911 Twin Turbo and stock 915 gearbox.What to do to make the transmission stronger?

[MrShades]

Twin Turbo(ca 350 hp)and stock 915 gearbox.What can i do to strenghten the transmission?
I cant use 1st and second gear without beeing very careful with the gas pedal.
A lot of you will probably answer "get a G50"

[ted]

Hayden at WEVO has some very nice 915 upgrades.
Welcome to Windrush Evolutions - WEVO - Porsche Products

[shahram]

get a 930 gearbox

[MrShades]

I want to have 5 gears

[Peter Zimmermann]

We had a "rule" of thumb that about 275 hp was the upper limit for a well-driven and properly assembled 915. Even at that care in first gear was always mandatory. Your 930 trans options include Ruf 5-speed conversions (probably very hard to find one of those!), and, you said it, a G50. Sorry!

[shahram]

It is also possible to convert a 4 spd 930 to a 5 spd 930. But the only shop I know doing that is located in Germany. you also can try to find a late 1988 - 1989 930 5 spd Tranny.
where ar you located MrShades?

[Gunter]

Even though it's easy to do, giving out location under their Avatar seems to be a real problem for a lot of people.

I know a couple of 915's that busted gears with just a NA 3.6 liter, never mind a TT. After '85, Porsche beefed up the half-shafts a few times due to increased HP.

Any major HP-increase requires upgrading drive-train, brakes, suspension etc.; it's only logical.

[ChrisBennet]

It is not unheard of to twist the mainshaft on a 993TT (a buddy of mine has repaired one with this problem). Using a 915 is probably a false economy in this situation.
-Chris

[MrShades]

I am located in Norway

Originally Posted by shahram

It is also possible to convert a 4 spd 930 to a 5 spd 930. But the only shop I know doing that is located in Germany. you also can try to find a late 1988 - 1989 930 5 spd Tranny.
where ar you located MrShades?

[Matt Monson]

How about a 6spd 930?

Porsche 930 Transmission Transaxle Short Bell 6-Spd 361 : eBay Motors (item 300339442567 end time Mar-14-10 17:28:08 PDT)

[Gunter]

MrShades: Post it under your Avatar, it's easy to do.

[RarlyL8]

I have been using a 915 behind (in front of?) a 300whp 930 for about 10 years.
You can do this if you avoid the dragstrip, do not track the car, and do not dump the clutch. Let the engine do the work, not the transmission.
I recently built a 2nd tranny for this car with custom gearing as the 4th and 5th of the 915 were too low. WEVO components were used in both 915's. The bearing retainer and the side plate are the weak links. Second gear is also weak so no speed shifting. A friend used a 915 in his 400WHP 930 so we learned quickly where the weak spots are, ha!
It sounds like I baby the tranny but I do not. The tires roast in 2nd gear and "haze" in 3rd gear. Rear tires are BFG TDK 315/35-17 so not skinny.
Drag strip time was 8.5sec @ 90mph in the 1/8 mile and cost me a rebuild so don't dump the clutch on concrete, ha!
I have recently added my headers which took the power to 350WHP. No issues so far.

[KTL]

Originally Posted by Matt Monson

How about a 6spd 930?

Porsche 930 Transmission Transaxle Short Bell 6-Spd 361 : eBay Motors (item 300339442567 end time Mar-14-10 17:28:08 PDT)

Nicely played Matt! Now that's how you bring a .357 magnum to a knife fight, Dirty Harry style.....

[harrisracing]

Originally Posted by RarlyL8

I have been using a 915 behind (in front of?) a 300whp 930 for about 10 years.
You can do this if you avoid the dragstrip, do not track the car, and do not dump the clutch. Let the engine do the work, not the transmission.
I recently built a 2nd tranny for this car with custom gearing as the 4th and 5th of the 915 were too low. WEVO components were used in both 915's. The bearing retainer and the side plate are the weak links. Second gear is also weak so no speed shifting. A friend used a 915 in his 400WHP 930 so we learned quickly where the weak spots are, ha!
It sounds like I baby the tranny but I do not. The tires roast in 2nd gear and "haze" in 3rd gear. Rear tires are BFG TDK 315/35-17 so not skinny.
Drag strip time was 8.5sec @ 90mph in the 1/8 mile and cost me a rebuild so don't dump the clutch on concrete, ha!
I have recently added my headers which took the power to 350WHP. No issues so far.

Lots of people say they use "WEVO INTERNALS" to make the 915 hold up but my question is: Are they talking about just the bolt-on bearing support plate or are they talking about the pocket machine work on the main case and final drive case with the shrink fit inserts? There is a SUBSTANTIAL price difference when factoring in those repairs.

I have a 77 915 case and am looking to rebuild / upgrade it while building my car. I'm very curious what people do to hold power.

Thanks,
Patrick

[RarlyL8]

Patrick,
I added my headers which bumped the power to 350WHP and added the same amount of torque. So far the 915 remains unchanged and is holding up. I really don't recommend the 915 at this power level though as I could break it at will.
The WEVO gear I used in both transmissions is the bearing retainer. I have my re-geared Carrera 915 in now so don't need the late model side cover as the Carrera unit is what I used in the SC 915.
These are the most important things to protect (bearing and side plate). To further protect these items an LSD should be used. This prevents the torque from slamming the pinion into the sideplate by re-distributing shock to the other side.

[spuggy]

Originally Posted by harrisracing

I have a 77 915 case and am looking to rebuild / upgrade it while building my car. I'm very curious what people do to hold power.

Here's a good thread on strengthening 915's. The "How to beef up a 915" thread. Parts and costs?

The '77 is a mag case 915. That will eventually be extremely sad if you start putting 300 ft/lbs of torque through it on a regular basis. I know mine was.

[Oh Haha]

RUF 5 speed transmission for sale or trade

[harrisracing]

Originally Posted by spuggy

Here's a good thread on strengthening 915's. The "How to beef up a 915" thread. Parts and costs?

The '77 is a mag case 915. That will eventually be extremely sad if you start putting 300 ft/lbs of torque through it on a regular basis. I know mine was.

This is EXACTLY the information I need. Thanks for the heads up before I get too far along.

I have a 77 narrow car that I'm semi-hotrodding and found another 78 w/ sport seats that is really in better condition that has a complete original turbo-flared body. I mean that somewhere along the way someone did ALL of the turbo body parts to it in metal. It came from California so the car is very straight and is in just great shape. SO, I bought that too...and well the look without the turbo is making me think twice about what powerplant I need to use. I also have a good running 3.0L here w/ 100k miles and was thinking that would be a damn fine powerplant to turbocharge, but I think I will have to rethink using a 915 case for that duty (mag anyway).

Now, on the 77 2.7 car (which will most likely still be a gutted-out hotrod), should I worry too much about the tranny with a nicely built modern-EFI'd 2.7? Definitely put the WEVO center plate in it and perhaps just a 40% LSD or a TBD in it and go ride and occasionally hit the big track?

Thanks
Patrick

[RarlyL8]

The '77 was made in both Mag and Aluminum. You need to figure out which one you have. The type number will give a clue (915/61) but not definitive. If you decide to stay with a 915 a Carrera unit is the strongest.

[harrisracing]

Here are the pictures I have on hand right now, but of course I didn't take any of the number.

Anyone want to guess until I can get to the shop later tonight? I also get all kinds of mixed history on these units. Some say that even half of the tranny could be aluminum and half could be MAG as well. I will clean it really well later and try to find out.