901 or 915

[Racerbvd]

Make sure you get a tranny cooler with what ever one you go with..
We are building a 901 to go with my 300HP twin Plug 3.0 for my GT clone, course I don't plan on doing any burn out, as tires are hard to fine for 9X15s... BTW, my gearbox will top out at 125

[larrym]

i just acquired a 3.2 engine with rebilt 915 -

and i have 2 spare 901 sideshifters -

so my new dilemma is whether to stick with the 901 and 3.2 setup for which i'd already bought the clutch conversion pak ($1050 from GPR), or undertake the hassles and new expense of the 915 conversion

any body have a BTDT price sheet on that 915 conversion cost?

or, maybe just leave well enuf alone and keep running the 2.7 that only has 5K since rebilt ??

recently retired with toooo much time on my hands

i'll keep watching the thread for opinions and advice

[Racerbvd]

Originally Posted by larrym

i just acquired a 3.2 engine with rebilt 915 -

and i have 2 spare 901 sideshifters -

so my new dilemma is whether to stick with the 901 and 3.2 setup for which i'd already bought the clutch conversion pak ($1050 from GPR), or undertake the hassles and new expense of the 915 conversion

any body have a BTDT price sheet on that 915 conversion cost?

or, maybe just leave well enuf alone and keep running the 2.7 that only has 5K since rebilt ??

recently retired with toooo much time on my hands

i'll keep watching the thread for opinions and advice

I had the sheet, but can't find it, the parts to convert the 915 run around $2,500, then in install, well, pieces have to be made to fit, and the box can be built, unbuilt, rebuilt a few times to get everything working just right.. I would just go with what you have, and enjoy the teener. This way you can hunt up deals from people who started & gave up..

[SirAndy]

Rumor has it McMark from Original Customs is working on a cable shifter setup for the 901 and 915 to be used in a 914.

My current plan is to run my 901 until it explodes. In the meantime, i'll add a LSD to my 915 and get it ready for McMark's cable shifter setup.

This should be fun ...

[Schwarzeritter]

On the 901 and 915 you will need to select new gear ratios to achieve the top speed you desire. Beyond that you have a lot of work cut out to achieve 200mph and have things stable. I have never attempted to max out a 901 gear box, I always have equipped them with new cogs and a oil cooler.

With modifed cogs and no oil cooler for the gear box I have had 300TQ on a 915 however the client was not the burn out king. I have seen some very high capacity large displacement forced induction and NA motors with 915's, but all the gear boxs were modifed and featuring oil coolers with pumps and a external resivor.

The G50 is good, but it's not invincible. Still I would up grade it and cooler.
Have fun flying fast!

[Matt Monson]

Velios used to make a 914 side shift conversion for the 930 4 spd. If someone wanted a bulletproof 200mph Bonneville sort of gearbox that would be a good way to go...

[mcfoo]

Originally Posted by SirAndy

Rumor has it McMark from Original Customs is working on a cable shifter setup for the 901 and 915 to be used in a 914.

My current plan is to run my 901 until it explodes. In the meantime, i'll add a LSD to my 915 and get it ready for McMark's cable shifter setup.

This should be fun ...

Whoever or whatever McMark is ,I hope his system is far better then the Patrick Mortporsports version.
The shifter in the Patrick version is like a soup spoon standing vertically in a bowl of soup.
No detents, no guides , no nothing.
If you are looking to select a wrong gear so you can blow up your motor, this is the shifting system for you.

[SirAndy]

Originally Posted by mcfoo

Whoever or whatever McMark is ,I hope his system is far better then the Patrick Mortporsports version.

That's why i included "McMark from Original Customs". Original Customs being the shop name and Mark being the owner.
Original Customs

[emenot]

Not to discourage your project, first think about stopping first, second if you have a frontal mishap your front bumper will be in direct contact with the rear bumper. Now if you do decide to go with a G50 tranny, you are looking at maybe $10K cost to get it into the car... I would suggest do a z28 sbc 302 rebuld the 901 for $2000 and have a **** load of fun!

[Matt Monson]

Why did you bump a 2 year old discussion? Leave the old ones in the coffin unless the op is looking for new guidance..

[johnnydee]

A couple of things. Do NOT under any circumstances go to a 915. A waste of money and time. Although only a four speed, you definitely want to go with a 930 gearbox. Flip the ring gear over and everything bolts right up. There are several very competent players out there that can do this relatively inexpensive conversion for you and you are good to go. It is bulletproof and shifts like a dream.

Secondly, consider very strongly the possibility of putting a Subie WRX STi motor in that thing. Light and powerfull as hell. I am convinced that if the "old man" had had good turbo technology available to him in the 60s they would have built a turbo 914 then. We have done one and it is amazing. 360 ft lbs of torque and 360 hp. All you will ever need. And that is in stock trim (although the experts at Vermont Sports Car reco'd changing pistons and rods for longevity which we did.) Car runs right along with the GT3s.

p.s. Don't forget to do a half shaft conversion on the car. Late long hood 911 stub axles (108mm) with 930 CV joints. Shafts best if they are 300M. Sway a way makes the shaf. Mckenzies Peformance in Ahaheim can put the package together for you. Get the "prepped" CV joint while you are at it. Not that much more $.

[Dave at Pelican Parts]

First, please note that this is an old discussion that was resurrected by a single-post user. Not sure why.

Second, the 915 conversion can work just fine. I've driven one that worked pretty well, at least in the lower 3 gears. The WEVO setup would probably have worked even better; those guys know how to make stuff that just plain works. You do have to fab up the rear shift rod if you use their setup, though.

