6 speed for higher HP questions

[SuperchargedWS6]

OK, I'm slowly collecting parts for my car build. At this rate I may be done in the next 2-3 years. I have a bunch of questions on drivetrain for a 650+whp setup.

If I do a 6 speed transmission with 300M output shaft, Billet end cap, and bellhousing brace will this hold up to hard street driving and launches, or should I be putting the money into a 5speed with billet transfer case? I'd prefer not to swap the car over, but I want to build this thing once and be done.

I guess the real question is what needs to be done to build a reliable 6 speed vs. a reliable 5 speed?

Is there an advantage to going with the MR gears at this HP?

I want to do an SCE front/center/rear diff setup, as I want this car to handle the power the best it can.

Is there much difference between the Quaife front diff and the SCE prepped OBX front diff?

Are there any quaife type rear diffs out there, or is only the clutch type KAAZ that is available?

I see everyone recommends the RPS 6 puck clutch. I'm worried about driveability/durability with a puck type clutch. This will be mostly a street car. Are there any reliable, not noisy, good engagement multi disk clutches out there?

I have/am building this slowly, so I am prepared to put the money into it to get a reliable, fun to drive car.

Thanks!

[anyonebutme]

Get the Quaife front.

Mitsu actually made a ATB rear diff, with a VCU inside the center. Was an option for the MR cars. Break out your wallet, it's like $2800.

[futurevr4man]

A built 6 speed is reliable, but the transfer case gears will still strip. There is no fix for it currently. I have 2 spare transfer cases ready and waiting for when mine decides it's had enough.

If you get a built 5 speed and all the billet stuff for the transfer case... that's probably the strongest setup you can get. I don't know which would be the cheaper route to go. 6 speed transfer cases are cheap if you keep your eye open and are ready to buy at a moments notice.

Make sure you get shift forks on your list. They are easy to grenade.

[anyonebutme]

be forewarned, the billet shift forks are a wear item.

[GrabberOrange]

be forewarned, the billet shift forks are a wear item.

Forgive my ignorance, does this imply that the factory ones are not a wear item compared to the billet ones?

[anyonebutme]

Factory ones are not, they just can break if abused and the roll pins can back out.

The billet aluminum ones had a wearing issue where they were too soft or something and wore out on a few cars within 20k miles, unsure if they were fixed or whatever. Elite racing trans also makes aftermarket forks out of steel.

[sergechronos]

OK, I'm slowly collecting parts for my car build. At this rate I may be done in the next 2-3 years. I have a bunch of questions on drivetrain for a 650+whp setup.

If I do a 6 speed transmission with 300M output shaft, Billet end cap, and bellhousing brace will this hold up to hard street driving and launches, or should I be putting the money into a 5speed with billet transfer case? I'd prefer not to swap the car over, but I want to build this thing once and be done.

I guess the real question is what needs to be done to build a reliable 6 speed vs. a reliable 5 speed?

Is there an advantage to going with the MR gears at this HP?

I want to do an SCE front/center/rear diff setup, as I want this car to handle the power the best it can.

Is there much difference between the Quaife front diff and the SCE prepped OBX front diff?

Are there any quaife type rear diffs out there, or is only the clutch type KAAZ that is available?

I see everyone recommends the RPS 6 puck clutch. I'm worried about driveability/durability with a puck type clutch. This will be mostly a street car. Are there any reliable, not noisy, good engagement multi disk clutches out there?

I have/am building this slowly, so I am prepared to put the money into it to get a reliable, fun to drive car.

Thanks!

Reliable 5 speed: Billet (or the discontinued SS) transfer case housings, 300M output shaft, Flexor input spool. If you want to go overboard, you could even brace the bellhousing, but the number of people who have busted it are incredibly small.

Reliable 6 speed: 300m output shaft, Flexor input spool, billet end case, bell housing brace, extra t-cases as back up.

