6 Speed Gearbox Question

[Daviewonder 533 3 Cars]

Hi All

 

Just a quick question as I've been doing a bit of research about fitting a 6 speed box into a 205 and I would like to a definate answer about the ratios. I have read 2 different accounts and would like to know what one (if any) is correct.

 

1. The 6 speed box has the same ratios as a 1.6 gti box and then the sixth gear has the same ratio as a 1.9 fifth gear.

 

2. The 6 speed box has the same ratios as a 1.9 gti box with an extra gear on top.

 

Are either of these statements accurate or are the ratios entirely different?

 

Cheers

[dumbiron 0]

try here maybe ?

[Tesstuff 222]

Or here maybe?

 

The DEFINITE search function for gear ratios.

 

[welshpug 1,657]

not forgetting that there were two final drives used, from memory they were 3.95 and 4.05, so not a massive difference.

[Miles 331 1 Cars]

Nothing like that at all, Cannot tell you the Ratio's as I;ve never got around to working them out but driving them is nothing like a 1.6 box, The closest you will get is somewhere between a 16v box and a 1.9 box for 1>5

[Anthony 1,003]

1. The 6 speed box has the same ratios as a 1.6 gti box and then the sixth gear has the same ratio as a 1.9 fifth gear.

This, roughly speaking. Assuming the ratios I have here are correct, this is the mph/1000rpm values for the various gearboxes:

 

1.6 GTi:

1st = 5.0

2nd = 8.8

3rd = 12.2

4th = 15.5

5th = 19.1

 

1.9 GTi:

1st = 6.3

2nd = 9.9

3rd = 13.4

4th = 17.1

5th = 21.0

 

GTi-6 (Phase 1 with 3.95 FD):

1st = 5.8

2nd = 9.2

3rd = 12.1

4th = 14.9

5th = 17.8

6th = 21.3

 

GTi-6 (Phase 2/3 with 4.05 FD):

1st = 5.7

2nd = 9.0

3rd = 11.8

4th = 14.5

5th = 17.4

6th = 20.8

 

As you can see, with the except of 1st being a little longer, and 5th a little shorter, the ratios are pretty similar to a 1.6 GTi gearbox, but with 6th equating to that of a 1.9 5th.

 

For what it's worth, I think that the ratios are great on a GTi-6 gearbox - I just personally can't deal with the lack of steering lock when fitted to a 205 (it's bad enough on a 306 GTi-6), and the finer pitch gears in the 6-speed 'box are weaker than the 5-speed boxes as well (not that it is a major issue on an 8v though)

[Tesstuff 222]

Anthony your figures differ to the main 205 Drivers Tech Info page.

 

Transmission:

 

Five-speed, all indirect, with synchromesh.

upto 1990 BE1/5 Reverse next to 1st, 1990 on BE3/5 1990 onwards

 

1.6 Ratios (mph per 1000rpm): 1st 3.31 (4.9); 2nd 1.88 (8.6); 3rd 1.36 (11.9); 4th 1.07 (15.2); 5th 0.87 (18.7). Final-drive ratio 4:06:1

 

1.9 Ratios (mph per 1000rpm): 1st 2.92 (6.2); 2nd 1.85 (9.8); 3rd 1.36 (13.3); 4th 1.07 (16.9); 5th 0.86 (20.9). Final-drive ratio 3:69:1

[Anthony 1,003]

It's calculated using the same ratios as your info above (other than a 0.87 5th for both 1.6 and 1.9) so the error factor in speeds will be the same across the gearboxes - I suspect it's from calculating the tyre size and how rotation relates to speed.

 

EDIT - I can match the figures above exactly if I enter a tyre size a profile too small (ie 185/50R15) which suggests that the speed calculation is fractionally out somewhere, but as said, it will be out by the same degree for each 'box and thus the figures are comparable which is what the OP wanted.

Edited January 2, 2011 by Anthony

[Toddy 7]

Autocar Data for the 306GTI6 Phase 1:

 

http://www.autocar.co.uk/CarReviews/RoadTe...-GTi--6/200082/

[Anthony 1,003]

Those Autocar ratios basically tie up with what I used in the calculation above (just rounding differences accounting for 0.01 differences between figures)

[Daviewonder 533 3 Cars]

Cheers for all the replys guys, lots of good info there I'm sure. To be honest I'm still trying to get my head around this ratio stuff, the only bits I really understand from the above is Anthonys info and I'm still not entirely sure what to look for to find out if a certain gearbox would be suited a certain engine and what would make it unsuitable?

[Cameron 16]

For a 16v or tuned (particularly cammed) engine the 6 speed gearbox is far superior, the ratios are great and keep you in the power at all times, you just need to change gear a bit more often. For an 8v you're best with a 1.9 box (IMO) as it works better with the more mid-range focused torque spread.

