How To Install A ($25) Shift Kit And Wake Up Your TH350

DIY TH350 Transmission Shift Kit Install

A solid transmission is the key to putting power to the ground in any hot rod, muscle car, or truck. Opening up a transmission to modify it can be new territory or really expensive to hire out.

With a little knowledge and a drill, any average Joe can beef up a TH350 to withstand the abuse of towing, racing, and hooning with a $25 shift kit and a fresh filter — toughening up your own transmission is a cheap and easy DIY project you can do at home.

Watch Mad Scientist Garage work through a $100 Craigslist TH350 find and turn it into a stout shifting transmission for a ’75 Pontiac Firebird

$25 GM Turbo 350 Transmission Shift Correction Package

Current Price As Of 12/1/2019: $19.65

This TH350 Shift Correction Package offers regular, heavy-duty and towing applications all in one package.

This valve body kit services TH350 and TH250 lock-up and non-lock-up units. It contains parts to convert a 350 lock-up back to a 350 non-lockup. Lube modification for heavy-duty units is shown in the kit to prevent loss of converter lube under heavy throttle.

GM TH350 Transmission Shift Correction Kit by Superior
GM TH350 Transmission Shift Correction Kit by Superior

This Kit Will Help Address:

  • Erratic passing gear
  • Premature clutch failure
  • Premature band failure
  • Erratic shift points
  • Weak shifts
  • Will convert a 350C to a 350 if wanted

A high-performance version of this TH350 kit is offered for street rods and racing only (K350-HP). The high-performance valve body kit allows manual low up-shifting at any speed as well as automatic control.

$15 GM TH350 Transmission Super Max Filter Kit

Automatic Transmission Complete Reseal and Filter Service Kit. This is the most complete kit on the market that contains all the new seals to stop leaks plus a new filter to extend the life of the transmission.

GM TH350 Transmission Super Max Filter Kit
GM TH350 Transmission Super Max Filter Kit

Kit includes input seals, o-rings, and grommets to reseal the whole unit: Amazon Filter Kit