preach (dudeist priest)
preach (dudeist priest) Dork
3/17/22 10:25 p.m.

This topic is for all wheels spinning.

I have had 3x Haldex cars and about 10 full on selectable 4wd trucks.

part time, full time, let's hash it out. Primarily cars.

idk what a gtr Nissan is or a gt4 s celica is.... 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
3/17/22 10:39 p.m.

Skyline GTR is a clutch pack to the front, like Haldex but in reverse.

newrider3
newrider3 HalfDork
3/17/22 10:40 p.m.

Somewhat nonspecific, but something I learned researching Honda AWD builds/swaps - if one wants to do away with the dual-pump clutch-pack Honda rear diff to gain full-time AWD rather than on-demand (delayed based on wheelspin) 4wd, a Land Rover Freelander driveshaft can be used. The viscous coupler is built into the middle of the Freelander shaft, making it a convenient option for full AWD conversions. 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
3/17/22 10:45 p.m.

In reply to newrider3 :

That is interesting to know!

Honda has several different mechanisms.  A lot of the V6 models use a setup that does not have a differential in the rear, but a clutch pack for each rear wheel.  Some of those have a gear arrangement that can overdrive the outside wheel, too. (some of the Type S models.. I think they are labeled SH)

One interesting thing is that Nissan makes a turbocharged device with torque vectoring in the rear... the Juke.  

preach (dudeist priest)
preach (dudeist priest) Dork
3/18/22 10:20 a.m.

My Charger is a sort of reverse haldex I think. 95% rwd but if it spins a tire the fronts kick in. My Golf is just the opposite.

BA5
BA5 Reader
3/18/22 10:42 a.m.
Pete. (l33t FS) said:

In reply to newrider3 :

That is interesting to know!

Honda has several different mechanisms.  A lot of the V6 models use a setup that does not have a differential in the rear, but a clutch pack for each rear wheel.  Some of those have a gear arrangement that can overdrive the outside wheel, too. (some of the Type S models.. I think they are labeled SH)

One interesting thing is that Nissan makes a turbocharged device with torque vectoring in the rear... the Juke.  

The "SH" is basically a tiny automatic transmission (clutches and planetary gearset and all) situated between the driven wheels.  As you said, depend on which clutches are activated it can overdrive the outer wheel, making the car turn in much harder.  It has more recently appeared in their RL and RLX models, but it was originally introduced in the 5th gen Prelude back in the day.

I have a 5th gen Prelude Type SH.  I'm a fan of the system.  Some said it was too heavy, but having actually held it in my hands it's not really that bad.  It's performance more than makes up for the extra weight, especially since it's situated about as low as it can be in the chassis.

CyberEric
CyberEric Dork
3/19/22 10:28 a.m.

Every time someone asks about all of the different AWD systems I get excited because I still don't understand them. And then, my eyes glaze over and I end up right where I started.

Oapfu
Oapfu New Reader
3/19/22 2:34 p.m.

This website has an extensive amount of info on various AWD systems: https://www.awdwiki.com/en/home/

Either I'm stuck overthinking it, or the "torque split" ratio thing seems like an oversimplification.
Systems (other than torsen or planetary center diffs) try to control the speed difference between the axles and therefore have to let torque sort itself out (based on actual slip ratios or traction limits at the contact patches)?

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
3/19/22 4:22 p.m.

In reply to Oapfu :

Yes.

One of my huge annoyances, and one of the reasons I am keeping my mouth mostly shut in this thread, is the idea that a locked differential is a "50/50 split". 

Torque is a concept independent of speed.   You can apply torque with no motion, as anyone who has fought a stuck fastener can appreciate.  You can have motion with zero torque, as anyone who has stripped a fastener can appreciate wink

If you had an AWD system and one axle was off the ground, and the vehicle can accelerate because the center differential is locked, the axle in the air gets 0 torque and the axle on the ground is getting 100% torque.  A 50/50 split would be both axles getting an equal amount of torque, in this case the axle on the ground getting an amount of torque equal to the axle off the ground, IE zero.  This is an OPEN diff, not a locked one.

Torsens and planetary diffs are, at their base, open diffs, but they apply torque with a bias. In the planetary diff the torque bias is fixed, usually 33/66 or so but in some cases, like the Subaru automatic trans I am leaning on, a double planetary arrangement is used to change that to about 45/55.  In a Torsen, the torque bias is variable by up to 2.5-4:1  (or roughly 70/30 to 80/20) depending on the wheel speed difference, thanks to the weirdities of trying to backdrive a worm gear.  But if one end is off the ground, the other end still gets 2.5-4 times zero, which is still zero.

Unless there are clutch packs involved to limit slip... which this Subaru trans has, controlled electronically as opposed to spring pressure, which is another way to do it (like a Wavetrac).

AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) UltraDork
3/20/22 6:10 p.m.

If it's a car, Audi or Subaru hands down.  Their transmissions are pretty magical.  If it's a truck or Jeep that's something entirely different.  And for Audi's I avoid the Haldex ones like the plague.  

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