Group buy / order: 0.65 / 0.643 5th for TDI

Skipton01 said:
Well, got my 0.622 gearset today:

Gears01.jpg


So, this afternoon, got to work (after buying a T60 torx bit for £8.09 from Helfrauds!!) and after the preliminaries, opened up the gearbox end case to get to the meat of the change:

Gears02.jpg


You can see the gears pretty clearly there and also, that the manual is wrong - the bolts holding the gears in situ are not Torx, but splines and I didn't have one big enough!!

So, end cap back on, refill with oil and re-assemble. Defeated, but I'll be back!!

Ideally, as I've a trip to London on Monday, I wanted to get the cog swap done so that I could report back in the economy findings, but it's not to be I'm afraid.

It's not the first time I've found discrepancies with the manual either.

Cheers,

Mike
Click to expand...

Hi Mike did you finally get this in?

Phil
 
Picked up a rattler gun on Friday, so will be attempting this job later in the week, weather permitting.

Cheers,

Mike
 
OK then, hands up who's got a 0,622 ratio for 5th in their A2 gearbox?

That'll be me then!!;)

After a lot of fiddling and filing, grinding and swearing, I have now completed the long talked about 5th gear mod on Tank.

First impressions? It'll come in very handy on longer M/way runs and should see economy figures rise substantially. The new ratio is not happy below and indicated 45-48mph, but then I'd not expected it to be. So far, the numbers are all working out as per the graph I produced a few weeks back and so I'm expecting decent returns on long runs (I'll be nipping over to Leeds later in the week, so can give a rough set of numbers for a motorway journey.

On the down side, if you've not got a mapped 90, then don't go for the 0.622. If you've got a mapped 75, think twice, but I'd suggest the 0.659 ratio better suited.

So, who's wanting a set of gears then? Apart from the prices I quoted before, I've now a set of surplus 0.700 gears, with no wear at all - not sure that I'm getting rid just yet, but will make a decision later in the week.

Cheers

Mike
 
Great news Mike so you think 0.622 is a cog to far for my Remapped 75, i don't tend to put it in to 5th untill after 45mph and upwards????

Cheers Phil
 
Bearing my torque figures and curves in mind Phil (346Nm torque from 1400-2100rpm), I doubt you'll be able to maintain it.

Take a look at that graph and apply your own torque readings to see, but I'd err on the side of caution and go for the 0.659.

Cheers,

Mike
 
Mike, sounds good! Can you order the 0.659 set for me and I will send a cheque by post, didn't call in last week as hoped due to waste of time ebayer who wasn't at home as arranged:mad:.... was pee'd off after nearly 2 hour drive to Macclesfield thru sh8t traffic and weather.
 
Yes, I'll get the set ordered Adrian. I think there's been a price update since I last posted the prices, but will advise of this when I've ordered them. VW/Audi update their prices on a regular basis - I would hope that with the Euro slipping a little, the prices have dropped, but this is a rare occurence!

Cheers,

Mike
 
Yes looking at it Mike will probably go for 0.65, the stealth graph post by another member that you put a link on earlier on this thread for, mine doesn't go up as high as there's but it holds it for longer and its not a peak like there's is (up to max then straight down again)my max is 178 torque so alot less than yours but it is up there in to 3000rpm's

so i'll probably go for the 0.65 then, cheers Mike for your imput on this


Phil
 
Nice on Mike -how long did it take you with the actual tools and parts in place this time round? What 'box oil did you use too?
Would be interested in your feedback on your perceived reductions in noise and vibration at m-way speed too - obviously subjective as I doubt we're into using dB meters to measure cabin noise before and after (although if anyone has a dB meter that would be a good idea).

I would only consider going as far as the .65 on a re-mapped 75 for sure. Its a real shame the .68 prices are so off vs the .65 as that would for me be the better compromise for lower speed bumbling, but at that extra price premium, no way.
 
Hi Dan,

I'd say in total it took me around 4 hours today, but an hour of this was down to modifying the puller and I was taking a lot of time over things, so for people travelling to have the work done, budget on around 2-2.5 hours.

I'd use nothing other than the (uprated) Audi transmission fluid and it's making for nice smooth shifts now.

I can offer both subjective and quantitative noise results and anyone with an iPhone can compare, roughly, with the results I'll post later in the week.

My first impressions are still good though, nice and quiet and very smooth on the cruise - been over the tops to Holmfirth tonight and at 65mph, the engine was barely audible over the wind and tyre noise!

You're right - forget the 0.681 ratio and go for the 0.659 as it's probably the best compromise for 75s, mapped or unmapped.

Cheers,

Mike
 
Mike,

If you've still got your .700 gear-set and wish to part with them, I'll take them. At the same time you install them maybe you could fit the iPod adapter.

Drop me a PM.

Cheers

Jeff
 
Hi Jeff,

Yes, I've got the 0.700 gearset and they are in perfect condition, with no wear or chips on the teeth.

I'm unsure of whether I want to part with them yet, but you have first refusal, should I decide that I can part with them later in the week.

