celica

OK here it goes with a dumb question so don't flame me.

I understand the difference between a locked vs. limited slip vs open diff. But I am a little confused. On a stock runner, when it is in 4wd, why does the front end bind and require a tire to slip? I though t that it was an open diff. ie - would it allow the tires to turn at differing rates? Am I missinf something or do I not have an open diff like in the rear?

So if I am on super slick ice would both of my front tires turn at the same rate or just one and the other sit stationary (ie- like it is on a traction surface)

Confused

ps - thanks for not flaming a totally screwy question

runethechamp

It binds because there is no diff between the front and rear wheels. The front wheels should turn independently of each other.

celica

the binding I am refering to is from front tire to front tire. Ie one will slip & that removes the pressure. Does the fact that the front & rear are turning the same effect this??

runethechamp

So how do you dtermine that the binding is front-end only?

celica

Wouldn't any difference between the front & rear be disipated by the other wheel that is on the slippery surface. Yet it feels & sound like on gravel or snow/ice the front is binding separatly from the rear. You don't normally hear the rear disipate the difference between the 2 wheels, but in 4wd you always hear the front, wouldn't it be the same as the back if it was an open diff?

I am looking for a technical answer here. I don't have a problem, just a wondering mind

tc

The reason it binds is because there is no center diff. With open diffs, the "driven" tire goes fastest, and only at the rate of the gearing. SO on dry pavement, the front outside tire and the rear outside tire are "locked" to turning the same speed, but are traveling different distances. The open diff allows the inside tires to travel at whatever rate they need to, which will be different from the front to rear axle. You only need a little slippage to accomodate the slight speed difference of the different path from the front axle to the rear axle.

tc

Not to hijack the thread - but what is requierd to install a locker in the front diff. Do you have to drop the whole diff, or is there a third member like in the rear that you just pull out after removing the driveshaft?

runethechamp

I don't know if I agree with you on that the front and rear outside tires are locked to turning at the same speed. I THINK that what is definitely locked is the average speed of the front and rear tires. In 2wd, the rear diff allows the two rear tires to travel at different speeds. As tc said, in 4wd the front and rear tires follow slightly different paths when turning, ans since the average wheel speed needs to be the same for the front and rear part, something will start slipping. Which wheel will slip should be determined by which wheel has the least resistance to slipping. I can imagine a scenario where the rear wheels and one front wheel are not slipping and the last front wheel is to make up for the the average speed difference.

celica

Now that answer makes more sense, thanks for clearing that up guys. So then will only one front wheel spin in the mud & one back tire & hence stuck.

runethechamp

That is possible, yes.

tc

Right - if you had an open center diff and lost traction on only ONE tire you're stuck!

(That's why there's a center diff lock switch on the newer ones)