914 Transmissions

[tomrichardson]

Not sure if this has been discussed yet or not. But, how strong are the stock 914 transmissions? Has anybody broken them? If so, how?

What are other alternatives if stock is too weak for high HP? I want to be puting about 250+ HP to the wheels on my lil 914. So, I want to know if I'll need a beefier trans.

Thanks,
Tom

[oredith]

how much depends on how you plan to put down that power..

by saying 250 to the wheel, you're either talking a pretty beefy flat-6, a V8, or something that's pretty custom. the general number is 300hp.. it's torque that kills the tranny though.. (like a v8).. if you don't do hard launches, the 901 should hold plenty of power, even beyond 300..

my car won't make anywhere near 300.. but even if it did, i'd never have to worry about the 901 because i'll never be making that much torque (VERY hard to build boost in 1st gear)..

Jeff - turbo 914 - in the middle of welding together my custom a-w intercooler..

[Jim Smolka]

The 901 xmission weak links are

1. First gear, you drop the clutch, you drop 1st gear

2. The intermediate plate is good for 300 HP. You could go with an after market, then it is good for 400 HP (so I have been told)

I have a little over 250 HP in my car, and the gear box is fine, but who knows what the future holds. If I wanted a bommer xmission, I would go with a G50 and mount it upside down and install an external cooler and pump. Also, the shifting would be fun to figure out.

Just my 0.03 worth.

[Roland Kunz]

Hello

Like Jeff said the trany is mainly limitet by the tourqe load. An other limit is the heatet oil.

Now the tourqe load depends on the clutch and the tires. If both is very good the trany and halfshafts gets twistet between them. The first weak link is the 1st gear so you replace it with a 906 main shaft.
The next weak link ist then the forward intermediate plate. replace it with a steel reinforced version. Then you can go up to maybe 300 NM tourqe load. The trany was basically designed for 250 NM load.

This is the reason why they made the 915 trany. They came as the 2,4 S reached the factory limits, the 2,7 210 HP is beyond the factory limits. But even a 2,7 175 HP will have to much torqe for safe full load play.

The other weak point is that the oil gets hoter then in the 911 and the oil will shear at the R&P starting piting and ending in broken parts. A oilcooler is to recomend.

Grüsse

[tomrichardson]

I plan on getting 250+ to the wheel via a larger displacement engine (2.5L, 4 cyl.), and a turbo-charger. And lots of other trick that I won't go into.

So, will I be ok with stock transmission?

Thanks,
Tom

[oredith]

uhh.. better "go into" details now, rather than finding out later..

i've got a turbo 2.0L -4 right NOW, and i'm having heating issues.. with a 2.4, you're going to have heat issues without the turbo, adding the turbo would just increase the heat you'd have to deal with. think it out first, or at least throw it out here, so other's can comment on it, either theory or experience..

usually the 2.4L P&C run a higher compression, one of the worst enemies of boost.. it's usually one or the other, both, and you get a grenade motor.. my current motor is tired, so is probably running in the range of 7:1 from the stock 7.6:1.. i'm going with bus 2.0L P&C which have lower compression, so i can push more boost..

regardless, you shouldn't have a problem with the 901 tranny if all you're doing is a turbo-4.. you can't build enough boost in 1st gear to rip the insides apart, and you're power range should be high enough that you're not putting any sudden load on the tranny, unless you're actually out to abuse it..

my $.02

Jeff

[DDS]

FWIW a local guy has reliably tracked a 3.2l six with no trans mods other than the aftermarket intermediate plate. No problems, consistent with above.

Dave

[tomrichardson]

Myself and my tuner have already worked out most of the details dealing with heat. One of the solutions it so over-fuel the engine. Therefore, acting as a coolant. I can-not tell you all of the details because he has specifically told me not to reveal everything he's got in mind.

I just want to know if the transmission will hold up to a good amount of HP and torque. Around 250 for both. If not, I want to find a new/used beefier tranmission (901 trans?).

Thanks,
Tom

[Brant]

Hi Tom.

I'm Brant, don't know if we have ever met but I noticed your colorado address. I'm also in Colorado so I thought I would ask who your shop/tuner was. Always like to keep my eyes open for a good referral.

About the trans. I have never had 250hp so can't say from personal experience, but I'm guessing you will have plenty of other things to spend your fund upon before you worry about the tranny. The tranny you have is actually an inverted 901 already and I would suggest you get the turbo project finished and find out if you need another tranny or not. If you do it need to upgrade the next step will be a 915 box that you and your tuner invert. I really don't know, but I'm guessing $5,000 for a complete/fresh set up.

good luck

[vw@micron.net]

Has anyone actually seen a broken first gear? I have heard a lot about it being weak and the first link to break. Has it happened? I am using a 68 901 911 tranny in my beetle. It will output 200 horsepower and 180 ft/lbs of torque from a hightly modified Type IV power plant. I am going to run slicks and drag race start very often. Will it break, or are people just repeating what they hear? I have spoken with Tracy Grimm that runs www.tgfab.com and he told me I will not break first gear even if I'm clicking off 11 second 1/4s using slicks and dropping the hammer! He has ran close to 8 second quarters in his pro turbo beetle so he has some experience with breaking trannys!
Steven Arndt

[Dave at Pelican Parts]

The 901 is not beefier than the 914 gearbox. The 914 one is essentially a 901 set up to work in a mid-engine configuration. In fact, the 914 version seems to lubricate the ring and pinion just a little bit better than the 901 version.

