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1973-75 Porsche 914 limited slip differential

Working on a 1974 Porsche 914 2.0L 4cyl. It has the conventional differential, wondering who sales a limited slip differential upgrade? Was this a a rare option to find on the Porsche 914 or more prominent certain years? Thanks Roy
Old 11-05-2008, 10:13 AM
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the LSD had the option number M220
from my knowledge it was available on all 914 & 914-6
I've no statistic if any year sold more M220 cars than an other

if the tranny number starts with HB (instead of HA) it's originally a tranny with LSD
Old 11-05-2008, 01:34 PM
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There are several things to consider about a limited slip. The factory one seems to be rare and because of that tends to be expensive. A few years ago when I was trying to find one to put in the race car, nobody would admit to having one for sale, so I bought a Quaiff for about $1200 and had it installed. A few months later 6 or 8 of the same people I had asked said, oh yeah I have one, etc, etc. For the second, short track gear box I just bought a GT limited slip and it seems to feel a bit better although I don't driver really hard. For auto-x and short track stuff a limited slip will make the car want to push since now both rear wheels are getting traction so the car has to be setup accordingly. I loaned a gear box to Herb Meeder a couple of years ago and that is what he found immediately and took it out as his car was not setup for it at all. Finally, unless you are a trans guy the cost of installing the limited slip is on top of a trans overhaul which can be pricey! Good luck.
Old 11-05-2008, 02:42 PM
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Roy,
I haven't had my hands on more than one or two factory differentials for that car per year for the last five years, and I am in the business. People just don't seem to cough them up very often. I do sell the GT diffs.

To elaborate on what John Rogers said, I would seriously consider intended usage. For a street car or an auto-x car I recommend the torque biasing versions. They don't push as much. The car has better road manners and definitely improved turn in at lower speeds like one would see in auto-x or around town.

For the circuit racers a true LSD is the way to go. There are several options of set up for the GT ramps. For the 914 I suggest the 40-60 set up. Go to the 50-80 option and it really does tend to make the car push more than most guys like. The factory one was a 40% locker for reference. Furthermore, some of the guys I know running this diff. at 40-60 take off their rear sway bars to offset the push effect of the diff. They still get the braking and exit acceleration advantages of the LSD while losing some of the midcorner push that comes with it. It's generally something to experiment with and figure out what works best for your customer and their personal driving style.
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Old 11-05-2008, 04:48 PM
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IMHO it's not worth it for a street car or an autoXer. For a Big Track car, check your rules carefully. Some outfits will let you run an LSD because it was a factory option for the 914, while others will put an LSD-equipped car into a fairly advanced class.

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Old 11-05-2008, 09:06 PM
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Thanks for all your help....both cars in question we're replacing the engines with higher horsepower output (250 +) and was thinking more about off the line traction. Again thanks..Roy
Old 11-06-2008, 02:00 PM
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For a 914 with some grunt a limited slip is the cat's ass.

I have now run a Guard TB diff for a season of AX.
It causes no push. For the slow in fast out style, rolling on the power in a turn causes the car's line to tighten and one can go to WFO sooner as you exit. It also makes the car perform more consistently. I didn't detect anything I didn't like about it. I got a good by on a new one and installed it myself (I luv OJT) which lessened that pain.
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Old 11-06-2008, 03:27 PM
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Quote:
Originally Posted by roywb46 View Post
Thanks for all your help....both cars in question we're replacing the engines with higher horsepower output (250 +) and was thinking more about off the line traction. Again thanks..Roy
Then get a true LSD.

And also put a short 2nd in there, run it as a 4spd and stay away from 1st gear. 1st gear launches with that kind of power will rip the end right off of the mainshaft.
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Old 11-06-2008, 05:30 PM
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It ain't the hp/torque that gets you, it's the amount that you can put to the ground. I run 10 inch slicks at the business end of a 901.....we light em' up in first ('B' gear set) regular like.....sometimes on purpose. Been running the same trans for 8-10 years with no breakage......only 210-230 hp tho.
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Old 11-08-2008, 07:47 AM
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Actually it is the torque that gets you. It's the low end torque. If someone's got 250ft lbs or more at 2000rpm or less then 1st gear is in jeopordy. It doesn't matter if you've got 7's or 10's on the rear end. What matters is the hit on it over and over again with that much twisting force. It will give up the ghost in that environment.