Third, you have to machine the inside of the diff housing to flip the ring gear on a 930 box. Not a lot, happily, and there are places that know how to do it--but it is not a simple bolt-up affair. There's also the minor issue of the box not bolting to the chassis. You could run the 930 box upside-down, but you have to do some plumbing to make sure the oil gets where you want it to go and you may need to cut out the trunk floor to make room. Again, not a bolt-on conversion.

Alternatives exist.

There are people who run G50s upside down. An even more complex conversion; you need the short-bellhousing version, plus the hassles you have of running the 930 version upside-down. But it is quite strong...

The Boxster trans is another possibility. It's already set up for the mid-engine location, and it is reasonably strong. I think you still have to cut up the trunk floor, because it is significantly larger than the original 901-based box. But it has been done; there are even a couple of posts on this BBS showing one such setup. (I think one was titled "the ultimate solution for vague shifting" or something like that.)

--DD

[johnnydee]

Hi Dave. We have done each of the alternatives that you discuss. Have a PCA Club Racer 2.0L turbo with upside down G50 box, 930 with swapped ring gear, and WEVO 915 conversion on the guts of 915 using a Velios kit. Before some one bad mouths the Velios conversion (many have beaten me to that) be aware that the WEVO internals were all done by one of the top shops in the country (hint Pac NW location and highly accomplished race team managers). The box was blueprinted to the max. Despite all this, the best shifting, least expensive to convert and most stout box remains the 930. Lots of tears and huge money spent finding this out over the last decade.

[johnnydee]

p.s. Cable shifted on each. See Jim Cunningham at cableshift.com for the best out there.

[Dave at Pelican Parts]

WEVO and Vellios are two different outfits. I'm not sure if you're saying you had both setups at different times, or different parts from each at once.

Vellios made replica 916 kits, which I think turned the 915 gearbox into a side-shifter like the 73+ 914 gearbox. Quality evidently varied a lot from piece to piece.

WEVO not only does reinforcements and modifications for the inside of the 915 box, but they also do a nosecone that mounts a 915 in a 914 and has a gear selector sticking out of it for you to hook to a new fabricated linkage. I have not used this setup, but I am pretty confident that it will work well--because the WEVO guys are really very good.

I have driven a 914/3.6 with a 915 box and a home-brew shift linkage. It worked reasonably well--at least as good as the "well-loved" stock 914 side-shifter that I was also driving that day. (The latter was my own car.) It was not a Miata shifter, but I don't think you'll get that in anything but a Miata.

All of the setups can be made to work with some level of effort. They will all work reasonably well if you put the work in on them, at least for a while. For applications with lots of torque, though, the 930 gearbox does seem to be the strongest reasonable option.

The Boxster trans seems like a cool setup, but again the installation is non-trivial. I'm also not convinced about how much torque it can live up to in the long run.


The original goal of a 200 MPH 914 is an interesting thought experiment, but to me is a total non-starter. Especially a streetable 914. You need a lot of down-force to keep the car from flying at those speeds, and that means drag. And even a little drag becomes a really huge amount at 200 MPH, so the power requirements would be pretty astonishing.

--DD

[Matt Monson]

Dave,
How does three different teams running 3.8l dfi Carrera engines for the 24 Hours of Daytona against the Cayman/Boxster gearbox? That's what was done this year. There was a blown cv (typical at Daytona) and a blown TO bearing (Ryan Eversley drove the car for almost the last 3 hours with no clutch manually rev matching ever shift without the help of synchros).

I think Kent, at Precision who has done both a Suby swap in a 914 and one into a Boxster, is going to become the go to guy when he releases his EJ engine to 986/987 gearbox adapter plate and flywheel.

The G86&G87 gearbox solution for the 914 is going to become the standard against which all others are measured. I just wish Kent's kit mated a Mezger crankcase instead of the EJ. But maybe he can be talked into making another version of it...

[Nostril Cheese]

Guy says turbo 3.6 in a 914 and then says he is on a budget for the gearbox.. ok.

[Matt Monson]

Guy says turbo 3.6 in a 914 and then says he is on a budget for the gearbox.. ok.

That's the story of my business. Guy starts the conversation bragging about his $20-25k engine with infinity hp and wants to know how to build gearbox "X" to take that power.

When he hears it is going to be another $10-20k to do it right 9 guys out of 10 respond that they can blow up and buy half a dozen used gearboxes on Pelican/RL for the same price. And that is frequently what they do.

Then after two or three years you start seeing threads about ,"why do I keep blowing up 3rd gear on my gearbox?" and they tell the tale of their junkyard dog gearbox saga...

[Mark Henry]

Just looking at how the boxes are built (in my case rebuilt) I say 901 or 930.
I wouldn't waste my time and money on the other boxes.

[johnnydee]

Just to clarify. We had all Wevo internals. The only Velios stuff left was the side shift housing, selector fork rods and the tail housing. Also, if anybody wants that Velios conversion 915 gearbox with trick gears, make me an offer. I would take a look inside before running it. Just in case. If you read my comments, you see how I feel. Seems that there are enough guys out there that still want the 915. The one change that I would make is to cable shift it despite the fact that it has side shifter setup for rod. Despite having solid motor mounts in the car, the torque of the motor creates enough rotation that the shift rod moves. This creates problems because the gates are very close so any rotation of the shift rod causes the shifter to move just slightly enough that you are between gates. The gears alone are worth $3K, the LSD (factory with 80%) is worth $1000+ used, the Velios tail housing and shift rods are no longer made. On that note, I have another Velios tail housing, side shifter, and shift rods if anybody wants them.