The next strongest one would be a 915. It's been done, but it is non-trivial. Figuring out the gearshift and clutch linkages can be a chore. Getting the ring and pinion flipped is simply expensive.

The 901 can handle "something in excess of 300 HP" (which is all that racer will tell us about the power his 2.8 race motor makes). That particular person has broken at least two 901s so far--he gets the pitting on the pinion gear, and then the teeth start shearing off. It has taken him a few years to blow up each one, though.

I think that the heat that Roland is talking about is heat in the transmission oil, not in the engine oil. You can fit an electric pump and cooler to the transmission, but it is definitely some work. A spray-bar that sprays oil down onto the areas where the gears mesh, and something to spray oil onto the ring and pinion junction, can help.

I would think that 250 lb-ft is possible, but pushing it. 250 HP is definitely doable.

--DD

------------------
Pelican Parts 914 Tech Support

A few pics of my car: http://www.pelicanparts.com/gallery/Dave_Darling

[tomrichardson]

Brant,

My tuner is myself and my great uncle - Len Seroka. We work on a lot of privateer stuff at home. We live up in Black Hawk... about 45 min west of Denver. We're not really an established shop.

If you follow drag racing, you might rememeber Len Seroka. He used to race NHRA top fuel funny car 2 seasons ago. We're looking for another sponsor now.

Later,
Tom

[oredith]

Hi Tom,
I don't know if you've followed the progress of my turbo project, and I won't pry on what your setup's going to be, but i'll share mine and some problems i've had, so that you might benefit from it.

I've got a stock 2.0L motor (totally stock, but tired, leaky rings). it's got a mitsubishi turbo from a chrysler 2.2L motor. i've made custom headers that pipe the turbo to where the battery was, intercooler (which is now VERY close to being an air-water intercooler, but all number given now are with a air-air IC with a fan).. i've got a front mount oil cooler, rising rate fuel pressure regulator, and a hobbs switch for the 5th injector.

with this setup, the RR FPR set to kick 5lbs of fuel pressure per pound of boost, 5th injector to kick on at 5 pounds of boost, hi-6TR timing retard module set to retard timing 2 degrees/psi of boost...

at 9lbs of boost, i'm getting EGT in the 1450 range, and climbing (i'm not ready to blow the motor, yet), pinging starts when i'm doing a long pull in 3rd gear at 5k rpm..

i think to push more boost, you'd need bigger injectors, better fuel management (i was experimenting with the stock D-jet, and what i could do with it), a walbro fuel pump, raceware head studs, stiffer valve springs (the turbo will pull up to and beyond 6.5K+ rpm easily). water injection would be nice..

that's it for now.. i'm sure there's plenty other ways to solve the same problem.. i'm just trying to give you a bit of warning on what you'd likely be up against when you start/proceed with your project.

Jeff

[oredith]

one more thing.. that setup was with LOTS of fuel.. my car's running so rich that standing near the car is like standing near a can of open tear-gas.. when i'm at full boost, the A/F gauge is fully pegged at rich..

Jeff

[tomrichardson]

Hi Jeff,

Thanks for your input. I have a little bit of experience dealing with turbos and fuel injected engines, as I was a Subaru enthusiast before a I was a Porsche enthusiast. So, what you say makes sense to me.

The big difference between my up and coming turbo project and yours is that I will be running carbueraters, not fuel injectors. I have two Dellorto carbs currently running on my lil 1.8L daily driver engine. The cam is a racing cam from Ed Iskendarian, so are the valve springs (I think they're 8K RPM springs), my pistons and jugs are 103 mm from Scat. My fuel pump is something aftermarket... not sure yet. I took it off a salvage auction 914 that I got for $350. The heads I will buy brand new and get them machined to fit the bigger jugs. My intercooling setup will pretty have to be air/water because of the engine layout. Haven't decided on exactly what turbo I want, but probably something modest... not too extreme. For the most part, this car is going to be a driver, not a race car.

Jeff, again, thanks for your input. It has been helpful. I will certainly keep the board and you updated as this project comes to fruition.

Tom Richardson, Jr.

[This message has been edited by tomrichardson (edited 06-26-2001).]

[Roland Kunz]

Hello

Sure I was talking about geting the oiltemperature in the trany down.

Limits are hard to determine, just try it and keep one trany in spare. I shreeded some 5 tranys with my 2,7 Carrera engine and 205/55/16 on the rear. But maybe caused more by to much high speed driving, hunting Ferraris and 928 GT with my ole VW.

Failures where; broken main shaft. Mostly craked in the 1st gear or sheared away nut on the end. Pitting on R&P with loosing theeth on the R&P. These made loud noises but brought you home. Broken spider gear inside the differential.

Other curios things; drilled trough speedo worm drive on a 911 trany in a 2,4 Oettinger 1303, big screw came loose.


One good thing is you will not find a clutch that will hold the tourqe. You will go to 228mm discs and Volvo Turbo Sport pressure plates. You have to reinforce the clutchtube at the firewall as it will get bend and break and your left foot will get more muscles then the right one.


Using enrichment to cool down the engine is very comon by simple designed turbo systems. Just look at the old SVO 2,3 Mustang or the Chrysler 2,2. You will run in some problems with a flat engine, ok, you don´t use it for constant full load high speed driving. Also most turbos will not like to get puddled in fuel so you have to pressurize the carbs.

Grüsse