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Old 05-31-2012, 05:35 PM   #1
turbotim3
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Default 944 torque tube

Hi, Does anyone know what sort of power and torque the 944 torque tube can handle. I am building a 2.7 16 valve turbo engine and I am concerned it won't take the power. Cheers Tim
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Old 05-31-2012, 07:04 PM   #2
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It's used in many big builds w/o a problem. Handles my 330hp/330T just fine so far...
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Old 05-31-2012, 07:26 PM   #3
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The torque tube will handle more torque than the transaxle and axles will.
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Old 05-31-2012, 09:40 PM   #4
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Quote:
Originally Posted by fortysixandtwo View Post
The torque tube will handle more torque than the transaxle and axles will.
+1

I wouldn't even worry about it. There is a guy that once built a 944 turbo that put out right around 700HP using the stock tube...all the V8 guys use it and they have 400+ ftlbs of torque, all day long.
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Old 05-31-2012, 09:50 PM   #5
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+2 if you are talking about a 944na then the clutch, trans & axles will fail way before the TT. I presume you will at least be using 951 clutch, trans and axles.
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Old 06-01-2012, 02:37 AM   #6
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Hi Guys, thanks for the info. At what power does the transmission start to give problems and what would you advise I use. Cheers Tim
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Old 06-01-2012, 02:59 AM   #7
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944 turbo or S2 or 968 transmission are more or less unbreakable...unless you reeaaally try to break it.
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Old 06-01-2012, 04:21 AM   #8
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I have heard of and seen a few 500-600hp++ variants of the 944/951/968 engines and also ChevyV8s using the stock 944 torque tube. As long as you do not damage the splines on either end when removing/re-installing it, you should be fine for anything you can throw at it.

Your biggest worry should be your CV joints. Over 350+trq and sticky tires and a transmission without a solid mount or some prevention from moving, and your CV bearings will self destruct within a matter of weeks if you do enough hard, jerky, launches and shifts.
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Old 06-01-2012, 12:16 PM   #9
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The calculated strength is about 450Nm assuming it is fabricated from grade 250 steel, and 720Nm assuming grade 400 steel. I would postulate it would be more like 400 grade steel. So a torque >720Nm (steady load) will cause it to yield. I think the TurboS had around 340Nm as stock. With a factor of safety of 1.5 (to account for shock loading, etc), I would say 480Nm (350 ft-lb) would be its safe limit.
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Old 06-01-2012, 12:26 PM   #10
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I would think the cast aluminum housing at the back would crack before the tube ever broke...
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Old 06-01-2012, 12:46 PM   #11
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I cannot see how the actual tube has any torque on it. Doesn't the torque go down the bar in the center. The only time the tube will have any torsional force is if the motor or trans mounts were shot, or if you have solid mounts at one end and rubber at the other.
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Old 06-01-2012, 04:39 PM   #12
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Before the t tube goes the clutch disc would go as well as the axels (cv joint area ) and then on... Don't forget you'll also need traction...then you'll see the weakest link go first .
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Old 06-01-2012, 05:07 PM   #13
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Quote:
Originally Posted by MAGK944 View Post
I cannot see how the actual tube has any torque on it. Doesn't the torque go down the bar in the center. The only time the tube will have any torsional force is if the motor or trans mounts were shot, or if you have solid mounts at one end and rubber at the other.
even with good motor mounts the engine twists, and if you have a stout trans mount (like early cars, or the solid ones for late cars) there'd be some torsion on the tube...probably not on the stock late trans mount banana hammock though
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Old 06-01-2012, 10:41 PM   #14
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The capacity is limited to the 25mm driveshaft. The TT itself will have to resist the torque transmitted by the engine as the trans is mounted like a pinned joint that cannot transmit moment. Therefore the tube will take the same torsional moment as the shaft/engine. If it didn't the whole trans would twist independently of the engine. Effectively, the engine mounts provide the resistance in the system to twisting. The tube has a much higher torsional capacity than the shaft and is not an issue. So much so that the S2 has a slit tube to try and dampen the torsional vibrations in the tube by reducing its torsional stiffness.
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Old 06-01-2012, 11:02 PM   #15
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You can't find enough power to mess up the TT. The rear axle sleeve is an other matter. The 968 sleeve is much more robust than the 944 ones. The transaxle is the weak link in the chain, and even then all 944 ( audi) boxes are pretty good. The best of all is the 88 Turbo S w. LSD box. It has an external cooler and hardened gears. The code on top starts with AOR.
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