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914World.com _ 914World Garage _ 915 in place of a 901 gearbox
Posted by: Tomcelica2 Feb 18 2015, 02:48 PM
Hi Guys:
I wondered if you can help me as I am upgrading to a 915 gearbox from the 901. I know the hubs have to be changed, but I do not know which axles are required.
Could someone tell me if the 911 100mm axles and CV joints fit or do they have to be modified in some way such as with spacers.
Thanks in advance for any help.
Rob
Posted by: Mark Henry Feb 18 2015, 03:14 PM
How are you going to shift it? 916 kit?
I don't know the CV's but someone will chime in.
Lots of cash required for putting a 915 in, I'm sticking with the 901.
Posted by: Tomcelica2 Feb 18 2015, 03:32 PM
It is a big investment, but necessary in the long run. We were not certain the 901 would handle the load even with further upgrades.
Using the Wevo kit.
Posted by: MikeSpraggi Feb 18 2015, 03:32 PM
Agreed, bring lots of cash if you want to do it right. Tell us something about your car, engine, hp/torque, what you will be using it for....
Posted by: Tomcelica2 Feb 18 2015, 03:33 PM
Agreed, bring lots of cash if you want to do it right. Tell us something about your car, engine, hp/torque, what you will be using it for....
Its a 914/6 race car with a 2.9
Posted by: naro914 Feb 18 2015, 08:43 PM
This thread is funny in that I was planning to start one describing my current (as in the past couple weeks) saga of swapping out our 901 with a 915 that already had a Vellios installed:
So...here's what you need:
- transmission with either Wevo, Vellios or the Martin Bott 916 kit and flipped ring and pinion
- new clutch and pressure plate. You MAY be able to use your flywheel depending on what you have. We could use ours but the clutch system is different now: the ring gear on a 901 is on the flywheel, and its on the pp for a 915.
- depending on the year of the trans, the connection of the clutch cable to the arm in the trans MAY be different than a 901. Mine wasn't different (early trans). Patrick Motorsports sells a nice adapter kit.
- New shifter, one that has a normal 911 shift pattern and reverse on the right instead of left - I chose the Rennshift 911/915 version...very nice.
- the rod in the tunnel needs to be changed*
- there is now a little guide bracket that needs to be installed under the shifter to guide the tunnel shift rod.**
- the 911 'cup' under the shifter is needed instead of the clamp that tightens on the shift rod spline. The 911 shifters have a ball, not the clamp at the bottom.
- the CV's on your axles MAY need to be changed. Mine didn't because I already had bigger ones, but the CV 'hats' need to be changed to 6 bolt instead of 4.
- I chose to go with Tangerine Racing's rear upgraded shift rod kit, which required a little modifying done on the Vellios shift console.
* Chris Foley at Tangerine Racing made me a cool little a adapter 'rod' that allows you to use the tunnel rod you have, just flip it around and use his adapter. This allows for length adjustment on that rod... Ask him...I'm still a bit in awe of what he made.
** However...if you use this method, you need an unobtanium adapter bushing for the shift rod guide bracket. The bushing is the same one that you use for the firewall when you convert a tail shift car to side shift. The tail shift tunnel rod (and a 911 tunnel rod) are thicker than a 901 side shift. This little shift rod guide bracket has a bushing for the 911 rod..meaning your 901 side shift rod is too small for the guide. the unobtanium bushing is the right OD, but has a smaller ID making the 901 rod fit perfect. I say unobtanium because...nobody has it anymore. AA doesn't...said it was made by Automotion, who doesn't have it anymore. We decided to weld a sleeve on the rod to make it fit the stock 911 sized bushing.
Clear as mud??
I THINK I got it all.
Oh...and you need a week or more to figure out that you don't have everything, fit it all together, curse a lot...and hope it all works next time you go on the track... 
Good luck!
Posted by: Steve Feb 18 2015, 08:56 PM
Don't forget to flip the ring and pinion.
There are a couple of good threads with info.
http://www.914world.com/bbs2/index.php?showtopic=102988
http://www.914world.com/bbs2/index.php?showforum=5
In the above thread there are links to axle upgrades.