 

I'd say for a proper 16v track car you should be using the 6 speed, but for a road car you may be better of with the 5 speed VTS box so you don't lose any steering lock.

[Tom Fenton 1,542]

I disagree about the 6 speed box, a track car with a decent engine with increased torque can easily pull the ratios in the 5 spd box.

[Cameron 16]

Not everyone bolts a turbo on though.. and while most 16v tuning does increase torque, it increases it at high revs and decreases it at lower revs i.e. increasing peak power. The rev drops with the 5 speed IMO are too severe for a 16v engine, whereas the 6 speed keeps the engine right in the sweet spot.

Edited January 7, 2011 by Cameron

[Tom Fenton 1,542]

I am not talking about a turbo.

 

From personal experience of a 5 speed Mi track car that went from 130ftlb to 145ftlb with a better spread, this happily pulls the 5 speed box, and a lot better with the torque increase.

 

Also having owned a Xsara VTS and driven plenty of 306 GTI6 I still maintain that the Xsara is the faster car point to point as the 5 speed change is slick and the engine has the torque to pull it, whereas the 6 speed change is obstructive and the ratios are shorter than is required to make the best of the torque spread of the motor.

 

In my opinion the 6 speed box in the 306 was primarily a marketing ploy.

[Cameron 16]

Weeeell, when me and Oli did a little back-to-back passenger ride in each other's cars at Oulton, we found that his was clearly struggling with the rev drop between 3rd and 4th in particular, and would take a few seconds to come on cam and start accelerating hard again. This was a 5 speed box, my 6 speed coped much better and on the sections where Oli's car would struggle mine was powering on through.

 

I don't want to draw us into an argument about quoting torque vs power, but this is the problem with only stating torque figures. That number is pretty meaningless unless you say the rpm at which it happened. Your better spread of torque could have been 1500-3000rpm, or 3500-7000rpm. Whether it was the former or latter depends on whether a 5 or 6 speed would be better suited.

 

Also, it's no coincidence (or gimmick) that most race cars have at least 6 speeds.

[Anthony 1,003]

I'm still not entirely sure what to look for to find out if a certain gearbox would be suited a certain engine and what would make it unsuitable?

What engine are you thinking of running it on?

 

In my opinion, a GTi-6 box would suit most 16v conversions and 8v's that rev well at top end, but I personally don't think that it would suit a 2.0 8v Turbo engine which I'm assuming you've got judging by your signature? For a 2.0 Turbo, with its wide spread of torque but distinctly lazy delivery that doesn't like to rev, I'd be looking at using a 1.9 GTi gearbox initially, and if you find that too short, whatever is the next step up (a 205 non-turbo diesel maybe?).

 

Generally speaking, a lazy slugger of an engine wants longer ratios spaced apart, whereas a peaky, revvy engine wants shorter ratios spaced closely together. The 6-speed box is more the later and a 2.0 8v Turbo engine the former.

[petert 586]

I'd say for a proper 16v track car you should be using the 6 speed, but for a road car you may be better of with the 5 speed VTS box so you don't lose any steering lock.

 

I'm with Tom on this one. I'd say the opposite. Specifically in relation to Pugs, the GTi6 box is great for the average 16V punter but for a proper 16V track car the ratios are way too long. The intermediates are nice and close, and Joe Average feels great as it keeps the revs close on the track, then he can slip it into that long 6th for the trip home. A good all round box, but not for a track car. Maybe if you could easily get a 4.5:1 or 5:1 cwp. With the 5 speed, it's so easy to mix and match gears, and build a low ratio track box, that's close enough for most occasions. How many times do you actually use six gears on the track? Or five? More like four? It would be different also if you could paddle shift with a 6 speed, but more often that not, there's time lost changing gears. It's often better to hold a wider gear through a tricky section that take your hand off the wheel to change. Here's what a serious 405 6 slot box looks like:

[Cameron 16]

Not sure I follow you there, there's a pretty much equal rev drop in every gear with the 6 speed, wheras the 5 speeds seem to have quite a large gap between 4th and 5th.

[brumster 135 1 Cars]

Tom/petert are bang on the money for me. Look at myself, I run a pretty peaky rally car, why did I plump for a hybrid 5-speed box (with gti6 ratios) as opposed to just dropping a gti6 box in?

 

Ignoring the steering lock issues (which are relevant for me, as rallying does often involve some nasty tight hairpins, but I accept that's not really relevant for track cars), the lack of final drive ratio selection - unless you're talking a PTS 6-speed competition box, which we're not - means the top end gearing is aimed at far too high a speed for me and everything is spaced according to it. I also don't really want to spend all my time swapping cogs if I can help it; certainly my 6 speed road car (not a Pug) may just as well be a 5 speed because 1st gear is next to pointless, it's so short.

