What's the advantage of torque tubes over driveshafts?
#16
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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.
#18
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Originally Posted by hosrom_951
Now, the 944 torque tube could be a PITA to remove, but at least the bearings inside could be replaced. Cheap parts, lots of labour for the Porsche, cheap labour and expensive parts for the BMW.
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.
#19
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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.
#21
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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.
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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
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
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Thanks, Kevin.
OOOOOOOOOOOOOH. I didn't know that. Thanks!
Yeah, lightweight "driveshaft" is great for getting more usable power.
Originally Posted by 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.
Originally Posted by pjburges
Most effeciency would be gained in the lighter rotating mass (which would be top priority on a small 4cyl.)
just my 2cents
just my 2cents
#25
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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.
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.
Last edited by MorganWright; 12-18-2023 at 10:38 AM. Reason: typo
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#26
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So, if I take my torque tube out, I can pop wheelies? That sounds like fun
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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!😂
#29
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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!😂
#30
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I wonder how GM managed this with the Corvette.