• Low line rise
  • 3-4 Clutch & band failure


A low throttle boost oil condition.


Stop excessive leakage by installing Sonnax oversized throttle valve with slightly larger spool diameters.


Required reamer 77968-RM is no longer in production. Check with your distributor for availability.


Oversized Throttle Valve
Part No. 77968

Not compatible with early '82–'90 aluminum sleeve units.

You need this if... View Instructions Find a Distributor

A low throttle boost condition is a common complaint in vehicles with a vehicles with GM 4L60 transmissions. This loss of throttle boost oil creates poor line rise and accelerates 3-4 clutch and band failure. In late-model transmissions, the hardened steel throttle valve continuously oscillates in the cast iron valve body bore and eventually wears the three bore diameters. This wear allows throttle valve feed oil to leak past the valve spool and exhaust, resulting in a low throttle boost condition. This excessive leakage can be eliminated by reconditioning the bore and installing Sonnax oversized throttle valve 77968.

  • The three spool diameters on this valve are slightly larger than the late-model OE valve, allowing the valve body bore to be modified to restore the hydraulic integrity of the assembly
  • Reamer eliminates miscalibration or similar wear when exchanging with another used valve body

Sonnax valve body layouts provide a detailed overview of individual units making it quick and easy to determine what’s available for the specific valve body you’re working on. See all Sonnax valve body layouts.

GM 4L60 (700-R4) Valve Body Layout

GM 4L60 (700-R4) Valve Body Layout
  • 4L60 Oversized Throttle Valve 77968
  • 4L60 Oversized Throttle Valve 77968

You need this if...

Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.

4L60 Oversized Throttle Valve Vacuum Test Locations