I believe I've seen this posted before, but my search did not find it. What is the technical difference between FT4wd and AWD (not limited to the world of Subarus)? I have been told in another thread that the EA82 4EAT FT4wd tranny is NOT considered an AWD tranny. WHY NOT??
After all, there are many varieties of AWD. Even the current Subaru AWD trannies are radically different between Auto and 5spd versions.
I know that the EA82/ER27 FT4wd 5spd trannies had open center diffs, so I can see why these might not be considered AWD by some people.
I was under the impression that the 4EAT FT4wd tranny operated in a very similar way to the later EJ AWD trannies. In what way is this not true?
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Guest Message by DevFuse
FT4wd vs. AWD
Started by
CIS Subaru
, Mar 05 2004 10:32 AM
18 replies to this topic
#1
CIS Subaru
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Posted 05 March 2004 - 10:32 AM
#2
Setright
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Posted 05 March 2004 - 03:03 PM
4WD and AWD are just jargon.
Subaru started using the AWD moniker to distance themselves from part-time 4WD vehicles. Which in essence means that AWD is permanent and 4WD is switchable.
Make your own rules
Subaru started using the AWD moniker to distance themselves from part-time 4WD vehicles. Which in essence means that AWD is permanent and 4WD is switchable.
Make your own rules
#3
GeneralDisorder
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Posted 05 March 2004 - 03:32 PM
Not entirely true. FT4WD, and AWD both have center differentials to allow the system not to bind up. The FT4WD's have a diff-lock switch (at least some do), allowing you to lock the center diff - making it very similar to a regular 4WD. The AWD's I don't believe have the center diff lock...
GD
GD
#4
CIS Subaru
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Posted 05 March 2004 - 07:26 PM
The diff lock cannot be the answer.
The WRX STi models have center diff locks, and some Audi Quattros had locks for both center and rear diffs. I've never heard anyone refer to these cars as anything but AWD.
The WRX STi models have center diff locks, and some Audi Quattros had locks for both center and rear diffs. I've never heard anyone refer to these cars as anything but AWD.
#5
WJM
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Posted 05 March 2004 - 08:21 PM
the center diff package DOES make a difference. Vicous coupling vs open diff....but the Autos, are the same in operation and theory.
The technology improved when subaru came out with the EJ series.....thus a better name, and something that stands out....no one knows about AWD. Plus, they still called the legacy AWD model...a 4wd car! I think it was 1993 or 1995...somewhere in there the AWD term was really starting to be used. Maybe that came along with the Impreza...
The technology improved when subaru came out with the EJ series.....thus a better name, and something that stands out....no one knows about AWD. Plus, they still called the legacy AWD model...a 4wd car! I think it was 1993 or 1995...somewhere in there the AWD term was really starting to be used. Maybe that came along with the Impreza...
#6
CIS Subaru
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Posted 08 March 2004 - 03:51 PM
So what you're saying is that you agree with me that the EA82 FT4wd auto cars could rightfully be called AWD?
#7
GeneralDisorder
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Posted 08 March 2004 - 04:05 PM
I agree with you CIS - I was previously refering to Setright's comment on the difference between 4WD, and AWD. I just sort of tossed in the center diff thing cause it struck me as a possible difference between the FT4WD and the AWD. I think the difference is just a different center diff in the case of the locker / non-locker tranny's, and that either could have or not have one. So it seems that FT4WD and AWD are indeed basically the same. One thing - a locker in the center diff, will make the tranny either 4WD (when locked) or AWD when unlocked. A simple 4WD tranny actaully disengages the rear wheels, and has NO center diff whatsoever - you cannot lock what isn't there.
AWD and FT4WD cannot be put into 2WD mode (at least not within reach of the driver), has a center diff which may or may not have a locker in it.
4WD is either 2WD, or 4WD (and in the case of D/R, 4WD hi, and 4WD lo), has NO center diff, and acts just like an AWD tranny with the center diff lock ON when in 4WD mode.
That is how I understand it anyway.
GD
AWD and FT4WD cannot be put into 2WD mode (at least not within reach of the driver), has a center diff which may or may not have a locker in it.
