Transmission advice / diagnosis

[d.n]

Hi all,

I have a 5speed (reportedly from a 95 with some 60-70k miles) that is extremely notchy in 3rd and 4th. All other gears are normal, but 4th and particularly 3rd are terrible even when shifted at the gear box with the cables detached and the car off. I have a hard time even putting it into 3rd sometimes with the engine off.

My question is what are my options? Is it possible that something was just not assembled correctly or is this box a dead duck and not even worth rebuilding? Should I just pop it back into the car and try my luck (it's currently out for a clutch change)?

I don't have any history on the transmission, but I do see some extra honda bond on the case seam so I would assume the box has been apart before. Also the fluid that drained out was very thick - similar feeling to 75-90 gear oil which I believe is too thick for this application.


Thanks in advance,
David

 

[nsxtasy]

Also the fluid that drained out was very thick - similar feeling to 75-90 gear oil which I believe is too thick for this application.

I don't think the viscosity is the problem. My understanding is that the viscosity of 75W90 gear oil (such as Redline MT-90) is similar to that of 10W40 motor oil, and 70W80 (MTL) is similar to 10W30. Both viscosities - 10W40 and 10W30 - are recommended for the NSX; in general, those in colder climates are better off with 70W80/10W30, and those in warmer climates with 75W90/10W40.

As for your other questions, hopefully someone with more technical knowledge than mine can assist.

 

[Sumeronthechain]

So with the shifter linkage detached the shifter is still notchy?

 

[Larry Bastanza]

I do not understand your experience level with manual transmissions, but if it is out, it should be looked at for sure. If it really had that heavy oil, it could just be worn syncros, bad slider, can't tell from here.

Remeber the trans shafts are not turning when it is on the bench, so sliding into gear when things are static is tighter. If you hear something, or it is really hard to get into gear you really need to find out why. It will just have to come out again, if the problem remains. Obviously I cannot judge how hotchy or know any history of this tranny, so I cannot say for sure what is wrong.

HTH,
LarryB

 

[nsxtasy]

I do not understand your experience level with manual transmissions, but if it is out, it should be looked at for sure.

In particular, you might want to look at all the components - the gears, synchros, hub selectors - to see if the teeth look worn, vs the squared off look when they are new. And if they're worn, replace them!

 

[goldNSX]

75W-90 is simply the wrong oil. Get MTF3 and try again.

A friend used 75W-90 for a short period. Well, the gearbox was very silent but shifting was a hell of a bitch.

 

[Huck]

Drain the fluid into a non-metalic container then put a small magnet into the fluid and see if it pulls any metal to it. Try flushing the trans then refill with a good synthetic fluid like mobil 1 dextron or GMs low friction fluid. I had a 97 corvette that would detent like normal into 1st gear but when you let up the clutch, it wasn't into gear. At the advice of a trans shop owner with 50 years experience I tried the magnet---no metal, then the mobil 1 synthetic ---which took care of the problem!! Much cheaper then a pull. Good luck

 

[nsxtasy]

Drain the fluid into a non-metalic container then put a small magnet into the fluid and see if it pulls any metal to it. Try flushing the trans then refill with a good synthetic fluid like mobil 1 dextron or GMs low friction fluid. I had a 97 corvette that would detent like normal into 1st gear but when you let up the clutch, it wasn't into gear. At the advice of a trans shop owner with 50 years experience I tried the magnet---no metal, then the mobil 1 synthetic ---which took care of the problem!! Much cheaper then a pull. Good luck

Good luck getting pieces of aluminum to stick to that magnet! :biggrin:

Disclaimer: I have no idea which parts of the transmission/clutch are aluminum and which parts are ferrous metals. But I just couldn't resist the joke!

 

[Thunder]

Good luck getting pieces of aluminum to stick to that magnet! :biggrin:

Disclaimer: I have no idea which parts of the transmission/clutch are aluminum and which parts are ferrous metals. But I just couldn't resist the joke!

the pinions and gears of the transmission are manufactured out of steel:smile:

 

[captainjman]

I don't think the viscosity is the problem. My understanding is that the viscosity of 75W90 gear oil (such as Redline MT-90) is similar to that of 10W40 motor oil, and 70W80 (MTL) is similar to 10W30. Both viscosities - 10W40 and 10W30 - are recommended for the NSX; in general, those in colder climates are better off with 70W80/10W30, and those in warmer climates with 75W90/10W40.

As for your other questions, hopefully someone with more technical knowledge than mine can assist.

Someone was telling me to put emc syncro mesh transmission fluid instead. Anyone ever hear about that? Feedback would be much appreciated!

 

[Huck]

My advice was pretty basic---if you have any significant metal particles floating in your trans fluid---it's dead and you may as well bury it. Trans gears are always high strength steel but can chip/wear over time and they do tend to be brittle. The syncros are often brass which wouldn't react to the magnet and obviously aluminum wouldn't either. If the trans has significant 3-4 and 4-3 resistance, the problem is probably mechanical but if someone put in 80-90 weight oil ----you might get lucky if you flush it and replace it with premium synthetic low friction fluid. If the trans is toast, I'm not sure I would replace it with another 5 spd but would strongly consider upgrading to a new 6speed from Dali or ? Good luck

 

[d.n]

Thanks for the advice guys. I don't have much transmission experience (have replaced a diff in a civic before), but I'll open it and see if I can't figure out what's making it bind. I do recall now somebody once told me that transmission probs don't fix themselves

There wasn't much in the way of shavings in the oil that drained out so that I guess is the bright side of it.