weird tranny issue...need help!
 

Okay, so i have an 87 S4 NA. It only has 87k, but the prev owner rebuilt it (wasnt needed, but wanted it done..)

So recently ive been developing a shifting problem. been going on for around 2-3 weeks. When i shift its a bit rough, it grinds the syncro, but never the gear. its not that kind of grind, not even a noise - but you can feel it.

now to the interesting part, i changed my trans fluid, put in 2 1/2 quarts of royal purple 75w90. drove around and no change. its a little smoother but not much.

NOW, if i make a left hand turn it shifts smooth! i made a 180 turn today and it was smooth. no grind feeling at all. after a stop and go it was back to acting up.

i have no clue what this issue could be, but if its preventable permanent damage i need to know!

Which gears grind? If you rev-match on a downshift, or allow the RPMs to drop before upshifting, does it go in smoothly? I would say you have synchros wearing out, and your turning thing is just a coincidence. You can't fix synchros, you can only replace them. The weak NA transmissions need to be babied or they'll wear out in no time.

forgot to mention, here is the other thing. when rolling to a stop like barely moving, first gear will be really tough to go in, if i jam it in it will upshift smoothly.

i will try what you are talking rotaryrocket88 on my way to school today.

1 , 2 , 3 grind. always, unless i turn left vigorously. rev matching does not help, nor does just waiting for the rpms to drop. i can be coasting with the engine at an idle and it will still not go in smoothly.

i noticed if i am in fifth, i downshift to forth, it is smooth. my thought is something controlling 1-2-3 isnt right. cause 4th and 5th are good, and even better if i do the left turn thing.

could it be a bad mount somewhere or something stupid?

also, coasting to a stop (5mph or so) 4th and 5th are fine, but 3rd, 2nd and 1st dont seem to slide in smoothly

Typically if some gears grind, it's those specific synchro rings. 2nd and 3rd are most likely to wear out. If it's all gears, you could need to adjust the clutch pedal, bleed the clutch system, or replace the master/slave/clutch hose.

I can't see a mount having an effect. I've driven with a broken front diff mount and passenger-side engine mount, and didn't have any issues shifting.

i have bled the clutch system, replaced the fluid, but have not thought of doing the hose, and didnt know the pedal could be adjusted. how do i do that, or should i search?

Okay well it cant be the clutch, cause wouuldnt it affect the way 4th and 5th shift? they are (fairly) smooth.

1st and 2nd have a bit of a wine on decel. very little in 3rd. is the throw out bearing or one of those going bad? Would that tie in anywhere?

Dude, its your synchros..

The whining is just the gearing, nothing strange about that

but why does it shift perfectly smooth if i make a swift turn left?

there is nothing in the entire gearbox that has anything to do with the steering.. so i'd say it just dumb luck

but didnt they teach you, you have to shift and brake before the turn, not during the turn ;)

I would suggest trying to find a good used transmission nearby (should find one for less than 100.00), get a new clutch, master, slave, and pilot bearing. Take half a day on a Saturday and swap them out. The pilot bearing is a pain to get out, probably easier with the proper tool.

I do have a parts car with a transmission, i'll look into it. just seems like a big job.. i appreciate it guys.

figured it out. i adjusted my TPS since i have been needing to set it to 1v. i did that and then took it out and it stopped my bucking issue which also got rid of my transmission issue. only 3rd gear has a small spot where its chunky but besides that its super smooth. it pulled really hard before i adjusted it and now its a little slower down low :(

You're imagining things. Adjusting the TPS could correct low-throttle bucking issues, but it has zip to do with the transmission. The TPS also is not going to affect power at full throttle. It's not even used past about 30% on an S4.

It's the way you're driving. Also 1st is just hard to downshift into. It sounds like you're not matching revs as well as you could on your shifts too.
Any transmission will feel notchy if you shift too slow because the Trans speed slows down too much from the time you pull it out of gear to put it back in.

Try different types of rev-matching. The left turn thing, I think you're just shifting quicker because you're turning.

I have a 15K mile Miata transmission in my car, it's smooth or catchy depending on how you rev match.

Have you checked the Fluid level in the Transmission?
This is often overlooked.Everyone assumes it's the Trans.

I had just replaced the tranny oil.

it sounds weird guys but yes it got rid of the bucking - and the notchy-ness. its a lot smoother now. maybe the syncros ARE on their way out but its way better right now.