1uz auto ideal diff ratio for 35inch tires???

[jonossiksilvia]

hi all.

have been searching all night on ore and google but no joy (maybe wrong keywords)

anyway im in process of putting a 1uz auto into my sas 1990 surf with 35 inch tires.

an wanting a ratio that is a good medium between ecomany and pickup for onroad and off road use.

for the the guys running 1uz auto on 35inch tires in there trucks what ratios are u running and how do u find it?-ecomany,pickup, revs at 100kph etc.

$ so good against usd and ratios cheap dealing direct.

thanks in advance

[lexulance]

What ratios are you running at the mo?
I think the 1uz autos are 6 speed any way so, maybe put it in and try it, you may not need to change the diff ratios at all

[jonossiksilvia]

What ratios are you running at the mo?
I think the 1uz autos are 6 speed any way so, maybe put it in and try it, you may not need to change the diff ratios at all

thats the tricky part lol 1uz getting dropped in this weekend was a 2lte before. rear is either a 4.3 or 4.5 and front i know for sure is a h/p 4.1. not sure they 6 speed though. thought they were 4spd with od aswell. mine 92 1uz from celsior

[kbushnz]

I only know of one that Jeremy has and I am sure he is running the factory prado diffs from a lj70 something which have a 4.88 ratio. And also the A340 auto (manualised) I am sure he will comment when he comes on the forum again.
It goes well.......

My own KZJ78 (still diesel) has the same auto you are about to run (A340) which is a 3 speed with OD and locking torque converter.
I am running 4.88 with 35's and it is running like it was when on the factory diff ratios (4.3) and 31 inch tyres. Speedo readings and shift points.

Search the forum here as many guys have done the conversion.

Calvin

[lexulance]

ok, 92 yeah its probly a 4spd.
I have a 1uz in my hilux but its manual and on 33s and has 4.8:1 diffs, great offroad but on road its sitting on 3000rpm in top at 100km/h so not that economical, my brother has a 1uz in his hilux and he's on 36s and 4.5:1 diffs seems a bit better at 100km/h not reving as hard.
In the soarers they sit on about 1800rpm at 100km/h, but thyre more like a 4.1:1 ratio, dont know how thatd go off road on 35s may be a bit tall geared?

[jonossiksilvia]

I only know of one that Jeremy has and I am sure he is running the factory prado diffs from a lj70 something which have a 4.88 ratio. And also the A340 auto (manualised) I am sure he will comment when he comes on the forum again.
It goes well.......

My own KZJ78 (still diesel) has the same auto you are about to run (A340) which is a 3 speed with OD and locking torque converter.
I am running 4.88 with 35's and it is running like it was when on the factory diff ratios (4.3) and 31 inch tyres. Speedo readings and shift points.

Search the forum here as many guys have done the conversion.

Calvin

sounds goods hopefully he sees the posts. the only things i can find when searching on here or google is either diesels and 35inch tires or 1uz manuals. have found couple in aus but they seem to be running 4.1s on 33s which i woulda thought would be to high for 35s and autos.

[jonossiksilvia]

ok, 92 yeah its probly a 4spd.
I have a 1uz in my hilux but its manual and on 33s and has 4.8:1 diffs, great offroad but on road its sitting on 3000rpm in top at 100km/h so not that economical, my brother has a 1uz in his hilux and he's on 36s and 4.5:1 diffs seems a bit better at 100km/h not reving as hard.
In the soarers they sit on about 1800rpm at 100km/h, but thyre more like a 4.1:1 ratio, dont know how thatd go off road on 35s may be a bit tall geared?

i think the magic point at 100kph in surf maybe 2250 given the weight it needs to keep at the speed but thats only a guess. what do u think? any idea what revs ur brothers is doing at 100kph? is his auto or manual?

