6-spd conversion vs. 5-spd?

[McTaff]

Plz lock and redirect if this has been asked but:

What are the differences between doing a 5-spd and 6-spd conversion; and,
Can someone submit a nice in-depth set to SVXipedia?

I'm considering the swap, and I'd like to go for the 6MT instead of the 5MT. I'd like to know what technical and build differences I'm going to encounter should I choose to accept this mission. (This isn't a money-is-no-object project, but I will keep re calculating the financial position as we go.)

Is there a final drive ratio conversion for this? (Excuse my ignorance if not!).
Should we be looking for a lighter rear driveshaft or flywheel or anything crazy, or will dropping the tranny in as per 5MT going to be no trouble?
What other ease-of-use mods are useful on this type of setup (can you wire the internal neutral circuit as per http://www.subaru-svx.net/forum/showthread.php?t=26596 for instance?)?

Driveability and reliability are my primary concerns. Obviously an SVX that is continually stalling like a mongrel, or that continually spits clutch bearings out is no good.

The goal: I'm looking to do the brakes first, and then the tranny, suspension and exhaust at around the same time. I may then consider the ECUTune Stage III S/C, depending on how this all works out. Subafreak seems to be the man on the spot here :D , as he has the advantage of "been there done that".

I've seen lovely cradles being built and so on, but unfortunately aquiring anything from the states is not an easy task - I'm in Australia and for the most part I'll be stuck to getting the instructions, measurements and super-explicit instructions from my bretheren in the US and forwarding them on to others to build for me if required.

Input is welcomed, and if everyone gets energetic and starts co-writing a huge technical book, I'll pay my US$49.95 to get one if it's published.

Cheers,
McTaff

PS. My baby is a '92 Black on Pearl White. She enjoys long drives, high octane fuels and social outings with her younger brother, my '93 Black on Gun Metal Grey.

[mbtoloczko]

There's quite a bit of info on the network, but its dispersed among many threads. There are a couple options for the 6MT swap.

Option 1:
6MT (incl clutch slave cyl, throwout bearing, and front stub axles)
5MT/6MT clutch & flywheel (incl pilot bearing)
5MT/6MT clutch master cylinder
6MT shift linkage
6MT starter (USDM WRX starter will also work)
6MT tranny mount
5MT/6MT pedal assembly
custom rear cross member
R160 3.90 ring and pinion to install in SVX rear diff

Option 2: same as Option 1 except...
use R180 rear diff instead of R160 3.90 ring and pinion
6MT front half shafts
6MT rear half shafts

Option 2 provides a stronger rear diff. (The SVX half-shafts are already pretty strong). Unless you are pushing really big HP, option 2 isn't really necessary. Even then, its not absolutely necessary. The biggest advantage of option 2 is that the LSD in the R180 has a stronger coupling.

There are several different 6MTs available:

1) JDM 6MT with DCCD center diff and Suretrac front diff.
These are expensive and a DCCD controller is needed which adds another $800 or more to the cost. The DCCD can only operate in manual mode which isn't so great.

2) JDM 6MT with viscous center diff and Suretrac front diff. Probably the best option, but these are difficult to come by. They were only installed on a few MYs.

3) JDM 6MT with viscous center diff and open front diff. Very common, so not too expensive. Open front diff is not so performance-oriented.

4) USDM 6MT.
These are all DCCD with a Suretrac or helical front LSD. DCCD controller needed. Different gear ratios than JDM 6MT.

I'll let someone else fill in the details on the 5MT swap and add corrections to my 6MT swap.

[McTaff]

There are several different 6MTs available:

1) JDM 6MT with DCCD center diff and Suretrac front diff.
These are expensive and a DCCD controller is needed which adds another $800 or more to the cost. The DCCD can only operate in manual mode which isn't so great.

2) JDM 6MT with viscous center diff and Suretrac front diff. Probably the best option, but these are difficult to come by. They were only installed on a few MYs.

3) JDM 6MT with viscous center diff and open front diff. Very common, so not too expensive. Open front diff is not so performance-oriented.

4) USDM 6MT.
These are all DCCD with a Suretrac or helical front LSD. DCCD controller needed. Different gear ratios than JDM 6MT.


Thanks!

Any ideas on what the breakdowns of the model/years for each of the JDM vehicles? (1 -> 3 you listed here?)

