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differential ratios on a LJ78/RJ77

dean780

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brunei
Hello guys, hoping to get more input from this site, i just finished a project converting a Lj78 (rj77) from a 22r engine to a 1hz, my question is, i want to change the gear ratios to suit the 1hz, possible a ring and pinion gear change to suit the new engine, does anybody have any ideas, i was thinking of 4.11 for the rear and front which i have heard and researched a bit is the preferred option, will be using it for daily drives only with 32' tyres. thanks.
 
Your RJ77 should have 4:5's if its a manual, slightly higher if its an auto.

Why do you want to go to a higher ratio like 4:1's?

Normally people go to a lower ratio when increasing tyre size, so something like 4:8. :icon-biggrin:
 
hi ben , thanks for the reply, my original ratios were 4.88, as the previous engine was a 2300cc 22r petrol. i changed the engine to a 1hz, 4200 diesel , as im planning to use the car for highway and normal road driving , and using now a 275/70/16 tyre size max, the current setup is abit loud on the engine revs when i go at 100kmh,
 
How very strange! :crazy:

The only light duty 70's to leave the factory with 4:8's were the manual transmission LJ's!

Manual tansmission LJ's are 4:8
Manual transmission RJ's are 4:5
Manual transmission KZJ's are 4:3

So someone must have fitted LJ70 diffs to your car, which are the lowest ratio factory standard diffs. :think:

Its also a big problem for you because the only ring and pinions available for the 4:8 diffs are 4:8!

All of the other factory ratios can be changed quite easily but not the 4:8's because they run a different housing because the ring gear is much thinner and the pinion off set.

I had loads of issues trying to re-gear my 4:8's. :thumbdown:

Have you considered running bigger tyres?

When I used to go from 35's to 37's my revs used to drop quite a bit at 100! :icon-biggrin:
 
hi ben, the diffs were written on my engine plate as G144, ran the decode on the axle hence it says 4.8, i was hoping to avoid bigger tyres on this one as i am already using a reducer spacer for a bolt conversion from 6 to 5, so i would think bigger tyres would add to stress on the spacer to wheel joint. the car was sort of a 1990 lj78 converted to a 30th anniversary LJ76. so i sort of want to keep it as stock as possible. thats scary hearing about the 4.8's though. would you think regearing my diff be the most economical way?
 
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let me do some more homework and see what i can get out of my setup and what to make out of it, thanks for the info ben, cheers.
 
How very strange! :crazy:

The only light duty 70's to leave the factory with 4:8's were the manual transmission LJ's!

Manual tansmission LJ's are 4:8
Manual transmission RJ's are 4:5
Manual transmission KZJ's are 4:3

So someone must have fitted LJ70 diffs to your car, which are the lowest ratio factory standard diffs. :think:

Its also a big problem for you because the only ring and pinions available for the 4:8 diffs are 4:8!

All of the other factory ratios can be changed quite easily but not the 4:8's because they run a different housing because the ring gear is much thinner and the pinion off set.

I had loads of issues trying to re-gear my 4:8's. :thumbdown:

Have you considered running bigger tyres?

When I used to go from 35's to 37's my revs used to drop quite a bit at 100! :icon-biggrin:

The kzj70 swb diffs should be 4.56, kzj78 was 4.3
 
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I stand corrected, thanks. :thumbup:

I wonder why they changed ratios for the 4 door on the KZJ and not the LJ. :think:
 
I stand corrected, thanks. :thumbup:

I wonder why they changed ratios for the 4 door on the KZJ and not the LJ. :think:

Yeah that's always confused me, I would think you'd want the lower ratio to help pull the heavier weight of the lwb, maybe they expect it to be a motor that's driven more miles so better for motorways?
 
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Yeah I think you must be right! :thumbup:

I wonder if the gearbox ratio is the same in the KZJ70 and KZJ78. :think:
 
Hi there,

Greetings.....
Got a Landcrusier RJ77 with a 1KZ engine.... do I need to change the gear ratio as I am currently using a 33" MT tyres?
 
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