TC and F/awd vehicles.
#51
06-05-2009, 07:09 AM
Re: TC and F/awd vehicles.
Locking, positraction, limited slip...
Different methods of getting to the same effect. I consider them to be functional equivalents and you are being disingenuous in what you are trying to say.
What you don't seem to get is that the two work in opposition to each other and offsetting the unintended effects of one when at low speed makes a difference.
I'll go to the shop manuals and look up the strict, technical definition of the axles in my 92 Suburban, 01 Mustang , & 06 Escape Hybrid.
BTW, if you go back 40 years (1969!) any kind of locking, limited slip or locking differentials were not in common use. The standard open differential was common through about the 80s.
I've learned over the years that when people pontificate, as you did with your "correct me if I'm wrong" lead in, they are frequently wrong.
Different methods of getting to the same effect. I consider them to be functional equivalents and you are being disingenuous in what you are trying to say.
What you don't seem to get is that the two work in opposition to each other and offsetting the unintended effects of one when at low speed makes a difference.
I'll go to the shop manuals and look up the strict, technical definition of the axles in my 92 Suburban, 01 Mustang , & 06 Escape Hybrid.
BTW, if you go back 40 years (1969!) any kind of locking, limited slip or locking differentials were not in common use. The standard open differential was common through about the 80s.
I've learned over the years that when people pontificate, as you did with your "correct me if I'm wrong" lead in, they are frequently wrong.
A open differential sends all torque to the wheel with the least amount of traction, a LSD splits the torque and a TC/AWD shifts the torque to the wheel(s) with the most traction.
Right, a open differential was common in a passenger vehicle but LSD, Posi, etc. was a option and is still is for high performance vehicles and trucks. My '66 SS96 Chevelle had Posi-Traction and my '97 Ranger had a locker in it also.
It would help to use quotes to know who you are addressing.
#52
06-05-2009, 07:13 AM
Re: TC and F/awd vehicles.
A little bit of knowledge can lead to real heresy...
Go to wikipedia and search for "Limited slip differential." You'll find a detailed discussion of all of the types and how they function.
Regardless of type of differential the TC & limited slip type differential work in opposing ways. At higher speeds this is unnoticeable but at low speeds it can seriously affect whether you can get unstuck in snow, ice or mud.
Turning off the TC removes this effect, then you turn it back on when clear. There's a reason they put these switches on some cars.
C'mon guys.
Go to wikipedia and search for "Limited slip differential." You'll find a detailed discussion of all of the types and how they function.
Regardless of type of differential the TC & limited slip type differential work in opposing ways. At higher speeds this is unnoticeable but at low speeds it can seriously affect whether you can get unstuck in snow, ice or mud.
Turning off the TC removes this effect, then you turn it back on when clear. There's a reason they put these switches on some cars.
C'mon guys.
#53
06-05-2009, 07:22 AM
Re: TC and F/awd vehicles.
Never said TC & AWD was a locking system.
I used "locking" in the generic sense to refer to any kind of limited slip differential. You guys have zeroed in on petty stuff and missed the bigger point I was making about how these two systems work in opposition.
Available as an option (or on high performance cars) does not mean general use. Limited slip differentials have been "available" since the 30s. But they weren't routinely installed on cars, trucks, etc until to 80s. When I bought a Jeep CJ in the 70s if I wanted a limited slip in mine I had to order it and pay extra. I'll have to go look, but as I recall when I ordered my Suburban 4WD I had to specify, and pay for, a limited slip differential.
Available does not mean general use.
I've had enough.
I used "locking" in the generic sense to refer to any kind of limited slip differential. You guys have zeroed in on petty stuff and missed the bigger point I was making about how these two systems work in opposition.
Available as an option (or on high performance cars) does not mean general use. Limited slip differentials have been "available" since the 30s. But they weren't routinely installed on cars, trucks, etc until to 80s. When I bought a Jeep CJ in the 70s if I wanted a limited slip in mine I had to order it and pay extra. I'll have to go look, but as I recall when I ordered my Suburban 4WD I had to specify, and pay for, a limited slip differential.
Available does not mean general use.
I've had enough.
#55
06-05-2009, 09:12 AM
Re: TC and F/awd vehicles.
It's mentioned above to be on a '06 FEH and you have a '08 FEH, so you such have a switch too.
Last edited by wptski; 06-05-2009 at 09:14 AM.
#56
06-05-2009, 09:37 AM
Re: TC and F/awd vehicles.
Where is this switch? I will take a look. I don't find anything in the owners manual...
