The last 3rd gear syncro problem post ever!

[DSC]

Ok, so a lot of people have problems with their 3rd gear grinding, refusing to go in w/out revmatching, or just feeling crappy.

I know I am definitely one of them. I tried redline mt90 (synth 75w90) and it didn't help, 3,000 miles later I swapped it for mobile 1 (synth 75w90) and it didn't help. So I'm faced with swapping trannys or rebuilding. (sr isn't an option so don't bother saying; "just get an sr")

I know a lot of us have troubles with this, so for me and others please help where you can with the following questions.
Note: PLEASE only answer if you know the answer. I have a lot of ideas about the answer to most of these questions, but I'm not 100% certain of any of them really so I'll let the "experts" answer...please do the same. If your one of them...HELP <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'>
If you have any questions to add on...feel free! I'd love this to be made FAQ-worthy.

What are syncros?

How do they work?

What causes them to go bad?

Is it my fault?

Is there anything I can do/something I should NOT do in order to save the syncros of my new/rebuilt tranny?

What material are syncros made of?

Can I get them in a different (better) material?

I had more questions but can't remember them...dono how much there is to cover.
So...go at it guys <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/thumbs-up.gif" border="0" valign="absmiddle" alt=':thumbsup:'>

[gh6o6]

This is how i know about syncros:
HowTheyWork (http://www.howstuffworks.com/transmission4.htm)

For the whole article on manual trasmissions:
&nbsp; &nbsp; HowTransWorks (http://www.howstuffworks.com/transmission.htm)

Hope that hepls to understand, as for everything else - i cant help

[tnord]

Q: What are synchros?
A: The mechanical systems that match the the speed of the desired gear on the input shaft to the actual speed of the matching gear on the output shaft.

Q: How do they work?
A: there are 2 shafts inside the transmission; the input shaft, which is directly connected to the engine (only when the clutch is engaged), and the output shaft, which is directly connected to the drive wheels at all times. for every combination of road speed and gear, there is an associated RPM. top gear will typically have close to a 1:1 ratio, which means for every rotation of the gear, there is a rotation of the drive wheel. lower gears on the other hand rotate faster than the drive wheels, so when you downshift, it is the synchros job to speed up the gears on the input shaft to match the gear speed on the output shaft. when you upshift, just the opposite occurs, the input shaft gears must be slowed down.

Q: What causes them to go bad?
A: they are a wear and tear item, some will last forever, some will go out at 50k miles.

Q: Is it my fault?
A: I would say no, afaik, the only way to avoid wearing them out is to not use them at all.....aka; double clutching. also make sure your gear lube is at the appropriate level at all times.

Q: What are synchros made of?
A: nothing special, when i saw my transmission torn down, they consisted of small plastic rings, some rubber seals, and maybe an associated gear as well.

Q: Can i get them in a better material?
A: i don't think they are available in the current market. i suppose you could have some fabbed for you.

Dave-if you actually read the book i told you to get, there is a pretty good description on how this works in Chapter 6.

if i'm wrong on any of this, please correct me and i'll edit out my mistakes.

[DSC]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (tnord @ July 20 2002,12:59)</td></tr><tr><td id="QUOTE">Dave-if you actually read the book i told you to get, there is a pretty good description on how this works in Chapter 6.</td></tr></table><span id='postcolor'>
<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/lookaround.gif" border="0" valign="absmiddle" alt=':look:'> &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/lookaround.gif" border="0" valign="absmiddle" alt=':look:'> &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/lookaround.gif" border="0" valign="absmiddle" alt=':look:'> I got frustrated and stopped reading it...sux to read about something you can't do. &nbsp;And as much fun as it is to practice on the streets, its just become "bla" after a while.

I did however read that article on syncros/trannys on howstuffworks before. &nbsp;I was mostly asking the 1st couple questions for others with the same problem as me.

Hey, travis, how much did your tranny rebuild cost? &nbsp;What all did you get replaced? &nbsp;I guess It'd be hard to tell exactly how much labor was since you did other stuff at the same time, but I usually get raped when I take my car somewhere so I'd like to get an idea of how much I should pay.

[Kreator]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (tnord @ July 21 2002,10:59)</td></tr><tr><td id="QUOTE">when you upshift, just the opposite occurs, the input shaft gears must be slowed down.</td></tr></table><span id='postcolor'>
Ok, so if i shift fast enough to let the engine rpms drop exactly to the level of the gear rpms and then let go off the clutch, i'm not using synchros right?

