Conversion to WRX 5MT, is the speedo gear different?

[DeusExMachina]

I'm planning on swapping over to a WRX tranny and rear end, and I'm wondering if and how big of a difference the speedo gear is in the WRX gearbox. Thanks.

[BAC5.2]

It's the same.

Why are you downgrading to the WRX tranny though?

[-K-]

I second that. WRX tranny gear ratios suck.

[BAC5.2]

...So do the gears in general. So does the center diff FWD biased power split.

Our gearbox utilizes the same internal structure as a WRX transmission, so all gears that fit in a WRX case (RA's like you mentioned to me), will stuff into our case.

[DeusExMachina]

There's only one guy who stuffed (is in the process, yes process, of stuffing RA gears into a Legacy Turbo case) and it required a LOT of custom fitting, retrofitting old crap tech from our boxes (weird 1st gear secondary syncro that breaks real quick) or else it doesn't fit due to size differences. RalliSpec has no idea on how to do this, even.

The WRX ratios are crap but I can deal, the gears are plenty strong for a Legacy Turbo and even for aspirations below 300 awhp. Joe P of Joe P MBC once told me, the faster your car is, the more you can baby your transmission because you don't need to beat the piss out of it to go faster.

Like I said to Phil on AIM, there's 3 reasons I'm doing this:

- Easy to find
- Relatively cheap (a lot cheaper than a new condition Legacy Turbo tranny, which doesn't exist)
- Straightforward and recently performed on a friend's '91 rally Legacy SS. WRX case, Legacy Turbo front axles, Legacy Turbo driveshaft, WRX rear diff, WRX SEDAN rear axles. In case anyone is wondering.

[THAWA]

downgrading? humorous
'
anyway, the speedo is most likely electronic on new transmissions instead of being mechanical like ours. Whether or not our cable with fit in the wire setup I dunno. Also depending on which tires you use it will effect your actual speedo and odo.

[DeusExMachina]

I was told the speedo gear is set up the same, the WRX just has an electronic box outside of the speedo wire.

[THAWA]

oh okay, so the connection to the tranny is still the same, it just converts it to a signal outside the tranny? coolio

[BAC5.2]

A) Yes, the new WRX tranny still uses a gear. I wish I had a picture.

B) Hmm, odd that he's having trouble stuffing the gears in. Maybe it's the whole main shaft setup that drops into our transmissions? I remember hearing that the internals would drop in, didn't know if it was the gears or the shaft set.

C) The WRX gears are not stronger than ours. If it's true that our gears are shot-peened, then we are already another step ahead. No WAY could a stock WRX transmission handle 300awhp, not a chance in HELL. They can't even handle STOCK power.

I really think everyone is overestimating the strength of the WRX gears, and underestimating the driver skill of said gearbox. The gears are TINY.

If you take advantage of the stock power levels of the WRX (and the advertised 5.4 second 0-60), you'll risk blowing the tranny. My friend did, and nearly sued SOA for not covering it under warranty.

Look at this picture. A comparison of the RA gears and the stock WRX gears.

The RA set is on the right (and broken), and the stock is on the right (with a chipped first gear drive tooth). Look at the tininess of the gears!

Now, a little Transmission 101: No chipping teeth actually occurs. It's sheering teeth that actually happens. The gears are always meshed, always spinning. The gears are stationary on the shafts always engaged, and when you move the shifter it just engages a collar against a gear. On the lay-shaft (constantly spinning as long as the clutch is out) the gears are fixed. They don't move. The gears on the main shaft are sitting on bearings. This is what allows all of the gears to be constantly meshed. Using dog teeth, it simply meshes with the gear and engages that specific gear. Now, dog teeth are STRONG. When you grind a gear, that's what's grinding, not the gear itself. I won't get into synchro's, as they don't have much to do with the strength of the gears in a box.

A grinding transmission means the dog teeth are being abused and hurt, not the drive teeth.

SO, breaking gears, really is all a factor of the gear itself, not so much the driver. While you CAN butcher the shifting enough to do some real damage to the gear, the synchro's usually prevent you from shifting so fast to do that. Flat shifting the transmission (barely lifting the clutch and burrying the gas to the floor) will hurt stuff, but even still.

Synchro's get in the way of breaking lots of stuff. Trannys without synchros (called dog boxes, because they are just the dog teeth engaging without any help), are built with strong enough gears to handle the shock associated with a flat shift.