I chose the 930 sway away axles with 108mm cvs on both ends, but you can convert the 914 axles with some machining to use 100mm cv
Patrickmotorsports.com specializes in the wevo kit. He has everything you need off the shelf or you can mix and match from various vendors. I also went with the above Martin bott 916 kit, so I mixed and matched various components and vendors
Posted by: veekry9 Feb 19 2015, 03:01 AM
http://www.bugat5speed.de/en/porsche-cars
Martin Bott,Prop
http://www.bugat5speed.de/en/porsche-cars/special-parts-for-porsche-transmission/102-slip-differentials
You know you need it 
Posted by: naro914 Feb 19 2015, 06:27 AM
Don't forget to flip the ring and pinion.
There are a couple of good threads with info.
http://www.914world.com/bbs2/index.php?showtopic=102988
http://www.914world.com/bbs2/index.php?showforum=5
In the above thread there are links to axle upgrades.
I chose the 930 sway away axles with 108mm cvs on both ends, but you can convert the 914 axles with some machining to use 100mm cv
Patrickmotorsports.com specializes in the wevo kit. He has everything you need off the shelf or you can mix and match from various vendors. I also went with the above Martin bott 916 kit, so I mixed and matched various components and vendors
Yeah, forgot about the flipped R&P. Mine was already done because the 915 I got came out of a 914 and already had the flipped R&P, Vellios and LSD done. I updated my post.
Posted by: Mark Henry Feb 19 2015, 06:58 AM
Like I said... expensive.
The 901 will hold up under race conditions if you add the cooler, spray bars, pump, etc.
Another option, if your trunk is cut out, is a 930 upside-down. But you have to figure out a cable shifter, etc. Nice is many are factory LSD and not so nice is gear sets are about $1200 a set. Still not cheap.
Posted by: Racer Chris Feb 19 2015, 08:15 AM
...
** However...if you use this method, you need an unobtanium adapter bushing for the shift rod guide bracket. The bushing is the same one that you use for the firewall when you convert a tail shift car to side shift. The tail shift tunnel rod (and a 911 tunnel rod) are thicker than a 901 side shift. This little shift rod guide bracket has a bushing for the 911 rod..meaning your 901 side shift rod is too small for the guide. the unobtanium bushing is the right OD, but has a smaller ID making the 901 rod fit perfect. I say unobtanium because...nobody has it anymore. AA doesn't...said it was made by Automotion, who doesn't have it anymore. We decided to weld a sleeve on the rod to make it fit the stock 911 sized bushing.
...
I'm rather surprised that bushing is NLA everywhere.
I guess not enough demand for Weltmeister to run another batch at this point.
The downside to welding a sleeve on the rod is that it won't fit through the firewall bushing anymore.
With a little more available time, a bronze bushing would be a good solution.
Another option would be an altered bracket to support the standard firewall bushing.
There's no value to upgrading to a spherical bearing in that location since there's no eccentric motion.
Posted by: naro914 Feb 19 2015, 04:51 PM
The 901 will hold up under race conditions if you add the cooler, spray bars, pump, etc.
Under normal circumstance I would probably agree, but with over 350 hp and 290ish torque, I kept shredding gears, even with a cooler, spray bar, pump, etc.
I'm rather surprised that bushing is NLA everywhere.
I guess not enough demand for Weltmeister to run another batch at this point.
The downside to welding a sleeve on the rod is that it won't fit through the firewall bushing anymore.
With a little more available time, a bronze bushing would be a good solution.
Another option would be an altered bracket to support the standard firewall bushing.
There's no value to upgrading to a spherical bearing in that location since there's no eccentric motion.
Yeah, I tried AA, Forbes, Automotion(Ecklers), etc. John said he can't find them any more either. You're correct, it won't fit the firewall bushing, but we just took it out to put the rod in, then popped the bushing back in.
So Mr. Fabricate-everything-that-makes-914's-better...maybe you or Mikey914 (since he does plastic/rubber stuff) could start making that magic bushing?
Posted by: larryM Feb 19 2015, 10:35 PM
. http://www.914world.com/bbs2/index.php?showtopic=248591
. http://www.914world.com/bbs2/index.php?showtopic=249697
. http://www.patrickmotorsports.com/package/transmission-porsche-915-wevo-to-914/
. axle cv adapters - http://www.patrickmotorsports.com/part/rear-axle-joint-flange-adapter-set-porsche-901-914-transmission/
.
Posted by: Tomcelica2 Feb 20 2015, 07:52 AM
Thanks for all the insights gentlemen.
I think I have all I need. You guys are a great resource.
Thanks again,
Rob
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