4WD is either 2WD, or 4WD (and in the case of D/R, 4WD hi, and 4WD lo), has NO center diff, and acts just like an AWD tranny with the center diff lock ON when in 4WD mode.
That is how I understand it anyway.
GD
#8
WJM
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Posted 08 March 2004 - 07:18 PM
I would call the SUBARU FT4WD 87-94 (EA82 trans) autos AND manuals AWD.
But then again, ALL of SUBARUs FT4WD, and AWD trans, either EA82 or EJ, COULD be called Full Time 4WD....but are rightfully AWD, cuz its the SUBARU name, and they earned it. No one else has.
But then again, ALL of SUBARUs FT4WD, and AWD trans, either EA82 or EJ, COULD be called Full Time 4WD....but are rightfully AWD, cuz its the SUBARU name, and they earned it. No one else has.
#9
GeneralDisorder
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Posted 08 March 2004 - 07:38 PM
No one else has.
As I recall, Audi had AWD long before subaru did. The 1981 quattro rally cars had AWD, and 200 HP 5 cylinder turbo's.... in fact, till Audi got out of the sport, Subaru didn't stand a chance. Not that I like Audi's, but I do have to admit they were first.
GD
#11
Zefy
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Posted 09 March 2004 - 12:19 AM
ok from what i have heard 4WD, FT4WD, and AWD are all different... 4WD is (duh) is you switch it on when you want it...
AWD is always active and will change whenever you do something, even when you turn it will switch power to the inside wheels providing more power with less rpm...
FT4WD is not always active! in normal conditions it will only you the front wheels... it will only turn on the 4WD when one of the wheels starts to slip like on ice...
sound good???
(i just like this banana)
AWD is always active and will change whenever you do something, even when you turn it will switch power to the inside wheels providing more power with less rpm...
FT4WD is not always active! in normal conditions it will only you the front wheels... it will only turn on the 4WD when one of the wheels starts to slip like on ice...
sound good???
(i just like this banana)
#12
WJM
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Posted 09 March 2004 - 07:34 AM
NO! SUBARU's FT4WD is ALWAYS there. ALWAYS on, to all 4 tires.
The difference with SUBARU FT4WD and AWD manaul transmissions is the center diff package...the AWD ones have a viscous coupling center, where as the FT4WD has an open diff with a locking mechanism controlled by the driver.
Some Audi Quattro systems, most of Volvo and the rest have so called AWD systems, that indeed only engage the rear when needed, same with most everyone else's FT4WD.
Audi DOES have its true Quattro AWD on alot of its cars.....but its an option on most. SUBARU has it as STANDARD equipment.
As for the Autos....both are the same in operation and theory from the EA82 trans, to the newer EJ ones....its just got newer electronics, case, internals etc...othereise, operation/theroy like i said are the same.
The difference with SUBARU FT4WD and AWD manaul transmissions is the center diff package...the AWD ones have a viscous coupling center, where as the FT4WD has an open diff with a locking mechanism controlled by the driver.
Some Audi Quattro systems, most of Volvo and the rest have so called AWD systems, that indeed only engage the rear when needed, same with most everyone else's FT4WD.
Audi DOES have its true Quattro AWD on alot of its cars.....but its an option on most. SUBARU has it as STANDARD equipment.
As for the Autos....both are the same in operation and theory from the EA82 trans, to the newer EJ ones....its just got newer electronics, case, internals etc...othereise, operation/theroy like i said are the same.
#13
CIS Subaru
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Posted 09 March 2004 - 10:37 AM
After looking around on the net, it appears that the general consensus is:
FT4wd usually refers to systems with an open center diff.
AWD usually refers to systems with some sort of lsd center diff.
Systems that are primarily 2wd, and activate the other 2 wheels only when slippage occurs at a primary drive wheel are called either FT4wd or AWD depending on who you ask.
Subaru AWD is vastly different between Autos and 5spds.
At least in gen 1 Legacy models, the auto tranny AWD system was of the 2wd until AWD is needed variety. (Hence the 90/10 torque split). On these models, it is nearly impossible to spin a rear wheel when neither front wheel is slipping. 5spd models were true AWD all the time.
So I guess it's a judgement call as to whether the EA82 auto FT4wd was really AWD or not.
FT4wd usually refers to systems with an open center diff.
