Gearbox whine solution?

[Vandermetal]

I have four gearboxes that have different ratios and the one I love the most has a 2nd and 3rd gear whine. Recently I've replaced all the main bearings, seals and have measured the synchros, inspected all the internals and all the gears measure and look good. The oil I am using is what the gearbox manufacturer prescribes. All the obvious things are replaced and checked, but it changed nothing about it! I know for a fact that it is coming from the gearbox because if I swap it for one of my other gearboxes the noise is gone, but then I am stuck with close ratios and I love this wide ratio gearbox...

There is a lot to read on the internet about whining in gearboxes and I have experienced this on many of the cars I have owned and with the one I have now it is not bad enough to call it very problematic, but it just irritates me. In the past I have tried all sorts of prescribed oil additives and that never really worked. Also tried slightly thicker oil, but to my experience that only means that before it stops whining it already shifts like [censored] because synchros just don't like thick oil.

So I thought I can always replace the lot, or get another 100 euro gearbox and start all over, I decided to try something radical and have thrown a little whack of CV joint grease (MoS2) in it to both thicken the oil a little and modify the friction. To my surprise this removed about 80% of the whine! And that's not the only thing, it actually improved the smoothness of gear changes!

Now I just wonder how bad it is to keep driving like this for a while? How do I know if this grease contains ingredients that are bad for the health of the rest of the gearbox?

 

[TallPaul]

What kind of gearbox is it? Muncie rock crusher transmissions had a characteristic while from straight cut gears. My sons S10 has a New Venture 1500 tranny and it has a whine too. These whines are usually more apparent in low gears and we like the whine, it sound great. Does the whining gearbox have straight cut gears? See if this site has any info on whine:

http://www.rsgear.com/technical.aspx

also http://5speeds.com/

 

[Vandermetal]

No, it is a ZF box with angled cut gears:

This is not my actual gearbox, but same type. And if anybody wonders, yes I have removed the seals from the bearings as they are inside the gearbox and need the oil. Some problems in the past were reported due to people forgetting this and the bearings would run hot, lose their grease and not get any oil....

 

[eljefino]

My NV3550 in a jeep liberty made all sorts of awful noises. Cure was Pennzoil synchromesh oil. It went in thicker than whatever unknown came out.

 

[Vandermetal]

Yes, I don't really see any problems in the thickening effect of the lithium soap of the CV joint grease. It isn't exactly hot weather here and it shifts just buttery smooth... And as there are tons of moly additives that people rave about I suppose that is safe for the gearbox as well?

I sure hope you guys agree that I can try this out for a while as it works a charm!

 

[Quest]

@OP:

is this an M/T gearbox you are talking about?

If so, try different kind of gear oil of the proper viscosity and additive level (or go back to factory specified lubricants and see if that helps).

Also: I'd refrain from adding any form of friction modifying additives into M/T or A/T gearboxes, citing that with M/T + synchromesh, you need to a certain degree of friction between the synchro mating surface to proper mate without clashing during shifting, Any form of improper coefficient of friction in your lubricant will lead to accelerated wear on the synchros, which is a rather common observation here when folks used GL-5 gear oil in M/T gearboxes specified for GL-4.

Anyways, good luck on that.

Q.

 

[Vandermetal]

Yes, manual transmission. As per the opening post, I am using the specified oil from the manufacturer of the gearbox, I've always used that and it has always given best results on all the close ratio boxes. All these boxes whine a little from day 1, I know because I learned to drive in the exact same car with the exact same kind of gearbox. This one just whines a little louder and in 3rd us a bit uncommon. This box does have a rather much lighter final ratio though, so perhaps that makes a difference, although I can not see why it would not whine in all gears then.

I have tried zillions of different oils in these gearboxes with the correct additive package (GL4) only different viscosity and this never made a speck of difference in whine. That's why I was rather surprised to see this help so well!

I would think if the synchros had problems with friction I would see poorer shifting behaviour, but instead that has improved quite a bit too!

 

[steve20]

Hey Van
The ZF in my Corvette was very loud until I drained and refilled with Amsoil Synchromesh 5-30 MT oil.
I am not an active supporter of Amsoil motor oil, but their MT oil and their gear oil for the differential made that 50K mile driveline sound like brand new. I used Amsoil Severe Gear 75-90 in the rearend
Steve