changing diff gear/ 5th gear....ppl/places???

[haven]

i wanna get either the rear diff gear replaced to a lower ratio or replace 5th gear with a larger number of teeth (think thats right), as you prob all know the gearboxes in mu's r so low geared by the time u get to 80km/hr your already in 5th doing nearly 3 grand on the taco, so im looking at getting a better high speed ratio in my mu for the long journeys to be a bit kinder on the engine.... anyone done this before or used another compatible mu gearbox?? know any places that can supply me a new diff centre or modify 5th gear in aus???

[slightlydodgy]

you should be doing 100ks at 2800 revs on a stock isuzu so whats been changed. If you need to gear up tyre size might be an easy way (I went from 28 to 32 inch and now do 2400 at 100ks)

[geeves]

The 2.8 Mu should have a 4.56 diff With the original 245/70/15 tyre this should be a little over 3000 at 100kph. With 31 inch tyres slightly under but remember that this is true 100kph not speedo which will read a little low.
You can fit 4.3 diffs from a 88 or later bighorn/jackeroo or 94 onwards mu but you would also need the speedo gear from this wagon as well

[turnturn]

I have an original 92 Mu running on the standard 31x10.5x15 wheels. I'm about 2800rpm at 100kph.

[Elysian]

I have a 93 MU , it had 4.3 diff's but I now have 4.556 diffs , 31 inch tyres .. 115 @ 3000 rpm .. and that's 115 off the GPS .. 120 in the speedo ..

[MARKx4]

My 1992 2.8 does 2500rpm for 100kph and 2800rpm for 110kph. Engine has just been rebuilt 6weeks ago and only done 1000kms and a complete rebuilt rear diff.

Mark.

[haven]

hmm i dunno then, my speedo reads almost 10k higher than actual speed (off gps) but like i said, doing close to 100km/h is easily 3500 rmp onwards which i hate. so either my tacho is dodgy and is telling me lies or somethings been changed in the past.....

just upgraded to 33" tyres so i'll see how much difference that makes...

[haven]

in regards to upgrading/changing to the 88 onwards jackaroo diff with the 4.3 diff, i'd also need the front diff from it to yea? does the front diff also interchange with the mu?

[pig75]

The diff centers are the same

[geeves]

Only easy way I can come up with to test the tako without getting a mechanic to put test gear on it at great cost is to run it to the rev limiter and see what revs you get. It should be about 4200.
Neither myself or clubisuzu takes any responsibility for any result from this test. If the rev limiter is faulty you could blow the engine.
There are only 3 diff choises for the isuzu. 4.3 in most bighorns and 3.1 Mus. 4.56 in most 2.8 Mus and 4.8 which no one has actually seen but they do exist if you belive