[mud_slinger]

if the front is a 4.1 ratio then the rear should be the same ratio too

[jonossiksilvia]

if the front is a 4.1 ratio then the rear should be the same ratio too

i know its not because it has a prado coil front swap onto it and the workshop that done the swap could only find a 4.1 diff for it, he knew my plans and we both agreed to chuck it in so could get it home. it came home and enginge was out 5 hours latter.

[jeremy]

Yup, 92 celsior should be an A341, which is a 4speed (inc. overdrive). The A343 prado/surf box has a lower first gear ratio, but the rest are the same.

Like Calvin said we're running 4.88s and 35" Simex's - the ratios are pretty good. 100kph at 2200 rpm, and low enough in low range. If anything, I would go lower (I think 5.13 is the next step down in the aftermarket gears?), but it works fine how it is.

[lexulance]

ok, 92 yeah its probly a 4spd.
I have a 1uz in my hilux but its manual and on 33s and has 4.8:1 diffs, great offroad but on road its sitting on 3000rpm in top at 100km/h so not that economical, my brother has a 1uz in his hilux and he's on 36s and 4.5:1 diffs seems a bit better at 100km/h not reving as hard.
In the soarers they sit on about 1800rpm at 100km/h, but thyre more like a 4.1:1 ratio, dont know how thatd go off road on 35s may be a bit tall geared?

i think the magic point at 100kph in surf maybe 2250 given the weight it needs to keep at the speed but thats only a guess. what do u think? any idea what revs ur brothers is doing at 100kph? is his auto or manual?

My brothers one from memory was doing about 2600rpm at 100km/h, hes running the R151 box,which im fairly sure has a different 5th gear ratio than mine aswell, mine is the w56 ln130 box will have to ask him? to be sure

[wjw]

With the 2JZ in the prado I went to 5.29's, motor sat at about 2100rpm at 100kph

[Cleary]

i know its not because it has a prado coil front swap onto it and the workshop that done the swap could only find a 4.1 diff for it, he knew my plans and we both agreed to chuck it in so could get it home. it came home and enginge was out 5 hours latter.

If you are running a prado high pinion front, then there are only a couple of factory ratios available - 4.1 and 4.88. (I have once seen a 4.3). Obviously you can go aftermarket - if you are prepared to pay, but if you want factory, your options are limited.

A mate has a LJ71 Prado with 1UZ and A340 auto on 33's. He has 4.1 diffs and it is fine on the road (a bit slow off the line but fine at 100k). But he is unhappy with the gearing offroad and wants to drop down to 4.88 diffs. I would say you would want 4.88's with 35" tyres.

However, both my toyota diff dealer contacts say that 4.88 high pinions are getting harder to find cheap.

[jonossiksilvia]

thanks heaps guys. will take note of all your comments. 4.88s sound the biz - good pickup and good ecomany with revs at 100kph. yeah i know they harder to find in h/p but with the dollar so good against u.s.a i will buy properly buy direct from there and they stonger too.

YOU GUYS ROCK

[jeremy]

...I should've also mentioned that we don't use the torque converter lock-up clutch, so if you are using it, the RPM when cruising at 100kph would be lower.

[jonossiksilvia]

...I should've also mentioned that we don't use the torque converter lock-up clutch, so if you are using it, the RPM when cruising at 100kph would be lower.

please explain to me bout you not using the torque converter lock up clutch not sure what ur meaning/understand

[jeremy]

The lock-up clutch in the torque converter allows a direct drive between engine and trans (no slip). The auto ecu engages this clutch when your cruising at highway speeds to improve economy.
A torque converter will always have a certain amount of slip - ours looks to be around a min of 5%. Because there is no slip in the torque converter when the lock-up clutch is engaged it's like having an extra gear ratio with lower RPM.

We don't use the standard auto ecu (manual shift), so don't use the lock-up clutch. It's not strong enough for anything more than cruising at a constant speed. Normally the ecu would disengage it as soon you started to accelerate or brake, so for us with everything manual, it would be too easy to forget to disengage it and break it.

