High mileage 87 6.2L 3/4T 4x4 4 Speed with bull low 1st gear transmission, presume same as what GM has been using in 1T and 3/4T Trucks since the 60's, Sometimes just called a 3 speed with low, seeing 1st is rarely used unless loaded or crawler speed needed.
Jumps out of 3rd gear way too easily, As soon as the throttle is lifted or coasting, All the other gears still work good and will stay in 3rd gear if held continually.

Was told there's a spring in the top of the shifter housing, Easy to get at by just taking the shifter boot off, then removing the shifter from the top of the transmission and replacing a spring,

Any one know for sure? Part number? As easy to change as told? Got a link to the repair or schematic?


Thanks in advance

By saying 3rd gear I am assuming high gear? I.e. 4speed= L,1,2,3 ?

The "poppet ball" is the little ball bearing that holds the shifter rail into gear, or neutral. If the spring is worn that holds pressure on the poppet ball, then this may be the cause for your trouble. Should be a little hex head screw, actually three in a line, or possibly two, and a switch for the back up lights, in front of the shifter. Unscrew these to access the springs.

You should notice if 2nd, and 3rd are easier than the other gears to move the shifter into. If that is the case I would guess the spring.

The other scenario would be that your transmission bearings are worn, and too much mainshaft end play is causing the shifter to walk. If you have bearing trouble this will require total teardown of the transmission.