Quote:
Originally Posted by john1981
thats not necessarily true, it depends on the year and all that. ive seen trucks with a 4.10 rear abd 4.09 front, but i wouldnt call it the norm. the idea is the have the front tires pulling a hair more and keeping the front exactly that, in the front.
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It is all in the math... BUT way more or less to it once you understand what happens..
the 4.10,4.09.411 stuff is MINOR in the grand scheme of things.
Most are not gear heads on this forum but I will try..
The Rear axle of a 2WD drive car/truck/tractor etc has a differential .. The word itself ..dif , differ , different . If the rear Axle was solid, side to side and you make a turn or any movement off a center line,, the inside tire will scuff or spin slower that the outside,,, or the outside turns faster...
The Rear Diff..... uses some internal gears that allows the inside and the outside tires the vary speed and stay in speed or motion without fighting each other,.
The Down side of the design is on slippery surfaces one tire can break traction and spin, it also spins at twice the speed or half the gear ratio... do to the split gearing design of the diff.....
Posi -Track, Traction-Lok, Limited Slip.. employs a way that overriders the diff .. allowing both tires to maintain equal traction,,, these rear diffs may chatter around a turn , squeal a tire a bit.. Limited slip uses clutch packs to allow some slip and as the slip occurs the oil between the plates heats and squeezes out allowing some lock up between both tires,,, the Track Lok or Detroit Locker used more of a gear sets that popped/ratchet instead of clutch packs....noisy around a turn but great in a straight line or under torque... Racers and $WD nuts like the better geared lock ups..
Why Am I rambling... here is why..
A Frt wheel Drive car has the same DIF up front in the transmission.
A ALL Wheel Drive or 4x4 has a frt and rear Diff,, at times the rear can lock mechanically or electronically. Some 4x4 trucks may have a Frt Locker also.
To make the Frt and Rear work together is a Transfer Case.. after the transmission this Tranfer case allows power to Front and Rear Wheel..
Old School and many/most 4x4 trucks have the type of T Case that allows a 1:1 locked Frt to Rear power split.straight power no slip.
This vehicle will divide power to one Axle / Tire in the frt and the rear equally.. When Turning that same fighting action can occur on hard full traction surfaces.. A the front turned tires have a different / longer travel space than the rear... they are being pushed,,, feels like binding... Hit dirt/wet roads/show etc all is better.. as tires will scuff around..
In the MID 70's the 4sx$ world saw a part time 4WD on there transfer case levers.. GM and NP205 I think case actually had added a Differential gear set to the transfer case that allowed some slipping lets say from Front to back to match the side by side of the normal axles.. WOW full time 4x4 .. sort of.. it is less efficient in deep mud/snow and allows a one axle spin out but works good all around.
Newer truck and cars can have a Lock over ride for FULL 4XA mode or some have a limited slip or viscous coupler in the transfer case that allows it to lock up and move power as need..
These systems in new vehicles combined with ABS systems make up what is called dynamic systems.. that when in 4X4 mode like modern SUV .. BMW X Drives and all the others.. one wheel looses traction the brake is applied by ABS to slow that spinning one tire or 2 that allows transfer of power to the remaining tire or tires to hunt for traction or stability in some cases.
System with an auto locking rear diff can be more efficient at times..
Systems Vary..
Back to the question of the OP...here
So much depends on the vehicle you are towing with and the type of system it has.. Many newer pick ups and large SUV have advanced transfer case and vehicle systems that the use of the automatic AWD can benefit overall handling..
If it is the older school. not real electronic assist .. the driver chooses 2wd mode , a part time 4x4 (hard road mode) or a 4x4 offroad mode.. I would just try to use some common sense.. bad weather then a part time mode can help braking and moving..
JUST remember it may feel better and speeds are maintained or improved.. THE DANGER of bad conditions are amplified, as once traction is lost , you are moving and there is no back up.
I say this from my own oh $h_t moment.. I got a New Murano.. AWD, with lock feature,,, it snowed, when to town for parts.. what a tank,. sticks in the turns ,, this is cheating... I came up on a sunny turn.. that had melted bu froze to black ice.. All those cool systems, 4x4, Lock, ABS, flash stability lights.. I was able control a bit of a slide into the upper berm where the snow and slush allowed some slowing and then back straight thru the intersection.. where than god a motorist was looking and saw me sliding, backed up enough to allow me room to stop close to where he was.. We both got out with flashers on and said WOW, I thanked him..
I learned to respect that there are still new limits.. I own a Collision Repair Shop and hear it all the time. damn I was going fine and XXXXXX moment.. thank god tech has made cars way safer that in those older days and units...
I'm super cautious when towing.
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