Cheers,

Mike

PS I'd do the iPod first, as it's the clean job and I'd hate to get transmission oil all over the place!!
 
First notes from a motorway run with the new 5th gearset:

Noise - engine barely audible at 70mph, even with the straight through exhaust. Nice low hum is all that's there, wind and tyrenoise is far more prominient.

Pick-up - not the smoothest of pick-ups from 50mph, but that;s more down to my worn clutch than anything else. Take it steady (and don't floor it!) and 50-70 is nice and smooth, though untimed.

Revs - 70mph=2150rpm, so as per the graph I posted a while back.

Economy - oh yes! I should start to see a return pretty quick at this rate. Forget the business of engine friction losses and such, on an instantaneous mpg readout from the DIS, I'm looking at 11% savings from the old 5th gear. Hopefully, 60+mpg should be very doable now, which in Tank was never really an option with the wider tyres and the tuning. If I bimble along on A roads, then I'd hope for 65-70.

Notes - the 0.622 gearset is NOT going to be for everyone and it's certainly not going to find use in town driving. I'd say that the 0.658 set would just scrape by for faster town driving (urban 40mph stretches, but not 30mph), but would be obviously not as efficient for motorways as the 0.622. Overall, the 0.658 is a good compromise for mapped 75 drivers, but even then, it's more of a 4-speed box and semi-overdrive.

There is still a case to be made for having a 6th ratio, say the 90PS gearbox plus a 0.622 6th, but for around £275 parts and labour, this is a worthwhile half-way house. I remember Vince at Stealth quoted around £800 to just change the final drive ratio a few years back, so imagine the cost of a full gearbox swap!

I did take some noise readings on the iPhone, but as it's uncalibrated, they're pretty subjective:

idle, car stationary - 82dB
70mph, motorway - 89dB
80mph, motorway - 91dB

The vast majority of this is tyre noise though - when I went onto a secion of old tarmac, the values at 70mph shot up to 106dB!!

Cheers

Mike
 
Hi Phil,

I used a standard gear puller (3"), but had to grind down the feet to fit the synchro hub.

I would do a fitting guide, but there'll be no pictures as I didn't take any! Also, this is not a job for the casual modder - get 1 tiny piece the wrong way round, or a spring in the wrong place (both incredibly easy to do) and you'll wreck a perfectly good gearbox - replacement cost around £2500 plus fitting!

You need a rattler gun as well and an M14 spline plus a heat gun. Oh and a 17mm hex key for the oil refill plug, so it's really not a job to be tackled lightly.

Cheers,

Mike
 
the grim reeper said:
Hey Mike you said on the phone about it spinning the wheels, is there a lock on the box to stop this from happening or is it just put a wedge of some sort under the wheel???

Cheers Phil
Click to expand...

I've now found out that it's possible to put the gearbox in both 3rd and fifth, so locking the input and output shafts together. This would stop the wheels from turning, but I'd be a little apprehensive about doing this as you could end up breaking teeth.

The rattler gun works great and is a gradual way of releasing the bolts on the shafts (which are more than 60Nm as the manual says!!).

Cheers,

Mike
 
In order to help people make a more informed choice, here's an enlarged portion of my previous graph, showing the rpm v. speed for around 35mph to 85mph.

A2TDiRatios-35to85mph.gif

[Right click and select open in new tab to see the big version]

The lower red and blue lines are 4th gear on standard 75 and 90PS cars respectively and the next red and blue lines up are the standard 5th gears.

As you can see, at 40mph, the 90 is doing approc 1360rpm and the 75 is doing around 1470rpm. Although these figures are just about do-able, the engine is labouring, so really, 40mph is better taken care of in 4th gear at 1750 and 1850rpm respectively. This is still below the recommended change up point of around 2100-2200rpm.

Let's take a change up from 4th point of 2250rpm (as it's easy to see!) - this would mean a change up at 48mph, which would equate to 1620rpm if you fitted a 0.700 ratio, 1540rpm if you went for the 0.659 and 1460rpm if you opted for the 0.622 ratio.

I'd suggest that the latter is not really do-able and the middle ratio is stetching it a little, unless you held 4th a little longer.

Now moving to the 90, holding 4th to 2250rpm gives you a speed of 51mph. THis then gives you 1640 and 1560rpm for the 0.659 and 0.622 ratios. The latter is stretching things again, unless you have a mapped 90.

The summary of this is that 0.659 is the best compromise for most owners I'd say. Choose the 0.622 if you've a 90 and want the best motorway economy, but be prepared to effectively have a 4 speed box plus overdrive. For un-mapped 75 owners, the 0.659 ratio is going to give similar results: 4 speeds plus overdrive. The adoption of a used 90PS 0.700 ratio will give a decent 5 speed box.

All of this is pretty much borne out by my findings so far with Tank, but 4 speeds+overdrive looks like it's going to be my best option (well, cheaper than a 6 speed anyway!).

Cheers,

Mike
 
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