JonnyBravo

I am far from a gearbox specialist so I'm going tohave to seek advice on this matter.

I know that syncro gearboxes generally don't like fast gearchanges, made worse by high revving engines from what I am told so I am looking for I presume a dog box.

The car is track only/sprint based, VERY little road use so not bothered at all about noise and how much of an arse cruising the town centre will be with one.

I assumed all dog boxes used straight cut gears but it would appear not, what exactly is the benefit of helical over straight cut in a dog box or even semi helical ? I was under the impression a dog box could atleast be used atleast on upshifts without a clutch and downshifts if you match the revs but does that depend on the type of gears the box has ?

Someone please explain it to me as I honestly need to know whats what with these boxes.

For reference if it makes any difference its a 275hp (max) NA engine with a 9500rpm rev limit, fitment wise unless its a Type 9 is going to require a bellhousing being made but I am prepared to do that if it came to it.

Gearbox suggestions are welcome, currently looking into a Glebe unit, T5 based but haven't rung up to find out the specs, I'd rather have half an idea what I'm talking about before I call than waste the guys time if its no good to me.

JonnyBravo

Bttt

TimC

iTrader: (1)

The gears being straight, helical or semi helical cut makes no difference to the gear change mechanicals inside a box. Helical and semi helical have more metal of each gear in contact so are generally stronger, but they induce side loadings, so its more likely cases and bearings can fail.

Dog boxes can be used on upshift without clutch, but do help with a slight lift of throttle to help disengage the dogs from the gear your already in.

Please note I have zero experience using a dog box, above is just memory from what I learned at colege.

S1

Dogbox refers to the engagement, it doesn't use synchromesh hubs to get both gears to the same speed before the hub engages the gears. The gears are castellated which mesh into corresponding castlations in the other gears. The use of straight cut gears is for differeing reasons, to cut helical gears uses much more expensive gear cutting equipment plus as already said helical gears impose a side loading on cases & bearings. The advantage of helical gears is they run quieter than straight cut.

JonnyBravo

So basically less losses with straight cut gears but apart from that no other gains ?

I had a Hewland dog box a while back that is now in a mates car, awesome looking bit of kit internally and apparently a very good box to use however it was fwd thus no good to me !

jammerrs

whats the point of having dog engagment with helicalcut gears?

being dog engagment will allow no clutch upshifts, and straight cut gears will mean less transmission loses.

strictly speaking theres no such thing as semi helical as its either helical or straight buts its commonly reffered to, and is just a middle ground between them allowing less noise but taking more engine power

TimC

iTrader: (1)

What I hate with transmisions is when people say buy a box for such and such a cost and its fit and forget. NOTHING IS FIT AND FORGET. Everything has a life expectancy and rebuild recomendation which should be adeared to, whether your box cost £15 or £15k upwards.

JonnyBravo

In my case its more to do with the gearing being any good and the work involved with going from the stock gearbox to another type.

I simply do not want to cut the shell up anymore after the box is fitted, I should of done this in the first place but thats how these things go.

I'll contact the seller tomorrow and see whats what with the box, thanks for the advice

TimC

iTrader: (1)

JB what are you using your car for? Is it a track day car or a rally car?

JonnyBravo

Trackday/sprint car.

Everyone I speak to says the same about the stock Honda box and its that it has rubbish ratios.

TWoods

always known doglegs just to be a name for shift pattern putting both 1st and reverse furthest left out the way. You never really use those 2 gears when driving fast, to get going shift up over and up into 2nd that pattern looks like a dogs hind leg. The dogleg clutch arrangement is what gives you clutchless upshifts just because box has dogleg pattern dont always mean it has dogleg clutch arrangement many Getrags dont. The dogleg clutch allows you to force the dogleg fork from 2nd to 3rd then 4th to 5th.