 

By running the 3/4/5th from a gti6 in a 5 speed box (albeit with modifications) I can keep the relatively taller gearing of 1st/2nd intact but shorten and tighten up the upper gears, and still have a wide selection of final drives from the 5spd box to choose from (4.4 tends to be a nice balance, but a 4.8 is another option if you're not after a 130mph top end).

 

Also, it depends what rev range your engine has available to it - having 8500 to play with certainly helps up the top end while still keeping short ratios!

 

edit: I suppose, in fairness, I should point out that for a road car my solution would be pretty unliveable with unless you are deaf and/or keep it below 60mph all the time

Edited January 7, 2011 by brumster

[Daviewonder 533 3 Cars]

What engine are you thinking of running it on?

 

In my opinion, a GTi-6 box would suit most 16v conversions and 8v's that rev well at top end, but I personally don't think that it would suit a 2.0 8v Turbo engine which I'm assuming you've got judging by your signature? For a 2.0 Turbo, with its wide spread of torque but distinctly lazy delivery that doesn't like to rev, I'd be looking at using a 1.9 GTi gearbox initially, and if you find that too short, whatever is the next step up (a 205 non-turbo diesel maybe?).

 

Generally speaking, a lazy slugger of an engine wants longer ratios spaced apart, whereas a peaky, revvy engine wants shorter ratios spaced closely together. The 6-speed box is more the later and a 2.0 8v Turbo engine the former.

 

 

To be honest, the 6 gearbox was an impulse buy as it was local and only 50 quid. I was just trying to research the ratios to see what one of my 205's (1.9, 1.6, 2.0 turbo) it would be best suited to (probably not any then!) but I think I'm gonna have to start at the very begining with this ratio stuff as at the moment it may as well be written in Chinese

 

cheers, Dave

[petert 586]

50 quid seems very cheap to me, but I have no idea of the market value in the UK. I'd flog it for a profit. Why not just start with the standard 1.9L box? There's really only two things to worry about, the overall ratio and the % change.

The overall ratio equals gear ratio x cwp ratio.

ie for 1.9L 1st gear

 

2.92 x 3.62 = 10.58:1

 

If you go any higher than that (lower number), you'll find it difficult to get the car off the mark. The turbo isn't moving so you're relying on the torque of the unblown engine.

 

% Change

 

This is the difference between two gears.

 

ie for 1.9L 3rd and 4th:

 

(1.036-1.069)/1.036 X 100 = 21.4%

 

As you move through the gears the gap should get narrower (smaller numbers). Cars with narrow torque bands need closer, cars with wider torque bands can be larger. Thus all the debate above. Once you get a an 8V turbo off the mark and the turbo spinning it can easily pull wider ratios and a longer 5th gear. Thus you might find an Mi16 set of ratios with a taller cwp(smaller number) is ideal for you. eg 3.94:1 or 3.62:1

 

Or even more simple, a 5spd from an 8V 1.9L or 2L 405.

 

Hope that helps!

Edited January 8, 2011 by petert

[Cameron 16]

By running the 3/4/5th from a gti6 in a 5 speed box (albeit with modifications) I can keep the relatively taller gearing of 1st/2nd intact but shorten and tighten up the upper gears, and still have a wide selection of final drives from the 5spd box to choose from (4.4 tends to be a nice balance, but a 4.8 is another option if you're not after a 130mph top end).

 

Also, it depends what rev range your engine has available to it - having 8500 to play with certainly helps up the top end while still keeping short ratios!

 

edit: I suppose, in fairness, I should point out that for a road car my solution would be pretty unliveable with unless you are deaf and/or keep it below 60mph all the time

 

Ok, we're starting to muddy the waters of the original topic now. I'm not debating whether a 5 speed with custom ratios would be better for a rally car that needs steering lock and a relatively low top speed, but that wasn't the original topic or question.

[brumster 135 1 Cars]

No, agreed. Not really relevant to the OP but there wasn't really that much detail on application. As you suggest, it's horses for courses, but just arbitrarily saying a 6 speed is best for high-revving screamers would be generalising as it depends upon application. For a road car, I suspect the 6 speed would be a nice option.

[Cameron 16]

Yeah I was just assuming we were talking about road / track cars, rally / sprint cars are a different story. My point was just that as standard unmodified boxes go, the 6 speed has the better ratios for a 16v; while the reduced steering lock can make it a pain for road use (although personally I don't have issues) it is the better choice for track where you won't be going near full lock.

Edited January 10, 2011 by Cameron