I suspect given the HP number you have quoted you probably don't have much more than 100-125 ft lbs of torque off the line, and thus why your first gear is still alive.
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Old 11-10-2008, 03:06 PM
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915 LSD in 901 box

About 10 years ago I had a 915 LSD installed in my 914'6's 901 gearbox. At the time the car was mainly a (successful) POC track car. (Now back to street and canyon blasting). It was set up at "80" (I am not sure what that means, but it is stiff). I loved the way it made the car handle, including on trailing throttle into the turns.
It meant that the inboard CV joints were also changed out to 911 SC units and that the inner "ball" of the CV joint had to be shortened slightly to be able to fit on the 914-6 half shafts. Also the 2 inner CVs are now not symmetric with respect to the gearbox case. However this is taken up in the total axial play on the two CV joints on either side of the gearbox. One side shorter, the other longer. It is not a problem.
Oh yes the reason for the choice was that I could not find/afford the rare 901 ZF SLD, but used 915 LSDs were more readily available and affordable.
Martin
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Old 11-19-2008, 07:34 PM
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Quote:
Originally Posted by Matt Monson View Post
Actually it is the torque that gets you. It's the low end torque. If someone's got 250ft lbs or more at 2000rpm or less then 1st gear is in jeopordy. It doesn't matter if you've got 7's or 10's on the rear end. What matters is the hit on it over and over again with that much twisting force. It will give up the ghost in that environment.

I suspect given the HP number you have quoted you probably don't have much more than 100-125 ft lbs of torque off the line, and thus why your first gear is still alive.

Thanks. This last para tells me you really haven't a clue and I can ignore any of your opinions.
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Old 11-20-2008, 02:55 PM
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Instead of using the 1974 Porsche 914 901 trans to handle the 300 hp WRX engine, what are your feelings about using a 911-912 trans 4-speed out of a 69 Porsche 911 instead of having the 901 trans rebuilt or blocking the 1st gear in the 901 trans? thanks Roy
Old 11-20-2008, 06:19 PM
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Thanks. This last para tells me you really haven't a clue and I can ignore any of your opinions.
Thanks, your post tells me that you are rude and would rather put someone down than help people learn. If I'm wrong, then politely correct me and explain to me and the others why I am wrong. It's really as simple as that and there's no reason to be an arse about it.
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Old 11-20-2008, 06:25 PM
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Quote:
Originally Posted by roywb46 View Post
Instead of using the 1974 Porsche 914 901 trans to handle the 300 hp WRX engine, what are your feelings about using a 911-912 trans 4-speed out of a 69 Porsche 911 instead of having the 901 trans rebuilt or blocking the 1st gear in the 901 trans? thanks Roy
If you go that route you're going to have to move the ring gear over to the other side and set it up again as well as figure out something to do with shift rods. Either you would have to make the car run with a tail shifter or more the 914 rods and forks over to the '69 transmission. It's a lot of work for not a whole lot gained.

If you are worried about 1st gear's strength, why not just remove it or not use it? It's more work to convert a '69 901 trans over for midengine 914 use than to rebuild a 914 trans.
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Old 11-20-2008, 06:34 PM
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Matt;
As usual my friend you have shed some more light on this project, I'll probably just do the most common sense thing and that's not use 1st gear. The trans we've appears to be in good shape therefore i feel like for now just keep it stock and drive it in stock form. We can always go back latter and build it to fit our needs, blocking first gear and possibly changing the gear ratio. Thanks again, we've finally got the 2007 WRX STI engine ready to go, just have to either purchase the kit from Renegade for the trans hookup & the Radiator conversion or start making our own parts, etc. A long ways to go but i feel like it will be worth it when we get finished.
Thanks again for the comments. Roy
Old 11-20-2008, 06:52 PM
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Quote:
Originally Posted by Matt Monson View Post
Thanks, your post tells me that you are rude and would rather put someone down than help people learn. If I'm wrong, then politely correct me and explain to me and the others why I am wrong. It's really as simple as that and there's no reason to be an arse about it.
I'll keep this short so as not to waste more of our time.

You know that a TB diff causes push.
You know that my thoughts on torque vs traction are wrong.
you know how much torque I'm putting down.
You know I'm rude.
You know that I should take time with a polite explanation.
You should know there is nothing I can tell you, politely or otherwise.

There's 5 wasted minutes.
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Old 11-21-2008, 02:39 PM
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Nevermind. A troll like you isn't even worth my time.
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Last edited by Matt Monson; 11-21-2008 at 05:13 PM..
Old 11-21-2008, 05:09 PM
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JP, you were a bit rude, but Matt you started it by being just plain wrong, so you can't blame JP.
Old 11-29-2008, 02:45 PM
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Quote:
Originally Posted by roywb46 View Post
Instead of using the 1974 Porsche 914 901 trans to handle the 300 hp WRX engine, what are your feelings about using a 911-912 trans 4-speed out of a 69 Porsche 911 instead of having the 901 trans rebuilt or blocking the 1st gear in the 901 trans? thanks Roy
It's essentially the same transmission. The shifting is different but some of the shafts, all of the bearings, the synchros and the gears interchange. It's actually a little more complicated than what I've said but for your purposes they're the same. a 915 is different and stronger, a G-50 even more different and even stronger, and a 930 trans is the strongest of the whole lot.
Old 11-29-2008, 08:56 PM
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