EvilBevel

Couldn't have happened at a better time (5 days before Catalunya trip) ...

Was driving slowly today, and noticed the gearbox started to whine a bit... 10 minutes later, the whine became an incredible rattle in 2nd gear. Trouble selecting it as well... even with clutch depressed & just coasting, 2nd gear makes the same noise. No problems in other gears.

Would I be correct in thinking it is 2nd gear synchro that is gone ?

Any advice would be appreciated

Theo

john banks

Like some of the other big turbo boys you may unfortunately be making friends with Subaru breakers for another gearbox, but then I am automatically assuming it is your increased torque that has done it which may be untrue, and that a replacement is cheaper than a repair. Sorry if that is not very helpful. This is what is putting me off a big turbo I am afraid. Unfortunately it seems the stronger alternatives cost megabucks.

Mo

Hi Theo,

don't go for a second hand box. I got one and it lasted 5 months before giving up, when I took it back to be repaired I was told it only had a three month guarantee. Expensive mistake.

Ended up getting it repaired for about the same price as the second hand box and it should, in theory, be as good as new.

EvilBevel

Thanks John,

Of course I could say "I only run 258 lb/ft" as shown by my PS dyno, but that would be opening another can of worms innit ?

I have now decided to go for a full dog/straight cut gear set. The new gearbox will be my 3rd, and I don't want to end up with an Evo 7

In the mean time ... after calling my dealer (I had already assumed my Cat trip would be down the drain ) he called me back 10 minutes ago ... he will sort me a new gearbox temporarily, take it back afterwards (charge me for fitting/removing etc), and will search with me for a stronger set... how's that for service eh ? I can get there on Sat to have the gearbox changed ...

If he weren't a bloke, I would kiss him...

Theo

EvilBevel

Hi Mo, sorry, just missed your post...

My dealer fitted me a new one last time minus the price for my repaired gearbox. It lasted exactly one year.

He now is convinced (and so am I) that with my car, a stronger set is needed.

Will look into a dog box now (again), as this is the last time I ever want to see that thing dropped from my car.

I could have done without the stress ... I'm at my 4th whisky at 6 PM ... but the fact that he can sort me out in 2 days is worth gold IMHO

This guy needs a medal (sure, he earns his money with this, I know, but still...)

Theo

john banks

I didn't realise you already had two I must stop the mods.

What's the deal on the dog box if I may ask?

EvilBevel

John, I'm an amateur as you know, but I will try to answer with what I know.

1. You can have "stronger" helical gearboxes. They may be either treated with cryogene (Prodrive does that for GrpN cars) or have "wider" gears. They may still fail. I assume you know how helical gears look like ? (if not, I'll search for the link on www.howstuffworks.com)

2. You can have a dog box / straight cut gearset. Straight is what is means ... the gears are not "helical" to one another, but are normal gears like you would get with Fisher Price

Advantage ... MUCH stronger, and less drivetrain losses, so more usable power.
Disadvantage ... say hello to a lot of noise (like when you pick reverse ? Those are straight gears, with no synchro) and rev matching. Almost beyond being a "road car".

To "tune" means to "balance". We often forget that.

The gearbox is a much weaker point on an Impreza than big ends or pistons.

Theo

PS: I see you decided to "dodge" my low torque figures

john banks

Yes I am dodging the torque issue

Don't fancy the rev matching. I should really resist making it any quicker, and just reduce boost for the track.

Do you think reducing your boost in gears 1 & 2 would help at all?

EvilBevel

>>Don't fancy the rev matching. I should really resist making it any quicker, and just reduce boost for the track.

Wise choice I would say.

>>Do you think reducing your boost in gears 1 & 2 would help at all?

Again, I'm not an expert, but I think ... nope. My first gearbox went in 3rd gear after half throttle... see Multipla driver up my rear... boot it... KKKKRRRKKRRR...

Theo

PS: it might even be that the synchro problem (if it is that ) is not torque related, but due to the fact that I do too much engine braking on track... (select lower gear too soon, car wants to jolt forwards, but I'm pushing the brake pedal commanding the 330 mm brakes etc...)

teknopete

Theo,

After my third Fisher price box I considered the dog box set that MRT do, the thing I didn`t fancy was the increase in noise
After a bit of fishing around I found another Austrialian firm that did a semi-helical gear set. This in effect gave the best of both worlds (good transfer % and quieter than a full dog set)
Can`t remember which co. it was, but if i find the old mails I`ll post the info up. Typical though after gettin prepared 4 another breakage the current std box has held up really well

Jus thought I`d mention it in case it`s of use to u

L8r
Pete

JamesS

How about a shot-peened Group N set?

