Question about ZF gearboxes

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STA 1440
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Question about ZF gearboxes

Post by STA 1440 »

Why is it that ZF transmissions howl, woo and whine so beautifully?

Do they use "straight cut" gears?


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MaxHeadway
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Re: Question about ZF gearboxes

Post by MaxHeadway »

You mean like this?
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mrobsessed
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Re: Question about ZF gearboxes

Post by mrobsessed »

No, they're all helical gears inside ZFs.
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Re: Question about ZF gearboxes

Post by Swift »

You have to wonder what modifications ZF have done over the years to their Ecomat range which were introduced in 1980.
The more updated ,the less charm they have.
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Re: Question about ZF gearboxes

Post by TOXANA »

I'd have to disagree with that in part.
Yes the Volvo 6 speeds are boring but the new 0500 CNGs have a beautiful sound to them, particularly the early ones pre 1821.
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Re: Question about ZF gearboxes

Post by Swift »

While they are surprisingly vocal and not without their charm,they sound wierd like a badly written tune and have nothing on an Adelaide MAN Sl202 or an early to mid 1980s vintage Volvo B10M with the 4 speed Wilson soundalike ecomat.
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Re: Question about ZF gearboxes

Post by STA 1440 »

Well if it's not straight cut gears making all that noise, what exactly is it?
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Re: Question about ZF gearboxes

Post by LowRider »

B58 Howler wrote:Well if it's not straight cut gears making all that noise, what exactly is it?
I'd guess its whine from the torque convertor.
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Re: Question about ZF gearboxes

Post by Maladjusted »

The planet gears have a tendency to wear the pins and bearings they sit on and change the tooth ontact and hence gear noise, once they get a few hundred K's on them. A lot of the other noises emanate from the actixation of the clutches in the box and lock-up in the TC
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Re: Question about ZF gearboxes

Post by Stan »

I followed a UBS Motorcoach in my car the other day, I'd guess it had an Allison box. As it took off from the lights, 1st gear fine, second gear fine too but third seemed like it missed. Under (naturally) full power, it changed out of second so the engine revved RIGHT out, then continued to rev for around 3-4 seconds before it found third. When it did, the torque converter let out a spine-chilling howl and the bus visibly jolted forward.

Having never really spent any time in Autos (other than the 5sp ZF "Whiplasher" in MGBS's Mary), is this normal? The engine (sounded Cummins-ish) would've been at around 2500rpm while it was shifting...

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Re: Question about ZF gearboxes

Post by Reecho »

Sounds pretty normal for an Allison MT or HT as they use Governor (or output speed) to control lockup points....modulated by the throttle position which is controlled by a cable. It can be adjusted in the valve body to lock up later however to better affect.

The whine in the ZF's is mainly caused by gear wear in the planetarys and ring gears and extra clearances everywhere.

But in saying that i have replaced gear sets and they still whine with load. The torque converter wont make any noises similar unless it is about to fail in a major way....
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Re: Question about ZF gearboxes

Post by PoweredByCNG »

I've found that (in Perth, anyway) the ZFs generally get quieter with age. For example, when [TP.1639] was delivered, it had an ear-piercing wind-up in 1st and 6th gears - often so loud that body panels would vibrate at certain engine speeds. It has quietened down considerably over the last couple of years.

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Re: Question about ZF gearboxes

Post by Reecho »

The type of Transmission fluid can have an affect as well...
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Re: Question about ZF gearboxes

Post by PoweredByCNG »

I'm almost certain that all ZF-Ecomat gearboxes have straight-cut gears. The 2nd to 3rd gearchange howl is produced by a sun gear that changes speed abruptly during the gearchange. ZF-EcoLife gearboxes have helical gears.
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Re: Question about ZF gearboxes

Post by Daz »

Only on Bus Australia would you find people who actually want noisy gearboxes...

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Re: Question about ZF gearboxes

Post by STA 1440 »

Hell yeah Daz!

I was brought up with the sound of ZF 4HPs screaming off into the distance.

Have a watch (and a listen): http://www.youtube.com/watch?v=m9-TofYg ... e=youtu.be
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