If you have any doubts, call him back and ask him why his advice goes against the owner's manual.
2010 Trail or 2008 Sport Edition
- Thread starter badburro
- Start date
If you have any doubts, call him back and ask him why his advice goes against the owner's manual.
I'd like to clarify this statement for some folks.
All 4wd vehicles have a transfer case, meaning its a splitter, than sends power to the front and rear drive shafts, allowing power to the front and rear axles, and then wheels/tires. A fixed transfer case requires an equal number of revolutions for the front and rear driveshafts, that presumably feed axles that have the same gear rations in their own differentials. (Axle Diffs may be locked separately.)
A center differential is a device that allows the number of revolutions of the front and rear drive shaft to differ, based on the distance the front and rear wheels are rolling, which would effect the axle rotation, and thus the driveshaft revolutions.
If the front and rear wheels are moving different distances, but the axle diffs are locked, and the transfer case is fixed, an undue amount of stress will be put on the driveshafts, transfer case, and axle gears, which can be very bad!
Many folks ( in other less educated web-wheeling communities) speak of center diffs and transfer cases as synonymous with each other, when in fact, they are not.
So, if you aren't on a surface that allows your wheels to slip (dirt, snow, ice, K-Y :wow
I think I got it about right. Please feel free to correct any typos, as this was real quick before a meeting...
Yes, that's right. And that's why they call a center differential, a differential. It simply allows different rotational speeds. Same thing as a rear differential. Imagine what it would be like turning in a vehicle that doesn't have a rear differential. Since each wheel takes a different arc during a turn, it would result in a lot of binding/skipping because the outside rear wheel would be turning faster and in a wider arc than the inside wheel.
And that's also why a vehicle needs a center differential to run 4wd on dry pavement.
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Actually, you can run in a straight line forever if you wanted to...but since I don't know of any roads that go straight forever, then I guess that's not gonna happen either! LOL
put your new Trail into 4Hi on dry pavement in an open parking lot and try doing a small circle. let us know how that goes. more research? if you don't believe what everyone is telling you on this forum, then why ask?
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bluebullet
New member
MATT3LIVI'd like to clarify this statement for some folks.
All 4wd vehicles have a transfer case, meaning its a splitter, than sends power to the front and rear drive shafts, allowing power to the front and rear axles, and then wheels/tires. A fixed transfer case requires an equal number of revolutions for the front and rear driveshafts, that presumably feed axles that have the same gear rations in their own differentials. (Axle Diffs may be locked separately.)
A center differential is a device that allows the number of revolutions of the front and rear drive shaft to differ, based on the distance the front and rear wheels are rolling, which would effect the axle rotation, and thus the driveshaft revolutions.
If the front and rear wheels are moving different distances, but the axle diffs are locked, and the transfer case is fixed, an undue amount of stress will be put on the driveshafts, transfer case, and axle gears, which can be very bad!
Many folks ( in other less educated web-wheeling communities
So, if you aren't on a surface that allows your wheels to slip (dirt, snow, ice, K-Y :wow
I think I got it about right. Please feel free to correct any typos, as this was real quick before a meeting...
Thank you. That is a great explanation for something I did not understand before. I suppose the center diff design is something similar to Honda's hydrostatic transmissions found in lawn mowers, snow blowers, and 4 wheelers. It allows for some slippage. Anyone remember the Chrysler products that predated automatic transmissions circa 1948? With a standard 3 speed on the column you could stop at a traffic control, leave it engaged in 3rd, and pull away on the green light ever so slowly. We have come a long way!
BTW I can really notice my 99 SR5 5 Speed binding in 4WD HI when turning it sharply. I immediately take it out of 4WD. Think it is less a problem on roads at 35 mph that are relatively straight.
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JB.
New member
Driving in part-time 4WD on pavement (or center diff locked) is a subtle, variable situation that is not well described by the over-simplified rule "don't do it". Wheel speed and turning radius matter a lot. With the center locked (or part-time 4WD), a typical surface street right angle turn can be accomplished with about 1/2 to 3/4 steering wheel revolutions. With the mild steering angle and revolving wheels, a driver is hard pressed to notice any difference in steering feedback. Revolving tires are nearly always slipping, if only minutely. In this case, they slip a little more and absorb nearly all the stress people are worried will be transmitted to the drive line. Contrast this with starting from a dead stop with a sharp steering angle, and the difference becomes instantly apparent as you experience the full tight corner braking effect. This is not to say anyone should run around in (part-time) 4WD all the time, but neither should they be scared to use it when needed if they happen to catch a whiff of dry pavement.
I suggest doing the street turn test. I also suggest doing the standing start, tight turn test to see the difference. In the latter case, I'd try to avoid clean, rough, concrete and look for something a little smoother or grittier unless you're particularly adventurous.
I suggest doing the street turn test. I also suggest doing the standing start, tight turn test to see the difference. In the latter case, I'd try to avoid clean, rough, concrete and look for something a little smoother or grittier unless you're particularly adventurous.
