Rebuilding a Spec B 6-speed - what non-OEM parts (if any)?

[Pleides]

I'm gonna be having my Spec B transmission rebuilt here shortly (yeah, @boxkitathe one I bought off you like 6 months ago... anyhoo).

The car is at 320 WHP on a VF52. I have no plans to make the car faster. I never launch the car. I don't plan to track the car. The car is a daily driver. At most, it gets a spirited drive every so often. The plan, originally, was to just rebuild it with all OEM stuff, but the transmission rebuilder can do whatever gears, synchros, etc. that I'd like. 

Any upgrades worth doing on a car that will have a stock clutch, perhaps just for the "feel" of the transmission? Not looking to spend big money to make an already durable transmission more durable, but if any internals would make the transmission better for a daily driver, I'm open to it.

[KZJonny]

Taller 6th gear?

[Pleides]

Just now, KZJonny said:

Taller 6th gear?

It's gonna have the gear ratios gifted to the Spec B that are already in the transmission, assuming the gears don't need replacement. The whole reason I opted for that transmission was for the gearing!

[KZJonny]

Sure. I would also probably go with a Spec B trans for the same reasons.

Don’t need a DCCD for my purposes.

But for cruising at 120-130km/h, why not get the rpms a little lower even than what you normally get with that trans?

Driving in my friends A4, that thing drop to something *really* stupid in 7th gear like 1700rpm. I mean, I can romp all over his car with my GT, but he kills it on fuel efficiency.

We’ve got enough torque with the 2.5L to get highway rpms down further than stock Spec B 6th, so why not? You’ve got 5 other gears for ‘fun’… (well, $$$…

Just sayin. It’s what I would do if I was in your shoes.

[KZJonny]

I don’t *know* this, but I assume the Spec B 6MT ratios were designed for the JDM 2.0L, and we just got the same ones, despite having a bigger engine with more torque to take advantage of.

If JDM Spec Bs don’t have the same ratios, my bad.

[Pleides]

10 minutes ago, KZJonny said:

I don’t *know* this, but I assume the Spec B 6MT ratios were designed for the JDM 2.0L, and we just got the same ones, despite having a bigger engine with more torque to take advantage of.

If JDM Spec Bs don’t have the same ratios, my bad.

USDM Spec B gear ratios are super, super long. You won't hit 3K RPM on the highway until 80 MPH. Highway speed limits everywhere in the Portland metro max out at 55 until you get to Wilsonville, where it's 65.

Edited April 29 by Pleides

[KZJonny]

Totally fair. Use case scenario.

Highway limits around me are like 120km/h which mean the fast lane is often doing 130km/h. Too late/I'm too tired to translate that into freedom units, but my 5MT is doing like 3300 on the highway. I would like that to be closer to 2200 maybe?

So, when I get a 6MT I would consider going even taller on 6th, but again, not the same application. I also miss the F out of living in the Portland area, what a great place.

I'll stop now. It was only what *I* would do with a 6MT.

[boxkita]

the jdm forester sti 6mt was, theoretically, good for 200mph if you could rev to 8000rpm.

320hp driving as you stated, I'd clean it up, replace the bushings and any wear parts with least resistance parts. 

@Pleides I would opt for the spec b gearing but make 6th gear as over drive as I could, mpg is mpg. Even on the 86, I skip shift to 6th gear and cruise as soon as I can. Unless Im being irresponsible, then 3rd gear only.

Get hardened gears? Micro-finish any parts that add drag?  Stretch goal - powder finish the outside sti pink

[Pleides]

I was gonna

On 4/29/2024 at 8:52 AM, boxkita said:

the jdm forester sti 6mt was, theoretically, good for 200mph if you could rev to 8000rpm.

320hp driving as you stated, I'd clean it up, replace the bushings and any wear parts with least resistance parts. 

@Pleides I would opt for the spec b gearing but make 6th gear as over drive as I could, mpg is mpg. Even on the 86, I skip shift to 6th gear and cruise as soon as I can. Unless Im being irresponsible, then 3rd gear only.

Get hardened gears? Micro-finish any parts that add drag?  Stretch goal - powder finish the outside sti pink

I'm definitely keeping the gearset if it's in good shape. If it isn't, definitely getting new Spec B gears to keep the ratios. As for cool factor mods, the pink might make it harder to ward off the Subaru stereotypes about their owners' sexual preferences...

[KZJonny]

Where are you getting these theoretical custom gears made up anyhow, and do you have a feeling about price?

This whole thing has me thinking about the 5th gear in my 5MT. I use it exclusively for highway cruising, as I am sure most do, and there is no reason not to make it taller than it is currently.

I mean it's cool that I am fully spooled and ready to race someone in 5th, but.... cool story bro? I would be very happy to change fifth out for something that would drop like a thousand RPM at 120 km/h for example. I really don't care if I need to rev just a little higher into 4th to get there.

If the cost of a custom 5th gearset is not insane, it would be a thing to think about. Manual transmissions are easy enough to work on, and there is some preventative stuff in there like new differential bearings that could benefit from pre-emptive replacement....

 

This would be a problem for another day, but something worth considering. I am sure there is somewhere around me that does this, but I couldn't name a place than does miuch work with specifically Subaru/Nissan transmissions for example, and surely it would be cheap enough to ship a couple of gears.