My 915 options at this point. Thoughts based on experience

[gint]

So my new 75 S needs a trans solution of some sort. 1st, 2nd and 3rd synchros are weak, won't stay in 5th. The latter probably was abused a bit since it started this behavior. It needs a rebuild; There is no debating that.

I have a chance to buy a 72 915 that came out of a front end collision 911 in 1991or2-ish. 28k miles on it, been sitting on a shelf for 20 years.

I know it's subjective, but if I rebuild the existing 915, what should I expect to pay for parts? A range is fine, 500-1k, 1k-2k, etc...

Will the 72 915 bolt right up to my 2.7 in the 75 chassis? No issues or fiddly parts that are on one and not on the other etc... I know internally there are differences on the early 915 units, but that isn't a concern necessarily, is it?

[Elombard]

The 72 has a 7:31 final drive which will be fun but a bit buzzy on the freeway - never bothered me.

I think the clutch operation is a bit different - horse shoe helper spring etc, so there may be some little fiddly parts you have to source? not 100% sure.

When I priced the parts from pelican to do a 100% rebuild it was ~$2K. I bet with labor and only the parts you "need" it will be in that neighborhood. maybe some savings if you take the gbox out and have them bench build it?


Others with more direct exp will have better answers.

[Flat6pac]

The 75 needs a build.
The 72 thought needs nothing BUT sitting on the shelf for 20 years doesnt do anything for the seals, including the imput shaft. The 72 imput to be replaced requires the internals of the trans be completely removed to replace the shaft seal.
The 72 has the faster ring and pinion and all other bolt right in, IE hubs and speedo cable.
There is a couple guys on Pelican in your area that do transmissions or I personally would call Gary Fairbanks Company in Norwalk, Ct, the Guru of the decades for 915.

Bruce

[Sboxin]

I just looked up the prices on Pelican--
Syncros = $100 per gear
Hub (dogteeth) = $150 per gear

Plus misc = $ ???

3 gears = $ 750+
4 gears = $1000+
5 gears = $1250+

How's that for ballpark - parts only?

IMHO -- I would rebuild not swap...just an opinion..

Regards,

[G450X]

I think it's a direct swap, let the 915 experts chime in. It has a few differences from the '75 version.

The input shaft seal requires transmission disassembly to replace which was corrected by the time your '75 was made.

It has a 7:31 R&P which will give your '75 (8:31 R&P) a bit more "punch." I think the general consensus is that Longevity is a bit of an issue when more h.p. and torque than stock are added to it. A '75S, even if tweaked for more power (SSI's/exhaust) should be fine. I would add a reinforced side cover on any mag box.

An original '72 915 with only 28k original miles has to be a rare piece. If the price was decent it would be worth grabbing regardless.

You could always rebuild your original 915. Unless you really trust the seller, I'd have the '72 915 checked out (and all seals replaced) while it was out.

[Porsche84]

Gint

If you are thinking of rebuilding the trans yourself, I have a bunch of really good used 915 syncros, dogs and sliders if you want to save some money and not gold plate the unit. If you want to send it out to be fixed I'd be happy to work with you. I also have some 78 and later transmissions if you want to trade your unit in.

I've attached a couple photos of some of the parts I recently purchased from a race shop no longer dealing with 915s.

[RWebb]

how much are they asking for the '72?

do you want more accel.? do you cruise for long periods on the fwy?

[gint]

If the input shaft seals requires take down anyway on the early unit, I'll get a good look at the internals while I'm in there. I would definitely want to replace seals after it sat so long. I thoroughly trust the seller, I've known him for a long time. Reputable small business owner here in town for decades. Asking price is $1200.

I haven't had 5th since I bought the car. I drove it home from S.F. without it, so a little buzzy due to a lower overall ratio probably isn't going to bother me too much.

If I rebuild the current box, I've got local sources for good used parts. I know of several local rebuilders for the job also, and I can pull it for sure, but I want to avoid the additional cost of having someone else do the rebuild.

The idea of a swap of my unit for a later one is appealing. I'll shoot you a PM Jerry to discuss.

I'm weighing my options. You guys know how it is. This is great input that will help me make the decision. Thanks all!

[RWebb]

for $1,200 you'd at least get a bunch of gears to pick thru to build your own custom set of ratios...

you could swap the earlier box in and run it while rebuilding & hotrodding yours too, then resell the original box

[gint]

Originally Posted by RWebb

for $1,200 you'd at least get a bunch of gears to pick thru to build your own custom set of ratios...

you could swap the earlier box in and run it while rebuilding & hotrodding yours too, then resell the original box

That option is definitely a good one. And one of the advantages of buying another unit.

[914/6]

buy the early one , your car has a 7:31 , Put the OGtrans on a shelf. you will need to use the 75 clutch arm. 28k is better than a rebuild IMO

[gint]

That's another option if the early unit is good. Is that you Jeff?

[914/6]

sure is

[gint]

Knew it! I have to get back to a pair of 40IDF's...