Second gear whine!

[kiwiaudio]

Recently returned from an amazing 3500 mile trip that taught me a lot about the old RT.

The transmission has always been a source of hair loss to me, and no matter how often I heard the old TADT phrase, it never seemed right.

 

After many miles I think I realize now what is going on.

I discovered that when the trans. is up to max operating temp. second gear screams like it has no hardening on the teeth. Third to a much lesser degree. When cold, this does not occur, and the other gears are fine.

This existed before my "chocolate oil" scenario repairs, and I could see nothing wrong with the gears when I had it apart. The input shaft bearing had not self destructed the way some do, and all the other bearings were OK.

 

The box is strong as hell and shifts just fine in both directions - I just spend as little time as possible in second gear !

 

Now, if I could run the trans. oil through a cooler .....Hmmmm !!

[Clive Liddell]

Ha ha

 

Yes, even though I know there is nothing wrong and that TADT I sometimes expect to find filings off the gear teeth in the oil. Truth be told, there is far less "wear and tear" on a straight cut gear compared to a helical gear (which would be silent). The efficiency of straight cut gears is also higher I presume because of no sideways force and possible more heating of the helical gears (no free lunch idea).

 

My two Oilheads were a bit noisy and have both quietened down at around 60 to 70000km with absolutely no problems (GL5 SAE 90 or 80W-90 only used).

[T__]

Recently returned from an amazing 3500 mile trip that taught me a lot about the old RT.

The transmission has always been a source of hair loss to me, and no matter how often I heard the old TADT phrase, it never seemed right.

 

After many miles I think I realize now what is going on.

I discovered that when the trans. is up to max operating temp. second gear screams like it has no hardening on the teeth. Third to a much lesser degree. When cold, this does not occur, and the other gears are fine.

This existed before my "chocolate oil" scenario repairs, and I could see nothing wrong with the gears when I had it apart. The input shaft bearing had not self destructed the way some do, and all the other bearings were OK.

 

The box is strong as hell and shifts just fine in both directions - I just spend as little time as possible in second gear !

 

Now, if I could run the trans. oil through a cooler .....Hmmmm !!

 

 

Mark, those straight cut gears are really critical to gear tooth profile in relation to the mating gear.. If the tooth face is at all flat at the mating area they will sing a song for you in certain RPM ranges.. Depth of engagement also plays a big part here.. It is very difficult to detect straight cut gear problems by looking with the naked eye.. Some are noisy & some aren’t.. Some get worse with miles & some get better with miles & wear in..

 

Type of gear oil used can have some effect on gear noise with stickier gear lubes that cling to the tooth surface & cushion contact sometimes helping the problem.. Probably the worst gear oil’s for tooth contact noise are the modern high efficiently 75Wxx gear oils as they are basically designed for low oil drag & less operating friction..

 

If your gear box is quieter when cold you might try an 85Wxx or 90Wxx gear oil.. The Red Line Heavy has about the best hot gear tooth cushioning but could hamper shifting in some gear boxes..

 

Twisty

[kiwiaudio]

Thanks Twisty,

I'd been considering a different oil or an additive that may help with this. I'm presently using Mobils 75/140 as I thought it the best available off the shelf here in my home town. The Redline is debated here, but seems to be liked by a lot of folks for its noise reduction abilities - maybe I'll give that a try.

The trans shifts fine for me as I've always retained the quick clutch/preload technique from my motorcross days, but I'll gladly give some of that up if this noise is reduced.

 

I remember years ago there used to be a ton of additives for manual transmission gear oils available, but I don't see many now.

Where are people getting this Redline oil?

[T__]

Thanks Twisty,

I'd been considering a different oil or an additive that may help with this. I'm presently using Mobils 75/140 as I thought it the best available off the shelf here in my home town. The Redline is debated here, but seems to be liked by a lot of folks for its noise reduction abilities - maybe I'll give that a try.

The trans shifts fine for me as I've always retained the quick clutch/preload technique from my motorcross days, but I'll gladly give some of that up if this noise is reduced.

 

I remember years ago there used to be a ton of additives for manual transmission gear oils available, but I don't see many now.

Where are people getting this Redline oil?

 

 

Mark, on my old R1100 with the 5 speed the Red Line Heavy was about the best I tried for both gear noise reduction & shifting quality.. But on my current R1150RT with the 6 speed while the gear box was quieter with the Red Line the shifting then became very notchy & 1-2 shifts were difficult to make without false neutrals.. That gear box shifts much better with a modern energy type 75WXX..

 

About all you can do is try different oil types & viscosities until you get the best that works for YOUR bike..

 

The good news on the Red Line is it holds it’s base viscosity for a long time & doesn’t shear easily, it also clings to the gear teeth like a booger..

 

Twisty