differential wanted

Front or rear differential?

I haven't got one of either, but anybody that has got one will need to know which one you are looking for.

It is seldom necessary to replace the entire diff, usually the internal parts (gears and bearings) are replaced.

Time to chuck in a air locker.

What do you mean by "which one you are looking for"? Would I have best luck going to the parts store and getting the gears, or is this a job that requires a machine shop to press out the parts or some special tools?

If thats a question you have to ask take it to a shop and get someone to do it for you.

Remember the longest way round is the fastest way out!

Which one? The Front or the Rear. You stated that you have a 4x4, this means you have two diffs. One on the front axle and one on the rear.

If you are not aware of this, odds favor you needing a mechanic.

I must have needed some sleep before posting this question. I do need the rear differential. I am not planning to do the work myself, although I could as long as a press is not required or some special spanner wrench or such. I guess you all are professional mechanics and never need to ask questions. So I will quit bothering you.

Thanks anyway.

We're not professionals. But you asked, "what color is it?" without telling us what "it" is. There was no answer to the question without knowing if you needed the front or rear diff.

Now that we know that you need the rear diff, maybe somebody will tell you what special tools are needed.

Having said that, the setting of the Ring and Pinion Gears is a precision setting of sorts. There is a particular way to do the settings, check them, and repeat as needed. Some diffs require a press, and some are adjusted via the use of shims. I don't know how Toyota accomplishes this.

As for asking questions, I'd have to ask the question you asked but I'd know which diff I was seeking information on. There are many different makes and models of differential, I don't know if Toyota uses one of these off-the-shelf axles, or if they make their own. You may have to figure out specifically which diff you have.

Alan, to remove and reinstall a diff centre you will need to remove tail shaft and axels. Then the centre should unbolt and pull out. If you have a fully set up unit from another truck (make sure that the ratios are EXACTLY THE SAME!!!! other wise you wont go far in 4wheel drive, well exactly nowhere to be precice) it should just bolt in and reassembles as you removed. Some say that you will need the diff back lash reset but thats your call. Ive never done in one the cars Ive changed diffs in just swapped em for other 2nd hand ones.

The only special tools you might need is a puller for getting the axels out.

Incidently, why are you changing the old one?

Do you do a lot of 4x4ing?

Is the old one a LSD or normal slippery diff?

knowing this will help.

Scotty

That's all true except fo the part about EXACT same ratios. A 4.10 in the rear and a 4.11 in the front will be perfectly fine together. If the meaning of "exact" is within a few numerals two digits to the right of the decimal place, then they have to be exact, otherwise "close" is okay.

Ummm, If my physics is still okay from 20 years ago (hell I scared myself then!) even a .01 difference will lead to different turning rates for front and rear wheels. How can this be okay? You like excessive tyre wear? To have all wheels turning at the same speed to maintain full control then all both front and rear ratios are required to be the same are they not?

If I can be proven wrong please do as this is what Ive been told when doing mechanical stuff.

A very slight axle ratio difference like that will be overshadowed by the turning ratio differences as you take curves - remember, the front wheels take a much longer path than the rear, the rear tires 'cheat' and cut well to the inside of the arc formed by the front tires.

Go out in the dirt and make a hard turn, you can see the tracks.

And that difference in rotation speed adds up to driveline torque that has to be taken care of one of three ways: One of the wheels slips on the low-friction surface to relieve the torque, the center differential (if equipped) will relieve it, or some weak point in the driveline (u-joint, slip spline, axle shaft, locking hub) will break to relieve it.

The slight axle ratio difference is fine IF you only engage 4WD on loose surfaces like you are supposed to, where the tires are allowed to slip a bit. Make a habit of engaging a part-time 4WD system (without a center differential) on pavement, and you WILL break something in the driveline.

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In truth, there are different turning rates from front to rear no matter what the gear ratio is. This is why 4WD must only be used on soft surfaces where the tires can slip on the dirt and release the very stress you are concerned about. Your concern is rightfully placed, by the way, but a small difference in ratios is fine when the stress that results can be released through the tires slipping on the dirt. The distance around a turn for the front tires and the rear tires is always different, and the distance is likewise different from the left to the right side of the vehicle. A Part Time transfer case has no ability to compensate for the distance differences from front to rear, so the stress that results is disipated through the tires to the dirt.

If the front end was a 3.07 and the rear was a 4.10 (for example), then the conditions you are warning the OP against would be true, but a 4.10 and a

4.11 work perfectly fine together.

AWD (all wheel drive) systems have a differential of sorts built into the transfer case, and they tolerate the speed difference from front to rear while being used on the street, but they would not tolerate a difference in gear ratios for very long. But this is not the system at issue here, and I'm sorry for the digression.

How can this be okay? You like excessive tyre wear? To

My concerns were that while driving on hard roads in servere wet weather I often engage 4wd for safety as the manual instructs for long distances. Any difference would wear the tyres or over heat them in super short time.

Your decscription of ratios while turning I cant make out as feasible (Unless my interpretation is up the duff) as when you turn in the dirt you will see that indeed the rears can travel less distance but due to the front AND rear having centre differentials that slip for loading purposes (and its the centre diff or transfer case thats locked at 1:1) the load is shed evenly around the four wheels. My concerns are for straight line travel with even slightly different diff ratios.

