WRX 6MT Swap -- Part 1
12-30-2002, 11:37 PM
#1
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WRX 6MT Swap -- Part 1
There are many differences between the 5-speed we get in North America as OEM and the 6-speed WRX transmissions that come on New Age STi’s in Japan, Europe and Australia. First of all, the 6MT is approximately 85lbs heavier than the 5MT. The added weight comes from stronger and larger gears, various hardware, internal oil pump and generally larger size. The teeth profile has been altered to improve the gear mesh and reduce gear whine. Shifting mechanism was also reworked to increase the shifting response and reduce the possibility of gear clash. “Short shifting” already occurs inside the transmission case and nearly eliminates the need for a shirt shift kit. Subaru also increased the performance of the synchronizer by installing two linear ball bearings on each of the five shift rails. The new double-cone cone synchros on 1st and 2nd and triple-cone synchro on 3rd gear also add up to the over all strength and smoothness of the 6MT transmission. Last but not least, gears and some other parts of the 6MT has been carburized and quenched as well as shot peened. These processed insure the maximum strength of the metal. Another important bit about the internal differences is the fact, that the center diff / final drive gear are enclosed and have its own oil passages, keeping the potential metal bits from the gears away from it. Finally, the clutch slave cylinder has also been reworked to improve the pedal feel and ensure its maximum performance during the most demanding conditions.
One of the main great advantages of the 6MT transmission, is that it allows the driver to use the engine’s power more efficiently and insure that there is enough “oomphhh” in every gear at any speed. That is where the gear ratios come into the game.
The 2 bottom tables show the gear ratios of 6MT and 5MT. 6MT’s in UK and Europe are available with taller 5th and 6th gears. They are shown in bold.
The JDM 6MT will turn about 400RPM faster in 6th gear at around 60MPH.
JDM/European 6MT Gear Ratios
1st Gear 3.636
2nd Gear 2.375
3rd Gear 1.761
4th Gear 1.346
5th Gear 1.062 / 0.971
6th Gear 0.842 / 0.756
Reverse Gear 3.545
Final Gear 3.9
US 5MT Gear Ratios
1st Gear 3.454
2nd Gear 1.947
3rd Gear 1.366
4th Gear 0.972
5th Gear 0.738
Reverse Gear 3.333
Final Gear 3.9
Regular 6-speed gearboxes offer a 50/50 front/rear torque split. However, some STi WRXs are also available with the optional digitally controlled center differential or simply DCCD. Normally, the DCCD is set at 38/62 split and can be set towards 50/50 and locked position.
The above were the most important differences between the 6-speed and 5-speed Subaru transmissions.
Now, let us take a look at some pictures and analyze the external structural changes.
Here are both transmissions side-by-side. As you can probably tell, the one on the right is much “beefier”. Not only it is longer, but also wider and more resembles a rectangle rather than a triangle. You can also see massive ridges that are cast into the case. They provide additional case rigidity and could also possibly improve cooling of the gearbox. Both transmissions consist of three main parts, the gear/bell housing, the center diff housing and the final drive housing. As you can tell, each of them on the 6MT is much bigger. The front/bell housing keeps the front SureTrack LSD nice and comfy with plenty of room and fluid. The front diff is kept separate from the gears and has its own oil galleries as I mentioned earlier. The bearings inside are also larger and stronger, according to my source. The middle, center diff housing is also separated from the rest of the transmission. Big bearings, large oil galleries and tranny fluid pump are all here. Finally, the rear housing is where the final drive gear resides.
This is a nice close up shoot from the rear of the transmissions. I know I said it many times already, but everything is “big” on the 6MT comparing to the fragile 5MT. Plenty of those ridges talked about already.
I personally think that the iron cast girdle that you can see in this picture is one of the most important structural improvements. Also notice the oil pump line that goes from the center section to the front one. That’s one of those special oil passages we talked about.
Girdle-girdle! I am pretty sure some of those plugs can be removed and used to hook up a tranny oil cooler. Also notice the dipstick.
If you aren’t convinced yet that 6MT is THE transmission of your dreams, please stay tuned for the next article, where I will talk about the rear diff, driveshaft, axles, hubs and shifter.
One of the main great advantages of the 6MT transmission, is that it allows the driver to use the engine’s power more efficiently and insure that there is enough “oomphhh” in every gear at any speed. That is where the gear ratios come into the game.