And what is the deal with the controller and manual mode only? (Is there a glossary of terms somewhere for this site? I run into so many acronyms here that I nearly have anuerisms reading it :) )

[svxpert]

mbtoloczko , whats the torque split if you don't use a DCCD controler in the USDM 6 speed. i have the 6-speed but no controler yet. thanks

[mbtoloczko]

Here's a chart that shows which MYs had which tranny:

http://www.rallispec.com/Transmission%20chart.htm

The controller can only operate in manual mode because there are some sensors that are absent from the SVX that the controller needs to operate in automatic mode. No one that I know of has been able to make a DCCD controller work in auto mode in a car that did not originally have the DCCD controller.

With no controller, the center clutch on a DCCD tranny is wide open (no LSD action), so the torque split is 36/64.

[Subafreak]

The six speed is stronger and slower in the 1/4mile becouse you shift alot. And it tops out around 130mph. ;)





Not feeling real technical right now. :D

[svxpert]

thanks for the reply. is that torque split 36/64
36 front
64 rear

or the reverse?
thanks

[mbtoloczko]

36 front/64 rear

[black beast]

so a 5sp is faster? wow never would have thought that :eek:

[mbtoloczko]

But its not stronger. The 6MT also weighs about 100 lbs more than a 5MT. Another reason why the 5MT is faster.

[Earthworm]

so a 5sp is faster? wow never would have thought that :eek:
But not as fastAr as an SRT-4

(sorry...had to do it once)

[TomsSVX]

the 5mt is more practical and has a couple different final drive ratie options. For someone who is looking to enjoy the speed of a naturally aspiratd engine or some mild mods, the 5mt is great. It turns some great times in the 1/4 mile and tops out around 145(i haven't done it so im lost on if thats right) The availability of the 5mt is probobly it's biggest plus, not to mention that 2 5mt's are cheaper than 1 6mt(I keep a spare trans in the garage :) )

On the other hand, the 6mt is more for big power applications. It is the strongest mt that suby ever came out with and will be a nice fit in the SVX. I have heard that the shifting can get to you quickly and the top speed and highway rev's are not too practical. If you are looking to run the stage 3 S/C I would suggest the 6mt. If you are looking for a fun car to drive around with some kick and play at track also the 5mt is probobly your best bet. Either way the mt in the SVX is a joy for me and many of the other owners who have them.

Tom

[Subafreak]

the 5mt is more practical and has a couple different final drive ratie options. For someone who is looking to enjoy the speed of a naturally aspiratd engine or some mild mods, the 5mt is great. It turns some great times in the 1/4 mile and tops out around 145(i haven't done it so im lost on if thats right) The availability of the 5mt is probobly it's biggest plus, not to mention that 2 5mt's are cheaper than 1 6mt(I keep a spare trans in the garage :) )

On the other hand, the 6mt is more for big power applications. It is the strongest mt that suby ever came out with and will be a nice fit in the SVX. I have heard that the shifting can get to you quickly and the top speed and highway rev's are not too practical. If you are looking to run the stage 3 S/C I would suggest the 6mt. If you are looking for a fun car to drive around with some kick and play at track also the 5mt is probobly your best bet. Either way the mt in the SVX is a joy for me and many of the other owners who have them.

Tom


Well put. :D

[Rotorflyr]

For those running the 5mt, how much would you say it changes the GT nature of the SVX in comparison to the auto.
Jesse can sit this one out as I have seen his car, and cool as it is, other changes he has made kill the GT aspect of it reguardless :D

[TomsSVX]

my suspension is bone stock, infact my struts are shot. My car still sticks to the road but seems to flop around. Anyway, I love the drivabilityof this car and it's comfort is unsurpassed by any other car I have driven. I think it is a sports car now since it does perform very well but still has it's gt atributes

Tom

[Earthworm]

other changes he has made kill the GT aspect of it reguardless :DIf you are referring to his suspension it can actually be quite comfortable when you adjust the Koni's to the softest setting. If the springs are too stiff for your liking there are definately alternatives.

As for cruising all day at high speeds, the WRX tranny will give you the lowest RPM's.

