Fitment question: 915 box into 930 body

[zztot]

What is needed to install a 915 gearbox into a 930.... Have had guesses but looking for solid information.
Thanks

[HarryD]

Don't know but it was no accident Porsche decided to put a different box in there.

Is your 5 speed 915 stout enough for the turbo?

[Tippy]

Why?

[zztot]

Begs the question ...Just need the answer ...comprende'

[RarlyL8]

Putting a 915 in a stock 930 was considered an upgrade in the 80's and is featured in Bruce Anderson's Performance Handbook. I would not however recommend this if the engine is modified.

The 915 is an inch shorter than the 930 4spd '78-'88, same size '76/7.
Both tranny mount and engine mount must be modified to fit.

[Flat6pac]

The torque tube on the turbo in the mid 80s was designed and built for both transmissions. With the intro of the turbo body Carrera the need was to have the body ready to accept whichever engine and trans was ordered.
Bruce

[zztot]

Thanks
Last two posts were precisely what I needed.
Terry

[jess p]

RarlyL8

Why was it. Considered an upgrade?

[RarlyL8]

Upgrade isn't a word I would use but that's the buzz word of choice for any modification, good or bad.
The late 915 has 5 spds and all 5 are lower gears than the horrifically long geared 930 4spd. Adding a 915 to a stock 930 pushed the power band, which begins at 4200rpm, into a usable speed range as 1st gear redline now comes by 50mph. The car would feel like you added 100HP with much improved driveability.

[skrufy]

zztot-

I have a 915 box in my '77 930. It was done over 25 years ago by a racer/engine builder buddy on mine in Pheonix. I have owned the 930 since, and it works very well and makes the 930 much more drivable vs the stock 930 box, as noted by RarlyL8.

The 915 picked for this 930 was a bit of a rarity because of it's gear ratios vs a stock 911 915 box. I am no expert on the gear ratios involved, but this box has what might be similar to 'airport gears', at least for 1-2-3, so all you gearbox gurus please chime in. My box came out of a '76 912E- the ratios were lower to give the 4 Banger a little more Ummph! off the line. The input shaft did have to be modified/changed from the 4 Banger box to fit, something you wouldn't have to do if you used a stock 911 915 gearbox. My friend said he had to really hunt thru his factory manuals and sources to find out info on the 912Ebox- he had 3 repair garages in downtown PHX at the time I bought the 930 from him. Of course, he keeps asking me just how long this "extended warranty" program lasts on that 930.......

The only other mods that you would have to do my experience of nearly -Gasp! 40 years of driving/turning wrenches on my 911s is to:

A) if you use the early 915 tranny mount bar which came with the 912E box and other early 911s, you can't change the tranny mounts- they are molded into the bar. I recommend getting the later tranny mounting bar- which of course are the same as the engine mounts- ie, replaceable.

B) for my '77, the 915 box is LONGER than the stock 930 box, which means you will have to re-drill the 4 tranny mount bar holes aft towards to engine by about an inch.
Don't hold me to that distance, it's been a while since I did that.... measure your own. If you don't do this, the 2 forward mounting bolts will never line up.........

C) The 930 torsion bar tube is larger than a stock 911. Adding the 915 box results in
metal-to-metal contact- very annoying: adds road/gearbox noise, vibration, etc- besides
the long term possibility of wearing a hole thru the gear box housing- not good. Of course, to fix this, I had to pull the engine again- will all those associated joys...... How
to fix? Your basic tool box 16oz. ball peen hammer works just fine to dent in those areas of contact - all you would be doing is widening the areas- left and right of center- of the area on the tube already forged by the factory- no big deal to do, just remember to clean and seal the area to prevent rusting. After cutting away areas with a utility knife where the factory undercoating had been lifted by the hammer blows, I used some spray undercoating, then covered with some grey primer paint to somewhat match the color of the undercoating- my 930 is Grand Prix White.......

Horsepower? unless you have some monster engine on steroids- no worry IMHO. My 930 has SC cams, intakes ported from stock 32mm out to 36mm, Euro exhaust and waste gate, no smog crapola at all, cockpit accessable variable boost from 0.75-1.25bar (or about 11 to 18 inches of boost), and since the 76-77s had no intercoolers, I have alcohol/water injection as well to cool the intake air while on boost. Out here in the Arizona heat, the stock intercoolers don't work all that well anyway. My 930 comes on boost at about 2500rpm if I punch it......

Now the trick set up IMHO would be to put a G50 in your 930, and really really trick set up would be to put in the later 6 speed G50 out of a 993...... if you want to send me a PM, I have a cost estimate, and parts needed, from Patrick Motorsports in PHX on such a conversion......

All in all, my 930/915 gives me a fairly mild street rocketship- more than I need really, as I used to fly F-16s in a former life, and most everything is a let down from there

Hope this helps a bit......

Tim

[zztot]

Tim:
Sounds like your experience is good (and fun)
Had not mentioned it because did not want to open a debate as to the logic but am planning to install 3.6..... HAve G50 (5 speed) so send me that estimate if you dont mind. (zztot at charter dot net...Budget may kill this deal yet.
Thanks
Terry

[Exclusive MW]

We can do it! Budget be damned...
:-)

[Tippy]

I want to go the other direction, the reason for the why. I want to put a 930 box removing G50.

1. 30 lbs lighter
2. Way stronger
3. Longer roll out for big turbo in 1st gear. 1st gear is over before boost even gets to 0.3 bar with a 1.0 bar spring.

[zztot]

Now that's not a self serving comment ! Or should I say "how's that working for you".
As my mother used to say....get back to work !

[Tippy]

Doesn't the G50/52 and 930 have equivalent 1st gears ratios overall? Meaning 1st gear ratio multiplied by diff gear ratio.

[zztot]

Tippy
My smart a__ commment was to Bob at Exclusive....
Have no clue about yours....someone knowledgable would have to answer that...
I am still at wanting to use 915 but figured I would at least check out estimate from Tim...
I wasnt to hopped up about cutting up car to install a G50......but having 5 speed and something that fit into the body because it was going with 3.6 was the idea.
Thanks

[skrufy]

Terry- zztot-

Just sent you the G50 quote from Patrick Motorsports in PHX. Note the estimate is 3 years old now, so prices may have changed a bit......

Tim