The 2 bottom tables show the gear ratios of 6MT and 5MT. 6MT’s in UK and Europe are available with taller 5th and 6th gears. They are shown in bold.
The JDM 6MT will turn about 400RPM faster in 6th gear at around 60MPH.
JDM/European 6MT Gear Ratios
1st Gear 3.636
2nd Gear 2.375
3rd Gear 1.761
4th Gear 1.346
5th Gear 1.062 / 0.971
6th Gear 0.842 / 0.756
Reverse Gear 3.545
Final Gear 3.9
US 5MT Gear Ratios
1st Gear 3.454
2nd Gear 1.947
3rd Gear 1.366
4th Gear 0.972
5th Gear 0.738
Reverse Gear 3.333
Final Gear 3.9
Regular 6-speed gearboxes offer a 50/50 front/rear torque split. However, some STi WRXs are also available with the optional digitally controlled center differential or simply DCCD. Normally, the DCCD is set at 38/62 split and can be set towards 50/50 and locked position.
The above were the most important differences between the 6-speed and 5-speed Subaru transmissions.
Now, let us take a look at some pictures and analyze the external structural changes.
Here are both transmissions side-by-side. As you can probably tell, the one on the right is much “beefier”. Not only it is longer, but also wider and more resembles a rectangle rather than a triangle. You can also see massive ridges that are cast into the case. They provide additional case rigidity and could also possibly improve cooling of the gearbox. Both transmissions consist of three main parts, the gear/bell housing, the center diff housing and the final drive housing. As you can tell, each of them on the 6MT is much bigger. The front/bell housing keeps the front SureTrack LSD nice and comfy with plenty of room and fluid. The front diff is kept separate from the gears and has its own oil galleries as I mentioned earlier. The bearings inside are also larger and stronger, according to my source. The middle, center diff housing is also separated from the rest of the transmission. Big bearings, large oil galleries and tranny fluid pump are all here. Finally, the rear housing is where the final drive gear resides.
This is a nice close up shoot from the rear of the transmissions. I know I said it many times already, but everything is “big” on the 6MT comparing to the fragile 5MT. Plenty of those ridges talked about already.
I personally think that the iron cast girdle that you can see in this picture is one of the most important structural improvements. Also notice the oil pump line that goes from the center section to the front one. That’s one of those special oil passages we talked about.
Girdle-girdle! I am pretty sure some of those plugs can be removed and used to hook up a tranny oil cooler. Also notice the dipstick.
If you aren’t convinced yet that 6MT is THE transmission of your dreams, please stay tuned for the next article, where I will talk about the rear diff, driveshaft, axles, hubs and shifter.
12-31-2002, 01:12 AM
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Josh,
AFAIK, the tranny will fit the GC. However, being wider, you might have to hammer the body a bit to make it clear. I am not sure about it. I need to dig up some of my old GC pics and I will be able to tell.
Yohei,
No, this is the regular 50/50 one. The DCCD has wires all over the place AFAIK.
I was trying to find some info on the SureTrack LSD's and couldn't find any. All I know that STi WRX's have SureTrack's in both front and rear. Both of them are LSD's. And, SureTrack is made by AP. If anyone know more about them, please let me know.
AFAIK, the tranny will fit the GC. However, being wider, you might have to hammer the body a bit to make it clear. I am not sure about it. I need to dig up some of my old GC pics and I will be able to tell.
Yohei,
No, this is the regular 50/50 one. The DCCD has wires all over the place AFAIK.
I was trying to find some info on the SureTrack LSD's and couldn't find any. All I know that STi WRX's have SureTrack's in both front and rear. Both of them are LSD's. And, SureTrack is made by AP. If anyone know more about them, please let me know.
12-31-2002, 01:52 AM
#6
Ok, I looked the broschure
TypeRA with DCCD ....F/suretrac R/clutch
TypeRA with Brembo (no DCCD) F/suretrac R/suretrac
STi .....F/optional suretrac R/suretrac
so your 6MT may or may not have suretrac in it.
Suretrac was trademark of AP but AP is absorbed by Delphi now
TypeRA with DCCD ....F/suretrac R/clutch
TypeRA with Brembo (no DCCD) F/suretrac R/suretrac
STi .....F/optional suretrac R/suretrac
so your 6MT may or may not have suretrac in it.
