Transmission syncro question

[jimtweet]

ok, i am about to pull the engine and trans next month. My third gear just started grinding, and first is getting difficult to get into sometimes...trans is dry as a bone and not leaking anywhere.

i want to have a full rebuild done locally before anything gets worse.

i know i will need a new third syncro ring and hub.

am i correct is saying the "syncro ring" is the part that wears out?

i want to have all the syncros replaced, just want to make sure i order the correct parts.

[DSPTurtle]

The terms you are looking for are: dog teeth, brake bands and stop blocks. Those are the parts that you end up replacing when you rebuild the trans. They are all really expensive by the way. But, at least you only need 4 not 5

[JFairman]

You never downshift into 4th so there's usually no reason to replace the 4th gear synchro parts - they don't wear out.

anchor blocks, stop blocks, energizer rings, brake bands, and synchro rings should be inspected by someone that knows the gearbox because some of those expensive little parts last a very long time and maybe ok to reuse.

The 1-3 synchro rings will be replaced. If it doesn't pop out of gear the slider and selector teeth may be ok to reuse but someone experienced with the gearbox should inspect and decide.

Most rebuilders will replace the special nuts that go on the ends of the shafts because they have a collar on one end that gets bent over into a key way on the shaft so they don't come loose. Reusing and rebending those is not a reliable rebuild.

Anyway, a BMW 2002 4 speed and the 930 4 speed gearbox are two of the easiest to rebuild... no intermediate plate with 2 piece roller bearings in a simple 4 speed.