2nd Gear crunch

[samfg92]

Hey :) I bought a '91 318i today and its pretty good mechanically, there is one problem that I'm not 100% sure on. As you shift down into 2nd it grinds, then goes in. It doesn't do it shifting up from 1st to 2nd or 2nd to 3rd, or when you shift down to 2nd with basically no rpm. For now I'm just coasting from 3rd to 1st for a full stop or just 3rd around most corners, but I'd be keen to know if it's a common problem or something I should definitely sort out ASAP.
Thanks in advance!

[jlevie]

That sound to me like a worn syncro in the transmission. A double de-clutch down shift will take the load off the syncro and eliminate the "crunch". Otherwise a transmission rebuild or replacement will be necessary.

[samfg92]

How difficult/expensive would a rebuild be compared to swapping in a second hand one? It's not yet a daily driver, more of a project car, so I'm planning on swapping the engine with something a little bigger. Would it be worth waiting and just swapping it all over when I eventually swap the engine?

[jlevie]

Rebuilding a transmission isn't really a DIY job. Special tools are needed. Drivegear offers rebuilts for ~1100 and they will give something for your core. Or you can get a used transmission for considerably less.

If you learn to double de-clutch and rev match downshift you can probably live with this for a long time.

[samfg92]

Yeah I saw a place yesterday who said it was a synchro and if I took the box out and brought it in they could replace the synchro for under 1k but they said there would likely be other things close to being worn so it may start I get expensive. I always try to rev match but it doesn't seem to work unless I'm just not double clutching right?

[jlevie]

If you push in the clutch, shift to neutral, rev match, and the select a gear all that happens is that the engine is at a higher speed. The transmission input shaft won't be spun up to match the lower gear speed. If you push in the clutch, select neutral, engage the clutch, rev match, push in the clutch and select the gear, and then engage the clutch, the engine and transmission input shaft will both be spun up. Syncro's in the transmission are then not necessary for the down shift. Learning this and making it a habit will reduce the wear on the syncros and make a transmission last a lot longer. It isn't that hard to do or to learn to do.

[samfg92]

Thanks mate, I'll give it a try next time I take her for drive and see if it sounds better :)