Normal gears are helical think of it as taper on each spline helps mesh the gears together smoothly whereas straight cut more sensitive to difference in engine to road speeds. If eithers stronger depends what way? on helical the spline tips wear out but less likely too because they guide the mesh, opposite to straight cut they are stronger but get road to rpm speed very wrong more chance splines immediate breaking. Straight cut with slight taper on thrust side known as semi-helical.

hope that helps

S1

Dog engagement and dogleg are two completely different areas mate A dogbox refers to the type of engagement when changing gears. Old boxes are crash meaning no syncro, the drive had to match engine speeds with gearbox speeds, synchromesh uses hubs to slow down/speed up gears so speeds are the same to allow the synchro hubs to engage, dog engagement which is a fairly brutal engagement but quick.

Dogleg refers to the layout of the gearchange, some getrag's ie 635csi bimmers had first out on a leg so 2-3 and 4-5 were just a gate away.

re-reading your post, youve completelly missed how a synchro box works. They are constant-mesh sychromesh. The gears are already meshed, its the synchro hubs that do the meshing which locks the gears to the shaft they are running on.

TWoods

rereading even makes no sense to dyslexic me, shit

JonnyBravo

A dogbox :

TimC

iTrader: (1)

Id so love to have a go of a car with a dog box, or even better a flat shifted, sequential change dog box.

JonnyBravo

I sold the box above but I know someone with one and it does seem to work very well, strange as everyone tends to slate them and he says it simply finished of the car it was that good.

I can imagine though that not all boxes will be as slick as that one so it would be nice to try things like this before you buy them but that is highly unlikely !

Edit for video

Same box as above in a 235hp 1.8 NA nova

http://www.youtube.com/watch?v=Tx9aWVQGYs4

Typically its a rubbish video so you can't really hear the box as such but if you have been out in a few Vauxhalls you would realise just how different that is !

ian sibbert

Pics of dog gears & rings....if you look at the leading edges you can see the slight damage as they slam into gear !!!

I personally upshift and down shift with the FFD on sequential with no clutch, you can easily do it without flatshift etc they just make the function idiot proof....gear change on most the designed boxes that I have driven is a lot better than the converted type 9's that used to prevail....Quaife 60g for example is a very sweet change, as are the elite, selholm, drenth and tractive....

RickyLee53

What car is it again? Theres a few honda boxes to switch ratio's between, and some custom final drives in the states for most boxes. That said, the syncro's tend to go on high rpm/multiple quick changes. A lightened flywheel seems to help.

Regards
Ricky

Chip

iTrader: (3)

S2000 engine in a mk1 escort IIRC

TimC

iTrader: (1)

Ian although you say you change gear clutchless, do you slightly left when changing to help disengage the dogs or just foot to floor?

JonnyBravo

close !

Mk2 Escort.

Thanks Ian for the pictures, the 60G is apparently brilliant, but at 6k its way ott for what I need. If I went for the Elite (which I am considering) then that is about £4500 iirc, the issue there is IF it turns out to be rubbish I may as well spent the extra 1500 on the Quaife.

This is a track/sprint car though, not a car I'm going to take on the world with so I just feel its a bit ott spending that sort of money, if the Glebe will handle it then its a better unit for me as long as it doesn't cost the earth to rebuild every year.

Cost wise the whole engine on throttle bodies and dry sumped has come in at under 5k, not bad for 255-260hp so its given me some spare money to throw at the gearbox.

jammerrs

i always thought straight cut was stronger

yes you could change without lifting your foot, i beleive anyway

surely there not that loud as a motorbike ueses a dog engagment and they dont whine and break all the time!?

can you down shift without the clutch to if its dog engagment?

Chip

iTrader: (3)

Stu is running an Elite on his westy, have a chat to him about it?

JonnyBravo

I should do really Chip, I'll maybe drop him a message, its not a cheap option though as you can't use the box I expect he is due to the weight of the car, the next one up is another grand or so but if its reliable then it would be worth having.

Chip

iTrader: (3)

Its stronger but less durable.


The straight cut is the bit that makes the noise not the dog engagement

TimC

iTrader: (1)

Chip, I was taught the helical is stronger then straight cut due to having more tooth contact at any one time over straight cut.

