from 911 gearbox to 915?

Gilbert '71 T · Post by **Gilbert '71 T** » Fri Feb 03, 2006 11:04 am

Hi all,

Bit pie in the sky at the moment but I'm considering upgading to 915 gearbox anyone know what's involved for the swap and rough costs of parts. My 911 box has always been a quite noisy, but now it's becomming annoying.

For the 915 swap I know the shifter needs relpacing for starters, and there may be some hammering required for clearance

Anything at the pedal end?
Shift rod?
Clutch?
Driveshafts? I know later 915's have 6 bolt flanges rather than the early ones with 4 bolts with and 2 locating pins, early 915 would be preffered.
Speedo?

Or should I avoid all the hassles and go for a rebuilt 911 box/rebuild mine and forget about any 1st gear drag starts with my 3.0, as this engine is beyond the torque limits of the 911 box? but I really like the 901 shift pattern

Any advice chaps?

Muchos gratis

Barry · Post by **Barry** » Fri Feb 03, 2006 11:34 am

Hi Darren, my car had a 911 box when it arrived (always wondered if it started as a sporto). The driveshafts were right on the limit (not really enough end-float) and were then fine with the 915, which is a fraction narrower between flanges. If you reach under the car when its on the ground, and see what the endfloat is like (i.e. the movement of the shaft left to right within the C.V.'s) I started with about 3mm (911) which went to a more sensible 8mm or so afterwards. I would guess that if you've got 10-15mm now you might need driveshafts?

As for the rest: poss clutch cable needed (I made an adaptor for mine

).

Shift linkage should be fine but the lever housing is different as the reverse lockout is in a different place: can be modified though at a push (easier to replace).

Speedo drive is the same.

Clutch release bearing and centre plates are different I think, but the good news is that the 915 clutch sets are a lot cheaper than a 901/911 (volume of sales I suppose).

If you go for a 915, make sure it comes with clutch release lever and foward engine/box mounting bar (with mounts) as they are different to yours. If your box is O.K. expect to get around £350-£550 for it. Good 915 seem to start around £750 (unknown) upto £1400 ish for freshly rebuilt.

HTH

Barry · Post by **Barry** » Fri Feb 03, 2006 11:35 am

Forgot to say, the earlier 915 have mechanical speedo drive (to match yours), later ones have a speed sensor for electronic speedo.

Derek · Post by **Derek** » Fri Feb 03, 2006 11:36 am

I'm looking at this at the moment.
So far I think I need to do the following.

915 shifter
915 shift rod
widen the tunnel slightly near the front.
I'm looking for a later box so will need drive shafts and electronic speedo.
I'm also changing to a Sachs power clutch.

Anybody have a late box with a 8.31 final drive ratio.

Also any other info on the swap would be good.

Barry · Post by **Barry** » Fri Feb 03, 2006 11:38 am

Is the tunnel different then, Derek? Also didn't know about the shift rod: I used the same one

Derek · Post by **Derek** » Fri Feb 03, 2006 11:46 am

Barry

I'm only going by what I've read, I haven't done the swap yet.

jtparr · Post by **jtparr** » Fri Feb 03, 2006 11:50 am

there's a 915 box on ebay at the moment

http://cgi.ebay.co.uk/porsche-911-gearb ... dZViewItem

jp

Derek · Post by **Derek** » Fri Feb 03, 2006 11:58 am

I'm sure James is on DDK sometimes.

Gilbert '71 T · Post by **Gilbert '71 T** » Fri Feb 03, 2006 4:27 pm

Derek wrote:widen the tunnel slightly near the front.

This is what I have heard too Derek.

Thanks for the input Barry, I'll check that endfloat see what it's like

so probably the best way to go if i decide to do this would be....

915 shifter
Early 915 gearbox w/mounting + lever (mech speedo drive + 4 bolt driveshaft flanges)
clutch setup: 72> cable/pressure plate/disc
big hammer for the seat pans/tunnel area
plus some other sundries no doubt....

Thanks again

davidppp · Post by **davidppp** » Fri Feb 03, 2006 5:06 pm

Hello, Darren.

The 911 box will break one day if you use 1st much..and the ball bearings in the int palte will also suffer with a high torque motor..

Much more seriously,there is also a well-documented and very dangerous fault with the differntial assembly flying apart and ripping the box open on all 901/911 boxes made between 1968 and 1972 approx.

This is a potential killer..so must be done if you intend to keep the 911.

The latter can be fixed with a factory kit of just a handful of parts ..at a price natch!

I do not think it is always necessary to tunnel-bash..and the 901/911 shift mech will work with a little tweaking ( early 915 cars used it anyway).

In summary, it is cheaper to swop than rebuild the 911, but some folk prefer the 911 for its hsift pattern and lighter feel..

I would take your old 911 for spares if you do swop..I have a mag case 915 to swop..or sell.

Kind regards
Davidl..

Alan @ CanfordClassics · Fri Feb 03, 2006 5:08 pm

I fitted a late 915 out of 3.2 in my 71 car. I used this one as it also has a oil cooler. Most of the changes have been mentioned. The shift rod is slightly different in that the 915 one is 15mm shorter. The 915 is also slightly larger around the nose cone and therefore you may need some slight hammering between the seat bases to take this into account.

I get to drive my car for the first time tomorrow !!! Can't wait

Alan.UK

Gilbert '71 T · Post by **Gilbert '71 T** » Fri Feb 03, 2006 6:02 pm

David I hear you on the 911 box weak 1st gear, I'm well aware of the simplified differential issue as well, exactly why i'm considering the 915, must be an early one though for the mech speedo, drive shaft bolts and the 7:31 ring & pinion, which would at least give me similar gearing to the 911.

So I guess in essence I could get a decent used early 915 and all the associated bits n bobs for under the price of a rebuilt 911 box/911 box rebuild, looks like it's a way to go

Alan, that car is going to be something

enjoy the drive tomorrow

davidppp · Post by **davidppp** » Fri Feb 03, 2006 6:33 pm

Hello Darren

What is the condition of yur box?

I might be intereted to do a swop..I have an early mag case 915 here..

Kind regards
david

Gilbert '71 T · Post by **Gilbert '71 T** » Fri Feb 03, 2006 6:44 pm

I'll pm you david

Dyno Soar · Post by **Dyno Soar** » Fri Feb 03, 2006 8:25 pm

Its really funny ain't it... we were at the ACE and I was trying to convince Darren to get a 915 rather then replace his worn 911box with another which he was sure to destroy!

He seemed dead set on the 911 box, that is until I was leaving the ACE in my 911 and slipped it in first and gave it some welly, had a nice little slide in the carpark. Later talking to Darren he said... ' I wanna be able to do that in my car with blowing up my box.'

So Yay!! Good for you Darren, get a 915 Geezer! I am glad you have decided to go for the late box.