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Q: Diff ratios - considering SAS Front axle from 80 series

Jano

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Hello 90 owners!
I am currently in process of disassembling and rebuilding entire front suspension (and rear aswell) - new arms, ball joins, bushings, springs, struts ... Knuckle stays.

We've had a discussion lately regarding the longetivity of the newly rebuilt IFS with 35" on - and an idea came up - to perform Solid Axle Swap (SAS) after the IFS goes to hell again.

I've dug into it and it seems the LC 90 has either 4.1:1 or 4.3:1 diff ratios (I think 4.1:1 is on V6 and 4.3:1 is on 1KZ-TE with lock - to be confirmed)

80 series has diff ratios of 4.1:1
Patrol axles can be fitted with 4.11:1 diff ratios.

Would it be possible to utilize front axle from 80 series WHILE keeping the rear axle the same?
In other words - if I get the diff ratios same (or close like 4.1:1 and 4.11:1) - will the centre diff be ok?

I know some have done complete swap (front and rear) and potentially the same :

Thanks!
 
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Hi Jano, I think you'll find there's a wider range of 80 diffs that that. Manual and auto are different to begin with before you get into what's on the shelf.
 
Noted, thanks.
Provided the ratios are the same example - 4.1:1 to 4.1:1 OR close enough like 4.1:1 to 4.11:1 - do you think the centre diff and ride would be OK?
 
The only successful 90 series SAS swaps i've seen all used Patrol axles though i couldn't tell you why because i only speak/read in English .

Vague memory suggests theres a few in Portugal i think it was .
 
Well I do know of two cases where it's been done, one was a member on here but I don't have any details I'm afraid. They do it to Hiluxes quite a bit and they share a lot of parts with the Prado
 
I found it impossible to discover the 'rules' for the diff ratios fitted to the 90 series when I looked into it a few years ago. Mine is a 3-door 1KZ-TE manual with 4.1:1 for example, but I believe other similar vehicles are 4.3:1. There was originally a big sticker on one of the front axle tubes saying R16 (4.1) or R17 (4.3).
 
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SAE70 (Steve) did post a chart some time back that had these all on for the 90. Not sure if I could find it.
 
He did , and he also fitted a Surf front diff to his 90 .

But because the forums search function is useless i've learned to search for old threads via google and this came up first from some strange bloke nobody has seen sight nor sign of for years :icon-biggrin:

diggerdave
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PostPosted: Sun Jul 10, 2016 18:34 Post subject: Front differential/diff codes R16, R17, R56, R57, R52?Reply with quote

I would like to replace my front differential, which is labelled R16 on the extension tube. I believe a 4.1:1 diff was fitted to vehicles like mine (manual diesel SWB with OE small 215/80/16 tyres and no wheelarch flares).

My questions are:

a) is it correct to say that R16 refers to the 4.1 ratio of my diff, so swapping an R16 for another R16 would be ok?

b) there are other codes out there. I believe R17 refers to the more common 4.3:1 ratio, BUT what do the labels R57, R57 and R27 (all of which are found on Colorado/90 series diffs) mean?

Does anyone have a definitive answer? R16 diffs are hard to find so need to know if I could swap another one .
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PS , i just watched the vid and i'm not convinced they are 35's ?

Looks no bigger than my IFS 90 anyway and thats been battered senseless without breaking a thing .
 
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:icon-biggrin: That's me! I'm just as in the dark about what diff ratios were fitted to what as I was back in 2016. I never found a chart anywhere (or found out what R57 etc meant).
 
So based on the fact that I'll probably won't be able to determine the actual diff ratio of my car - it's pointless to consider front axle only swap then.
Both patrol axles then.
 
Turn the wheel TWO revolutions and count the number of driveshaft turns. The number of driveshaft rotations will help you determine your rear axle ratio. For example, if it turned 3 and a half times, it's a 3.50:1 ratio. If it turned 4 and a quarter times, it's a 4.25:1 ratio.
 
I did the wheel test to determine mine, as Shayne suggests. It was straightforward. It's just that you can't assume what it is based on vehicle/engine/gearbox/year.
 
And again are you sure they are 35's in the vid ?

This is an IFS truck on 33's

1642428649804.png
 
Shayne - do you have the actual dimensions of the tire? I was considering either Cooper STT PRO 315/75R16 which is sitting somewhere at 87cm height or to go nuts and get INSA TURBO K2 MT - 285/75 R16 which actual height is 84,5 cm
 
They are Toyo open country 305/70R16 on a 16x10 rim , I can't remember the offset but i'm thinking -32 .

2 inch body lift and 2 inch suspension lift .

Ironically they are slightly smaller than 285/75 cooper stt on a 16x8 rim but look much bigger .
 
Hi all -
so an update and a mental excercise
I've checked mine and its R17 - so its 4.3:1 ratio.
I've also noticed that the drive shaft is actually offset to the left side of the engine - so theoretically -
It might be possible to get a Patrol GU front diff assembly with its 4.3 diff ratio
- so in order to use the same gearbox/engine/transfer case - it would require to re-weld and move the diff to the other side of the assembly so it sits on the same side as transfercase driveshaft.
This would enable to use the same driveshafts from the transfer case as well as inner driveshafts within the diff assembly.
1644859887068.png



It sounds far-fetched, but is there something obvious I am missing?

Thanks,
Jan
 
Everything is possible but i suggests you look at the chassis . Currently the front propshaft runs above and very close to a crossmember and would demand at the very least a 4 inch lift in order to run under it and thats to the SAS axle bump stops . You will probably decide it needs to be removed and the chassis somehow otherwise braced .

Its been done but i firmly believe never successfully without removing the body for access .
 
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