Hi All, Gearbox oil additives, what are they? what do they do? are they any good? are they all a con? Anybody any ideas and could they help with a grinding 2nd gear? All the Best. Ian.

clifford59 said:

Hi All, Gearbox oil additives, what are they? what do they do? are they any good? are they all a con? Anybody any ideas and could they help with a grinding 2nd gear? All the Best. Ian.

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Snake oil. Manufacturers of gear oil make oil that has all the additives added as necessary. Adding something you nothing about can disrupt the workings of the gearbox oil. A grinding gear needs investigation.

While I agree about investigating. I have had success on several occasions with Moly Slip I think Moly8 now. It add Molybdenum Sulphide that acts as a particularly smooth added lubricant and can quiet noisy bearings. Its not a Long term solution as a bad bearing is eventually going to break up and cause much damage but its not caused any issues on a variety of cars.

This is the thing, most will shove in an additive to engine or gearbox not having a clue if it makes a difference. All oils have the correct amount of lubrication agents and other things that are needed. Adding something else that most do not not know what it will ultimately achieve is guesswork. Even in cases of quietening things, this may just be masking the problem.

My initial reaction is to say don't go anywhere near them - gear oil additives that is. If you think about it I think most work by introducing some extreme pressure substance, Like the Molybdenum Disulfide in Molyslip products and this, theoretically, gives the gearbox a big problem because the synchromesh cones rely on a carefully worked out amount of friction to work properly. This is all very carefully calculated to work correctly with the lubricant specified by the manufacturer so NEVER put any in a gearbox which is working well.

Then I read Panda Nut's post about Molyslip Gearbox additive and I remembered that I'd stuck it in my old Anglia's gearbox way back maybe 50 years ago? when it had worn layshaft bearings and it did indeed quieten it down a lot until I had time to rebuild the box. So, if the box is knackered anyway, why not see if you can make it run just a little longer by feeding it one of these "brews" - You're going to have to rebuild it anyway in the near future.

On reflection though the Anglia had a very simple old type gearbox, much more "agricultural" when compared to what we have today. So I wouldn't use additives in either the engine or gearbox of a modern car - and absolutely not in an automatic.

Fuel additives are perhaps a slightly different prospect and might be of limited efficacy in certain circumstances, but there is a small voice in the back of my head which is muttering "Snake Oil" in my ear, just like Jim above.

Aye Jock, back in the day cars were a different animal. Serving my time back in the early 70s I learnt things both good and suspect remedies from my elders. A relatively modern vehicle these days requires different measures. In fact some manufacturers do not require any interference with their gearbox such as an oil change at all.

Just so Jim. When much younger I heard "tales" of all the "dodges" for quietening gearboxes. Fine sawdust mixed with the oil was one - not so sure if that would really work? but one I think would was to stuff old pairs of ladies nylon tights in!

Need I say I would never have anything to do with such nefarious practices - Honest M'lud!

As a motor dealer way back when, we had success with Mazda gearboxes that had problems with synchromesh in gears. We exchanged the gear oil with auto trans fluid. The gearboxes became a tad noisier if you really listened hard but the synchros started to work properly again. We ran many boxes with it for long periods with no ill effects. Worth a try before going to the expense of a pulldown.
Ian.

As a motor dealer way back when, we had success with Mazda gearboxes that had problems with synchromesh in gears. We exchanged the gear oil with auto trans fluid. The gearboxes became a tad noisier if you really listened hard but the synchros started to work properly again. We ran many boxes with it for long periods with no ill effects. Worth a try before going to the expense of a pulldown.
Ian.

Ah Ha! I see the old double post problem is still alive and well?

I have a cloudy memory that some of the old BL manual 'boxes ran on auto fluid? and I think there were others? Haven't come across it in recent years though.

Ah Ha! I see the old double post problem is still alive and well?

I have a cloudy memory that some of the old BL manual 'boxes ran on auto fluid? and I think there were others? Haven't come across it in recent years though.

Oh no! It's done it to me too!