308 Gtb jumping out of reverse

His advice was to replace the shifting gate?? Don't think I would be using him again.
Jumping out of gear is usually a sign of worn Syncro's or linkage adjustment.

 

No baulk rings for reverse, I'd suspect it's either out of adjustment or the gears selector sleeve is thrashed from forced engagement over the yrs. When sitting at a stop in neutral the shafts are spinning away, it takes a moment or two before it stops to allow reverse to engage. Many times people are in a hurry and 'crunch' the gear a bit, the sleeve takes a beating and the teeth wear down, in some cases they get sheared off if forced hard enough. Got a bunch of sleeves laying about that have been replaced due to that.

First check the adjustment, 90% of the time that's the problem. Usually due to the 'forcing' of reverse and over time the rod moves out of alignment.

 

yes this happened in my ex 308 a couple years after I first bought it. It was a simple linkage adjustment under the car. start there before you crack open the box

 

Find a new specialist. Check the adjustment and don't be afraid to drop the sump pan to take a look at the levers and if they are setting the shift forks properly. Don't freak out when the three balls drop out but be sure to place them again. Also inspect the silent blocks while down there.

 

This is not totally without merit if the reverse lockout feature is heavily worn, but having it "help" hold the gearstick in reverse only works if the gearstick is free to move up and down (and also isn't heavily worn). Is your gearstick stuck in the down position? It should move up and down ~10mm, and is spring-loaded to be in the up position (i.e., it should always be up, and, if pushed down the 10mm, it should pop back up to the up position when released), but if it has never been cleaned/relubed since birth, it could be stuck -- just a thought...

 

Not sure what is causing your reverse issue. But a trick I use an ALL my manual transmissions cars to stop grinding when shifting to reverse is to always shift into a forward gear (1st) prior to engaging reverse. Reverse doesn't have synchronizes.