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Choosing gearbox ratios


Chris Perry

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Hi James,

Steve's boxes are still helical so comaprison to a SC tooth is chalk and cheese in terms of noise, the increased helix angle on the 5th tooth leads to more tooth in contact and less noise still, bear in mind Steve's toloerances are very tight you will have a superb boc that is unrivaled in terms of quailty by anyone else out there, as unlike other he has his own gearsets made to his desgin, no recclaimed gears etc here!

My previous box was a SC and audible up to around 40mph after which the wind noise drowned out the gears !

New box is a 2.29 helical Tracsport

 

 

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Quaiffe have a gear calculator which you can put in several different combinations of ratios, tyre sizes etc, then run a print from the PC and it will show in various colours the relationship of one to another.

I previously had a BGH 'box, what a screamer, but also what dream to use, think the gear change, and it was done, never missed a beat, slick action, but sing, oh yes, noisy, but not any worse on the over run.

I now have a straight cut, close ratio Quaiffe 'box, which due to external influences I have not yet got a good feel for, however, the 2.04 first does seem to be way to long, don't be to ambitious here, as it can be slower, well, in my limited use of the car it seems so, also the old X flow had a very much lightened flywheel, but the Zetec is lightened but by less of a percentage, so doesn't appear to spin up so quickly,but that might change later  *evil* 

Nigel.

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I fitted an SPC gear kit earlier this year (2.48 first). Ive only had the opportunity of one test run but my early impressions are:

1. the car feels a lot quicker through the gears with the new ratios

2. there is a definite whine in 2nd and 3rd but I actually quite like it and its certainly not loud enough to be an annoyance

3. the 2.48 first paired with my 4.1 diff certainly does not feel too tall. If anything I might have gone for the slightly taller ratio (this is with a 2.0 Zetec with stock cams; anything less torquey might be a different story?)

4. rebuilding a type 9 for the first time is relatively challenging but certainly not beyond a competent amateur mechanic if you are methodical and take your time. The main issue is that neither of the two shop manuals that cover the procedure are brilliant

5. must have tools are a pair of special spring clip pliers (they have flat, serrated jaws that grip the pointed internal tips of the spring clips on the mainshaft) and access to a press

Overall, its a thumbs up for SPC. I did plenty of research and my conclusion was that there's nothing else on the market that compares to their kit.

Rob

 

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For What It's Worth:-

In general - with my Crossflow with an Ital (somewhere over 150BHP) I find first is a bit low and can easily pull away in 2nd. So, if I was going to spend even more on my car, I would lengthen first (a fair bit) and then second (a bit). Third is great, fourth could be a long longer but fifth is great, it could even be a bit longer (yes, I can cruise in the Seven).

The feel in the 21, with a K Series with a Sierra diff, is very different. needing much harder work.from the driver's point of view (higher revs).

It's all about how it feels to you, how you prefer to drive, what part of the performance you value for your fun and enjoyment.

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Echo the comments above and in Black Sevens previous post and I'll add my 2p worth too...

Just to set the background: I'm running a 2.0l Zetec 190bhp and 167lbs/ft previously fitted with the standard type 9 ratios.

At last, after nearly 5 months, the 7 is back on the road and I managed to get out for a short 30 mile blat this morning. Strange how the car seemed so much faster *yes* . Yes, 2nd and 3rd gears do indeed whine a little more but with the Brooklands it's not unbearable.

I have to say, that the long first (mine's the 2.29) seemed so natural with the torquey Zetec engine that it makes me wonder how I coped with standard ratios when I installed the Zetec.

With the gear ratios better spaced out it seems to make changing up and down the gears more effortless. Overall a big *thumbs_up_thumb*

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