[mbtoloczko]

For those running the 5mt, how much would you say it changes the GT nature of the SVX in comparison to the auto.
Jesse can sit this one out as I have seen his car, and cool as it is, other changes he has made kill the GT aspect of it reguardless :D

If by GT aspect, you mean long road trips at or above the speed limit, I'd say that the 5MT does diminish the GT aspect a bit. The car still cruises great on the highway, but it just doesn't have quite as nice of a feel as with the AT when it comes to opening it up on long stretches of empty highway. The 5MT does allow the car to work better in heavier two-way highway traffic on where lots of passing on two lane roads is required.

My feeling is the the 5MT also makes the car feel a little less "finished". This is due entirely to the minor glitches associated with the 5MT swap which include occasional stalling when slowing to a stop, the large tolerances in the rear diff support freeplay which make the car tend to jerk back and forth at low speeds in 1st and 2nd gear, and some odd behavior with the cruise control that I haven't yet figured out. In defense of the 5MT, not everyone seems to have all of these glitches with their 5MT swap, and some of these glitches I will eventually sort out.

Bottomline though is that even with the minor glitches, the 5MT is easily worth it. Not having to worry about when the AT is going to die, the improvement in acceleration, and the control over the power delivery and gear selection easily make it worth it.

[Rotorflyr]

Dave,
Actually I was refering to the "long road trip" aspect of the car as Mychailo talked about. The "finished"/"cruiser" feel of the car. While Im sure the koni's are nice, the stock suspension is fine for me (as I don't race/auto-x) though I do plan on doing Mychailo Type-A Drop Springs at some point in the future. Just thinking about when the time comes, if I want to do a 5MT swap or do an 4.11/4.44 auto (waffling back and forth between manual/auto)

[McTaff]

If by GT aspect, you mean long road trips at or above the speed limit, I'd say that the 5MT does diminish the GT aspect a bit. The car still cruises great on the highway, but it just doesn't have quite as nice of a feel as with the AT when it comes to opening it up on long stretches of empty highway. The 5MT does allow the car to work better in heavier two-way highway traffic on where lots of passing on two lane roads is required.

My feeling is the the 5MT also makes the car feel a little less "finished". This is due entirely to the minor glitches associated with the 5MT swap which include occasional stalling when slowing to a stop, the large tolerances in the rear diff support freeplay which make the car tend to jerk back and forth at low speeds in 1st and 2nd gear, and some odd behavior with the cruise control that I haven't yet figured out. In defense of the 5MT, not everyone seems to have all of these glitches with their 5MT swap, and some of these glitches I will eventually sort out.

Bottomline though is that even with the minor glitches, the 5MT is easily worth it. Not having to worry about when the AT is going to die, the improvement in acceleration, and the control over the power delivery and gear selection easily make it worth it.

What kind of issues are you having with the cruise control?

Is there anything that can be done about the diff - would a diff rebuild help?

[mbtoloczko]

What kind of issues are you having with the cruise control?

Is there anything that can be done about the diff - would a diff rebuild help?

The cruise control is working perfectly except that its constantly making slight adjustments to the throttle position so as to make the car constantly accelerating slightly and then decelerating slightly. Its almost imperceptible, but its enough to drive me crazy. I think I may know the cause of it, but I haven't checked yet. Once I check this possible cause then I'll write about it.

The rear diff itself is ok. Its more that there is lots of freeplay in the rear subframe bushings that hold the rear diff to the chassis. Its just how Subaru made the SVX. The free play allows the diff to rotate some in the axis of the driveshaft when the throttle is pressed, and the bushings are fairly rubbery. Some people with older Imprezas and Legacys also have this problem. The solution is to remove the freeplay by inserting some firm rubber/plastic/urethane spacers into the subframe bushings. Impreza owners have had success with this, and Subafreak has also done this. So, this is just an additional step in the finishing-touches of a 5MT swap. It hasn't been done yet by many people though.

My feeling is that fixing these little glitches make the 5MT much more enjoyable for day-to-day commuting. I'd like to see the 5MT swap instructions updated to include fixes for these minor glitches when solutions are found.

[GreenMarine]

Just thought I would clear up something about where the 5MT actually tops out at.... Assuming that you have the "balls" to do this then the WRX 5MT swap will top out at around 168-174mph. How do I know? Because I saw 155mph about 2 years ago on stock wheels. I was sitting just above 6,000rpm's and the engine would have kept right on pulling.... But truthfully, I chickened out... If something had happened at that speed, I would have had almost no chance to walk away from it.... Honestly, I have no desire to ever go that fast again on any public road (Interstate Hwy). I truly scared myself that day.