VF30 going on soon........(oh dear!)

chuckster

You were told not to run more than 1.1bar through your gearbox.
Glad to hear the dealers sorting you out mate, have fun in Spain
Chuck

EvilBevel

Hmmm, just realized it should be "woes" ... anyway

Pete, will look for it, but I think in the mean time MRT do a semi helical set as well. Just want to avoid having to go through this again, I don't really mind the noise, just a bit afraid of the gearchange antics in slow traffic etc.

James, thought of that too, but it seems to be a) expensive and b) they still fail given enough torque/clumsy gear changes.

Chuck, I knew someone was going to say that Guess I deserved it Although SportAuto managed to break a box on their longtermer (bog standard) MY00 as well.

I now have to drive 170 km to the dealer on Sat ... anyone know if it is dangerous to do so (I'll avoid 2nd gear) ? Maybe finding a low loader would be a better idea ?

SecretAgentMan

It's the nitrux Theo, I warned you about that along with the gearbox'd 1 bar of CRAZY boost.

Theo, sorry to hear about your problems, kinda makes me wonder though...since my gearbox is still intact - am I driving like Charles here, or is my car low on power being a turnip one?



Have a 3-fingered one on me mate.

/JMuppet

JamesS

Bits of metal swarf going round the other (still healthy) gears, syncro rings and diff gears!!!

I would transport it there.....

EvilBevel

Jerry

Like I said, it may be my driving (gearchanging) style or just bad luck, but I don't think that 260 lb/ft is crazy torque.

James, I agree, just arranged the transport to the dealer. Costs me 100 UKP, but compared to the potential further damage that is next to nothing. It may only be a synchro or a bearing, but swarf metal would defo do incredible damage. (been there done that )

Anyway, I wondered if anyone on here drives a dog box ? Would be interested in some experiences.

Theo

Cosie Convert

I'd also be interested to hear from anyone running a MRT dog box on the road. Even better, get a run in one Anyone ?

I know Townend garage advertise the latest MRT box. There are a number of different ratio sets available too. Guaranteed unbreakable for approx 2800 ukp I think ?

Think of the launch available with a paddle clutch

YES PLEASE !!!!

CraigRA

Had gearbox probs myself got loads of silly quotes, found a guy that was real good and honest check out www.gearboxman.co.uk they do loads of race boxes with no bull****.

johnfelstead

hmmmmmmm, not so sure you are going to like driving a dog box theo. You have to match the revs on downshifts otherwise you are gonna be destroying the dogs very quickly.

People forget that dog engaged gears do actually wear on the dog edges and after time need stripping and gears/engagement rings that have their dogs worn replacing.

Basically a dog engagement is just two sharp 90 degree metal edges banging against each other to engage. Now if you turn out to be crap at driving one of these boxes it wont be long before it starts jumping out of gear.

Basically i am saying, it's a gamble and you may find you hate it plus need rebuilds too. If you can, find someone who has a set in their car and try it.

Personaly i wouldnt use a dog box in a road car, pain in the ****. I would more likely go for a GroupN uprated gear set.

Cosie Convert

All those Superbikes you see on the road have dog boxes, no double declutching there Try finding neutral between 2nd and 3rd on a bike

Downshifting a dog box just needs to be swift and positive, no need for dd clutch crap. All that the dogs do is synchronise the clutch driven plate speed to the mainshaft. The dogs are tapered so that as soon as they touch they grab one another and engage instantly. Ideally you fit a decent competition clutch like an AP cintered with a nice low Moment of inertia.

Competition dog boxes also tend to be very close ratio so the difference in clutch speed on a downshift is likely to be only 1000 rpm or thereabouts.

[Edited by Cosie Convert - 3/16/2002 1:25:55 AM]

teknopete

Theo,
U r right, IMHO 250 lbft of torque is about the norm for a mildly tweeked mota, one of our club members runs 305 lbft through a std box, an he doesn`t treat it with kid gloves

Andy,

The launch even with a std box & a paddle clutch is mad
I had an AP paddle fitted 2 mine bout a year ago, u could launch
at 5-6K an not feel bad about it Thing was the clutch only lasted 9 months and I recon the shock loading of the xmission was the reason 1 of my gboxes went boom The clutch wasn`t that good for town driving either.

