I am just toying with the idea of a replacement gearbox in case I ever manage to get my car back on the road.

If it all goes to plan, I should be running close to 400bhp and (hopefully) similar torque.

Very worried that my std 2002 5 speed box will implode if I run this much power through it.

The number of different gearbox codes is mind blowing !

I was just wondering if the 5 speed box that came standard on UK 2.5 turbos (Hawkeye onwards) was uprated to handle the increased torque over the 2.0 ?

If so, how much power and torque are people reliably putting through them ?

 

No, not really, they normally go just as easily as the 2ltr ones with similar torque levels, the nice people at subaru dont normally go out of the way to make new gearboxes for anyone you know

Tony

 

just get a 6 speed conversion they are tough

 

6 speed set up usually goes for £2k, I could get a (2.5) 5 speed for £500 !

I presumed that the different model numbers denoted some internal changes or improvements ?

Classic 5 speeds usually had a TY752 designation, the latest ones are now TY758's ?

As an example the US spec TY754VN2BA has uprated (RA) gear clusters, just wondered if this was an improvement that they introduced on other boxes ?

 

I know an equal number of people who have destroyed both...

dunx

 

is it not better to just bite the bullet and get a 6 speed rather than risk it and end up going through 5 speeds like jordan go's through men imho

 

An expensive bullet to bite though !

Four 5 speeds for the price of one 6 speed ?

 

people do get away with but the choice is oyurs to make but the six speed is a fit and forget job but try and get a latter jap box

 

Any gearbox experts on here who can tell me what changes were made on the later boxes ?

 

Better bearings and uprated same for the drop gear assembly... casing is stronger too ( not much tho' )

dunx

 

Cheers Dunx !

I also found some info on NASIOC but by the time I had finished reading it all the fossil fuels had run out !

 

That's 'cos I'm only doing 20 mpg...

LOL

dunx

 

One thing to note is that, the hawkeye 5 speed has a 4.111 FD, which when compared to the bug's 3.9 FD has a mechanical advantage. All things constant, there will be less load on the gears. Imagine riding a bicycle: Using a constant force peddling on its highest gear, now imagine dropping a gear or two, instantly the forces on the gears frees up. It's quite similar in theory to the 4.111 vs 3.900.

 

What is this 'bicycle' of which you speak ?

Just kidding !

 

20mpg ?

You were lucky !

I used to have to live in a hole int' road !

Oh, hang on a minute...........................

Actually on the rare occasions mine has ever been running, I think I was averaging about 15mpg or so..............................

The only car I have ever driven with worse fuel consumption was a Mazda RX8 (230 BHP version ?)

I managed 12 to the gallon over a two week period !

Somewhere, someone in the Middle East has a new gold plated Lambo because of me !

 

The Hawkeye WRX boxes ARE stronger than the previous TY754 boxes. They have been significantly changed, if you sit two side by side you will see that the box is much wider around the front diff. It uses the male ended shafts and as mentioned requires a 4.11 rear diff. The main problem with fitting these is the clutch set up, some have a pull clutch and some have a push clutch. The easy way to tell is the pull type do not have the pin going through the fork the way the normal set up is. This means its not a straight forward mod. To do it you would need the box, obviously, the front shafts or stub shafts to use with your normal front shafts, the clutch set up and the slave cylinder.

Just in case I have got my push and pull mixed up then most of the hawkeye wrx boxes have the opposite clutch set up to the normal impreza set up

 

One of my biggest regrets of Scooby ownership, was not biting the bullet and going for a 6 speed in my wrx before I started modding, many thousands later and much downtime while they were being fixed, I went through 5/6 I think.

 

The TY754VG boxes from the Hawkeye WRX's have been holding up consistently at 350-400lb's ft. That said 6 speed is the way to go for strength as long as you dont mind the extra weight and crap ratio's.

 

Erm no they haven't... I know of two people who have broken theirs after a re-map.

dunx

P.S. I accept that some are more careful than others...

 

Hmmmm............

I hadn't factored in the replacement rear diff and other bits !

It sounds like the beginning of another odyssey !

 

The arguement ref gearbox stengths will always be debated, I also know several who have used these boxes competatively at 400lbs ft + with no issues, so your statement is purely what you have seen not a fact.
I also know several who have broken 6 speeds at lower power levels than others. I used a TY754VN4AA box for two years at 400lbs ft in the Scottish Hill climb and sprint championship and believe me I am not sympathetic in its use, and it is still in good order living the quiet life in the garage. People have also broken 754 boxes at 300lbs ft on the road.
My point was that the Hawkeye boxes were redesigned to cope with the greater torque of the 2.5 engine and they ARE stronger than the previous TY754 boxes. Because of the clutch arangement and the rear diff ratio these boxes can be picked up for next to nothing.

 

Everything mechanical that I touch commits suicide shortly thereafter !

Does anyone make a gearbox from sweetcorn (the worlds most indestructable substance) ?

It looks like I need to do more research into which 2.5 boxes have the std clutch set up, if any !

 

I've seen two re-mapped 2.5 WRX's **** their gearbox...
I have also seen two bugeye WRX's **** theirs.

So the 2.5 WRX may be slightly stronger, but add in the lack of a rear LSD and the "odd" clutch and it all starts to cost.

FACT !

dunx

 

Hmmm interesting points here

I think the gearsets are the same, ie no change in design or strength between the 2ltr and 2.5's, now if the clutch setup reduces shock from the transmission no doubt that would take some strain off as that can make or break, BUT the torque will still break the gearsets as they still put the same ammount of stress on the gears, just not with as much jolt?

Tony

 

This makes interesting reading ?

http://flatironsrally.typepad.com/fa...-and-more.html

I don't understand 'links' !

 

Something to add to spice up the debate

I used to own a uk bug wrx with a complete set of STI RA gearset. It was purchased from Rallispec in the USA and from what i was told and read, the STI RA gears are 1mm thicker in width to cope with the extra abuse that these cars are likely to receive.

IIRC, i read that this increase in tooth width was carried over to the hawkeye 5 speed box, so they were 1mm thicker than pre 06 cars. I'll see if i can find the article. Like i said, i can't confirm this fact, i think i remember or I could well be dreaming that i read something like that.

 

Is that the STI grp N gearset?
If it is then you may find that those are "after production" and just for rebuilding the box

Tony

 

They might be Tony. This is where they were purchased http://www.rallispec.com/prod_trans.htm

Anyway, whether they are Group N or not, the STI RA gears are 1mm thicker AFAIK, so there should be a tiny improvement in reliability?

 

The transmission FAQ that I read claims that 2003 onward 5 speeds got the RA width 1st 2nd and 3rd gearset (not ratios !)

This was on US spec cars, don't know about the rest of the world !

 

Ah OK. I was definitely not dreaming then. I may have gotten the facts a bit mixed up though.

I guess then from MY03 onwards the 5 speed boxes were a tiny bit stronger.