Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

Check out Ebay#4358052867. Never saw one before but I think I'm in love!

Must be Valentines day,

Marc

F Y I That Cub Cadet 4x4 sold on e-bay.  They got the min bid allowed of 500 dol-lazs.

I think good deal if lived close enough for pick-up.   

Ben07 wrote:

From what I have read, the AWD (All Wheel Drive) is like for 4wd but no low range transfer case, not built as tough,  more likely to be automatically engaged, but light in overall weight too.  Like you pointed out ben07, most of us drive a one wheel wonder.  i liked your post          

                                                                18 degrees

Do you think they have a belt to link the front wheels to the rear on this snowblower?

Hi 18 degree,, sry for that long post, and as you recognized thest things are more easily answered in a conversation, preferrably over a beer, so the actual question can be answered by staying on center,  then explore the periferial things.  I know you know what I mean.  And I am no rear-end/ differential expert,  I was however good at blowing them up  .  So with that in mind I can best fast answer your question, not necessarily with the facts first but with some examples,  sry about that.  First the transfer case in your thoughts can be completely left out of the thought process at first., cause it is not directly part of the question,  yes it is part of a 4 w drive.

So here goes  you can indeed have a trans case on an all wheel drive that has 4 high and 4 low.  You can also have an all wheel drive with only the 4 high.  example Jeep G Cherokee has the full blown all wheel drive on their top complicated system and it can all go into the 4 wheel low.

Your question would be then why do some vehicles come without them. (the actual predominanent reason is they started going that direction when putting 4 w d options on front wheel predominanent vehicles  and the following.   The manufacturers and some owners know they will never need or use 4 wheel low even when taking the kids to sports practice in the winter.  So the manufacturers, like that 4 wheel ford thingy, don't put the extra expense in it for a two speed option in the transfer case. It is also very cost effective to leave out on a front wheel based car .. .. A good advertisement I read when like the Acura MDX first came out .  is they noted clearly  the vehicle was very good to get you to your hunting camp on dirt roads,  but it is not meant to be used for things that High and low transfer cases will do. cause it don't have one

I am not an expert on some of the all wheel drive things on like the BMW's and Mercedes,  I did go over a subaru, a little but they don't actually have what I would call a transfer case.  they had some kind of gismo the size of a grapefruit  underneath doin the job,  why,  cause it was obtaining it's all wheel drive from a front wheel drive not fron the standard rear drive models that then goes to 4 w d.  

As you see there are various aspects of things called thus consider to be somewhat the same thing, however it that example you can see if one cones off a front predominant veh and one comes off a rear predominant thing .. the results can be called the same all wheel drive,  but how they accomplish it can be very much different.

Hope I made some sense    Re question if you like as I am sure there are lots that can field your questions better than I and I will still get in and muck it up  a little too

Thx again

Ben07

Ben07 wrote:

Ben,   I think there are a few misconceptions in your post.

-rear wheel drive     The differential shares torque EQUALLY between both rear wheels.  This leads to problems if  traction is poor.  For example if you jack one wheel off the ground torque goes to zero and the wheel spins.  This means torque is zero on the other side too and that wheel can't move at all even if the traction is good there.  Front wheel drive is basically the same except with the drive axle in front

-positraction rear wheel drive  Also called limited slip differential. This design adds a clutch pack or viscous coupling inside the differential to limit the difference in wheel speeds, overcoming the problem illustrated above.  More recently  Electronic Traction Control   does the same thing with a computer sensing each wheels speed and applying the brake to the one that's spinning faster.  There are also special off-road differentials that can be locked to inhibit the differential action completely.  

-Four wheel drive  Also called part-time four wheel drive.  This adds another differential and axle to the front, driven through a transfer case that allows the front to be disengaged. (and often allows a hi/lo range).  Disengagement is crucial because there is no differential gearing between the front and back.  This makes it very hard to turn the vehicle on pavement when engaged and causes excessive wear on the tires and drivetrain on the highway.   Torque is still shared equally left/right but not front/back.  Serious rock climbers like this system often with the full locking differentials described above.

-all wheel drive  Also called full-time four wheel drive.  Same as 4WD except a third differential gear or a viscous coupling is added between the front and back drive shafts to eliminate the problem with part-time 4WD described above.  This system can be left on all the time and no disengagement is required.  May have electronic traction control too.

Naturally there all all kinds of variations to these systems and even the manufacturers are not always consistent in their terminology.

-Bob

Bob, how you worded all of it is correct except  posi-trac is not limited slip. Limited slip is limited slip and posi-trac is posi-trac. With true posi-trac, both rear wheels share the load equally and constantly, they are locked, I used those rear ends on my off-road racer. Limited slip diff's are what you find as optional rear ends on our trucks, suv's and some cars, usually accompanied with a lower rear gear as well.

