Grinding the gears

[Warped]

I have a 90 240sx with a manual tranny, if i shift hard into second it grinds going in. Even with the clutch all the way to the floor. It also gives me trouble going into reverse sometimes, i have to go into 5th before reverse will go in. So is it the syncro's or what? Do i need a rebuild?

[malcolm]

Originally Posted by Warped

I have a 90 240sx with a manual tranny, if i shift hard into second it grinds going in. Even with the clutch all the way to the floor. It also gives me trouble going into reverse sometimes, i have to go into 5th before reverse will go in. So is it the syncro's or what? Do i need a rebuild?

grinding into second: likely dead synchros. The more you grind it, the worse it will get. If you have to downshift into second, I would suggest learning to double-clutch when you heel-and-toe. When you shift from first to second, double clutch a tiny bit when you're in neutral. (the double-clutching itself might not do a whole lot, but it will force you to take more time between shifts, thus allowing the input shaft to synchronize with the output shaft without the aid of the synchro itself.

As for going into reverse, a fair amount of gearboxes I've driven with are like that. Sometimes the dog-rings are just lined up perfectly so the tops of the teeth line up, and it stops it from meshing. A simple push into a different gear, or letting out the clutch a little bit will usually rotate it enough to allow it to slip into reverse, and have the dog-rings mesh perfectly.

[Warped]

thank you, so am i looking at a total rebuild or is this something that may actually cost me less than 600 to fix.

[malcolm]

Originally Posted by Warped

thank you, so am i looking at a total rebuild or is this something that may actually cost me less than 600 to fix.

that I don't know.... if I were you, I'd try to find a used gearbox from a wreckers or something.

The guys that do hundreds of motor swaps would likely know where to get a cheap 'box better than I would...

[Buddyworm]

If all else fails, just become obscenely good at rev-matching :P Save yourself a couple hundred, become extremely skilled. It's a win-win!

B-Wurm

[santi]

rev matchin and double clutching will only be effective if it's not that bad.. it's they are crap like my second gear then it wont matter what you do it'll grind anyways.. i got my tranny out of a junker to make my car a 5spd about a yr ago and it's been grinding since the first day.. it'll last a while..i shift fast and heal toe.. but nothin is gonna make the car not grind

[Warped]

it only happens at very high revs, the car is going into the shop on monday so i can get a better idea of the possible damage.

[DV_S13SIlvia]

Is it normal to have first gear grind?? when your going over about 10mph?? It happens whenever i hit a stop sign and i dont coma to a complete stop. I know i should be more careful but i was just curious to why it does this?

[Tuner]

Originally Posted by malcolm

grinding into second: likely dead synchros. The more you grind it, the worse it will get. If you have to downshift into second, I would suggest learning to double-clutch when you heel-and-toe. When you shift from first to second, double clutch a tiny bit when you're in neutral. (the double-clutching itself might not do a whole lot, but it will force you to take more time between shifts, thus allowing the input shaft to synchronize with the output shaft without the aid of the synchro itself.

As for going into reverse, a fair amount of gearboxes I've driven with are like that. Sometimes the dog-rings are just lined up perfectly so the tops of the teeth line up, and it stops it from meshing. A simple push into a different gear, or letting out the clutch a little bit will usually rotate it enough to allow it to slip into reverse, and have the dog-rings mesh perfectly.

What about the clutch slave cylinder?

[santi]

Originally Posted by DV_S13SIlvia

Is it normal to have first gear grind?? when your going over about 10mph?? It happens whenever i hit a stop sign and i dont coma to a complete stop. I know i should be more careful but i was just curious to why it does this?

mine does that too.. but if i heal toe it it doesnt.. but i'm not sure first gear is made for that atall in our cars.. maybe i should stop

[malcolm]

Originally Posted by Tuner

What about the clutch slave cylinder?

i thought about that... but then it should grind in most gears, right? and wouldn't it creep a bit too when you're at a stop?

[WanganEfini]

Originally posted by Warped
thank you, so am i looking at a total rebuild or is this something that may actually cost me less than 600 to fix.

iF it's the dog rings like Malcom said then you're definitely looking at less than a 600 buck expidenturE. jusT find the right person to do iT. I can, but I don't have the toolS. I coulda maybe have told you the problem, but I've spent more time on automatic trannies than manual aaand...yeA....the only thing I'd guess would be most likely the synchroS. iT would need a complete dismantling, but not a complete rebuild. jusT make sure you get the right parts numbers.

