Rear Diff Info Required

[Jimmu]

I am looking for a LSD for the rear of my 1993 MU 2.8.

I have been told by truckbits NZ that the 2.8 and 3.1 have different diffs and that the 2.8 came out with several different diff ratios.

Can anyone shed some light in this or point me to some online resource for the diffs?

Thanks

Jimmy

[James W]

It doesn't matter what info you find. Work out the diff ratio yourself;

Jack up one wheel and put a marker on it with a bit of tape or simular. The also mark the drive shaft. Climb underneath and get a mate to turn the wheel slowly while counting the marks. Do many turns for accuracy, say 10 at the wheel. Because one wheel is on the ground divide by two (or multiply by 2?)
you should have 50 ish on the shaft for a 2.56 ratio.

This assumes an open diff

[Jimmu]

Will a 3.1 diff fit onto my 2.8?

Are the diffs with one ratio compatable with vehicles with a different ratio?

What I am trying to work out is what diff I can use to convert my beast to LSD...

Jimmy.

[MattMU]

Mate, if you are converting the CENTRE to LDS then it wont matter a squat what ratio you have!

The diffs are constructed the same dimentionally, just the ratio refers the number of teeth n the crownwheel to the number on the pinion.

Even if you diff was different ratio to the diff you purchased, all you have to do is remove the centres and swap the LSD centre for the open centre.

you end up putting hte same ration (crownwheel and pinion) back in your car!

But I grabbed a second hand diff centre when mine was shot, threw it in and it was the same, didnt know they were different. Nearly every MU I have driven with does the same revs at 100 as me!
But I wouldnt doubt truckbits, they wreck so many MUs its not funny!

Matt.

ps, yes if the ratio is different you cannot drive in 4wd, 2wd will be ok, but speedo will be out and the vehicle will bind up in 4wd!

[Jimmu]

Just to confirm... That applies to the 3.1 diff centre as well???

Jimmy.

[Harry]

Of the 5 UBS55 Bighorns I have 2 have 31 10.5 15 tyres as standard [R models].Diff ratios on these 2 are 4.56:1.1 has an lsd rear and the other not.Of the other 3 1 has after market flared guards and 31 10.5 15 tyres.I borrowed the motor for this truck [after the original ran a bearing] from another of my trucks which had 30 9.5 15 tyres [Firestone RVs which measure out at 28" od].Both diffs are 4.2ish:1.In this truck the motor was much more responsive than the truck with the bigger tyres.Most MUs I've seen have 31 10.5 15 tyres so I'd say the would have the 4.56 diff standard.Fuel economy is worse with the bigger tyres as the motor is working harder.Incidentaly I'm amassing quite a collection of spare parts.
Yours in confusion,Harry.

[Jimmu]

I have bought Yarno's old LSD from his 2.8

Try fitting it this weekend along with the Lokka.

Will let you guys know how it goes.

Thanks for the pointers.

Jimmy.

[MattMU]

Jimmy, I am 99% sure Yarns will fit straight in and same ratio. but as I said if the ratio is different just rip the two caps off, pull the centre out, drop the crown wheel off the centre and swap the centre. You will end up with the LSD centre with your crownwheel going back into YOUR housing, ie the crownwheel and pinion are the matched pair from your housing and you now have Yarns centre in it.

Your only problem will be adjusting the backlash. Done by screwing in and out the adjusters either side of the diff centre. This is best done by an expert but not that hard, just important to get right. Would take them about 5minutes.

But I still think Yarns will be the same ration. Just count the teeth on the crownwheel and pinion and make sure its the same number on Yarns! If so , you are good to go!

Matt.

[Yarno]

Yeah I would think it would be 4.56 unless someone has changed them but this is unlikly.

Matt, these diff's are shimed and don't have the adjusters, you should know that!!

[MattMU]

Yarn, I havent had the need to stip my centre down ..as yet! Maybe in the future, thats the reason I have held onto the open centre rear, if the LSD ever gives up then it Air locker time!

I will be putting a front locker in the near future, following JimMus lead and great deal!!

Hey BTW has anyone ever bought the Mecatech CV boots??

I thought if Im pulling the front apart for the locker, might as well do the CV boots at the same time! You know, while Im there!

Matt.

[geeves]

Matt Ive just chaged one of my boot with one of these . It only takes just over an hour to do the boot the old fasioned way as you still have to remove the front hub assembly and the its only a matter then of opening the inner joint and pulling out a spring clip to get at everything. Dont use the instuctions in the Haynes manual They want to start by dropping the whole front diff