[jonossiksilvia]

The lock-up clutch in the torque converter allows a direct drive between engine and trans (no slip). The auto ecu engages this clutch when your cruising at highway speeds to improve economy.
A torque converter will always have a certain amount of slip - ours looks to be around a min of 5%. Because there is no slip in the torque converter when the lock-up clutch is engaged it's like having an extra gear ratio with lower RPM.

We don't use the standard auto ecu (manual shift), so don't use the lock-up clutch. It's not strong enough for anything more than cruising at a constant speed. Normally the ecu would disengage it as soon you started to accelerate or brake, so for us with everything manual, it would be too easy to forget to disengage it and break it.

So for the mean time I'm planing on ecu to have full control of auto so will this be ok? Would it just mean I would have to turn off od when not doing more than 80kph? Sorry but I new to this auto stuff for a 4wd.

[jeremy]

It will work fine - the auto ecu will handle it, no need to do anything special.

I just mentioned it because, it means that your cruising RPM would be lower, so it's something to consider when picking gear ratios.

[wjw]

The lock-up clutch in the torque converter allows a direct drive between engine and trans (no slip). The auto ecu engages this clutch when your cruising at highway speeds to improve economy.
A torque converter will always have a certain amount of slip - ours looks to be around a min of 5%. Because there is no slip in the torque converter when the lock-up clutch is engaged it's like having an extra gear ratio with lower RPM.

We don't use the standard auto ecu (manual shift), so don't use the lock-up clutch. It's not strong enough for anything more than cruising at a constant speed. Normally the ecu would disengage it as soon you started to accelerate or brake, so for us with everything manual, it would be too easy to forget to disengage it and break it.

If you don't use the lock up clutch, the pack will wear out quicker. Are you using electronic gear up and down?

[jeremy]

If you don't use the lock up clutch, the pack will wear out quicker. Are you using electronic gear up and down?

How come? Just because of the extra heat in the box, or is there something I'm missing?

We have manual shift, so the solenoids are wired to the shifter to select the gear according to the position of the shifter.

[wjw]

If you don't use the lock up clutch, the pack will wear out quicker. Are you using electronic gear up and down?

How come? Just because of the extra heat in the box, or is there something I'm missing?

We have manual shift, so the solenoids are wired to the shifter to select the gear according to the position of the shifter.

Don't shoot, me as this is what I was told by one of the auto reconditioners in chc when I was looking to do this. When its not locked there is constant slip in the clutch, whether it be when you put your foot on the gas, when you coast etc. This in turn causes premature wear on the clutch pack. Also without the lock you won't get full engine breaking. You can stall the engine with the lock-up engaged, I tried it when I was messing around with my auto.

[wjw]

actually tbh I probably wouldn't worry about it, I have a knack of buyins A343F's at <$300... so at that price they are pretty much throw away...

[jeremy]

Sorry, didn't mean to sound like I was shooting the messenger - just curious, that's all

For a daily driver, the lockup would be a good thing to have, but our hilux is just a toy (only driven on sundays) so we opted for simplicity and reliability.

...and you're right about them being a throw away. Much easier to swap one out than to fix it if something does go wrong.

Sorry Jono for the thread hijack.

[jonossiksilvia]

Sorry, didn't mean to sound like I was shooting the messenger - just curious, that's all

For a daily driver, the lockup would be a good thing to have, but our hilux is just a toy (only driven on sundays) so we opted for simplicity and reliability.

...and you're right about them being a throw away. Much easier to swap one out than to fix it if something does go wrong.

Sorry Jono for the thread hijack.

allgood bout the hijack its profiding info for me. plus not much of a hijack cos still in relation to topic in a way. as long as it doesnt turn into another lift laws topic

[wjw]

If you want full manual with lockup, you need a few relays to hook up the brake pedal.

If you don't want to do that, a manual switch to lock it up is a good idea for downhills, gives you full engine breaking. Would have loved that for some of the downhills in central.