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The principal of the Voith DIWA

PostPosted: Sun Jan 21, 2007 1:33 am
by Swift
For the mechanically minded ,I discovered this rather fascinating insight into the operation of a Voith transmission.
Click on the items in the list to the left and prepare to be enlightened. ... _diwa3.htm
I finally know why they feel "different" when you take off from a stop.
The torque converter doubles as the retarder as well!!

PostPosted: Sun Jan 21, 2007 3:10 am
by mrobsessed
Interesting that the torque convertor is in the middle of the box than between the engine and box in place of the clutch. Perth has a fleet of Voith equipped 0 405NHs and they are just the best things. I had the displeasure of driving an OC500 CNG with a 6 speed ZF today and after that reminder, I am sold on Voith. The Willoughby SL202s are perhaps the exception to the rule.

PostPosted: Sun Jan 21, 2007 10:02 pm
by PoweredByCNG
The Voith DIWA.5-series continues on from the DIWA.3E's success. Notice that M.A.N. has struck a deal with Voith for bus transmissions - say nothing and you get a Voith.


PostPosted: Mon Jan 22, 2007 12:11 am
by Swift
mrobsessed wrote: The Willoughby SL202s are perhaps the exception to the rule.

Yes ,even though I love them for their character,the Voith doesn't extract the best performance out of them.
The Sl202's engine lacks low down torque compared to other leading citybuses.
They only go well once the revs build up abit ,which is why the Allison fitted to 3271 worked so well.
The Randwick one I drove with a ZF ecomat didn't really feel any faster off the mark.It just had more gear changes doing it.

PostPosted: Mon Feb 05, 2007 3:08 pm
by Herbert
Thanks for the link, Swifty. Confirms my hunch that 1st gear on a Voith isn't really a "gear" but rather is via the torque converter. The only downfall of that, in my opinion, is that on cornering or low speed the torque converter unavoidably comes into operation again, peaking engine revs unnecessarily, instead of being activated when required via kick-down.

So, DIWA means "Differential Wandler (Converter)".

Have to agree with the brochure's opening section "Economy and comfort through convincing technology", where they claim that multiple initial gears are not only unnecessary and uncomfortable, but potentially more costly.

The compartively high malfunction rate of their major competitor's transmissions at just 200,000km could well nullify multi-gear claims to efficiency & cost savings in the longer term.

PostPosted: Mon Feb 05, 2007 7:45 pm
by Swift
I agree with most points you make on this masterpiece of a transmission.
If you have a look at the graph demonstrator on the Voith site,you will see that first gear is a combination of lockup gear and torque converter before becoming a pure lockup gear in second.
The competitor's are pure torque convertor on take off before going into pure lockup.This occurs several times in the sequence from 1st to last ratio,resulting in "unnecessary" changes,where the Voith's long stepless hydro-mechanical 1st takes the role of at least two of ZF's often clunky gear changes.
There is just less to go wrong with the Voith principle.It avoids unnecessary complexity.You get the smooth takeoff into the bargain.
This design makes it necessary for the Voith to go back to 1st when it slows down below 40km/h because that is simply the operating range for the long 1st gear.
If I have anything to gripe about with the Diwa,it is it's rough down change from 3rd to 2nd when encounters a hill.Otherwise ,I hink they are fantastic the way they operate.

PostPosted: Mon Feb 05, 2007 9:31 pm
by Stoney!

PostPosted: Mon Feb 05, 2007 9:33 pm
by PoweredByCNG
Many Voiths have very sudden and rough retarders too, whereas the ZF retarders are smooth when applied.


PostPosted: Mon Feb 05, 2007 10:57 pm
by Swift
What do all those dots mean Stoney?I hope the STA get some Volvo B12BLES with Voiths ,your favourite combination I'm sure.

PostPosted: Tue Feb 06, 2007 9:39 am
by Stoney!
BEcause i edited it because i thought it was wrong of me to say what i said, but now that your also being a complete moron, i will repeat myself. You really do speak some XXX you know that.

Being smooth is probably one of the only good traits of the voith, ive heard complaints from only a couple of companies about voith gearboxes, namely because there are not many operators with them. But specially with the older ones which i know more about, there seem to be a lot of reliability issues, not to mention lack of power, making the engine work harder which would shortern its life, and high fuel consumption.

Apart from that with the same ill maintenance given to most ZF's because of how robust they are the voith an become quite a thumper also, I have experienced it.

With the zf it has a lot to do on how the box is mated to the engine, back in the days of the O405 they were some smooth ones and with age they tend to get rough, even worse when services weren't kept up, but then the B10BLE's and L113's were as smooth as silk with continued servicing.

Bring the picture to the present and out of the many O500LE's I have driven I cannot fault the shifts of the gearbox, you never feel a thing, the volvo's can get rather thumpy but this is what happens when you pump a rediculous amount of power through a gearbox that is barely designed for it.

THe only problem I find with the ZF these days is sometimes they lock up to early and can jerk around a bit when you de-accelerate, this can also be programmed out of and they would follow what the O405NH's and L113's do(which is drop straight frm hydraulic 1st to hyrdaulic second then lock up, and extremely smooth action)

It is the voiths long semi hydraulic first gear that makes it so fuel ineficient. There are many pros and cons to both gearbox so I don't think it really deserves the merit that you are reaving on about it for, I stil think the ZF is the better gearbox. With the new ZF 'ECOlife' transmission coming to a bus near you soon, i think your opinion will also change, with new shift patters, a newer smoother torque converter which is also good for transfering 30% more power and a 10% saving in fuel.


PostPosted: Tue Feb 06, 2007 9:42 am
by Windy
Totally agree with the above about the ZF. I'm not enthused thaty the ECOlife will also allegedly be 30% quieter than the Ecomat. I guess there won't be much ZF howlage down our streets in the future...

PostPosted: Thu Feb 08, 2007 5:04 pm
by Swift
A ZF Ecomat without character.What a nightmare!
I actually find the Merc 0405s with Ecomat an intrigueing combination.
Also the Scania L113s match them so well that you would think that the Ecomat was designed exclusively for it.
I just have a personal preference for the way the Voith operates.It's elegantly simple.

PostPosted: Thu Feb 08, 2007 11:20 pm
by Stoney!
Swift obsessor wrote:A ZF Ecomat without character.What a nightmare!

Its not an ECOmat it's an ECOlife, totally new design, ZF put a lot of money into their many gearboxes in the range. Including the many car gearboxes and truck and bus gearboxes.

They are a massive company making all sorts of things from steering systems found in volvo and merc buses to suspension systems found in the new VE commodore.


PostPosted: Fri Feb 09, 2007 7:29 am
by Windy
Yes and not only that but hypoid axles, tag axles, and other componentry.

PostPosted: Wed Mar 21, 2007 8:35 pm
by VQ
The MAN SL200's that National has in the Mk2's with the more powerful motor's use the Voith transmission that was in the less powerful Mk1's and as a result, they break, but the gearbox when the engine and drivers abuse haven't damaged them, are great.