front diff whine

[dave friday]

hi all,my vans front diff had been very quiet untill i changed both front tires for the back tires[after i had adjusted the front toe in]the viscous coupling doesnt work[a bit of drag if i rotate a front wheel!] but i now have a front diff whine!.the front tires are more worn than the rears!.this has got me thinking,should the tires with the largest circumfrence[as mine were] go on the back wheels?
happy easter.

[Horza]

Either your VC does work; in which case you should have the same size tyre front to back or it doesn't in which case the diference front to back should have no effect.

I'm guesing the VC is doing something hence the whine when you have the wrong sized tyres on it.

[mister smith]

To clarify, it doesn't matter whether the bigger wheels are on the front or the back, its not good either way.

When you say VC doesn't work, it depends on whether it is 'open' or 'locked'.

If it's open, like Horza says, it shouldn't matter.

If it's locked, then you need identical wheel circumference front to back.

A different size front to back, which ever way round, will cause a working VC to lock, and a different size front to back with a locked diff will quickly destroy your transmission if driven on the road.

In fairness, if it is locked, even with identical tyres all round, it will cause problems on hard ground (ie roads, not mud etc), dangerous.

Not good.

[dave friday]

thanks,points taken, the vc is open[with a slight amount of drag].if i stop on my steep drive and try to pull away the back wheel spins,no drive to the front.i will put the wheels back in their orignal positions to see if the whine goes,i can hear the whine when driving on loose ground[river bed].i do plan to replace the tires that are worn[they are worn on the inside edge]and replace the viscous coupling.i am aware that i need to have all the tires within 1 to 2mm.

[dave friday]

hi all,just a comment after adjusting the tire pressures now43 front 48 back the whine has gone!