Whether or not MR gears are worth it is going to depend entirely on how you plan on using the car. If you're chasing time slips at the drag strip, you need to do math to see what's closer. If you're doing road course or autocross, you probably are going to be better suited just getting a feel for each to see which you prefer.

The Quaife front is lightyears ahead of the OBX in terms of quality (and warranty covers damage from racing even.) If you're willing to shell out 2k+ for the SCE center, spend the extra money for the Quaife front vs the OBX IMO. As ABM pointed out, there was a "hybrid" rear diff made for the car, but pricing is old so likely isn't accurate anymore (think they're over $3200 now.)

That said, with diffs front and rear, you will have some pretty serious binding issues with low speed turning. There's little benefit to upgrading the rear diff though unless you are tracking the car, the stock rear diff works fine and can more than support the level of power you're talking about. Even the front and center aren't necessary, you'd probably notice a bigger bang for your buck getting a quality set of Ohlins or JRZ coil overs versus $3k+ in diffs (to say nothing of if you need to pay someone to rebuild the trans with them and set preloads properly which adds at least another grand.)

Multidisk and not noisy aren't going to come together. The closest you'd be able to do would be to take an Evo VIII/IX 8 leg clutch, have the ring gear machined off and a 3S ring gear put on in it's place (obviously big bucks.) The older Exedy 6 leg clutches weren't too terrible about noise, but power holding was weaker than we get out of single disc set ups. There's not much call for a twin disk on a street car though, and few have taken the plunge on this platform to a multidisk set up for street usage.

The 5 speed is the cheaper and stronger option of the two, but everyone's opinion will vary on which is more enjoyable to drive. There's not many who have done 5 speed, 6 speed and 6 speed MR to offer feedback for a street car.

[Chris@Rvengeperformance]

Things tend to build over the years because one guy breaks something and suddenly you gotta have the latest strength mod. With a 650 wheel car, if you drive like a sane person with a little thought into the level of abuse you do with your left leg a six speed setup will survive for years with just a bellhousing brace. Run shockproof heavy in the t-case and don't DUMP the clutch and it will hold.

The six speed doesn't break output shafts and the 300m spool from mark williams is about $300 direct from them, but if your stock spool is okay its fine.

I have driven both the 5 speed and 6 speed MR/JDM on this car. It had a USDM 6 speed when I first got it. I strongly prefer the 6 speed for driving the car in real life. In a high power 1/4 at a time type of car the 5 is probably best, but that's not where my car lives most of the time.

FYI, the upgraded center diffs will try to break the t-case a lot more because it sends more power to the rear. I've even seen a high power 5 speed car with an all billet t-case break the driveshaft yoke on a carbon fiber shaft from a launch with the SCE center diff. You'll chase "weak links" eternally if you are an abusive driver no matter what setup you have.

So far I love my spec 4+, very drivable.

Edit: I wanted to point out, if I had a new car starting over with 9bs and all that, that came with a 5 speed, the first thing I'd do is go JDM 6 speed. It makes more difference than a mild turbo upgrade for a pump gas car IMO. Maybe not on a time slip, but for the fun factor.

[familyMAN]

Auto. Welded diff. $55 shift kit. $100 main clutches. =reliable 650awhp setup. Sell manual trans=profit.

Carry on. :D

[SuperchargedWS6]

Something tells me not quite that simple. Thanks for all the responses and information. They bring up a few more questions but I'll ask them in this thread when I'm not on my phone.

[familyMAN]

If you are responding to auto, yes it is that simple. I've done it and beat on my car harder than most.

It's not for everyone though and I recognize that not everyone wants to get from 0-120 quicker than a manual at the expense of 120+. Not everyone wants a flawless launch every time either or logged 0-60 times of 2.65 sec on the street with only 235F/275R street tires;)

Edit: or spend only $350 on the entire trans with tcase for an auto awd 6g72, plus $100 max to mod the driveshaft.

[2fnloud]

There is a upgrade in testing to help with the strength of the 6sp T-case PermanentGrin is putting it though the paces right now.