[SidewaysGts]

Auto trannies? Sorry this is off topic but mayb you can help- have a mazda tribute that was recently in an accident, killed the tranny oil cooler. Long story short, theres a delay when going into 3rd, also it seems to slip a bit the engine revs a bit higher (about 500 rpms) before going into 3rd. Any helpful info on whats going on or what i can do?

[WanganEfini]

Originally Posted by SidewaysGts

Auto trannies? Sorry this is off topic but mayb you can help- have a mazda tribute that was recently in an accident, killed the tranny oil cooler. Long story short, theres a delay when going into 3rd, also it seems to slip a bit the engine revs a bit higher (about 500 rpms) before going into 3rd. Any helpful info on whats going on or what i can do?

youR clutches are slippinG. therE are two symptomS. thE fluid keeps moving the same direction as the clutches between them and the clutches have to spin faster to force the fluid outwards so they can graB. thE other is plain and simplE. thE clutches are just burnT.
iN any of these cases they should be replaceD. iF you do get them replaced and would like to get some longevity out of theM. unlesS you do the work yourself, some way or another, get the person doing the job to get Grade 80 to 100 sandpaper, (96 is the best to use, but anything between is just as good). sanD the mating faces of the steel clutches outwards, from the center, all the way around the clutch only enough to take the glaze off of theM, noT to the point where you can see markS. DO NOT FOLLOW THE CLUTCH AND SAND ONE BIG CIRCLE ON IT YOU'LL JUST END UP WITH THE SAME PROBLEM YOU STARTED WITH. thiS way when it comes time to shift, the fluid between the clutches will move outwards away from between the clutches in the direction that was sandeD. yoU don't need to have the clutches sanded thougH. thiS is just a trick I learned from a veteraN.

[SilverGhost]

yes, it sounds as though the 1/2 syncro is going bad, perhaps its just wear on your blocking rings which is natural with high milage, and blockingrings are cheap to get, like 20 bucks or so i think. its just the labor that is expensive. but i cant see it every going over 600 bucks if you find a good shop to do it.

[SidewaysGts]

Originally Posted by WanganEfini

youR clutches are slippinG. therE are two symptomS. thE fluid keeps moving the same direction as the clutches between them and the clutches have to spin faster to force the fluid outwards so they can graB. thE other is plain and simplE. thE clutches are just burnT.
iN any of these cases they should be replaceD. iF you do get them replaced and would like to get some longevity out of theM. unlesS you do the work yourself, some way or another, get the person doing the job to get Grade 80 to 100 sandpaper, (96 is the best to use, but anything between is just as good). sanD the mating faces of the steel clutches outwards, from the center, all the way around the clutch only enough to take the glaze off of theM, noT to the point where you can see markS. DO NOT FOLLOW THE CLUTCH AND SAND ONE BIG CIRCLE ON IT YOU'LL JUST END UP WITH THE SAME PROBLEM YOU STARTED WITH. thiS way when it comes time to shift, the fluid between the clutches will move outwards away from between the clutches in the direction that was sandeD. yoU don't need to have the clutches sanded thougH. thiS is just a trick I learned from a veteraN.

Thanks for the info much appreaciated- just to be sure though the problem you described can be a single gear specific problem? It ONLY does it when upshifting into 3rd, all other shifts are perfectly normal

[Whisky]

Of course your downshift to first is crunchy at higher speeds, you don't have a synchro into first.

[NeveR]

If I remember correctly, you have two synchros: a lower one for 2nd and 4th and an upper one for 3rd and 5th.

There's no 1st or Reverse synchro.

And yeah it definately is your synchros, they're probably shot.

I have the same problem on my SR, which sucks for me. It's my lower one, scratches if I push her revs too high and shift into 2nd or 4th. I either have to ship a lone SR tranny, or rebuild using KA internals and the SR bellhousing.

Expensive no matter what.

[TrendLineMotor]

Probably a throw out bering, or a pilot bushing issue. No pilot bushing would cause those symptoms