Outer Limits 4x4 Board

I know Sam posted a similar topic a while ago but that didn't really answer my question...

I have a 4.7:1 front and rear diff at the moment (Rover & Dana60/Salisbury respectively). I want to put a Hilux centre in the front for added CW&P strength. The closest ratio is 4.88:1. Do you guys see any problems with a 4.88:1 front and 4.7 rear. Part time 4x4 so only used off road. I know the usual acceptable difference is .1 and I think it would be worse having the lower ratio on the front as the back would always be trying to push the front along faster - maybe causing more rear wheelspin??????

Any thoughts???????

It's fine - if you want to run different sized tyres
Or if you don't want your transfer case any more

This very topic came up on Trail Talk about a year or so ago.
All the tech guru's and engineers all agreed that the drivetrain can handle a 5% diff ratio mismatch for part time 4x4 set ups. I make yours at a 4.7% variation so according to them it falls within their agreed tolerance.
But if I were you I would talk to a few automotive gear places first and get their opinions.

Technically, if your driveshafts are doing 1000rpm, then the rear wheels are rotating at 208rpm(4.88) and your front wheels are rotating at 213 rpm (4.7) i.e. the front tyre is trying to spin faster (this is around 30km/hr in high range for a 33")

For a 33" inch tyre, approx rolling diameter is 2.36 metres, therefore every minute, the front tyre travels forward 502m, and the rear tyre travels 490m, a difference of 12m, every minute!! Now the wheels obviously can't travel like this, so something has to give. On greasy mud, the wheels will spin ok, but any hard packed surface will start to cause wind up, skipping, funny steering..... This can result in locking into 4wd at best, at worst.... BANG!$$$$$


Depending on the vehicles use, you may find this acceptable, but in my opinion is only going to cause grief in the long term

Roktruk

seems to me that it would make your rig less capable, before you even start up the hill two of your wheels are spinning ! :(