit Gm TH400, Red Eagle & Kolenee, Kit

RTS Performance Transmission Duluxe Rebuild Kit Gm TH400, Red Eagle & Kolenee, Kit

$695.00

TCI TH400 High Performance Frictions Forward Drums

TCI TH400 High Performance Frictions Forward Drums

$77.12