Suretrac was trademark of AP but AP is absorbed by Delphi now
Last edited by go go go; 12-31-2002 at 02:02 AM.
12-31-2002, 02:40 AM
#7
Suretrac info
all right,
I found info on Suretrac, if Suretrac related stuff needs to move to another thread, please do so.
Suretrac was jointly developed by Automotive Products (AP) and Fuji Univance. Somehow AP has the trademark.
I found this press release of Fuji Univance
read this
http://www.uvc.co.jp/news_release/00-10-26_e.htm
and then here is how it works...although I still don't understand...
http://www.uvc.co.jp/products/coupli.../axc_cld_e.htm
I think what it does is..
less torque = more like open diff
greater torque = becomes more like LSD
and the slip is proportional to the torque input.
So..when cornering or under brake, it's open diff so that you can turn in well, but while you are on the gas, it's LSD for stability.
Suretrac is not very strong so if want more LSD, I suggest you to change it to clutch type. Cusco LSD typeMZ
I found info on Suretrac, if Suretrac related stuff needs to move to another thread, please do so.
Suretrac was jointly developed by Automotive Products (AP) and Fuji Univance. Somehow AP has the trademark.
I found this press release of Fuji Univance
read this
http://www.uvc.co.jp/news_release/00-10-26_e.htm
and then here is how it works...although I still don't understand...
http://www.uvc.co.jp/products/coupli.../axc_cld_e.htm
I think what it does is..
less torque = more like open diff
greater torque = becomes more like LSD
and the slip is proportional to the torque input.
So..when cornering or under brake, it's open diff so that you can turn in well, but while you are on the gas, it's LSD for stability.
Suretrac is not very strong so if want more LSD, I suggest you to change it to clutch type. Cusco LSD typeMZ
Last edited by go go go; 12-31-2002 at 02:47 AM.
12-31-2002, 05:01 AM
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Location: New England
Posts: 75
Here is some terrific info to read about the six speeds suretrack LSD. There is also excellent info about all of the sti's major components, engine, trans, diff's, suspennsion ect ect., enjoy... Maybe this info should be made into a sticky ??
http://subaru.com.au/downloads/63748.pdf
Tom
P.S. I can't wait until my sti motor and trans gets here..
http://subaru.com.au/downloads/63748.pdf
Tom
P.S. I can't wait until my sti motor and trans gets here..
Last edited by Sloppy Joe; 12-31-2002 at 05:08 AM.
12-31-2002, 05:06 AM
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Location: New England
Posts: 75
oops, he, he..
Tom
Tom
12-31-2002, 05:59 AM
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Location: Albany, New York
Posts: 31
6MT Article
FANTASTIC!
Thank you for this artile and all the work that went into it. This sort of information is like gold. One request, please include citations for the sources of information. So readers can dig around too. I am new to subarus and don't know where to look for primary sources, stuff like this.
Two questions: Will one of these fit in the 2002 USA cars? (see how unfamiliar I am with these things?)
Will a Torsen differential fit? If not in Transmission in front and / or rear?
Again, this is great stuff.
Thank you for this artile and all the work that went into it. This sort of information is like gold. One request, please include citations for the sources of information. So readers can dig around too. I am new to subarus and don't know where to look for primary sources, stuff like this.
Two questions: Will one of these fit in the 2002 USA cars? (see how unfamiliar I am with these things?)
Will a Torsen differential fit? If not in Transmission in front and / or rear?
Again, this is great stuff.
Last edited by Karaya Eins; 12-31-2002 at 06:07 AM.
12-31-2002, 01:28 PM
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Alex's, and my 6MT are both "sure-track" front diffs. How do I know you ask? We both bought them from the same dude.
There are not too many non sure-track trannies out there.
There are not too many non sure-track trannies out there.
12-31-2002, 03:19 PM
#12
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Here is what I found out:
Part numbers for the 6MT trannies:
32000AF460 Standard
32000AF500 w/ SureTrac
32000AF470 w/ DCCD and SureTrack
My tranny is the one with SureTrack.
- Alex
P.S. Thanks Jude.
Part numbers for the 6MT trannies:
32000AF460 Standard
32000AF500 w/ SureTrac
32000AF470 w/ DCCD and SureTrack
My tranny is the one with SureTrack.
- Alex
P.S. Thanks Jude.
