915 Common Problems / Syncro Only repair

[stewartjp]

Hi Guys,

I have got an 85 Carrera 3.2 with 109,000 miles on the clock.

The syncro on my first is completely gone, second is poor and third is starting to show signs of wear.

Syncros aside the box functions well and has no undue noises, though it does wine in 5th a bit but I believe the is common and often doesn't change after a rebuild.

My question is if I decide to pull the box and replace just the syncros are there any other standard 915 faults I should be looking out for?

Cheers

Stewart

[0396]

I'm no expert but based on my readings and mileage, I would not be surprised if the 915 will need: first & 2nd gear dog teeth, syncro and a few bearings. Last year I had my 915 LSD upgrade, and it needed 1st gear dog teeth, bearings and syncro 1-4th. The 915 only had 85k miles. Good luck

[zelrik911]

You will probably need at least one 'slider' as well as new needle bearings under the gears. So it may get expensive fast!

I would also look out for a good used 5th gear set too. 5th gear wears when there is too little oil in the box. Its easy to underfill a 915 box - I always fill them in 2 goes, with a rest between because you can have oil coming out the fill hole when its only 2/3 full.

[stewartjp]

Cool, thanks, I plan to do the work myself so it's only parts prices fortunately.

I see, where do I look for a 5th gear set? Can you buy them new?

Cheers Guys

[MetalDoc]

I rebuilt mine using the tutorial from Peter Zimmerman. This information is very helpful. I am thankful he put it together.

How-To: Porsche 915 Transmission Repair Tutorial Part 1 - Porsche Wiki

Paul

[KTL]

915 transmissions have PLENTY of common problems. Bearing retention, synchro wear, broken dog teeth, main shaft spline issues, chewed up reverse engagement teeth...........

The "synchro" is a multi-part assembly in the trans. The mistake a lot of people make when servicing them is that they only replace the synchro band itself (because it's the most obviously worn part) and often ignore the dog teeth pressed on to the gear and/or the engagement ring/sleeve that is operated by the shift fork.

If you want it to shift well again, the band, the teeth and the shift sleeve should all be replaced for any difficult gear you are experiencing.

The needle bearings for the free/loose gears are NLA new from Porsche. So we have to source good used ones or go with aftermarket suppliers.

[914efi]

Sounds just like mine, I plan to dig into it this winter.

[KTL]

You're just being a pain in the can for the sake of doing so. That's fine if you wanna be an instigator, but your comments can mislead others and make their assessment of how to deal with their trans problems that much more difficult.

Fine if you love the 915. I like mine too. It's served me very well in the racecar. But the fact is, as much as you despise it, the G50 is a better trans and that's why people tout it so much. Sure most of these promoters are just passing along what they've been told & haven't really experienced the two transmissions in order to make a fair comparison.

That said, the G50 is certainly not an infallible trans. It's got it's share of issues too. But it's still a much more durable trans than the 915. In my experience the G50 is akin to a phrase I once heard about older GM cars. A GM car can run bad longer than many other brands run their whole life. The parallel is a G50 can keep on truckin' even if its really worn out and noisy, which many are becoming. On the other hand a 915 is eventually going to bite you if you continue to ignore its problems.

How many threads have you seen on here where people post or document their internal problems with the G50? Hardly any. The 915 has hundreds of threads dedicated to its troubles. I've worked on both of them and I see what problems each has. The 915 easily loses this argument.

[KTL]

While there's a much larger sample population of cars for the 915, the G50 is still plenty old enough to demonstrate problems and lack thereof in this case. But whatever. I can say all sorts of crap and you'll refute it just to do so. Have your fun being a pain.

So in your analogy, is the 915 the domestic and the G50 the AK? That's how I see it.

[pmax]

Hey Rich,
Buy this ... FS: 1987 911 Carrera G50 97k miles blk on blk

My 915 is a great transmission except 3rd gear's starting to crunch, 1st gear sometimes refuses to engage, 5->4 hits reverse and I'm starting a budget for an eventual rebuild.

[KTL]

Viewpoints are one thing. Takes all sorts to make the world go 'round and I have no problem with that. But causing trouble for the sake of doing so (on various G50-related threads) is another thing and that's what you're doing. You're trying to say you're being faulted for having a different viewpoint, when in actuality you're really doing nothing more than being a troublemaker. I'm just calling you out on it.

Thanksgiving = give thanks to the harvest. One could say a harvest that is this forum? You're the one pissing on the crops......

[KTL]

Troublemaker outed & irritated. My work is done here!

Having a race car and lots of posts means nothing. Do a search of me if you want smart guy. You'll find i'm an avid contributor with good advice. I'm not always right, but I contribute positively and try to help people. What's your explanation?

[KTL]

The G50 is the greatest transmission since sliced bread!

Rich Gas is a study in contradiction and he who calls me a dork is the pot calling the kettle black!

[pmax]

Happy Thanksgiving Rich.

Hey, Christmas is just around the corner, the G50 will make a nice gift for yourself.

[Matt Monson]

Last night I saw the posts(this thread and others) and thought Rich must have been hitting the holiday cheer a bit too hard. Unless he's on a full 4 day bender now looking at making Thanksgiving with the family an extra special super memorable experience I don't know what he's on about this morning...

[winders]

Originally Posted by Rich Gas

Come on dude, really....ok smarty pants....check the list off on why the G50 is better than the 915.
You're starting to annoy me....you race, you got opinions, tons of posts, blah, blah, blah

Let's get it on then dork...

I would rate the 915 a 9 out of 10 9/10, the g50 a 2/10.

Changing search results one hit at a time.

I have mag 915 in my race car and it works quite well. But, it needs to be taken out of the car and refreshed each year...mostly because of the balk-ring synchromesh system which is quite inferior to the Borg-Warner cone synchromesh setup in the G50.

The G50 is a better transmission and can handle quit a bit more torque than the 915. It can be shifted much faster than a 915 too. It is a more durable design. But, it does weigh more than a 915 by quite a bit too. I think I would prefer to have a G50 in my car but the cost to get the setup I want would be prohibitive.

[Matt Monson]

I do like 915s better. But them I am not a horsepower junkie and actually like 901s better yet. One of these days we will bit Borg-Warner synchros to 915 gears and make the perfect air cooled 911 gearbox. Until then people will argue opinions, mostly just because they can...

[winders]

Originally Posted by Matt Monson

I do like 915s better. But them I am not a horsepower junkie and actually like 901s better yet. One of these days we will bit Borg-Warner synchros to 915 gears and make the perfect air cooled 911 gearbox. Until then people will argue opinions, mostly just because they can...

When can I send you my 915???

[KTL]

Originally Posted by Rich Gas

A song about 915s ( in F minor) mmmmmmmmm

Got my 915 shiften smooth
Gotta G50 too
Can't seem to get the 50 in gear
The 915 was voted best this year...

Chorus....yeah 915, gonna go drive
,,,, yeah 915' gonna go drive

A dude singing praise about a 915 is most definitely somebody with a meth problem. Because usually sane drug free people are singing the blues.........

[mikedsilva]

Originally Posted by MetalDoc

I rebuilt mine using the tutorial from Peter Zimmerman. This information is very helpful. I am thankful he put it together.

How-To: Porsche 915 Transmission Repair Tutorial Part 1 - Porsche Wiki

Paul

great post... now, how do I find part 2?

whoops, found it!
http://porsche.wikidot.com/system:list-all-pages