Bob I am aware of the additional applications etc and other things that complicate the issue that is why I started that post out with the following statement.  and there are variences to this such as limited slip   and I am not gonna distinguish there, too many keystrokes this is just general OK

If I would have added all the stuff about part time full hook-up  and full time viscus joints and chain slack viscus slippage etc etc.   I don't think the person would have been able to get thee general idea etc.  And yes  I am glad to see that there are those (Marshal in this case)that understand there is a difference between limited slip and full fledge posi traction.

Now for your question of jacking the car up and the power transferring. etc.  If you take a vehicle with an old fashioned rear end , no limited slip, and no posi,  just the standard ring and pinion (called a single action rear end),  you raise the right rear wheel and that car will not go anywhere  and that is the only wheel that will spin. And I stated I was leaving limited slip out of the equasion,  your disagreement assumes that limited slip is there. mine does not.

Best way to describe limited slip, is that it doesn't quite transfer power to the left side. However it will pick up some (absorbe excess thru the system) of the power if there is an excessive amount of slippage in the primary drive tire.  Here's an example  limited slip rear end   Fast start so you will put down some rubber,  only the right rear wheel will spin.  now do a real agressive fast start, as in dumping the clutch and really spinning the rear,  in this case both rear wheels will break at first, at the beginning of the burn  then the left one will stop after lets use some nunbers here.  from start of dump  both wheels will leave a tire mark for say 20 feet then left will stop leaving the rubber trail and the right one will continue marking for say another 20 feet.  Summary.  two tire marks  but the left one will be shorter..  ( I am sure you have seen these type tracks out on like country roadds where some one was doin a little excessive horsepower burn outs.  One tire line longer than the other.  Take that same vehicle on some dirt, hit he gas just enough to spin the wheels and both will spin in the dirt, hard to diffrentiate there.

Take your standard dual differential 200 hp suv out on some drive pavement and jump on it,  you may be be able to get a little chirp out of it,  get out and look and you will see the only two tires that marked are the lf and the rr.  even if they do have limited slip. 

Thanks for your key strokes on the posi units Marshall,,  and remember when you change the gear 90 w oil,  don't forget to add the posi clutch additive  which I might add the limited slip or single action don't need

Ben07

Marshall,  I recall "Positraction" is a GM name and perhaps they performs differently  than other limited slip diffs. However, the use of a clutch to prevent one wheel from spinning with respect to the other while still allowing slippage in turns is essentially the same.  I always felt the difference was more a Chevy - Ford thing than anything fundamental.  

Ben,   I thought you were saying in a conventional diff. axle only the right wheel drives.  The torque is shared equally in an ordinary diff.    The reason why the right wheel on the back axle tends to break free first  (and the left front in your SUV)  is because of drive shaft torque.   Think about it.   Under hard acceleration the drive shaft wants to twist the axle and this takes some weight off one wheel.    -Bob

Bob, GM did use to use "Positraction" as a name back when it was truly posi-trac, you're right. But when they switched to offering a clutched type diff, they went to calling it Limited Slip. Ford used to use the term Trac-Lok but uses the term "Limited Slip" as well today. Doge uses "Anti-Spin". None of them offer true posi-trac anymore due to liability reasons, and really, no one wants to have it either whether they know it or not. It's too dangerous and just not practical.

Hi Bob how r u?

Sry been busy.  Yes there is a little bit of axil twist involved, and I am very glad you brought that up. Seriously I am not kidding you.  Shows you are a thinker and have much more understanding than someone who more or less just reads brochuiors. Tells me you are somewhere in between a rocket scientist mechanic and an above average mechanical person.  Point you are quite capable of understanding practical application, and have fun with it as two heads are better than one etc. 

So it may at times sound like I am disputing you, however you understand that is the way it is with mechanical processes, it is not as surface level as some may think.

You were dabbling in something like conventional rear ends.  So lets clarify that.  Limited slip diffs were not put on any production cars till the late 50,s  Therefore cars were being made with rear ends in them for 50 prev years.  Their rear ends I would thus call them the conventional ones.  They were called single action, or ring and pinion yada yada.  Then to the consumer (not the race enthusiast as there were LSD's and full lock units avail there) came the advent of the Limited slip diff.  A device that was suppose to transfer power at torque sensitive applications/speeds and different driving conditions, with slippage between two wheels that have to travel different distances around bends.   on the same axil plane.    That is why they named it  "differential. "

At the same time they started calling the older style rear ends,  simple diff's. which can just confuse everybody cause everybody just started calling every rear end a differential.

