Straight cut gearboxes

[craig green]

For discussion.

Typically how much better are they for power loss (transmission losses)? What other benefits do they serve? Quicker synchros? More strength, simply in the gears themselves or bearings aswell.

Where from?

How much?

Gamble to buy 2nd hand?

I'd go for an F20 I think & mate that with a smallblock which will mean I have max scope to use with a big block (the shame) if it ever came to it.

[Lee]

The main problem with Helical gears is the sideways force from the angled teeth which saps the power, thats why a straight cut box is much better to reduce tranny losses.

SC gears are actually weaker than Helical gears, but they are made a lot stronger which cancels this out. I would expect an SC box to be stronger than an OE box, but its because its been built into the box rather than the gears themeselves, but build an SC box and a Helical geared box with the same size gears, the Helical box will manage more torque.

Not a lot of people know that lol

[tom_beverley]

Is it possible to mate the F20 upto a small block? Gearboxes are the my least experienced component and one of the last parts left to take apart and (try) to re-assemble on the Nova lol

I may aswell disclose the information now that I've just been a little hot headed and bought a 2nd hand SCCR cluster (was on MIG) with a damaged input shaft. Laddo was very helpful and has even offered to write me guide to dismantle/assemble/service it too, top man!

I'm just going to bide my time and wait for a second hand shaft to come up, although eventually I may have to cough up about ?300 for a new shaft from HH which is the only place I've found so far to get a replacement from.

EDIT- Craig, I bet hearing Dar's SCCR around Combe has got you thinking of these!?

[craig green]

F20 will go onto small block if you use the correct fly & clutch. Obv the same tweeks to get it in (as per 2.0) & conversion shafts.

Its just a thought but, a SC box & Tran-X diff seem like great places to make gains rather than spunk the cash to gain 10bhp.

[Lee]

Its just a thought but, a SC box & Tran-X diff seem like great places to make gains rather than spunk the cash to gain 10bhp.

Thats called intelligent tuning Craig :thumb:

[craig green]

So where from?

How much?

I assume they exist for F13/15?

[tom_beverley]

Yes the F15, F20 is still serviced, (unsure of F13, but the F10 is NLS)

HH sell the kits, as do Quaife, check out their websites. Go balls out and get a dogbox :cool:

Roughly looking about ?1500 for an F15 SCCR (new). I think these hold their value well too like the LSD's.

On the subject, whats the differences between F10 and F13?

[craig green]

F10 & 13 are much the same really except the 13 has a larger bell housing to use a bigger clutch & flywheel & the box/bearings are a tad stronger.

Someone else may correct me.

[Martin]

Glad you started this thread craig, ive been looking(trying) into getting one of these for my xe build along with a diff of some kind..

More info would be great..

DARRR!!??

[craig green]

2 F20's on the bay...

http://cgi.ebay.co.uk/vauxhall-rally-quaife-gearbox-lsd_W0QQitemZ300150244957QQihZ020QQcategoryZ10404Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem

http://cgi.ebay.co.uk/quaife-vauxhall-race-gearbox_W0QQitemZ180157424650QQihZ008QQcategoryZ43 120QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

No pics. Not cheap!

[Martin]

cheers for the links craig, think i'm going to buy new sometime next year just want some info for when i come to buy etc..

[Stuart]

F10's and F13's share the same bearings and everything... jsut bellhousing differences (and ratios)

[Dar]

BT told me about this thread. This is the info I have.

You can get a SCCR box from Quaife. Looking at the F20 options becuase thats the only ones I have prices for.

Synco = ?1350+VAT
Dog = ?2450+VAT
6 Speed Dog - ?3295+VAT

Dog boxes are great but they are expensive as you can see. Also if you order one make sure you can wait up to 3 months for it. Quaife sometimes have the stock and sometimes don't, and have to wait for gear kits to be manufactored. This fact alone decided what box I bought in the end. I ordered a syncro box and then was told I had to wait but I could have a dog box. So I ordered the dog box and was told that I would have to wait for the parts to be made but the syncro box I ordered in the first place was now available.

Quaife will also build your box for you for ?125+VAT

I also took this option since I decided there was no one better qualifyed to build the box up and it was cheap enough. They will also currier your box to and from your home.

Another difference between the syncro box and the dog box is that you also have more gear ration choices for the dog box. PICK YOUR GEAR RATIOS CAREFULLY!! It took me along time to pick mine. I found Stuarts gears calculations spreadhseet invaluable! Cheers Stu:thumb:

The big advantage with a straight cut box is that it cuts down on transmission losses, so more power gets the the wheels where its needed. Also you can gear your car so that it uses all if the gears. I don't think I will explain this well but I will have a go.

Your cars gearing is perfect if at the longest part of the circuit you hit the rev limiter for 100yards before breaking(rule of thumb). You have wasted performance if for example you cannot hit 5th gear around a circuit, if you just tickle 5th gear for a short while. So if you put two identical cars next to each other, one with a SC box and the other with a standard box. The car with the SC box will be faster due to two things.