Am I incorrect, please correct me if I am.

Scotty

What you say is accurate. But, your error is that you might use 4WD on the road. Severe transfer case damage can result from using 4WD on the road because there is too much friction with the tires to allow the stress you are describing from being released. This is a particular problem with chain driven transfer cases.

There are two types of 4WD, Part Time and Full Time. Full time systems have a differential (centerj diff) built into the tcase, and the 0.01 difference between front and rear is not a problem on the street. Part time systems haven't got the center diff, and the speed differences that result from the various angles involved in a turn will be a problem for these systems without regard to the straight line difference that arise out of the 4.10 and 4.11 ratios. Changing lanes can make the stress created by the 0.01 difference, so this illustrates that using 4WD on the street is not a good idea.

If you feel the steering wheel wobble and fight while using 4WD on the street, this is the result of the tires giving input that should be transfered out to the ground.

You can't dissipate that much slip through tire squeal or squirm - something else will snap. If you make a habit of engaging a part-time

4WD system on clean pavement (even if it's wet) you WILL explode something to relieve that stress, the only question being what's the weakest point on your car. Front axle locking hub, a gear inside one of the differentials, a U-joint, a slip spline, a gear or the drive chain in the transfer case...

Part time transfer cases do not have center differentials. The front and rear axles do have differentials, but they are meant to dissipate the left/right differences /in that one axle only./

The axles can't dissipate torque that adds up as the difference in overall rotational speeds /between/ the front and rear axles - they are solidly linked together by a set of gears in the transfer case.

Look at it this way - I'll make up some nice round numbers so it makes more sense. When you make a hard 180 turn the front outside and inside wheels travel 100 and 90 feet respectively, and the front diff evens that out to 95. Because the rear axle 'cheats' to the inside in a turn, the rear wheels travel 80 and 70 feet on the same curve, and the rear diff evens that out to 75.

But if there is no center differential to even out the remaining 95 to 75 difference between front and rear axles, that stress will build up in the axles and driveshafts, and eventually it has to go somewhere. If the tires can't slip in mud or sand to relieve it...

When driving in severe weather you are smart to engage your front hubs, that way you don't have to wade out into hip-deep mud and dig for them to do it. That's my usual practice.

But DO NOT take that final step and engage the transfer case into

4WD on the paved highway AT ANY TIME unless you are actually in trouble (as in having slid off onto a soft muddy shoulder and need to extract yourself) or the trouble you end up in will be entirely of your own making.

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Or, linked by a chain and sprockets instead of by gears ...

Bruce et. al.,

Thanks for the educational information ! As someone who has never owned a 4WD vehicle before, your comments have been informative.

I bought a new 4WD Tundra in 2004. After having driven it to the grocery store (in 4WD), I noticed it was very difficult to turn into the parking space I thought something must be wrong until I did a little research and learned to NOT do that anymore ! Fortunately, I didn't blow anything up, but I now know that the tire "slip" is essential, and I only use 4WD in the ice/snow when I know the stresses can be relieved. They probably ought to offer a course for 4WD "newbies" on what the system can and cannot do before they let us behind the wheel ! I see a lot of people in the ditch on crappy days that probably overestimated just what their trucks can do...I understand another common misconception is that 4 WD somehow makes you "brake/stop faster"

I've always had 1 question, though : the maintenance manual says you should engage the 4WD system every so often to keep the diff oil circulating and the diff lubricated. I have a long stretch of straight,

2 lane highway on my commute....once a month, I kick in the 4WD on this stretch....no turns, no lane changes, etc. Does this do any harm (or really any good) ?? I kick it back down to 2WD when I approach the highway turn-off.

Comments/opinions welcome....just don't flame me for being an idiot !

Dean.....

"Bruce L. Bergman" wrote:

That is the result of the tires all going different distances, and not slipping on the ground to release the stress. If you really pay attention in these instances, you will actually feel the vehicle buck and jump, and the hear the tires chirp as the drive train objects to the treatment you are giving it.

I thought something must be

The only benefit of 4WD in those conditions is added traction and steering control that comes from driving both axles instead of only one. You are 100% correct that stopping faster is a misconception. And, the steering benefits only come if the speed is reduced to an appropriate level considering the conditions.

It does more harm than good. You should never use your 4WD system unless the tires can slip on the ground and release the stresses that build up in the tcase.

You should seek out a dirt road where you can put your dog out to run, and use the 4WD there for a while ...

The truth is, if you don't know how to drive it right 4WD will just get you into the ditch and/or turned turtle a lot faster.

If it's raining or you /may/ get into a sticky situation you lock the hubs before you're up to your ass in alligators. But you don't engage the 4WD until you actually need it.

The only dumb questions are the ones you don't ask.

You can do the same thing in two stages - just not both at once. First, engage the front hubs and drive around a while to work the front differential, then open the hubs and engage the 4WD in the transfer case and drive a few more miles. Gets everything moving and lubing just the same.

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