Then there was an enhancement made to LSD's and for an example we will use GM's Positive traction.  Then everyone started calling them posi and also calling the LSD's posi.  To boot, two of the three are very complicted mechanical applications, that are suppose And the key word here is suppose to do a lot of the same type things. Truth they all try and some succeed and some don't. Basically because there are differences in their design.     

Positraction, works well The GM Version.  It primarily, not secondarily now, it primarily splits the torque between the two wheels.  Then it allows for differential in turns,  and under low torque situations it can and does at times transfer the entire 100 percent of power to one wheel or the other.  It's primary function is 50 50 split.

Limited slip  Is named well , it is limited and it slips.  Now keep this in mind when I make the statement of LDS having a primary dependency on the righr rear wheel when going forward.

When you raise both rear wheels on both type vehicles, and put the car in neutral no brake etc and you by hand turn lets first say the posi unit one of the wheels, you can look under the car and see the other wheel spinning the same speed in the same direction,in relation to forward or reverse. You go to the car with the limited slip diff and turn one of the rear tires, lets say to simulate the direction it would turn when traveling forward, you look under at the other wheel and  the funny thing is it will be turning opposite direction.

That is also a quick test to see if you actually got posi on your vehicle.  They are different systems.

Where is this all going is here the posi units work well .. the production limited slips hardly work at all when driving the car.  They are little better if any better at all than a simple diff.  They are a very cheap version of a true differential. 

It gets complicated  there are I believe they break them into classes,  like class1  and class 1.5 and class2  etc.  ,Clutch strength  and torque applications,  LSD's are very sensitive to torque applications, posi's are not , only low torque conditions low revolutions, like in up hill snow driving.  Other than that they are primarily 50 50.

Most people I know will tell you they never found a LSD that actually worked except for an aftermarket one. 

Every one I owned , and I live in a very hilly environment, actually at the start of the Allegheny mountains. When you go up a hill in the snow the only wheel that will spin is the right rear,  How can I tell cause when the car will not go up anymore or I am going at a crawl I can feel it and hear it number one, but I can also open my door and look at the tire, and I have never found one of them spinning,  Different engine rpm's feather the gas on and off etc.  It is almost always a dead wheel.  Now the right one is spinning it is suppose to transfer power to the left,  never had it happen,  never knew anyone who had it happen, and never saw it happen , and tried many times to make it happen.  It was always a constant gripe by everyone who ever had them in these hilly environments, It has been written about in the standard auto magazines for years and the articles on them are often titled  the Myth of LSD.  Except if you are reading something that is basically trying to sell or not knock the manufacturer, then you get a blurb like it comes standard with LDS.

It also has a limited factor to it by it's design where someone may think well if I spin the rear wheel faster then I might be able to get some more power from the other.  Under those conditions it transfers all the power to the spinning wheel, thus nothing left over for the otherside.

Front wheel drive.  I never saw any of them spin any more than one wheel in the snow.

Had to push a guy out of an establishment after a Monday N NFL game, in an adjacentlot half paved half cinders, partially snow covered. LF wheel only spinning, it's in the muck  Right f wheel on solid dry surface,  No matter which way he turned that wheel, or any other thing he did was there any sign at all from the dead wheel..  How do I know cause I knew it was gonna happen that way so that was the side I was pushin on and the other fellows were really swearing as they were getting covered with muck.

I have never found one or knew of anyone who found one that works with any amount of appreciable. force

The only time I have seen the Left tire grab is on a sudden High speed burn out, like a neutral to drive or a high rpm clutch dump. 

The other instance.  Is the one that comes into play with your realization of the axil twist.  The left one will spin on a left turn burn out in reverse,  (weight slitly shifted off that wheel in reverse torque of the drive shaft. )

Oh forgot have seem many people brake torque them to the limit,  Not my personal preference so I don't like to go to an extreme in that situation.  You would think that the added effect of brake pressure on the system would further enhance some of that power to the left wheel.  Seen it I don't know how many times, with an lsd only the right rear spinning

 

Now there is a lot of different type stuff out there that work, I believe Jeep is suppose to have one, it might be called full lock-up  One that I know that worked for sure was the VW bug, and most of the all wheel drives with the Viscus joints and few posi type"s, Tranfer torque, but don't know of any LSS's doin the job

Which reminds me How do the diff's work on the snowblowers, like the ariens,  I would have to think that under those conditions they could have to be able to make a differential that gives you power to both wheels,  I never tested one, but I constantly see owners saying that they really have to lock the mechanism in deeper snow or up hills,  I just cring, and say I hope they are not as bad as the automobile LSD myth

 

Ben07

boblloyd wrote: 

Hi Bob,