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4WD & AWD systems explained

1372 messages,  Last post on Sep 25, 2009 at 8:26 AM

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What is this discussion about? Chevrolet Suburban, Jeep Grand Cherokee, Subaru Outback, Ford Explorer, Nissan Pathfinder, GMC Envoy, Performance Mods, Tires, Suspension, Transmission, Truck, SUV

#1359 of 1372 Re: Chevy Suburban 2006 LTZ [arrie] by ateixeira Apr 10, 2009 (11:14 am)
Replying to: arrie (Apr 03, 2009 5:02 pm) That's just it, you have to qualify the definitions.   I'm gonna guess the rear axle gets about 40hp or the equivalent nowadays, probably less when the original Highlander Hybrid came out. Torque is better and peaks just off idle, though.   Funny thing is it was based on a FWD Highlander, not the AWD model.   I saw a cut-away at an auto show and studied it closely, it was just .... odd.
#1360 of 1372 Re: Chevy Suburban 2006 LTZ [steve_] by kdshapiro Apr 19, 2009 (12:22 pm)
Replying to: steve_ (Mar 31, 2009 7:08 pm) I don't think electric motors at every wheel could contribute anything more than neglibile torque. There is a reason 28KV are used to run electric locomotives on the nations commuter railroads. Replies to this message: steve_ (Apr 19, 2009 1:55 pm) arrie (Apr 19, 2009 4:18 pm) steve_ (Apr 19, 2009 4:49 pm) and 1 more...
#1361 of 1372 Re: Chevy Suburban 2006 LTZ [kdshapiro] by steve_ HOST Apr 19, 2009 (1:55 pm)
Replying to: kdshapiro (Apr 19, 2009 12:22 pm) So, better just to stick it (or a couple of them) in the drivetrain somewhere?   I'm thinking a fun application would be to reroute the brake lines so you could brake the right side wheels while goosing the left side wheels. Be a bit of tire scrub but think of the turning circle. Replies to this message: arrie (Apr 19, 2009 4:18 pm) steve_ (Apr 19, 2009 4:49 pm) ateixeira (Apr 21, 2009 10:44 am)
#1362 of 1372 Re: Chevy Suburban 2006 LTZ [steve_] by arrie Apr 19, 2009 (4:18 pm)
Replying to: steve_ (Apr 19, 2009 1:55 pm) Transmission that accelerates one side and decelerates the other already exists.   The way this works is the power from gearbox comes to a drive gear just like it normally comes to the differential, i.e. a pinion gear turning the big ring gear. Normally ring gear turns differential gear housing that connects right and left side wheels with differential gears allowing speed difference between the wheels.   In this "forced" speed difference system the ring gear does not turn differential housing. It turns the sun gear of a planetary gear for both sides, i.e. there is a planetary gear for both right and left sides and the sun gear for both is turned at the same speed by the ring gear. Then for both sides there of course are planetary gears and the ring gears of those.   The speed difference between sides is made by turning the ring gears of the planetary gear systems of each side at different speeds and this different speed actually means same speed but in opposite directions.   The speed control is done by having the ring gears of the planetary gear systems connected to each other by a pinion gear, i.e. the two ring gears on each side of the pinion gear are in mesh with the pinion gear and turning the pinion gear automatically means that one of the ring gears turns ahead while the other turns backward. This means that on the side where ring gear turns ahead the turning of the planetary gears is accelerated and on the other side where ring gear turns backward planetary gears are slowed down and this generates the speed difference between right and left side wheels.   Speed difference pinion can be driven by any normally used means but I think it typically is driven by hydraulic motor, which can provide very easy control and high torque.   This kind of steering system is used in modern advanced military tanks and perhaps in some bull dozers.   The benefit of this system is that instead of using brakes on each side of the "tank" for steering, which wastes a lot of energy and cause wear and tear in the braking system steering is done by just changing the speed between the right and left side. As one side accelerates the other slows down by the same amount and no energy is wasted at brakes that would turn it to heat that can not be used for anything.   This steering system is far advanced compared to brake steering and allows the "tank" to literally turn at the spot as one track turns forward while the other turns backward. When on the spot turning happens the main drive gear from main gear box is locked in place and the turning of the vehicle is done by just turning that extra pinion between the left and right side planetary ring gears.   This might be a bit off of the topic but I though you might be interested of hearing it.   Arrie Replies to this message: steve_ (Apr 19, 2009 4:49 pm) ateixeira (Apr 21, 2009 10:44 am)
#1363 of 1372 Re: Chevy Suburban 2006 LTZ [arrie] by steve_ HOST Apr 19, 2009 (4:49 pm)
Replying to: arrie (Apr 19, 2009 4:18 pm) I once cut a Simca in half with a sabre saw for a guy who said he was going to reroute the brake lines. He never finished anything. This was after tanks, but before skid steers.   But I can still imagine some appeal for independently driven wheels with the power source at the wheel, and electric would be the way to go for that.   Want more power? Just swap out your tires.     Green Car Advisor Replies to this message: ateixeira (Apr 21, 2009 10:44 am)
#1364 of 1372 Re: Chevy Suburban 2006 LTZ [steve_] by ateixeira Apr 21, 2009 (10:44 am)
Replying to: steve_ (Apr 19, 2009 4:49 pm) Cool concept but makes me wonder about the unsprung weight. The suspension would be working overtime on that puppy.
#1367 of 1372 4 wheel drive problems by bielss Aug 02, 2009 (2:22 pm)
I have a 1989 Cherokee, when I shift it into 4 wheel drive the gears engage (hi & low) but not the front axle. Anyone have a guess???

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