dacula951

With the front engine and rear transmission layout, if there was no torque tube, there would have to be rear motor mounts to counteract the torque being applied by the engine. Likewise, the front of the transmission would have to have transmission mounts to counteract the applied torque. The torque tube connects the engine and transmission together beautifully, eliminates the need for the extra mounts, and prevents this torque from having to be transmitted through the vehicle's body. Anyone that has taken the system apart when doing a clutch job will know what I'm talking about.

Trucho-951

Advantage, torque tubes have bearings that can go dry and squeak, and annoy you.

FRporscheman

Yep. I'd totally rather have the expensive parts and easy labor.

Weight distribution? How would a TT create better weight distribution than a driveshaft?

I understood that the TT eliminated the need for extra mounts. I didn't realize the lack of extra mounts meant a lack of extra torque being transfered into the chassis until you said it. Now that's a huge advantage. But then it's just like having 4 mounts, and making the rear ones solid.

njwilser

The tourque tube creates better weight distribution by permitting the trans in the rear and the engine up front. This cannot be done either at all or well with a standard driveshaft.

ibkevin

Good question Arash.

Mike C.

The main job of the torque tube, as I see it, is to maintain a very tight dimensional relationship between engine and transaxle. This is why no u-joints are needed. Even if you mounted the engine and transaxle very rigidly to the shell, there would still be some relative movement which would require u-joints and perhaps a sliding joint to take care of. Is it impossible to build a driveshaft to spin at engine speed? Certainly not I would think. It would have to be balanced more carefully and perhaps heavier duty u-joints. No doubt it was studied before they decided on the torque tube.

pjburges

Well, Im a mech engineering student down here in Texas, and while Ive never had to do a clutch job on my 944 Id say those krauts were probably thinking t. tube for a few reasons:
As pointed out previously its a pretty rigid mount and the tube absorbs gear backlash and applies load evenly with the mounts being so far apart. in the most simple form: T=F*d

Also they had to consider servicability b/c Porsche put a warranty on these cars. The transaxle design is labor intensive and could cost Porsche alot of money in the service department. The very lightweight inner shaft combined with a series of large bearings meant that there was not much stress in load, so it made a durable link that they didnt have to service all the time.

The fact that everything is centered down the drivetrain is nice, and there is effeciency gained - but nothing to go waving your hands in the air about. Most effeciency would be gained in the lighter rotating mass (which would be top priority on a small 4cyl.)
just my 2cents

FRporscheman

Thanks, Kevin.


OOOOOOOOOOOOOH. I didn't know that. Thanks!

Yeah, lightweight "driveshaft" is great for getting more usable power.

marksportcts

And it also has the collision lugs to prevent the motor from going onto your lap in a hard crash.

MorganWright

It's 2023 now and this thread is from 2007 but there is something not answered in the thread. First of all, the torque tube doesn't spin at all. The driveshaft spins inside the torque tube. Secondly, the whole purpose of a torque tube is to transfer the wheel torque from the axle housing to the transmission housing and engine and body of the car, so the car doesn't pop a wheelie like a bicycle. In cars with just a drive shaft, and no torque tube, the wheel torque is transferred to the body of the car through the rear leaf springs, this is called a Hotchkiss drive. The rear leaf springs attach to the rear axle via spring perches which don't move, so the car doesn't pop a wheelie. With a torque tube, you don't have to worry about the leaf springs, you can use coil springs in the back or a cantilever suspension in the back, neither of which you can do without a torque tube to get rid of wheel torque. On a bicycle, you could never pop a wheelie if there were a torque tube attached to the front wheel. Just think of that.

Gage

So, if I take my torque tube out, I can pop wheelies? That sounds like fun

MorganWright

If you take out the torque tube, stepping on the gas will make the rear axle housing pop a wheelie. That will snap the drive shaft like a pretzel stick.

Tiger03447

I just wish that Porsche made the tube out of aluminum instead of steel. It is a pretty heavy unit. Constantine probably can tell you what the exact weight of the entire assembly or just the tube itself. A rough guess would be around 50 lbs for the whole unit IMHO. I think they built the whole car around it and added the engine later..LOL!😂

MorganWright

You cant make torque tubes out of aluminum, it's not strong enough to move all the torque to the front. It would be like making aluminum leaf springs on a Hotchkiss suspension. An aluminum torque tube would break the first time you hit the gas.

Gage

Fascinating
I wonder how GM managed this with the Corvette.