Pete

johnfelstead

Double declutching isn't the same thing as matching the revs on downshifts, common misconception.

Cars and bikes are a totally diferent proposition when it comes to gearbox design and usage. It would be a mistake to use one as an example for the other.

EvilBevel

JF, as you know I value your opinion a lot, and I just had visions of a clumsy 6'7" dude wrecking yet another dog bog

My dealer just told me the same BTW ... he said that they *are* stronger if you know how to use them, but in less capable hands (i.e. mine ) they would probably break very soon.

So ... that leaves me back where I started. Any further suggestions would be appreciated. The dealer did say that he is investigating with Subaru if the STi7 box would fit a MY99 UK car ...

BTW, my gearbox broke on Wednesday, today Saturday 4 PM my car was on the road again. Big thanks to all involved ! Small miracle IMHO.

johnfelstead

Thats why i made the comments theo as i know how you drive. LOL

I genuinely believe a dog box would be a mistake for you, you wouldnt enjoy driving the car, which at the end of the day is the most important thing!

I am not an expert on making a scoob box last with big increases in power. If i were you i would have a chat with people who run GroupN cars. Bear in mind a year or so ago the groupN rules changed and you can now use any gear engagement you like as long as the ratios match production so you need to speak with people with old GroupN spec knowledge. Barrets know how to build a good groupN car, have done for a very long time. That might be a good starting point for you? TSL have run good spec groupN cars too in the past.

Cosie Convert

A competition dog box in a car is almost identical to a bike.
The main difference being no reverse What differences are you referring to John ???

dd clutching is letting the clutch out in neutral between gears, blipping the throttle to match the speed of the clutch driven plate (which is connected to the input shaft) with the gear about to be selected. Then clutch in again to select lower gear. This gives a 'clunk' free shift. Good for old trucks
It's the 'old' way to drive an 'old' design dog.

If you had to dd clutch car dog boxes then sequential boxes wouldn't be quite so popular would they

Nice if you've got the time but totally unnecessary. My Reynard F3000 'dog' box was a delight to drive. As fast as you could move your hand, up or downshifting. No dd clutching required, just a blip to stop lockup on a downshift. Not a problem on 4WD



[Edited by Cosie Convert - 3/16/2002 9:17:32 PM]

johnfelstead

not sure why you brought up DD if you now say that you dont need to use it, which was my point in the first place. LOL

The basic design is similar but the aplications are very diferent when comparing a bike to a car. The inertia involved is much greater in a car, the gears are much larger and the engines dont spin up/down at anything like the same rate.

I dont agree with you that getting the downshift right doesnt matter on an AWD car. You will notice it less in a rally car but your still doing the same damage and rounding off the dogs, that leads to a bolloxed gearbox pretty quickly. It's no big deal in a rally car though because every 6 events you strip the box and inspect it.

What we are talking about here is a guy that wants a reliable road gearbox that he can fit and forget. Knowing the way most scooby drivers cant match revs very well and the fact they like to rely on hard braking on track days and arnt very acrobatic with their footwork i dont think a dog box is the right choice, the dogs would be bolloxed in next to no time. Sure they would be able to select the gears most of the time but they would be doing damage that will lead to a stripdown. As to driving in trafic, dog boxes dont cut the mustard, it's a complete pain in the *** driving the escort cossie rally car in trafic. I dont think it's a good option for theo or the average scooby driver.

Cosie Convert

Hee hee, you're right about the ddc bit. I'd argue with myself in an empty room me

I just had a 1300cc bike box apart a few weeks before my scooby box broke and the gear sizes are actually very similar !! As you correctly say, there is a difference in the inertia of the bike v car.
The gearbox dogs however are unaffected by the vehicle or downstream drivetrain inertia !
Assuming one uses the clutch to change, then the clutch centre plate is the only item that the dog accelerates during a downshift. That's why I suggested an AP cintered clutch for low MOI.
Matching the revs as you change down with the clutch disengaged will do nothing to assist this. (even less use than ddc )
All it will do is reduce drivetrain shocks when the clutch is re engaged as the engine is up to speed. This would also apply to a syncro box.


Synchro's a girly thing

johnfelstead

LOL

The scooby box is pretty puney compared to most car boxes. I was looking at a couple in bits the other day from a USA pro-rally car. That wasnt pretty.

Getting back to the plot in question I dont think a dog engaged box is the right choice for a road car due to the reasons above. Think i'll leave it at that. LOL