Not really sure what you mean by that, but I can assure you that the differential is what allows the wheels to turn different speeds, even when you're talking fractions of 1 MPH. If you've ever see a rear diff working, you know that the entire carrier rotates as a unit only when you're driving completely straight and only if both tires are exactly the same diameter. In fact, if one tire is even a few PSI lower than the other, there's often a slight difference in the circumference of the tires to cause differential action. So what I'm trying to say is that the differential is what "absorbs" the motion when there is a difference in speed. When you apply that to a 4wd system, it makes sense that a differential is needed to turn when driving in 4wd on dry roads. In other words, if the tires can't slip on the road surface and you don't have a center differential, then the stresses will be transferred to the drivetrain and that's never a good thing.
JB.
New member
I don't dispute anything you're saying about differentials but I think you're underestimating how much tires routinely slip on pavement. Even mild acceleration will produce subtle wheel slip. Maximum traction during hard acceleration, for instance, occurs, typically, at roughly 15% slip. Then there's braking slip and turning slip.
Take the example at one extreme with center locked, from a standstill with the steering wheel turned at full lock. If no tire could slip or slide at all (hypothetically), the vehicle wouldn't move. The front and rear drive shafts oppose each other and nothing can happen until a tire slips. Under these circumstances, the slip becomes obvious with the chirp of a tire. As speed picks up and the tires revolve faster and faster, slip gets spread out and steering effort feels less severe. Reduce the steering angle, as well, and slip becomes more subtle still. Reduce the steering angle to only enough required for a typical surface street turn, coupled with already revolving wheels, and tire slip absorbs much to most of the stress, whether felt by the driver or the drive train. That's my take.
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Okay, that's fine, but any time a wheel slips (even a little bit), the slip is transferred to the differential. It's a rigid connection all the way from the tire to the differential gears, so any slip of the tires ends up as rotation of the differential gears. That's all I'm really trying to say. Of course it's easy to understand if you're talking about rear tires and a rear differential, but when you apply it to 4wd systems, if the slip isn't transferred to a differential, then it gets transferred to the transfer case and driveline. That's what should be avoided.
MikesTE
New member
A way to install a center diff?
So is there any way to upgrade an SR5 or TE 4WD system to work comparably to an LE at highway speeds in 4WD? Can the hub or differential be swapped out? Most of the previous posts are well over my history-major head but I'm curious if there's any way to tweak how the system works to gain the benefit of the LE without losing any innate 'trail-ability.' Is cost the only reason a SR5 or TE weren't made with this cape?
So is there any way to upgrade an SR5 or TE 4WD system to work comparably to an LE at highway speeds in 4WD? Can the hub or differential be swapped out? Most of the previous posts are well over my history-major head but I'm curious if there's any way to tweak how the system works to gain the benefit of the LE without losing any innate 'trail-ability.' Is cost the only reason a SR5 or TE weren't made with this cape?
I'm sure it's possible, but to do it successfully would require a LOT of money. It involves much more than just the mechanicals....electrical and control modules are all tied in together. It would be much cheaper to just buy a Limited if you want a center differential.
And yes, I think cost was the main reason for Toyota's decision to only equip the Limited with a center differential. Toyota was obviously trying their best to cut costs during the development of the 5th gen. That's why things like projectors and LED lighting disappeared, in-glass antenna, etc...
Snowfox
New member
I just re-read the owner's manual page 223 again about using 4wd Hi (On the Part time 4wd system), they did not say anything about what road surface will cause damage about Drive train System, all I find they suggest to use the 4wd system at least 10 mil (16 km) each month.
However I found on the Full Time 4wd System, while driving on a dry hard surface road, you have to unlock the central differential to prevent damage.
So i guess, on a part time 4wd it doesn't a central differential is it correct ? please educate me if this is wrong. Thanks.
However I found on the Full Time 4wd System, while driving on a dry hard surface road, you have to unlock the central differential to prevent damage.
So i guess, on a part time 4wd it doesn't a central differential is it correct ? please educate me if this is wrong. Thanks.
On the Limited, you have a lockable center differential (which is the same as all 4th gen 4Runner models). When the center diff is locked, it behaves much in the same way as the SR5 transfer case. That's why driving on dry pavement isn't recommended with the SR5 in 4WD and with the Limited's center differential locked.... That said, if the Limited's center differential is NOT locked, you can drive in 4wd on dry pavement all day long without any issues. And since the SR5 only has a transfer case (and not a center differential), driving it on dry pavement in 4WD isn't recommended.
Just think of it this way-- The ONLY 5th gen 4Runner that can be safely driven in 4wd on dry pavement is the Limited models. The other two models lack the center differential needed to do that without causing damage to the drivetrain.
Yes, keep in mind that a rear differential lock will "lock" both rear tires together. You never want to drive on dry pavement when both rear wheels are locked together at the same speed. Think what would happen if you tried to turn like that....since each rear wheel would try to go a different speed, it would bind and drag the tires around a turn.
Now apply the same principal to a center differential lock (which you do not have). With the center differential locked, the power is split evenly 50/50 between the front and rear wheels. Your 4Runner has a transfer case that basically behaves the same way as a locked center differential. You never want to drive on dry pavement in 4wd unless you have an unlocked center differential.
Snowfox
New member
I park side by side with a friend of mine's 4th gen with both head lights on and mine head lights are much brighter.
The brightness is determined by the bulbs. But projectors are superior to reflectors because they disperse the light better and more consistently. That's why they are so commonly used on new vehicles.
My guess is that the 5th gen headlights will go back to projector headlights in a couple of years as part of the mid-generation upgrade. That's what Toyota did with the 4th gen, so we might see it happen again with the 5th gen.