I guess overall, tooth/gear size and material choice is more important then what choice of gear cut you run.

ian sibbert

Tim,

Yes it was a little sweeping, I have run the car with a gear cut and without, without the gearcut the change is still slick, as you say a little lift (and you'd hardly notice) just to de-torque the engine to change...all the gearcut strategies are a very similar, there are advantages though to moving towards paddle shift (as i'm developing at the min) as with the flat shift the cut durations are fixed whereas with a paddle shift you can create an intelligent input that can react to changes in things like tyres, surface and grip level....

Straight cut gears are noisier than helical typically they also typically have bigger teeth and less of them which makes them more durable for competition use. Helical gears are in generally stronger and cut with an offset opposing tooth pattern which typically runs quieter than straight cut gears. The real advantage to helical gears is the offset pattern which will pull the gears together when in rotation and under load which removes stress from the bearings on the shaft, in every day street use gives a quiet & reliable service to the gearbox...

Chip

iTrader: (3)

helical wont generally take massive loadings as well as there is too much side loading and although there is tooth contact, its not squarely accross the tooth which makes it more likely the tooth will be damaged

straight cut are horrid though for high mileages as the case hardening gets a massive hammering from all the shock loads as it slaps from one tooth to the next

there is a reason manufacturers only use them for reverse normally, lol

ian sibbert

Johnny,

I might know where there is a 60G, low milage, nice ratios and 5K...if your interested, he may have sold it though as an irish lad was coming over last weekend for a look...

I would never compromise on transmission, better to spend the cash on the transmission than the engine lol.....good gearboxes are about design (casing & cluster), material selection, machining & heat treatment, if any of those is weak the whole thing will fail IMO.....and thats why Xtrac are so expensive....lol.....

TimC

iTrader: (1)

Ian that what iv learnt since going rallying with Tony. A rally car with a better transmission and diff setup but standard engine is better then a tuned engine with standard box (not only probably quicker through a stage, but also more reliable)

As they say, power is nothing without control and one of those variables is definetly transmission choice.

JonnyBravo

I totally agree Ian, sadly others don't see it like that but there is so many times that you want to keep replacing boxes then you may as well of spent the extra and used something suitable in the first place, time is money and for you if your racing its not worth using anything than the best you can afford.

5k is a good price, however I don't have that sort of money at the moment, 3k is around my budget for now so I either wait (which tbh is probably best) or settle for the Glebe whilst its about but it is a bit of a grey area it would seem.

The engine IMO was cheap, if it ever grenaded itself I wouldn't be that fussed, everything is simply ready to bolt onto another stock engine and would give the same hp, give or take a few possibly. I've invested a lot of money into this car (in terms of what I earn) and I don't see the need to cut any corners really, you can get away with a lot of stuff to keep the car fast and reliable but the gearing would make the car.

I've spent 3 years on and off throwing money at bits so if it took a bit longer I really don't care, I'm far from completion but a lot nearer financially than I was a year ago but still want to spend my money wisely which is why I was looking for advice.

ian sibbert

Johnny,

Your right pal, I try and explain to people about throwing good money after bad, but they insist on spending on the same thing 3 or 4 times before they learn and incur so much extra cost....I have never driven a car with a Glebe box so I can't comment, and I've never looked at the design, but the quaife type 9 seqentials were really poor, they only got their act together when they re-designed the fork and barrel arrangements...

Tim

You at Weeton this weekend pal?

TimC

iTrader: (1)

Possibly. It has been mentioned. Tony might be doing chasecar at Bulldog on the Saturday and im out Karting Saturday night so ill have to wait and see.

JonnyBravo

I'll have to see how things are looking at the end of the month, I probably won't be as well off as I hoped once the bills arrive

I'm itching to get the running gear in the car, doesn't mean its going anywhere but clears a space and I'll have my motivation back if I get to that stage !

Thanks for the advice though