AWD usually refers to systems with some sort of lsd center diff.
Systems that are primarily 2wd, and activate the other 2 wheels only when slippage occurs at a primary drive wheel are called either FT4wd or AWD depending on who you ask.
Subaru AWD is vastly different between Autos and 5spds.
At least in gen 1 Legacy models, the auto tranny AWD system was of the 2wd until AWD is needed variety. (Hence the 90/10 torque split). On these models, it is nearly impossible to spin a rear wheel when neither front wheel is slipping. 5spd models were true AWD all the time.
So I guess it's a judgement call as to whether the EA82 auto FT4wd was really AWD or not.
#14
XSNRG
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Posted 09 March 2004 - 11:19 PM
FYI-Mazda has the late 80's 323 GTX turbo with full time 4wd and a locking center diff. Very cool little cars and still competetive at rally's...
#15
bushbasher
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Posted 10 March 2004 - 12:33 AM
I would call the manual ft4wd trannys awd because they are permanent. however the 4eat ft4wd trans has an electronically actuated clutch to engage the rear when the fronts slip. Also, older jeep and dodge products (quadra-trac etc) also have a mechanically actuated clutch which engages the front axles, these are labelled as ft4wd.
#16
nkx
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Posted 10 March 2004 - 02:54 AM
i might be wrong, but AWD is computer controlled. my 89 gl-10 is fulltime 4wd, but even with the center diff locked, not ALL the wheels spin... then again, i did have the car lodged in the snow off to the side of a snowy mountain road...
#17
scubaroo
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Posted 12 March 2004 - 08:41 PM
:-\ 4wd, 4x4, or FWD are terms used to describe a vehicle in which all for wheels can powerd, either part time or full time. AWD means all wheels are powered all the time, be it 90/10 or 50/50, all whells recive power from the engine be it an open diff lockable or not, or limited slip type. In some later model Jeeps they a NV-242 transfer case in which 2 wheel drive, full time 4 wheel drive, or 4 wheel drive HI, LO can be selected. I believe it is called by Jeep comand trak. They ar called 4 wheel drives.
#18
WoodsWagon
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Posted 20 September 2004 - 08:30 PM
Why didn't subaru use the same viscious (sp?) coupling in their auto's? I think that they could have just installed it after the transmission setup and been the same as the manuals. Maby i'm just cluless to how the auto's are set up. I have vauge notions of brake bands and planetary gears and torque converters, but I may be missing a crucial point.
#19
bushbasher
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Posted 20 September 2004 - 08:47 PM
It's a mystery to me too. Maybe they decided to use autos as a test bed, with systems more designed for luxury than performance, while keeping the simple and more effective performers in the manuals.
ft4wd and awd are pretty much interchangeable terms. They all have some sort of device that allows slip between the front and rear axles. 4wd's generally are 2wd or 4wd selectable by the user, with no slipping device between the front and rear axles.
Jeep command-trac or quadra-trac or the various things in dodge trucks and cherokees etc are 2wd, or 2wd with a clutch activating front drive when slippage is detected (similiar in effect to early subaru ft4wd autos, or volvo awd systems), or locked 4wd mode which just locks the clutch keeping the front engaged at all times (which you can do to a ft4wd subaru transmission, you just have to hotwire the solenoid to keep the clutch engaged and keep rear drive on at all times) More confusion is added, because cherokees/dodge trucks are branded as 4wds, but the t-cases are considered ft4wd.
ft4wd and awd are pretty much interchangeable terms. They all have some sort of device that allows slip between the front and rear axles. 4wd's generally are 2wd or 4wd selectable by the user, with no slipping device between the front and rear axles.
Jeep command-trac or quadra-trac or the various things in dodge trucks and cherokees etc are 2wd, or 2wd with a clutch activating front drive when slippage is detected (similiar in effect to early subaru ft4wd autos, or volvo awd systems), or locked 4wd mode which just locks the clutch keeping the front engaged at all times (which you can do to a ft4wd subaru transmission, you just have to hotwire the solenoid to keep the clutch engaged and keep rear drive on at all times) More confusion is added, because cherokees/dodge trucks are branded as 4wds, but the t-cases are considered ft4wd.
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