[SR20Fastback]

Alright I've got one for you guys... Since I got my car back from getting a new clutch/flywheel... a few days later I was on my way to get the car tinted, and Im sitting in traffic, the light turns green and I go to put it into first gear...It wont go in first gear. I was so screwed so I had to do 2nd gear launches the whole way there. But the weird thing is, this doesnt always happen, and I cant figure out why. Sometimes it just takes a lot of force to go into 1st gear. This guy fromt he shop I usually take my car to said it could possibly be a shift fork. But I have no idea, anyone have any thoughts on wtf is wrong with my car now?

[240 2NR]

Have you tried letting the clutch out and reclutching to get into first? &nbsp;Not sure what causes it, but sometimes first just sticks (same with reverse) and you need to just stop and start again. &nbsp;Sometimes it helps to blip the throttle or let the car roll a few inches (in rare cases). &nbsp;

Any idea what causes this condition? &nbsp;I've had it happen in every manual car I've ever driven.

[SR20Fastback]

Yeah I've tried letting out the clutch then re-engaging it... I'm personally stumped. I still cant figure out why it only does it sometimes, and others its fine. The only other difference I noticed when I got my car back was, I used to be able to put it in 1st gear while rolling, but now it grinds the gears whenever I do that...Kinda gay, that was one of my favorite parts about driving the car cuz my prelude couldnt do that (stupid cable transmissions!!<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=';)'>

[240 2NR]

I could always get into first while rolling a bit in other cars. &nbsp;What I couldn't do was engage reverse with ANY movement forward or back. &nbsp;I must have looked like a retard the first time I drove my parents accord after months of driving my car. &nbsp;Rolled down the hill on our driveway, engaged reverse <CRUNCH> and drove off.

[DuffMan]

I didnt think our cars had 1st gear syncros, and that was why it wouldnt engage at anything faster than 5mph without rev matching.

I know a lot of newer cars can engage 1st while going pretty fast, but not all cars.

Anyway back to the original topic at hand. My 3rd gear is okay normally (well just a little bit notchy) but if i powershift and slam it into 3rd real fast it will grind. I've tried keeping the clutch all the way down, and it will still grind if i shift fast enough. Apparently the syncro isnt fast enough to slow down the input shaft to engage 3rd.

I'm going to try putting in redline to see if that helps. Since my car is in a very early stage of 3rd gear syncro failure, maybe i can deduce whether it is gear oil related or not.

[Natty]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (DuffMan @ July 22 2002,6:52)</td></tr><tr><td id="QUOTE">I didnt think our cars had 1st gear syncros, and that was why it wouldnt engage at anything faster than 5mph without rev matching.

I know a lot of newer cars can engage 1st while going pretty fast, but not all cars.

Anyway back to the original topic at hand. My 3rd gear is okay normally (well just a little bit notchy) but if i powershift and slam it into 3rd real fast it will grind. I've tried keeping the clutch all the way down, and it will still grind if i shift fast enough. Apparently the syncro isnt fast enough to slow down the input shaft to engage 3rd.

I'm going to try putting in redline to see if that helps. Since my car is in a very early stage of 3rd gear syncro failure, maybe i can deduce whether it is gear oil related or not.</td></tr></table><span id='postcolor'>
Yes, first and reverse are not synchronzied. This is a safety feature. &nbsp;With no synchros, you will have a very difficult time mis-shifting into those gears.

My third gear is starting to go bad too. I have been getting good at rev-matching tough &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/tounge.gif" border="0" valign="absmiddle" alt=':p'>

I have caught this early, maybe a 2 month old problem. I went in to have some redline put in and 3 different shops refused to do it! I was offering money to change my fluids and they all refused! They said I was dumb to think "service" would save the tranny. While they do make sense, I guess none of those guys knows that alot of Nissans do this.

I can't do it myself because I only have 2 jack stands and the car would not be level. &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/confused.gif" border="0" valign="absmiddle" alt='???'>

Jeff

[tnord]

it wasn't so much as transmission rebuild. all they did was replace all the bearings. and that friggin came out to 1200 bucks. thank you 100k warranty. anyway.....i think labor around here is about $70/hour.

btw....the specs for the fluid level in the transmission changed. now it's supposed to be about a half quart-1qrt
ABOVE the fill plug...at least that's what the tech told me.