Transmission noise

Basic question about my 5-speed manual transmission, 89 honda accord with over 500k miles. Starting to whine in 5th, jumped out of 5th a few times, no trouble shifting any gear, clutch fine, engaging fine, other gears fine. 5th is whining, getting worse. I’m not going to drive it (much) until I get it to a tranny guy, but will ANY driving be fatal to the tranny, like will 5th gear “let go” and deposit parts of the gear throughout the tranny, ruining the rest of it? Also . . . can just 5th be replaced? I’m thinking of looking for a used tranny with less miles and swapping it in. I expect that since most of the miles are highway miles on this car . . . most are on 5th gear and it’s just worn-out. But I’ve changed the manual tranny oil every 25k, sometimes sooner than 25k (if I’m doing something close to it and I’m dirty anyway). . . a used will be a gamble, maybe no maintenance. Best bet here? I’m thinking used. Rest of the car is great . . . some rust, engine is strong, very little oil use/loss, just did a bunch of replacement stuff on the suspension for safety sake, hate to park it with all those new suspension parts on it.

Congratulations for keeping your car running that many miles. I think that you are on the right track by installing a used or rebuilt transmission. Never heard of replacing a single gear in a fwd manual, but maybe one of the real experts knows if this is possible or cost-effective.

The only way I would say “junk it” is if the “some rust” you describe is structural and not just cosmetic. I had to junk a similar Accord due to frame rust.

Thanks! The rust isn’t bad, I fix things as they come up . . . keep it kind of clean of junk in the winter . . . wash off the salt when I can. Any tranny guys here have any suggestions about my 5-speed?