Which gearbox?

DJ 190 said:
Please help me to understand what this is all about!
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I agree, this is a really interesting thread. I've had my head in gearboxes a lot recently and like that another option is suddenly developing.

David - The longer 5th results in an unusually large gap between 4th and 5th, as you'll well know. The idea here is to increase the length of all gears by the same proportion, meaning that 5th gear is closer to the longer 5th, but the gears needed to get there are evenly spaced. In effect, the large gap between 4th and 5th is cut into pieces and distributed between the other gears.
Cars like the Polo will compensate for the very small rolling circumference of their wheels by having longer gearing across the range from 1st to 5th gear. Put their gearbox in an A2 and you'll travel fractionally further for each rotation of the engine, across all gears.
Of course, this means using more of the engine's rev range between gear changes, meaning the car becomes pickier about which gear you use. For instance, while a standard A2 TDI will do 30mph in either 3rd or 4th, this might no longer be possible, meaning 3rd might be the only choice. In essence, while there are some benefits, there's also a loss of flexibility.

Fitting a 6-speed VAG box to an A2 has been looked at in the past and no solution has yet been found. However, even if a 6-speed 'box could be found that would mate with the 1.4 TDI, its ratios would also have to be suitable. There's no point having 6 gears if 6th is only as long as your current 5th; you end up with loads of gears in a relatively short range, resulting in precisely the opposite phenomenon. Really flexible gearing just results in loads of gear changes. The VW Touran is set up like this and it's my biggest criticism of the car.

Tom
 
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Don't forget that this whole thread has been precipitated by Hooley's need of having to replace a failing gearbox in the first place, which opens up the question of "what else could you replace the existing box with most cost-effectively". If it's possible to source an alternative (2nd hand) gearbox that mates to the Tdi at low cost, and also has the advantage of providing gear ratio benefits, then I think that's what Jason is looking to achieve.

It's always going to be a less labour-intensive job to simply swap an existing gearbox than modify one in situ, let alone buy additional custom-manufactured parts to bolt on as part of the work.
 
Yup
As I need a gearbox anyway I was looking at the options (and also to see if I could save a few pennies as I've just paid out for a clutch). I wanted to change the gearing if possible for the money and must say its been interesting.

The permutations are numerous but boil down to only a few true options for the AMF engine, and it depends on what you want

I'm torn between the EXB of similar to standard but each gear extended by about 7%, or the Bluemotion gearbox which really ramps things up. Looking at the costs either are reasonable (below £500 fitted) so it's a bit of a gamble.
I might go and stalk Zoltar (Simon :D) once his is done to see if it works to my liking. Although I do lots of motorway work, I also try to drive the wheels off cross-country so might miss the closer (sportier) ratios

J
 
dan_b said:
Don't forget that this whole thread has been precipitated by Hooley's need of having to replace a failing gearbox in the first place, which opens up the question of "what else could you replace the existing box with most cost-effectively".
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Yes, this is the reason the thread has sprung up, though Simon's already well underway with this project. I've answered David's question with reference to the longer 5th because that's what he's currently got.
I think we'll all be keen to hear the results, as this could open up an extra gearing option for those who which to stray from the OEM setup.
 
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An interesting approach, I'll be watching this one keenly.

David, if you look back at the original 6th speed gearbox thread, you'll see that it started off with the idea of swapping gearboxes. So it has always been an option. However Mike could not find a straightforward way to fit it. I don't think that the bluemotion gearboxes we are discussing here even existed then...

Personally the kit was the best option for me - I wanted a very wide range of gears without excessive gaps, more than a standard 5 speed or 6 speed gearbox would give me.
 
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MikeMarsUK said:
Personally the kit was the best option for me - I wanted a very wide range of gears without excessive gaps, more than a standard 5 speed or 6 speed gearbox would give me.
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Same. The 6th gear kit allows you to keep all the benefits of the standard gearing whilst also increasing the total gearing range. It is, to my mind, the no-compromise solution, but there's no doubting it's costly! I'd love to drive Simon's car (or Jason's, should he go ahead) once the work is done.
 
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You guys are SO helpful and friendly! I understand it all so much better, now! Thanks! Ideally, I would like an even longer 5th gear than my current 0.681 ratio ... These other alternative gearboxes .... what is their 5th gear ratio(s)? However, I do "cruise" through lots of narrow, Welsh lanes and typically I'm doing around 40 mph .... With the standard gearbox's 5th, I could easily pull that gear. With my 0.681 ratio 5th, it sometimes doesn't feel "comfortable" ... But that's not very often, I hasten to add! I know that I can be somewhat frivolous by nature and I wouldn't put it past myself for still going for that 6th gear mod. ( I do keep vehicles for a long time and continuously improve them). My current mod is having both electric seat heating (seat base+backrest) AND lumbar support installed on Thursday! Lots more to do after that .... TV antenna booster, headlight mods, DRL's .... MFSW? I'll never stop! LOL!

