View Full Version : I need help with truck transmission parts nomenclature and diagnosis.

10-21-2011, 07:52 AM
The shift lever on a large truck transmission is mounted in a ball socket (?) on the top cover (?). There's a tang (?) on the bottom end of the shift lever that fits into a rectangular box or gate (?) made up of three segments (?) that are part of the arms (?) that connect them to the shift rails.

The right side of the rectangular box is connected to the 1st/R rail. The middle is connected to the 2nd/3rd rail. The left side is connected to the 4th/5th rail.

What's the correct nomenclature for the parts with the (?) following them?

Also, the truck started locking up in 1st, and they had to remove the top cover to move the rail back to neutral each time it happened. When the transmission was disassembled, you could see a gouge on the arm below the 1st/R segment of what I'd call the gate, where the tang had hit it.

I think the ball socket must be worn enough that it lets the tang on the shift lever drop below the gate segments. That puts it where it would gouge the arm and cause the lockup.

Does that diagnosis make sense? Can the ball socket be adjusted or repaired?

The truck is a late-'70s GMC with a V8 2-stroke supercharged diesel engine.

10-21-2011, 08:48 AM
hows this

i presume youre talking manual gearbox


from here


all the best.markj

10-21-2011, 09:18 AM
Thanks!! That's exactly what I needed to identify the parts correctly.

Now for the diagnosis...any ideas? Please keep in mind that the striker jaws in this transmission are on the upper ends of curved arms, and are about two inches above the rails. The assembly in the above diagram is much more compact vertically.

10-21-2011, 09:30 AM
sometimes the top chamber in which the selector shafts run can become dry and unlubricated....especially after a long time period..this puts extra strain on everthing ..your nylon ball will wear out ..as so other components ..with the effort needed to shift gears.

the stuff up top, doesn't seem, to get any lube from the main oil reservoir ..

it's best to take the top plate off and lube everything up..every 50.000 miles or 5 years or so,,,or as soon as you notice things stiffening up ..sometimes can be done just by taking the stick out.

this is just findings from when i used to run rear wheel drive cars .

was usually a separate housing in which the shaft from the stick to the box ran.

as here

all the best.markj