1) More power gets to the driving wheels
2) The car will be geared with a lower top speed and will get to that speed quicker.

These are the options you have

Syncro


1st 2nd 3rd 4th 5th
2.540 1.760 1.420 1.190 1.040
0.958
0.870

Final Drive Ratios
4.200 4.500 4.850 5.180


Dog


1st 2nd 3rd 4th 5th
2.308 1.688 1.389 1.200 1.045
2.910 2.071 0.970

Final Drive Ratios
3.190 3.550 3.740 3.940 4.200 4.500 4.850 5.180


I have the Syncro box with a 4.2FD and 0.958 5th gear.

I hope this all makes sense and gives you guys the info you need:thumb:

[Ash]

christ thats a low 5th gear. I thought 4th gear was normally about 1:1

[Stuart]

also a dog box will break your wrist if your not ready for it and tell it whos boss lol

I need to add to my site to allow for the user to input any gear ratio setup they want rather than the pre defined vauxhall range

[Dar]

Oh forgot to add. What I have gives me :-



Gear Speed
1st 49mph
2nd 70mph
3rd 88mph
4th 105mph
5th 130mph


I think its about a 2,000rpm drop between gears

[craig green]

Thanks Dar.

So yours was a new one (bought from Quaiffe)?

[Dar]

Yup I bought mine from Quaife and got them to build it for me as well.

[Andy_L]

Ok tool question time.

What's the difference between a Syncho, Dog and Sequential box.

Ta

[Stuart]

in order to engage the gears you need to "synchonise" between the current gear and next gear. The synchros sort this out (wiki it would be best).

a dog box does away with synchros and means you have to "force" the gears into engagement. again wiki might be best.

a sequential box is where you can only select the next one up or down from your current location. so there is no 5th to 3rd changes without going through 4th for example. The benefit is you can get up the box "faster" than with a standard H pattern (like we all have)

[Dar]

and sequential gears are like you see in rally cars. The gear selection is done by either pushing or pulling a lever instead of using a gear stick and selecting the gear you want. A bike gearbox is sequential for example.

[Andy_L]

Thanks Stuart

P.S. I found the PDF file you mentioned about the 2.2 engine, thanks for that too

:thumb:

[Andy_L]

and sequential gears are like you see in rally cars. The gear selection is done by either pushing or pulling a lever instead of using a gear stick and selecting the gear you want. A bike gearbox is sequential for example.

I take it people don't use bike gearboxes as there are too many complications in getting them to fit/work as I'd have thought they would be ideal for some engines due to high BHP and not small torque bikes generally produce.

[Stuart]

bike boxes tend to be packages into the engine casting hence why they arent adapted for road cars.

not sure why manufacturers stick with H patterns when the auto boxes are sequential.... hmmm ill ask my mates in the transmission department :)

[Adam]

Oh forgot to add. What I have gives me :-



Gear Speed
1st 49mph
2nd 70mph
3rd 88mph
4th 105mph
5th 130mph

I think its about a 2,000rpm drop between gears
Fook me thats a long 1st gear :eek:


So whats the benefits of a dog box? Quicker gear change as the syncrhos dont have to equalise?

[Stuart]

clutchless gear changes wihtout risking damage like you do with a syncrho box

[Dar]

Dog boxes use big teeth gears and you can change gears without using the clutch. The boxes are very strong. This is not to be confused with a dog leg gearbox which puts 1st gear on its own with reverse and then 2,3,4&5th gears are in a H pattern.

[Lee]

Fook me thats a long 1st gear :eek:



We decided on a long first as its never actually used on track, and it inabled us to work more with 3rd 4th and 5th which are the main boys that get abused.

If we decided on a short 1st, that would have spreaded the rev drop between shifts if we kept each one the same, and wanted the final speed at max revs to be approx 130.

We spent ages talking about it on the phone, I hate to say it but we got the box fairly well matched to Dar's GTi-6 gearbox (obviously omitting the 6th gear) as a starting point.

[Martin]

i know have a head ache haha..


thats alot of info for my tiny brain, maybe i'l get you to order mine dar pmsl...

[Ash]

I hate to say it but we got the box fairly well matched to Dar's GTi-6 gearbox (obviously omitting the 6th gear) as a starting point.

It might sound really silly, but on Forza I entered my standard F13 ratio's with a 4.18FD on a civic with a standard 165bhp, and it drove ****. But I thought it could be a good way to plan what gears you would want. If I ever went for a straight cut, I'd probably choose something around the standard civic ones

[Stuart]

its tricky as you have to match the gearbox to your circuit of choice AND the torque curve of the engine as the box is a torque multiplier.

probably a better car to chose is the astra vxr for ratio messing...

[Ash]

Well, it's only forza 1 so no VXR and also a VXR is turbo'd with 240bhp, I thought civic was an ok choice with lowish power, N/A, fwd. But yea, I see what you mean with the torque and circuit.