Rebuild 915 or replace with G50?

[HardDrive]

My gear box is not a disaster, but the 1st syncro is on the way out, and I can imagine a clutch in my future. Rather than sinking $$$ into a rebuild and clutch for the 915, would it be a better long term strategy to pick up a G50? I realize there are additional costs involved.

If the answer is yes, are there models years to avoid? As with all things porsche, typically that later the better, correct?

Can Carrera owner who has also had and SC give me the lowdown?

Oh yeah, its an 82 SC.

[frencjas]

I am happy with my 77 915 tranny, even with the 3.6 varioram behind it! 915 is lighter, and plenty strong IMO.

[dd74]

Yes, additional cost, weight, and from what I hear, a general PITA to accomplish. Rebuild the 915 - maybe with some gearing better matched to your engine's power curve. All-in-all, it's a great gearbox.

[klaucke]

The G-50 requires torsion tube modification. And a new clutch pedal assembly for the hydraulic clutch, plus the line for that, etc, as well as a new shifter assembly. All in all, basically more trouble than I think it is worth. A lot of members are quite happy with the 915 box when it is functioning well. In fact, some prefer it (just as some prefer the 901) over a G-50. When in proper tune, the 915 clutch should actually be lighter, and the trannies can be plenty smooth even if they are slightly idiosyncratic. I think the 915 is one of the things I enjoy about driving my Porsche, part of what makes the car unique and fun.

[stuartj]

Nothing wrong with a 915 in good order. A delight to use. A most unfairly maligned gbox IMHO.

[Sumotang]

Rebuild the 915.
Here is a recent thread on the 915

Proper way of shifting the 915 gearbox

[JeremyD]

7 responses from people with 915's - 7 positives re keep the transmission. Hmmmmm. Now is it worth it (to upgrade to the g-50) probably not unless you are going to coil overs anyway.

[drsimonwong]

Rebuild your 915 but upgrade with all of Hayden's bits and you should have a better than G50 tranny.

Simon

[stuartj]

Originally posted by Jeremy964
7 responses from people with 915's - 7 positives re keep the transmission. Hmmmmm. Now is it worth it (to upgrade to the g-50) probably not unless you are going to coil overs anyway.

Well, I have both, or did till just recently anyway. I drove a (properly rebuilt) 915 in an 86 as a DD for 5 years. 915 is just fine- different to the g50, but IMHO, in some ways better.

[Craig 930 RS]

A 915 with WEVO goods is the cat's Kahunas -

[Brother]

What kind of money are we talking for a 915 rebuild and WEVO parts. It looks like I'll have this on my plate in the next few years.

[Carrera3.5L]

Well, I've never "owned" a 915 equipped car, but working at a shop and having friends with 911's have driven dozens and dozens of cars with 915's. I prefer a G50 anyday.

Too many "ifs" with a 915. This has to be perfect and that has to be perfect and if everything is perfect and the stars are aligned than it is a great tranny. Fact is, many of them are not adjusted correctly or properly maintained and thus shift like crap.

It seems to me that if you throw enough money at a 915 than it can be as good as or better than a G50. However, most people don't do that.

Also, does anyone have any definitive proof that a G50 is actually significantly heavier than a 915? Is this actually true, or simply an internet rumor that has now become a fact?

That all being said, I don't think it is worth the expense to convert a $10K-$15K car to a G50.

Ralph

[HardDrive]

Wow, thanks for the input all. I had someone tell me that the switch was a simple bolt on deal.

915 it is.

[dean]

Originally posted by Carrera3.5L


Also, does anyone have any definitive proof that a G50 is actually significantly heavier than a 915? Is this actually true, or simply an internet rumor that has now become a fact?


Ralph

Hi Ralph,

Funny about the internet rumor mill

In my case the G50 I installed weighted 20 lbs more than the Alu 915 that I took out.

Dean

[Shuie]

If you want a G50, buy an 87-89 car.

I would rebuild the 915. Or better yet buy one that has already been rebuilt w/custom gears, WEVo, etc. Carquip will do a swap and take yours as a core.

[Carrera3.5L]

Originally posted by dean
Hi Ralph,

Funny about the internet rumor mill

In my case the G50 I installed weighted 20 lbs more than the Alu 915 that I took out.

Dean

Dean,

Thanks for the info! I'm glad to see that there is a side-to-side comparison.

Ralph

P.S. - I'll still take the 20 lb weight penalty. If I ever stopped drinking beer and exercised, I'd make that up myself.

[Grady Clay]

Klaucke is right on. It is not only the transmission but many
other components.

Here are two views of the pedal assembly:

IMAGE: G50PedalAssembly01
"
"
(C) Dr. Ing. h.c. F. Porsche A.G.
and

IMAGE: G50PedalAssembly02
"
"
(C) Dr. Ing. h.c. F. Porsche A.G.

Then there is the common brake fluid – clutch hydraulic fluid reservoir:

IMAGE: G50HydraulicFluidRes01
"
"
(C) Dr. Ing. h.c. F. Porsche A.G.

Here are some images of the shift linkage:

IMAGE: G50ShiftAssembly01
"
"
(C) Dr. Ing. h.c. F. Porsche A.G.

and

IMAGE: G50ShiftAssembly02
"
"
(C) Dr. Ing. h.c. F. Porsche A.G.

Here is the ’87-’89 911 Carrera torsion bar tube to fit the G50.

IMAGE: G50TorsionBarTube01
"
"
(C) Dr. Ing. h.c. F. Porsche A.G.

Here is the 911 Turbo and 911 Carrera Turbo Look torsion
bar tube (T) for the G50/50 compared to the torsion bar
tube for the 911 Carrera (C).

IMAGE: G50TorsionBarTube02
"
"
(C) Dr. Ing. h.c. F. Porsche A.G.

For reference, here is the earlier 901 & 915 torsion bar tube
replacement part. Note where the torsion bar tube is reinforced
by attachment to the tunnel structure.

IMAGE: TorsionBarTube03
"
"
(C) Dr. Ing. h.c. F. Porsche A.G.


I haven’t researched the back-up light switch wiring or the
compatibility of the electronic speedometer. There is also
the plumbing for the hydraulic clutch.

Dean, what else did you have to address in your conversion?
Are the G50 transmission axle flanges compatible? Is there
sufficient clearance to the body between the back seats? Other?

Sounds like a fun but very expensive exercise. I think the only
way it would be feasible would be with a donor car.

Best,
Grady

[strother]

I've had a lot of work done on my 915, and I really love it now. I still wish that I could do a quicker shift from 1st to 2nd, however!!

[dean]

Hi Grady,

There are 3 ways to do the G50 conversion that I know of. Replace the torsion tube is one. Go to coilovers and cut the tube is another.

And the way I went was shorten the bellhousing and input shaft. The drawback to that method is the the shortened tranny still doesn't fit so I ended up moving the motor back .75" to make it clear the torsion tube.

You have to use Carrera axles. And you need a different clutch set up.

The conversion was a no brainer for me. Cause I got no brains

My 915 needed some work. My CV joints were blown and my clutch was slipping. The total parts costs for my swap was about $4400. Oh and I gained 20 lbs

I would do it again in a heartbeat but I might go with coilovers next time. If I didn't have a turbo motor I would probably rebuild the 915.

Dean