David
 
I started looking at the options 6 months ago, it was really the newly recalcitrant nature of my 5th gear that has forced me to bring forward my plans. These gearboxes seem to have a weakness in the synchro, so there may be several people who would need to replace theirs sooner rather than later.

I've just found out the jdd gearbox has the same speedo drive ratio so it looks like I'm going for this one as well

I'll be happy to let anyone test the car once done :). I'm looking at about the beginning of May.

Jason
 
Look, you might have just read that I am of a frivolous nature! LOL! There seems to be a few of these boxes (JDD) around .... as low as £200! Should i go and buy one? What does "Stealth" charge for installation? What exactly am I going to gain? What IS the 5th gear ratioof the JDD box? Just look what you Guys have started! LOL!

David
 
DJ 190 said:
Ideally, I would like an even longer 5th gear than my current 0.681 ratio ... These other alternative gearboxes .... what is their 5th gear ratio(s)?
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A bit of maths is needed to answer this...
The EXB gearbox uses the 'standard 5th' 0.755 gearset and the JDD uses the 'longer 5th' 0.659 gearset as their 5th gears. However, both these gearboxes also use a slightly longer final drive compared to the A2, meaning these figures can't be directly compared to the ratios in the A2.
Adjusted for comparison with the ratios we know and love, this means the EXB's 5th gear ratio is 0.704 and the JDD's 5th gear is equivalent to a 0.613 gearset.

So, if you want a longer 5th gear than the 0.681 or 0.659 'longer 5th' setup, you'll have to use a JDD 'box. However, 0.613 is long! This is longer still than the 0.622 5th gear in Mike Skipton's seriously-torquey TDI90. Ok, it's not quite as long as my 0.588 6th gear, but there's one step fewer to get there. Every gear would be an average of 23% longer. In other terms, a change that you'd currently do at 2200rpm would have to wait until 2709rpm!
I don't know about others, but I would not want that, either from a 'driveability' or efficiency perspective.

Interestingly, fitting the EXB 'box results in a setup that's very similar to that of the standard A2 TDI90. For comparison, the TDI90 uses a 0.701 5th gear and also employs marginally longer gears throughout to keep the spacing even. So, if anyone has a TDI75 and would like the TDI90's ratios, this could well be your solution! :)

Tom
 
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I must admit to second thoughts about the JDD box......it does seem very looooooonnnnngggggg
What I would like is something halfway between the two

Anyone??

J
:)
 
Hooley said:
I must admit to second thoughts about the JDD box... What I would like is something halfway between the two
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Gear it back down at the wheels! To get a setup almost exactly halfway between the two, you'll need 185/45/R15 ... you car's appearance may suffer, but the Gatsos will never get you because your speedo will massively over-read. :p
 
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I'd investigate the EXB 'box further. If it'll fit ok and the speedo drive ratio is the same, then it could be highly suitable.
It's an average of 7.2% longer than standard. With your 205/50/16 tyres also gearing things up, you're looking at an average increase of 10.9% for each gear when compared to a TDI75 with an EWQ 'box with standard 185/50/16 tyres.
That means changing up at 2440rpm instead of 2200rpm and you'd do 70mph at 2240rpm instead of 2580rpm.

David - The 0.681 5th gear is also 10.9% longer than standard, meaning that this option would result in a cruiser gear exactly like you've currently got, but with the previous 4 gears evenly spaced. However, you'd have to fit tyres with a rolling circumference approximately 3.4% larger than standard, otherwise your motorway cruising revs will increase slightly.

Tom
 
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Phew! On impulse, I nearly bought this box! http://www.ebay.co.uk/itm/VAG-Seat-...s_Vehicles_CarParts_SM&hash=item4d02cc4d8chew! It looks in nearly mint condition! Tom, thanks for your knowledgeable input! My tyres are 185/60 R15 .... do they "fit the bill" as regards to rolling circumference? Well, I'll now be looking for an EXB box! I'm just a bit fickle ..... just a bit .... LOL! It would appear that I'll get just what I want, though ..... better flexibility through the Welsh lanes and still have a more relaxed gear for motorway cruising .... I hope that that is right?

David
 
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Hi David,

An A2 TDI with the EXB gearbox and 185/60/15 tyres will have gears an average of 9.4% longer than standard. This means that your 5th gear would be a bit shorter than your existing 0.681 gear, meaning slightly increased cruising revs once in top gear.

