4th gear grind

[accident]

88 325is

when i shift into 4th gear there is an angry grinding noise, almost like the clutch is still engaged. if i get it into 4th and pull it out and put it back into 4th, there is no grind. if i hold the clutch and shift from 4 to 3 and back to 4 it grinds again. if i put it into 4th and then neutral, let out the clutch, and go back to 4 it grinds. i really hope my synchro isnt bad. could this be caused by the trans fluid needing to be changed? i dont know when it was last done. i've had the car for about a year and havent done it. my brake fluid is also kinda low, and dirty as fuck. i was planning on doing fluids this weekend anyway.

[jlevie]

That sounds like a bad syncro.

[accident]

oh happy day. :(

[alpinee30m50]

Yeah thats exactly what my second and sometimes third does. Im pretty sure its bad synchros as well

[accident]

if i rest the shifter on the gate for a second before pulling it in there is no grind, however if i wait that same time in neutral it still grinds

[bimmer_E30]

change the oil in the tranny, it will shift 90% better than it did before

[gearheadE30]

yep, definitely synchro. When you rest the lever on the gate, what is left of the synchro matches the gearbox speed just enough for it not to grind. My old transmission did this in 2nd, 4th, and 5th going up and down, but that in itself isn't an issue. Learn to double clutch and you'll be golden :). Basically, for it not to grind, the transmission input shaft speed needs to be matched to the engine speed before you shift. On upshifts, when the lever is in neutral between 3rd and 4th, let the clutch out for an instant, push it back in, then shift to 4th. Going down is harder, but easy if you already know how to heel-toe.

EDIT: unless you're really lucky or have terrible fluid in there or something, new fluid won't fix it.

[accident]

if the fluid looks anything like my brake fluid, it's black and dirty as fuck.

[accident]

also i tried letting the clutch off in neutral and then going to 4, still grinds no matter how fast or slow i do it.

[McGyver]

rev match so you dont r3v it?