18 replies to this topic

[allen405]

In an attempt to get to know these vehicles better I was wondering something. What is the torque tube for? Its the weirdest thing. Whenever I get asked what it is I always end up saying I don't know

[jahjah]

Quote

The "torque" that is referred to in the name is not that of the driveshaft, along the axis of the car, but that applied by the wheels. The design problem that the torque tube solves is how to get the traction forces generated by the wheels to the car frame. The "torque tube" transmits this force by directly coupling the axle differential to the transmission and therefore propels the car forward by pushing on the engine/transmission and then through the engine mounts to the car frame

[Goddard]

Your first quoted sentence is correct for our cars, the second is not.  The second would refer to a car such as the Corvette where the torque tube connects directly to the gearbox.

[Chad]

It also acts like a spirng, it dampens some torque shock.

I belive the primary purpose of it is to anchor the diff to the rear subframe.  The longer a support is, the more stable it will be, so they put in a nice long torque tube.  If they just put in the pumpkin and attached it with regular diff mounts, the torque of the motor and the wieght of the car would tear the mounts up real fast.  The diff need sto be able to  rotate a little to take up some of the tranient stresses, so they didn't built supports lateraly (parallel to the CV axles), builidng the long support longitudinaly allows it to move some, while still being well anchored to the car subframe.  

Some high torque cars (like the Viper) have the long mounts laterally, but that setup also doesn't have room for the lngitudinal mount anyway, the trans tail shaft is very close to the diff.

Also, the longer yoru driveshaft is, the less stable and weaker it is.  The torque tube shortens the shaft quite a lot, leading to a very stable assembly.

[jahjah]

Goddard, on 04 March 2010 - 09:04 AM, said:

Your first quoted sentence is correct for our cars, the second is not.  The second would refer to a car such as the Corvette where the torque tube connects directly to the gearbox.

I just copied mine from wikipedia.

[Goddard]

^ That's what I figured.

[jahjah]

Goddard, on 04 March 2010 - 12:22 PM, said:

^ That's what I figured.

good call though

[ucw458]

Chad, on 04 March 2010 - 11:15 AM, said:

Also, the longer yoru driveshaft is, the less stable and weaker it is.  The torque tube shortens the shaft quite a lot, leading to a very stable assembly.

More importantly for car manufacturers, the longer the shaft is the more suceptable it is to harmonic vibrations when in an OD gear.  The harmonic vibrations are caused by the U-joints ocilating.  The best ways to dampen that vibration so you don't get a strange noise in OD is to either have a short driveshaft or a larger diameter driveshaft.

I forget where I read this from, it was a long time ago.  But basically it was a problem unique to cars with OD.  The vibration was always there and for the most part not noticed due to the vibration coming from the engine.  But when OD became an option people became aware of the vibration because in OD the driveshaft is spinning faster than the engine.

[patra_is_here]

i thought in our case the TQ tube helps launch traction by momentarily dampening the initial shock during clutch release.

[ucw458]

patra_is_here, on 04 March 2010 - 03:16 PM, said:

i thought in our case the TQ tube helps launch traction by momentarily dampening the initial shock during clutch release.

I don't think there is just one right answer.  It could be dampening driveline shoch a little by letting the TT shaft twist like a torque stick for an impact gun.  It's a stable mounting point for the rear diff.  It shortens the driveshaft for a couple beneficial reasons.  It might be reducing noise from diff to chassis.  etc

[Chad]

ucw458, on 04 March 2010 - 03:04 PM, said:

More importantly for car manufacturers, the longer the shaft is the more suceptable it is to harmonic vibrations when in an OD gear.  The harmonic vibrations are caused by the U-joints ocilating.  The best ways to dampen that vibration so you don't get a strange noise in OD is to either have a short driveshaft or a larger diameter driveshaft.

I forget where I read this from, it was a long time ago.  But basically it was a problem unique to cars with OD.  The vibration was always there and for the most part not noticed due to the vibration coming from the engine.  But when OD became an option people became aware of the vibration because in OD the driveshaft is spinning faster than the engine.

yah that is what i was getting at with my "stabilizing" statement.  It also is less likely to deflect under load if it's shorter.  There are some older sports cars that have an intermediate joint in the middle (2 dirveshafts) to get arround this.

I don't know what mitsus thoughts were, but I do see many reasons for it.

I have considered removing mine and putting a companion flange on the pinion input (a 4 bolt CV flange fits perfectly 8) ) and adding diff brackets to simulate the purpose of the torque tube, but I don't want to toss out a system that works just fine, and I say that while I push a butt-load of power though mine.   It's not broke, so I'm no inclined to fix it.   Trick is to get a good torque tube shaft and splined pinion hub (hard to find these days), along with good stiff diff mounts.  That solves all the slop in the rear portion of the drivetrain.

[allen405]

Wow thanks for the abundance of answers, that helped alot

[patra_is_here]

ucw458, on 04 March 2010 - 04:51 PM, said:

I don't think there is just one right answer.  It could be dampening driveline shoch a little by letting the TT shaft twist like a torque stick for an impact gun.  It's a stable mounting point for the rear diff.  It shortens the driveshaft for a couple beneficial reasons.  It might be reducing noise from diff to chassis.  etc

exactly. the shaft in the TQ tube is spring steel and it's diameter is engineered to allow for a specified TQ load to flex it, EXACTLY like the TQ sticks on impact guns. great observation.

[psu_Crash]

Great information guys! I vote sticky

[ucw458]

patra_is_here, on 04 March 2010 - 08:32 PM, said:

exactly. the shaft in the TQ tube is spring steel and it's diameter is engineered to allow for a specified TQ load to flex it, EXACTLY like the TQ sticks on impact guns. great observation.

I wonder how many people here have actually dissasembled a torque tube and seen the small shaft running through it.  Most would be suprized.  I know I was.

[JohnnyWadd]

ucw458, on 04 March 2010 - 09:48 PM, said:

I wonder how many people here have actually dissasembled a torque tube and seen the small shaft running through it.  Most would be suprized.  I know I was.

my shaft was big i dont know what your talking about.

[ColdScrip]

[TexasQuest]

JohnnyWadd, on 04 March 2010 - 10:01 PM, said:

my shaft was big i dont know what your talking about.

LOL!

[Shelby]

another thing about short drive shafts and working angles,, the working angle on the ujoints is  very small makeing  them hard on the brgs and cross arms , thats the reason  younts  tend to wear out quickly ,, the rollers are much harder then the cross shafts and  once they  wear it creates a rought spot that  causes  vibration  every  half turn ,, the last thing you want is a inline shaft alignment , the shaft must have an angle to  turn smoothely