#57
06-05-2009, 10:09 AM
Join Date: Sep 2006
Location: Beautiful Pacific NW
Posts: 1,678
Re: TC and F/awd vehicles.
Too far...
It is not at all unusual for an AWD system, especially R/awd, to have a mechanical "LSD" (using the term generically), probably a torque sensing type. But it is true that MOST F/awd vehicles these days will have TC and therefore likely a "virtual" rear LSD.
LSD implementations using TC on a FWD or the front of of a F/awd vehicle are unusual in that it would/might SUDDENLY induce a level of torque stear for which an inexperienced driver might be unprepared.
VC...Viscous Clutch.
It is not at all unusual for an AWD system, especially R/awd, to have a mechanical "LSD" (using the term generically), probably a torque sensing type. But it is true that MOST F/awd vehicles these days will have TC and therefore likely a "virtual" rear LSD.
LSD implementations using TC on a FWD or the front of of a F/awd vehicle are unusual in that it would/might SUDDENLY induce a level of torque stear for which an inexperienced driver might be unprepared.
VC...Viscous Clutch.
#58
06-05-2009, 10:19 AM
Join Date: Sep 2006
Location: Beautiful Pacific NW
Posts: 1,678
Re: TC and F/awd vehicles.
TC/AWD just isn't a locking system.
A open differential sends all torque to the wheel with the least amount of traction,
Common misunderstanding, miss-statement.
The wheel with the least amount of traction "saps" the level of torque available to 4X (AWD) the amount of torque required to rotate/spin the wheel with least traction.
Disable TC, jack one wheel off the ground for an AWD vehicle with three simple open diff'ls, say an HL, and try to drive off.
a LSD splits (biases) the torque and a TC/AWD braking or the wheel(s) with least rtaction elevates (shifts) the torque to the wheel(s) with the most traction.
Right, a open differential was common in a passenger vehicle but LSD, Posi, etc. was a option and is still is for high performance vehicles and trucks. My '66 SS96 Chevelle had Posi-Traction and my '97 Ranger had a locker in it also.
It would help to use quotes to know who you are addressing.
A open differential sends all torque to the wheel with the least amount of traction,
Common misunderstanding, miss-statement.
The wheel with the least amount of traction "saps" the level of torque available to 4X (AWD) the amount of torque required to rotate/spin the wheel with least traction.
Disable TC, jack one wheel off the ground for an AWD vehicle with three simple open diff'ls, say an HL, and try to drive off.
a LSD splits (biases) the torque and a TC/AWD braking or the wheel(s) with least rtaction elevates (shifts) the torque to the wheel(s) with the most traction.
Right, a open differential was common in a passenger vehicle but LSD, Posi, etc. was a option and is still is for high performance vehicles and trucks. My '66 SS96 Chevelle had Posi-Traction and my '97 Ranger had a locker in it also.
It would help to use quotes to know who you are addressing.
#59
06-05-2009, 10:27 AM
Join Date: Sep 2006
Location: Beautiful Pacific NW
Posts: 1,678
Re: TC and F/awd vehicles.
TC "off" capability on a FWD or F/awd is yet another matter. IMMHO NO FWD or F/awd vehicle should ever be shipped absent a TC system that always defaults to operational status with each and every engine restart. It was only after a fairly high level of public outcry, justifiable outcry IMMHO, that the TC disable function has begun to be added in the past 2-3 years. Even so, even on FWD and F/awd I really don't see the usefulleness of TC other than the initial activation to prevent an inadvertent loss of control episode and allert the driver to current roadbed conditions.
Like I have suggested for ABS, maybe TC should NOT activate unless VSC detects an actual yawing condition, the vehicle not travelling in the correct or desired direction.
Last edited by wwest; 06-05-2009 at 12:09 PM.
#60
06-05-2009, 01:35 PM
Re: TC and F/awd vehicles.
Can't seem to reply with your quote but I'm not sure which statement you think is wrong and your bold text sentence is confusing.
Here's a link to a site that explains a Open Differential; http://auto.howstuffworks.com/differ....htm/printable, scroll down to On Thin Ice.
Yeah, FWD with TC OFF won't move with one wheel off the ground and a AWD with three off the ground won't move either.
TC defaults to ON every time it's started.
Here's a link to a site that explains a Open Differential; http://auto.howstuffworks.com/differ....htm/printable, scroll down to On Thin Ice.
Yeah, FWD with TC OFF won't move with one wheel off the ground and a AWD with three off the ground won't move either.
TC defaults to ON every time it's started.