DJ 190 said:
It would appear that I'll get just what I want, though ..... better flexibility through the Welsh lanes and still have a more relaxed gear for motorway cruising .... I hope that that is right?
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Hmmm... yes and no. It depends what you mean by 'flexibility'. As mentioned, all the gears will be evenly spaced, meaning that you'll not have to 'manage the gap' between 4th and 5th. However, there's a slight loss of flexibility across all gears. I quote from a few posts back...

timmus said:
...this means using more of the engine's rev range between gear changes, meaning the car becomes pickier about which gear you use. For instance, while a standard A2 TDI will do 30mph in either 3rd or 4th, this might no longer be possible, meaning 3rd might be the only choice.
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For those Welsh country lanes, having closer gearing is better. As your car is currently, your first 4 gears are quite flexible but your 5th is very inflexible.
The EXB 'box would result in a small, even distribution of inflexibility across all gears.

The only way to retain the flexibility of gears 1 to 4, without having to manage a large gap between 4th and 5th, but still having a long motorway cruiser gear is to have the 6-speed kit installed.

I hope that makes sense.

Tom

PS: That JDD 'box that you've linked just happens to be in Southam, where Vince is based. Had the JDD been suitable, it would have made the logistics very convenient!
 
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I thought i would do a little reading about the Polo Bluemotion which is the 80bhp 1.4 TDi engine with the VNT turbo (allegedly for low rev torque)

This is from Autotrader:

Around town, we didn’t spot any differences in the driving experience, either. But once on faster-moving roads, we soon noticed the longer gear ratios in third, fourth and top. In fact, the Polo’s gearing is the longest in this test, with 70mph pulling only 2,000rpm. This is a real benefit on the motorway, but the gaps between ratios mean you have to hold on to one gear for a comparatively long time before changing up on A-roads. We often found ourselves driving around in a gear lower than normal, which isn’t great for economy.

The VW has 165/70 R14 tyres, which are so low on rolling resistance, they enable it to coast a long way without appearing to lose momentum. As a result, it was the most fuel-friendly car during our motorway test. But we were surprised its returns dropped to fourth best in the cross-country section.

And so the Polo struggles to justify itself. The technology isn’t as clever as the premium on the price suggests. It costs £12,845, which is £1,128 more than the much better-equipped 1.4 TDI SE. Yet the Bluemotion 2 is only 7kg lighter, 0.02Cd cleaner through the air and 4mpg more efficient. The VW is a step in the right direction... but a small one.
Details

Price: £12,845
Model tested: VW Bluemotion 2
Chart position: 4
WHY: Tweaks to the engine and bodywork help set this Polo apart – but just how effective are they?

Economy

Urban: 40.2mpg Cross-country: 61.2mpg Motorway: 68.5mpg Combined: 58.0mpg



Read more: http://www.autoexpress.co.uk/car-reviews/38178/vw-polo-bluemotion-2#ixzz2NzNPWtPu


Interesting reading, in that this confirms that the cross-country driving is not what this gearbox is about, but does benefit those of us that do lots of motorway miles.

J
 
Hooley said:
...But once on faster-moving roads, we soon noticed the longer gear ratios in third, fourth and top. In fact, the Polo’s gearing is the longest in this test, with 70mph pulling only 2,000rpm. This is a real benefit on the motorway, but the gaps between ratios mean you have to hold on to one gear for a comparatively long time before changing up on A-roads. We often found ourselves driving around in a gear lower than normal, which isn’t great for economy.
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This neatly summarises what I've been saying over the last few pages of this thread.

Good find, Jason.
 
I spoke to "Vince" at Stealth Racing ..... Only £200 +VAT to change a gearbox! Changing the clutch at the same time makes sense! The cost of the 6-speed conversion seems to be rising, though ... he now likes to do it with the gearbox out of the car ..... takes the cost up to £1700! That is getting out of my league! At the moment, my car is running "sweet as a nut" .... so why change things? I think that, if I should loose syncro or the clutch starts to play-up, then that is the time to think of these "upgrades". So, time to move away from those three words that I fear might apply to me :- compulsive, frivolous and fickle? LOL!

David
 
I got a bluemotion polo.
its true the last three gears are longer.
Average mpg doing 45-55 mpg is around 83 mpg
Crank it up to 70-75 and it dives.......


to 74 ;)

Revs wise its at 2,000 rpm at 70mph on its 14" winter wheels

NB.
This is on a 1.4 tdi Bluemotion not the newer 1.2
 
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