Grinding down shifting into 2nd?

Any one have this issue? I know the synchro is bad as it will grind going 1st to 2nd above 4500 rpms but its never done it down shifting, I'm really confused that its doing it even doing slowing down from 15-20 mph. I could see it if I was being hard on it but not babying it through the city

Are you rev matching or double clutching? Might help. Downshifting is much harder on synchros because the shafts have to be accelerated wheras upshifting everything slows down on it's own if you time it right.

Synchros worn affects going into gear from either direction any time things are moving.

^well an upshift from 1st gear to 2nd gear is the largest change in gear ratio you can put the box through entirely, at least that you'd regularly use (shifting into 1st while moving is actually the biggest, but you rarely need to do that, or ridiculous stuff like completely skipping gears)...more so than downshifting at even crazy revs...this is exactly why most manual gear boxes have double or triple cone reinforced synchro's only on the 2nd gear collar...

you can make both upshifts and downshifts helplessly horrid on gearbox internals if you purposely do it...but in general, yes, downshifts are generally easier on the gear box...harder on the engine (gear box parts are slowing down, engine parts are speeding up)...but that is mostly related to how you drive...

whats likely happened is that the 2nd gear synchro has just been wearing down more and more from normal 1st to 2nd upshifts...with 'normal' synchro wear on 2nd gear, you'll notice it from 1st to 2nd only at first...but as it wears more and more, it'll stop properly synching even less aggressive ratio changes (i.e. 3rd to 2nd)...

you can slow wear as much as possible during deceleration by pulling out of 3rd, letting the clutch OUT, then precisely matching revs with light pressure on the shifter into 2nd...if you do it right, the collar will slip in with the clutch engaged (i.e. pedal out) and no fuss...but obviously that takes practice and a lot of paying attention...you can also just get in the habit of just skipping 2nd gear haha...luckily the FS has enough torque to lug around in 3rd pretty easily, just wind out 1st a little more before the shift...remember though, thats just going to put a s*** ton more stress on the 3rd gear synchro (MAJOR ratio change for that)...but it'll hold out until you simply find a cheap used gear box...

1st to 2nd is fine as long as its under 4500 rpms. I can go 3rd to 2nd as long as I'm doing under 20mph. There's a totaled 626 in a local junkyard with a good motor and trans I'm saving up to get its just gotta hold out for a few months. For now I'm double clutching going into 2nd and babying it so it can hold out

Out of curiousity install shield what's my compression supposed to be? Iirc 150-170 is acceptable right?

InstallShield: you're partially right. the greatest ratio change IS the hardest shift, 1-2 is the hardest upshift. 2-1 would be the hardest downshift but it's seldom done (most drivers will stay in 2nd unless coming to a complete stop). but downshifting without double clutching is much much harder on the synchros than upshifting. You can upshift without the clutch if you time it right because the parts naturally slow down. You cannot downshift without it (unless you double clutch and you're darn good) because you have to accelerate the gears and shafts to a higher speed (matching the engine) before engaging the gears. you're even less likely to do that in 1st so 2nd gets the most abuse.

Tweety: Do you shift that high for normal driving? no wonder the synchros are going. another suggestion: wait longer before engaging 2nd on the 1-2 shift. shifting fast is cool but shifting too fast wears parts out (as you've found). Both my truck (with 250k miles) and the firebird (40k grampa miles, most of the last 10k by me on the highway sitting in 6th) sorta kachunk/grind when shifting too fast. Just waiting to shift about as long as it takes the engine to get to the rpm for the new gear is enough to go in silently and smooth as butter. Reason is if you're shifting too fast, the sunchros are acting as a brake on the gears to slow them down faster than drag would normally do it.

I never rev that high unless I'm playing around a bit, I normally shift around 2500, 3000 at the most