How Many Miles does a 915 Transmission Usually Last?

[IAN]

I have a 72 911T 2.4 MFI.

There are 137k on the entire car. The engine had a top end re-build at 100k. So there are 37 on the rebuild.


When do transmissions start to get bad?? Everything works well now, just curious.

thanks,
ian

[s_wilwerding]

It all depends on who's been using them. If you have someone who always carefully shifts and makes sure to always fully depress the clutch pedal, the transmission might last 200K miles. On the other hand, if you have someone who likes to race off the line and often misses the shift into second, the transmission can go out in 50K miles. On average, though, I would say that most 915 transmissions start to get worn around 100K. Mine's got about 150K miles on it, and it could definitely use a rebuild - the synchros, especially 1 & 2, are nearly gone.

[Colby]

255k on my '84 915, and still works flawlessly!
Original motor still also...gotta love Porsche quality!

Colby

[jwetering]

I got a 160,000 miles out of my 915. Supposedly it was apart once at 100,000 miles, and put back together without replacing any parts (drunk PO) finally I ended up shearing the teeth off of the dog gears for first. Otherwise the trans was pretty good.

jasper

[Porschephanatic]

My car had 4 POs and my 915 lasted 120k, so it must have seen minimal abuse.

[zotman72]

Well I have this sweet 72 911T that was a Seattle garage queen for 13 years before I got it ten years ago. It had 87K on the clock before my torture began. I got into DEs in '98. Downshifts at speed took its toll. At 120K I replaced all the dogteeth and syncro rings, and one roller bearing that disintegrated ($$) when we opened the tranny up. I had the second to third grunch sound which was the catalyst to do the job. My rebuild experience was quite insightful but repeated woes with the input shaft seal kind of tainted things. Parts were about $900. I have used SWEPCO in the past, but now I got Redline synthetic in there. HTH.

[david c.]

Just out of curiosity, what do you guys think the 915's are worth? I'm thinking about selling mine. It's from my 912e so it's never had a lot of horsepower pumped through it. It has new syncros in the last 15k or so and shift beautifully-never grinds. Thoughts?

[s_wilwerding]

Originally posted by dave cardone
Just out of curiosity, what do you guys think the 915's are worth? I'm thinking about selling mine. It's from my 912e so it's never had a lot of horsepower pumped through it. It has new syncros in the last 15k or so and shift beautifully-never grinds. Thoughts?

I know there is a company that advertises in Pano that sells 915s for around $1500. If yours is absolutely new, you may be able to get a little more, but I'd say that's about the price you'd be looking at.

[david c.]

thanks!

[Aurel]

My 915 has 104K miles on it, and needs at least new 1st and 2nd syncro rings. The differential is noisy too...I will get a quote from my mechanic to fix that, while the engine will be deposed for new exhaust head-studs, new rings, valve job and pressure-fed tensioners... If his quote exceeds $1300 for just the transmision work, I will tell him to swap it for a rebuilt one from Vertex, this is what a rebuilt 915 costs.
BTW, I have a question: my clutch has only 5K miles on it. I`d like to keep it. Is it part of a rebuilt transmission or not ?

Aurel
78 SC Targa

[Aurel]

I went to the Vertex website.

here

It looks like you get a clutch with the transmission. If this is the case, then it is a no brainer: Just replacing my clutch has cost me $1600 (parts+labor), while I could have had a full rebuilt transmision for $1300, and just had the labor cost to install it...Geeesh, I feel bad...
And wile the engine was deposed for the clutch job, I should have had the head-studs done too...I wish I knew all I know now at that time...

Aurel

[hgray]

I have been reading Peter Zimmermann's "The Used 911 Story",(thanks to our hosts). Peter says that 100,000 miles is the expected life of 915 tranny. Obviously, this is an estimate, and actual results may be more or less, depending on usage. (Highway versus city miles; driver habits; number of DE days, etc.)

To verify Peter's estimate, I phoned the local dealership, and they confirmed the estimate, saying that the synchros are made of molybedium (sp??). Peter also points out that a Valet parking attendent who only engages the dog teeth synchros in first gear (and not the gear itself) can destroy the synchros, in one move. HTH

[logician]

Hi,

My old '85 Carrera had 137K when I bought it (915 transmission), and the synchros were gone. From what I've seen, I would agree that on average, you should expect 100K, maybe a little more from a 915. But it all depends on how the car has been used. It's usually the synchros that are in need of attention. Also, different drivers may be more or less sensitive to weak Synchros. I lived with very weak synchros in my second Porsche, my 930, for 3 years because by then I had learned to match engine revs to car speed.

-Juan

[Geary]

I've seen shift sleeves in a 901 dragrace tranny go bad after about 10 passes. Since these are virtually the same as 915 shift components, this gives you some indication of what extreme abuse (speed shifting) can do to your 915. On the other hand, treated nicely, the 915 will likely last well over 100,000 miles.

[pwd72s]

Originally posted by s_wilwerding
I know there is a company that advertises in Pano that sells 915s for around $1500. If yours is absolutely new, you may be able to get a little more, but I'd say that's about the price you'd be looking at.

Unless Dave, your transaxle happens to contain the factory limited slip...if that's the case, you might do well to consider upping the price just a wee bit...a grand or so...new factory limited slips are well over 1K...

[Adam]

My '76 915 lasted almost exactly 100k (160k kms) before it went Ka-Fluey! Synchro Hubs, Synchros, dogteeth and approx $1300 (US) later it shifts like butter and is better than ever.

My mechanic told me that they tend to last 100k miles in "weekender" type cars. Maybe they get thrashed more than the babied daily-drivers.