Front differential and ability to rotate one wheel independently of the other

[Yetta Lurker Find all posts View Profile Close Yetta]

Hi All

I'm hoping you might be able to answer a question.

Recently, I've bought a 98 VZJ90 3.4 auto and am in the process of refreshing fluids, brakes, bushings etc.
I'm pretty new to home car maintenance (this is a car to learn on) and have a question on the front diff and what behaviour I should expect if only one front wheel is in the air and I try to rotate it. Should the wheel rotate freely? I thought that with an open front diff that there should be no real resistance but that's not the case.
If both front wheels are off the ground, it's easy.

Anyhoo, hope you can offer some guidance.

Many thanks,
Shane

[Boxy1 Lurker Find all posts View Profile Close Boxy1]

I think that is right. The path of least resistance is always taken, so with both wheels off the ground, when you spin one wheel only the spider gears within the diff turn and this means the opposite wheel will spin in the opposite direction. If you have that opposite wheel on the ground and unable to spin, the ring gear and the front drive shaft into the transfer case now has to turn as well. More things turning, more resistance, this is why its slightly harder to rotate the wheel while the opposite is on the ground. I think that's correct anyway, maybe test it and see if the front drive shaft spins with one wheel down and stays still with both wheels off the ground.

[Guest Close Guest]

Was the transfer case on neutral?

[Yetta Lurker Find all posts View Profile Close Yetta]

Was the transfer case on neutral?

No, it was in high. Should it be in neutral?

[Guest Close Guest]

Yes

[carco Advanced Member Find all posts View Profile Close carco]

Mate, car is constant AWD so unless you put transfer in neutral, remove the front tail shaft etc, you're trying to move the car when you lift one front wheel and try to rotate it.
Even with transfer in neutral, there's a fair amount of resistance as you're turning lots of components.

[Yetta Lurker Find all posts View Profile Close Yetta]

Thanks all for the input; it's a steep learning curve.
I'll give it a try with the transfer case in neutral.

Cheers

[RobboMC Junior Member Find all posts View Profile Close RobboMC]

Tell me to pull my head in if you already know this, but I'm jumping in as you say you are pretty new to home car maintenance;

"never EVER remove a drain plug from a diff or transmission unless you already have the filler plug loosened, removed or finger tight"

This really applies to the front diff of a Prado, many ( like mine before I got it ) have rarely been removed, especially in city cars.
I suggest you get yourself a 10 mm hex key in 3/8" drive for the job.

A mechanic also told me to use ( at least ) semi-synthetic oils ; or synthetic if you have the money, in the drive train. The car runs much smoother and the mechanic reckons it increases the life of the shaft seals buy a lot.

I also invest in the correct grade of oil for each diff and transfer case, many dodgey mechanics just put the same LSD diff oil in all three, but I believe if I am saving the labour by doing it myself I may as well use the right grades.

[Yetta Lurker Find all posts View Profile Close Yetta]

Tell me to pull my head in if you already know this, but I'm jumping in as you say you are pretty new to home car maintenance;

"never EVER remove a drain plug from a diff or transmission unless you already have the filler plug loosened, removed or finger tight"

This really applies to the front diff of a Prado, many ( like mine before I got it ) have rarely been removed, especially in city cars.
I suggest you get yourself a 10 mm hex key in 3/8" drive for the job.

A mechanic also told me to use ( at least ) semi-synthetic oils ; or synthetic if you have the money, in the drive train. The car runs much smoother and the mechanic reckons it increases the life of the shaft seals buy a lot.

I also invest in the correct grade of oil for each diff and transfer case, many dodgey mechanics just put the same LSD diff oil in all three, but I believe if I am saving the labour by doing it myself I may as well use the right grades.

Thanks for the heads-up. I had heard that one about the filler plug but always best to say it and be sure rather than not say it! I have been really lucky with all the drain and fill plugs on the car so far (front and rear diff + transfer case), all of them have come out with no trouble at all.

I didn't know about using semi or fully synthetic (so thanks for the tip) and can't remember if the oil I used in the front and rear diffs was synthetic or not. I know it was SAE 90 LSD compliant to suit the rear and was told it was fine to use the same in the front diff. Oh well, I can always redo the front if needs be.

For the transfer case I used Fuchs Titan Sintopoid LS 75w90, which it turns out is synthetic and listed transfer cases as suitable applications.

All good, or a problem?

Cheers,
Shane

[RobboMC Junior Member Find all posts View Profile Close RobboMC]

SAE 90 LSD is fine for the front diff, looks all good to me.

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

Alternatively you can put the transmission in neutral.. or transfer.. whichever. Either way it should be reasonably easy to rotate one raised tyre. If the tyre is removed, and you're man handling the hub instead, that will be difficult.