First, I'd check the shifter adjustment, and bushings, and make sure it's going all the way into gear. (Might need to adjust the stop bolt) If the shifter adjustment is good, and the bushings are good, you likely have worn engagement teeth on third gear. If that's the case, you could try "Torque lock sliders", or replace the gear.

 

I'd bet your bushings/linkage is worn, or your shifter is out of adjustment.

 

Ok, the shifter needing to be adjusted sounds like the most popular reason causing this condition so this is where I will start. I have never had to do this and need some guidance.
I appreciate anyone's advise on how to do this right.

Thanks,
Steve

 

If you look at the shift mechanism, you see three arms, attatched to 3 rods. At the shifter, there is a threaded collar to adjust the length of the rods. There is a 1/4" hole bore thru the shifter side plates (on some it's more like a notch) and all 3 shift arms. With the trans in nuetral, you should be able to easily slide a 1/4" drill bit all the way through. If you can't, locate and adjust the offending rod(s).

On a hurst shifter, there are stop bolts to adjust the limit of shifter travel. They are located on the front and rear of the shifter mechanism, fiarly long, going up at an angle. They have locknuts to lock them in place. The rear one does first and third. Best thing is to loosen it several turns, put the trans in third, screw the bolt in till it touches, then back it off one turn and lock it with the locknut.

Here's a link to a magazine article on installing and adjusting a hurst shifter:
http://chevyhiperformance.com/howto/97440/

 

HEY, THESE GUYS HAVE ALMOST COVERED EVERTHING THAT MIGHT BE THE REASON FOR THE JUMPING OUT OF GEAR PROBLEM. HERES A LITTLE CHECK LIST THAT MIGHT HELP YA.

1) CHECK THE SHIFTER BUSHINGS AND ADJUSTMENT
2) MAKE SURE THE NUTS OR BOLTS THAT HOLDS THE LEVERS TO THE TRANNY SHIFT SHAFTS ARE TIGHT AND NOT WORN.
3) IF ALL THE OUTSIDE THINGS ARE OK THEN THE SHIFTER FORKS ON THE INSIDE COULD BE WORN EXCESSIVELY.
4) IF THE FORK IS OK THEN THE SLIDER ON THE SYNCRO HUB COULD BE WORN AND CAUSING THE PROBLEM.
5) AND IF NOT ANY OF THE ABOVE THE HOLDING TEETH ON THE GEAR ITSELF ARE PROBABLY WORN OFF. ONE OTHER THING I HAVE RAN INTO IS THE SYNCRO KEYS IN THE SYNCRO HUB ASSEMBLY HAVR FALLEN OUT OR MAYBE BROKEN. MAYBY THIS WILL HELP

 

caps off please......