Mitsubishi diff gears??

[Ian Sharpe]

Some trucks like the Hilux have their gears cut in such a way that they are weaker when operated in reverse & sometimes give way. You hear a lot of stories about this.

Does anyone know if this problem effects Pajeros??

cheers

[J Top]

Post 92 paj's have reverse cut gears in the front diff which makes the front diff stronger in drive but weaker in reverse. You can tell this style of diff by the driveshaft entering at the top of the diff instead of the bottom
J Top

[Bitsamissin]

Yes I've read articles where it has been stated that high pinion set ups are about 30% stronger in the forward direction compared to an equivalent low pinion design and 30% weaker in the reverse direction.
All super select Paj's have a high pinion front diff NH-NJ 3.0 auto's & 2.5TDI have a 7.25" unit everything else right up to the present has an 8" high pinion version.
Gen 1 are all low pinion front diffs 7.25" for all diesels & 2.6 but 8" for the 3.0.

[Ian Sharpe]

Ok Frank, so that means doent pull big stumps out in reverse, use forward instead??

cheers

[Bitsamissin]

Absolutely Ian.
Never reverse (ESPECIALLY WITH FRONT LOCKER ENGAGED) under load such as snatching etc.
80 and 100 Series (anything else and I woulda been stuffed) are notorious for blowing front high pinion diffs in this situation.

[Ian Sharpe]

Ok guys, by having a high pinion front diff, what parts then exactly are prone to strenght issues.

Is the it crownwheel & pinion, side gears or hemishpere, because I believe when ARB make their lockers they actually beefe them up, is that correct, so perhaps by having the arb front locker , one gets an inherintaly stronger diff.

But if the weekness is in the c/p, well then thats still stock.

cheers

[Bitsamissin]

Good question.
With the Tojo 8" high pinion diff the centres are weak and will flex under load helping the pinion to separate from the crownwheel.
This is basically whats happening in reverse the pinion is sort of trying to spin away from the crownwheel if it moves too much and only engages on the edge of the teeth they can snap off.
So a locker is a strength upgrade if the standard centre is known to flex especially in the Tojo.
The Paj centre is stronger IMHO and won't flex as much.
Then it's down to the outright strength and design of the crownwheel & pinion itself. If you ever see a Mitsi C&P there is no comparison to the Tojo one (heaps more meat on the Mitsi ones with greater gear meshing surface area).
Ian you have nothing to worry about with your front diff as long as you don't snatch in reverse with the locker in under full noise.
There are other things such as the gear ratio which effect strength (higher the numerical ratio the weaker the C&P assembly) for example a 4.90 ratio will be slightly weaker than the 4.636 as there are more teeth on the pinion which are smaller to achieve the higher ratio.
Also the use of a solid pinion spacer vs a collapsible one.

[Ian Sharpe]

OK , thanks Frank, that sort of makes me a bit relieved

cheers

[J Top]

You should never snatch in reverse as it is the weakest gear, being straight cut and low ratio which means small gear tooth area and support.
J Top