transmission whine

[Timothy Keith-Lucas]

Here's a simple question that reflects my ignorance. Thanks in advance.

 

The non-synchronized first gear in my seven (1962 S2 America SB1160, Austin A engine) whines, the same sound I'm used to hearing from a reverse gear in which the gears are cut in only one direction. I don't expect to hear that going forward.  Is that normal for this gear box? Am I looking at a worn bearing? The box appears to work smoothly, it just whines. Thoughts?

[MV8]

Don't know. It may not have a bearing and just slide on the shaft with thick oil. Could be chipped or just straight cut (normal noise).

[jbcollier]

First gear in that transmission is straight-cut, just like reverse gear, and that is why it whines, perfectly normal.

[Vovchandr]

+1 on straight cut whine.

 

5 out of my 6 gears are straight cut (not counting reverse) and it's quite a fun noise to get used to. I can see how it would be concerning in just 1st however.

[jbcollier]

Do you wear ear plugs?  I've driven a full-rally spec AH 3000 and you couldn't hear absolutely anything other than the gearbox unless you were in direct.

[Timothy Keith-Lucas]

Hey, thanks, guys. That's both informative and reassuring. I was not looking forward to pulling the tranny.  I've done that on other vehicles, but it's a long slow process.

[Timothy Keith-Lucas]

I love it, JB. I'm hearing impaired, and wear hearing aids.  I added a muffler to SB1160. I found one to a Ford tractor that fit. She had a straight pipe for racing. In the usual case, once I accelerate my hearing aids identify a noisy environment (yeah!) and become ear plugs.

[jbcollier]

A straight cut first used to be very common Fords, Jags, MGs, Triumphs, etc, all had them.  You're not in first very long so the extra noise is inconsequential. Cruising along in 3rd with the tranny howling like a banshee being immolated, is a completely different matter.  You don't get used to it.

[sagamore]

The A-Series gearbox has, as the previous posts state, an unsynchronized straight-cut first gear. It also uses engine oil for lubrication. Most use the same oil that they put into the engine while some prefer a nondetergent 30wt.

[CatManDo]

Everything stated about the A series box is correct and 1st gear is noisy. That being said it also had rather weak layshaft bearings and the bearings loosening up will make it noisier. Replacing the layshaft and the needle bearings is usually requires at overhaul. For driving conditions in the US SAE 30 is too light. An SAE 50 would be a better choice. 75W90 is too heavy and doesn't circulate in the needle bearings.

[Timothy Keith-Lucas]

Thanks a bunch.  I'll check the lubrication just to make sure.

 

--Tim.

[jbcollier]

Plain old 20w50 is what we always used.

 

Noisy in the three lower gears but quiet in 4th?  Layshaft bearings.

 

Whines in first but quiet(ish) otherwise?  Normal.

[ashyers]

Note that the SAE viscosity scales for motor oil and gear lube are not the same! Check out the chart below:

 

[jbcollier]

Yes, but I hope no one is getting the idea you can substitute one for the other.  Gear/hypoid oils are NOT engine oils in different packaging, or visa versa.

[oilteq]

The weakness of Comparative Viscosity Charts is they are tied to Viscosity Index—the rate of viscosity change with temperature.  The posted chart looks like the typical 95 VI straight viscosity oil.  So, comparing SAE grades (100 C test temperature) with ISO grades (40 C test temperature) does not work.  I know ISO grades are not used in automotive fluids, but the point is that viscosity is always tied to temperature and VI. 

 

A typical transmission will run at 150 F or so.  Although SAE 50 engine oil and SAE 90 gear lube may be the same viscosity at 212 F, a synthetic 75W-90 will be significantly thinner at 150 F than a straight 90 petroleum oil.

 

GL5 gear lubes can be aggressive toward yellow metals, so GL4 is preferred if you have bronze syncro gears.  I think you will find a straight 90 petroleum oil will quiet it down noticeably, but may make shifting slow during warm-up if you venture out at sub-freezing temperatures.

[Timothy Keith-Lucas]

This is Florida.  What is this "sub-freezing temperatures" of which you speak?