The 2.5RS Tranny's probably only top out at around 140-145 or so. That is with the 4.11's or 4.44's...

The WRX Tranny provides the easiest swap with the best gearing (for me anyways) for crusing on the Highway. I still lost an average of about 2-3mpg after the 5MT swap though... Not sure if it is because the car is so much fun to drive now or if it is just that the engine is turning slightly higher RPM's...

[GreenMarine]

.............occasional stalling when slowing to a stop,

.....................some odd behavior with the cruise control that I haven't yet figured out.


I have had the Same Stalling problem in the past man.... Ya know what it has to do with??? I am interested in troubleshooting it when I get my car back...


My cruise works just as it did origionally.... Porter did all the wiring for my cruise... Possibly ya should talk to him about it... I'm sure that he can help ya out with any issues on the cruise control :)

[McTaff]

The 2.5RS Tranny's probably only top out at around 140-145 or so. That is with the 4.11's or 4.44's...

The WRX Tranny provides the easiest swap with the best gearing (for me anyways) for crusing on the Highway. I still lost an average of about 2-3mpg after the 5MT swap though... Not sure if it is because the car is so much fun to drive now or if it is just that the engine is turning slightly higher RPM's...

Ok, so the 4.11 / 4.44 swap is still an option for those with 5MT? Sorry if this is a dumb question, but I don't know about the final drives. I know that the WRX did have a 4.44 final - but you can still swap others in and out?

[SVXer95]

Ok, so the 4.11 / 4.44 swap is still an option for those with 5MT? Sorry if this is a dumb question, but I don't know about the final drives. I know that the WRX did have a 4.44 final - but you can still swap others in and out?
There is actually someone on Nasioc selling an STi ver 6 tranny with a 4.11 final drive..

USDM WRX has a 3.90 final drive.

[GreenMarine]

There is actually someone on Nasioc selling an STi ver 6 tranny with a 4.11 final drive..

USDM WRX has a 3.90 final drive.

Correct.... The USDM WRX Tranny has a 3.90 front diff... However it also has a 1.1:1 Step up in the center Diff which makes the Rear Diff a 3.545. Just so happens that that is the SVX's Final Drive :D:D:D That is why a USDM WRX Tranny is the absolute easiest swap to complete. Ya don't have to mess around with the rear diff :D

[Earthworm]

Did Reading 5 with the 5MT (1600 miles each way) and with 2 passengers. the 5MT never caused an issue. In fact if you want you can get away with 30MPH (or even a little less) in 5th gear so you really don't have to shift if you don't want to.

Cruise issue: I noticed the cruise issue with my 4EAT with the TC locked up. The cruise issue never changed after the 5MT was installed. Actually now I notice it even less.

Rear diff mount issue: I'm currently working on a solution to the rear diff mount issue.

Mileage: highway mileage - almost the same. city mileage - improved. This is once you get over how much more fun the car is to drive with the stick.

Stalling issue: resolved after changing knock sensors and cleaning the throttle body (could be IAC related as well).

[McTaff]

Please keep us posted on these, and we look forward to seeing these in the SVXpedia.

In particular, can we see a little more info on the final drive, and why you'd need to change them, and all that jazz. So far I've heard a lot of stuff that I don't understand. I know they can be changed, but what EXACTLY are we changing? The rear diff? Or what? What changes from 'box to 'box, and if I have a 'box with a different final, what do I need to change to make the drive equal, for both directions (making one bigger or the other smaller to match).

I can't find a lot here that covers these points in one big go. The reasoning is what I'm after, as well as the how-to. I'm not a total n00b, but it could be extremely confusing for non-mech heads. My problem is that I need to explain this to other people, and having a nice definitive source would make my task a lot easier.

[Earthworm]

Basically you have 3 things you have to keep matched up:

1. front diff built into the transmission
2. center diff built into the transmission
3. rear diff

eg. USDM WRX has 3.90 front diff, 1.1:1 center diff and 3.545 rear diff
3.90/1.1 = 3.545

All the other trannies have a 1:1 center diff so both the front and rear diffs must match.

What's normally done with the SVX rear diff is that it's opened up to put in the correct gearing to match the transmission. The LSD from the SVX rear diff is kept for functionality.