So you see, a broken gear is 95% the result of a weak gear, not driver mishap. The biggest load a gear will see, is when the dog teeth engage, and even that is pretty fluid thanks to synchro's, the clutch, and proper driving technique. 99% of the shift-induced drivetrain shocks are when there is no throttle applied after the shift. Like when you do a WOT pull through 2nd gear, shift to 3rd and don't give it gas when you let off the clutch, that kind of shock. A WOT pull kind of shock comes from dumping the clutch on a shift or flat shifting. No one in their right mind would flatshift a car they want to be able to drive home, and dumping the clutch on a shift still doesn't shock TO much, unless not enough throttle is applied, again.

The stock clutch is pretty forgiving on a WRX, so lots of those shocks (like the WOT clutch dump shift) are absorbed by clutch slippage.

The gears are just tiny and weak, and that sucks . The case is nice though!

Sorry for the long reply.

[BAC5.2]

Picture of RA compared to stock:

[dkopp]

old thread resurrection...

my 1993 sport transmission is approaching 300k miles and the shifting from 1st to 2nd and from 3rd back down to 2nd grinds if i'm not really careful. i notice this more in the warmer months and i think it's because the viscosity of the gear oil gets too thin. now, since it's arse cold in maryland, i'm grinding much less. the gear oil isn't that old, but i was contemplating switching to motul 300 or getting a newer box. there's a freshly inspected WRX box with an RA gearset available on NASIOC within driving distance, but after reading the preceding information and checking the gear ratios:speed calculators, i'm thinking the RA gearset would not only be weaker, but kill me on my long distance mileage.

this is the only information i could find on the individual gears (identified as a 1994 legacy on the website):

1994 Legacy 3.545 2.111 1.448 1.088 0.780 3.90

the RA gearset:

WRX RA 3.083 2.062 1.545 1.151 0.825 3.90

so, i don't completely hijack the thread about one gear oil vs one "cocktail" vs. which oil debate, i would really appreciate whether there's been more current thought about the strength of the original transmission. unless i hear otherwise, i'm better off looking for a low mileage box than swapping to the WRX box with RA gears.

thanks!

[Legacy777]

To be quite honest with you, I think a lot of what you hear about the t-legacy tranny being stronger than the newer WRX tranny is somewhat internet folk-lore. I obviously can't confirm or deny it, but the fact of the matter, the number of WRX's out there and the demographic of people that drive them and how they drive is going to vary pretty heavily compared to the SS. As a result, there's going to be more failures of the WRX trans compared to the SS. As a result i believe everyone has come to the conclusion that the trans are weaker on the WRX.

I know that may not necessarily answer your question, but just something to think about. Personally, I like the gearing in the SS trans over the RA stuff, but that's me.

[dkopp]

To be quite honest with you, I think a lot of what you hear about the t-legacy tranny being stronger than the newer WRX tranny is somewhat internet folk-lore. I obviously can't confirm or deny it, but the fact of the matter, the number of WRX's out there and the demographic of people that drive them and how they drive is going to vary pretty heavily compared to the SS. As a result, there's going to be more failures of the WRX trans compared to the SS. As a result i believe everyone has come to the conclusion that the trans are weaker on the WRX.

I know that may not necessarily answer your question, but just something to think about. Personally, I like the gearing in the SS trans over the RA stuff, but that's me.

I don't disagree one bit with you, Josh. I prefer the SS gearing over the RA set as well and that might be the deciding factor.

Although, I will say that the earlier Subaru cars are built pretty stout. I am not as impressed with the newer manufacturing. The fact was that the Yen to USD value in the early 1990's allowed for more favorable conversion and, thus, manufacturing. While I can't prove that my 1993 is better built, I think things like the oil cooler and the VLSD offered on the 1991 year only suggests that the original car was very well engineered. Good thing I picked up each for my 1993!

If anyone has a lead on a low-mile 5mt box, let me know.

[Deride]

The only problem with the WRX 5 speeds is the asshats that drive them. Thanks to Ken Block and Travis Pastrana every d-bag asshat thinks they can be a rally driver. Now that used WRX's are affordable they can all buy them. It only takes a launch or two on dry pavement with traction to do some serious damage to the gears. I know plenty of people with stock WRX 5 speeds making near double stock whp that haven't had an issue. It's all in how you drive it, not the "strength" of the gears. Oh and I absolutely hated the WRX 5 speed gear ratio.... They needed a gear between 3rd and 4th for daily driving... 3rd at 35-40mph was pretty high RPM then 4th would be so low the car would bog. Musta been made for KPH speed limits not MPH. T-LEG gear ratios are much better in my opinion, but I highly doubt anything is "stronger".