TheSamba.com :: View topic - Reduction box whine increases with gear wear?

Wed Jul 09, 2025 10:11 am

I feel like my big nut reductions gear wine is getting loader over the last few years. I replaced all bearings about 18000 miles ago (8 years). Gear oil was changed 10000 miles ago. Wine is most noticeable between 35 and 45 mph and doesn't go away unless I have my foot almost completely off the accelerator. They are completely quiet gearing down. I am not that concerned and it may just be my deteriorating hearing but brings up a question...

Will gear wear increase the wine? Is it common for some reductions to be louder than others?

I plan to take them apart and inspect bearing and such after bus season is over this year. Would any wear be noticeable? Could moving stub axels and gears from left to right help?

Any insight welcome.
Thanks.

Wed Jul 09, 2025 11:19 am

You should try a Bordeaux or a Rosé, maybe a Pinot Noir instead.... ;-P I kid! It is "whine", though.

Every bus I've owned whined like a banshee. With that said, I've never had a rebuilt box/s. I think it is Yukon gear that has a great write-up about gear whine and when it happens. It means wear is in a certain place on the R&P on accel and a different side on decel. Obviously, they don't refer to RGBs as most cars/trucks don't have them or as off-roaders call them "portal axles". Do a search for gear sounds and maybe that will help you track down the sound. Maybe it is the R&P and not the gear boxes making the "wine" ;-))

Here is a similar write up to the one I was talking about. Obviously, this is not VW specific.
https://www.onallcylinders.com/2012/03/30/quick-guide-to-diagnosing-differential-driveline-noises/

Wed Jul 09, 2025 12:16 pm

It’s gear lash, as the gears wear the lash increases. Why it’s quieter on deceleration is you changed the load from one side of the gear teeth to the other. Basically it’s like running it backwards as far a load goes. The teeth are not as worn on that side.

Besides gear whine is kinda cool. As long as you change out your trans fluid regularly and you’re not making a bunch of metal you’ll be fine.

Wed Jul 09, 2025 12:22 pm

Maybe Muir's suggestion of adding some MoS2 grease to the gear oil would help quiet it? CV joint lubricant comes to mind.

Thu Jul 10, 2025 12:57 am

pondoras box wrote: It’s gear lash, as the gears wear the lash increases. Why it’s quieter on deceleration is you changed the load from one side of the gear teeth to the other. Basically it’s like running it backwards as far a load goes. The teeth are not as worn on that side.

Besides gear whine is kinda cool. As long as you change out your trans fluid regularly and you’re not making a bunch of metal you’ll be fine.

Very true. The question is whether the wear is in the RGBs or the R&P, the gear stack, or any combination of all or just one of those. There is the rub...I mean whine.

Thu Jul 10, 2025 4:55 am

swharris wrote: pondoras box wrote: It’s gear lash, as the gears wear the lash increases. Why it’s quieter on deceleration is you changed the load from one side of the gear teeth to the other. Basically it’s like running it backwards as far a load goes. The teeth are not as worn on that side.

Besides gear whine is kinda cool. As long as you change out your trans fluid regularly and you’re not making a bunch of metal you’ll be fine.

Very true. The question is whether the wear is in the RGBs or the R&P, the gear stack, or any combination of all or just one of those. There is the rub...I mean whine.

I see what you did there. Without tearing it down it’s impossible to tell. But if it’s not popping out of gear and it shifts smoothly the center section is probably fine. The reduction gears are not hard to get to so I guess if it’s bugging you that would be where I would start.

Have you drained the fluid from the boxes to check for metal shavings?

Thu Jul 10, 2025 5:26 am

pondoras box wrote: Have you drained the fluid from the boxes to check for metal shavings?

Thanks everyone.

This is defiantly reduction whine. I do understand that straight cut gears are going to be very noticeable. Again this may just be me and not the reductions actually getting louder.

Transmission works great.

Fluid was replaced 10000 miles ago with no excessive metal. I will drain and inspect reductions this winter but don't expect to see anything obvious. More of a preventive thing as we travel a lot with this and don't want to have a bearing failure a long way from home. I have no indication the bearings are anything but prefect but not sure it would be very noticeable if they weren't.

Just thought I would check if swapping gears side to side or some other trick may help. Or if some other issue could cause them to get louder. I don't remember seeing any examples of gear wear so was not sure if that was a thing to be concerned about.

Thanks again

Thu Jul 10, 2025 6:42 am

I'm curious how you absolutely know it's the reduction boxes?

Thu Jul 10, 2025 9:14 am

thom wrote: I'm curious how you absolutely know it's the reduction boxes?

Sounds like straight cut gears and tone has not changed noticeably over the years. Sound changes like one would expect with speed and acceleration. Transmission was rebuilt (popping out of forth and some bad bearings) with no effect on the sound.

Thu Jul 10, 2025 10:51 am

sgellis wrote: pondoras box wrote: Have you drained the fluid from the boxes to check for metal shavings?

Thanks everyone.

This is defiantly reduction whine. I do understand that straight cut gears are going to be very noticeable. Again this may just be me and not the reductions actually getting louder.

Transmission works great.

Fluid was replaced 10000 miles ago with no excessive metal. I will drain and inspect reductions this winter but don't expect to see anything obvious. More of a preventive thing as we travel a lot with this and don't want to have a bearing failure a long way from home. I have no indication the bearings are anything but prefect but not sure it would be very noticeable if they weren't.

Just thought I would check if swapping gears side to side or some other trick may help. Or if some other issue could cause them to get louder. I don't remember seeing any examples of gear wear so was not sure if that was a thing to be concerned about.

Thanks again

Does this work? Swapping the gears to the other side?

Anything above 40 MPH and i can't hear the engine over reduction boxes!

Thu Jul 10, 2025 5:32 pm

I used to live at nearly 7,000 feet above sea level. The rear axle often yelled like a banshee “climbing the hill” but was as quiet as a mouse going down hill. The engine too for that matter.

Thu Jul 10, 2025 6:38 pm

Someone with CNC skillz should whip up a set of herringbone gears

Fri Jul 11, 2025 9:57 am

With helical (?) type gears you would have too much thrust wear or I think VW would have done it . Alot of touque multiplication occurs out there .
SL

Mon Jul 14, 2025 11:28 am

pondoras box wrote: swharris wrote: pondoras box wrote: It’s gear lash, as the gears wear the lash increases. Why it’s quieter on deceleration is you changed the load from one side of the gear teeth to the other. Basically it’s like running it backwards as far a load goes. The teeth are not as worn on that side.

Besides gear whine is kinda cool. As long as you change out your trans fluid regularly and you’re not making a bunch of metal you’ll be fine.

Very true. The question is whether the wear is in the RGBs or the R&P, the gear stack, or any combination of all or just one of those. There is the rub...I mean whine.

I see what you did there. Without tearing it down it’s impossible to tell. But if it’s not popping out of gear and it shifts smoothly the center section is probably fine. The reduction gears are not hard to get to so I guess if it’s bugging you that would be where I would start.

Have you drained the fluid from the boxes to check for metal shavings?

I'm not the one with the issue, the OP is. With that said, the rumble of the generator bearing, the whine of the old tires, the air leaking past the 64 years old rubber seals all mask the gear whine on my '62 SC so I cant hear it... :-)