transmission oil weight question

[Tom239]

I bought a '95 NSX earlier this year; this is my first winter season with the car.

It doesn't go into second gear easily when it's cold. I have service records from the previous owner (who lived in an area with warmer winters than I do), and I note that the tranny was refilled with 90W oil (Redline brand) at the last service. The service manual calls for 10W-30 or 10W-40; I'll be changing to that right away.

My question: was it bad judgment that 90W was used instead of what the manual calls for?

Thanks in advance for any info.

 

[MarkB]

There may have been a reason for the 90W. Some dealers and even some owners use a heavy weight to hide tranny problems. I would be careful going back to the standard weight and be prepared to have some tranny work done.

 

[Larry Bastanza]

Tom,

The Redline MTL90 (I think that's what it is called) is not really 90W oil. It is thin like the 10w30/40. Both that and the Honda MTF are considered acceptable for the NSX transmission.

I typically use the Honda MTF, it is 10w40 and it is very cost effective at only a few $/QT. I would not be all too worried about the Redline.

The symptom you are experiencing is very common. Changing to Honda fluid may help, but if you had Honda fluid, maybe changing to Redline would help.

The syncro in second gear is a "Dual Cone" type , and just is a little slow when cold.

HTH,
LarryB

 

[nsxtasy]

Redline rates the viscosity of its transmission fluids based on gear weight, which is a different scale from that of motor oil. So don't worry about the fact that it sounds like they're vastly different in viscosity from the recommendations in the manual; they're not.

Redline makes two different transmission fluids. Redline MTL is rated at 70W80 gear weight, which is similar in viscosity to 10W30 motor oil, and Redline MT-90 (at 75W90) is similar to 10W40. As noted in the FAQ section on Fluids: "in general those in colder climates will do better with MTL and those in warmer climates with MT-90." But either one should be fine.

In my transmission, I've tried synthetic motor oil, Redline MTL, and Honda MTF, and I've noticed no difference among any of them. I now stick with the Honda MTF.

 

[Tom239]

Thanks to y'all for the responses.

I had mistakenly assumed that gear oil and motor oil viscosity grades were comparable. (I'd once assumed that shoe sizes and sock sizes were on the same scale, too.)

But it's easy to experiment, and I put synthetic 10W-30 in yesterday. (Thanks to DanO for the nice illustrations on his how-to web page.) I drove it this morning with the oil cold; my first impression is that it's slightly better now. I'll see how it goes.

In any case, it's nice to know this is common and not something to worry about. The FAQ entry for transmission troubleshooting talks about instances where the clutch drags when it's cold, but I don't think that's what I'm seeing.