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Taller overdrive gear on AutoBox?

Beau

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Jan 28, 2011
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guyana
Hey guys,

So now that my cruisers all well and nice, further projects are sparking...

When cruising on the motorway it feels pretty nice doing 80mph but I feel like it could always use a taller 4th gear to drop the revs. At 80mph I believe it's at about 2700RPM. If I could drop it to 2200-2400 I'd be pretty happy and feel the motor is strong enough to pull at this rpm happily.

I've read a few people changing over taller gears on manual boxes in 80 series and a couple surf boxes, but nothing on the Autobox.

Wiki tells me the box is used in these vehicles...

Land Cruiser:
1986-1990 2LTE J70-J73
1990-2002 1HZ J70-J79
1990-1997 1HZ J80
1998-2002 1HZ J100/J105

Hilux/Pickup:
1986/1987 22-RTE N90-N120
1997-2005 1KZTE N140-N170
2006-2015 1KD-FTV N15-N26

4Runner/Surf/Prado:
1990-1993 2LTE N130 4runner/Surf
1994-1995 1KZTE N130 4runner/Surf
1996-2002 1KZTE N180 Surf/J190 Prado
2002-2005 1KZTE N210 Surf/J120 Prado
2006-2009 1KDFTV N210 Surf/J120 Prado
2009-2015 1KDFTV J150 Prado

Ratios:

  • First Gear: 4.313:1
  • Second Gear: 2.330:1
  • Third Gear: 1.436:1
  • Fourth Gear: 1.00:1
  • Fifth Gear: 0.836:1

I don't want to run larger tyres or change my diff ratio as this changes acceleration at lower speeds.

Anyway, does anyone know if this is possible, are there any other boxes than run a taller gear that are interchangeable? I know a lot of Toyota 4x4 R series boxes are very similar.

Beau :icon-biggrin:
 
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Further research shows I might actually have this box - A343F, as I have a Auto!
 
Isn't it the case that the overdrive kicks in and out as the gears are changed up and down? I mean, I think I have the 4 speed electronic box on my 81 but there are definitely 6 changes.

If this is the case wouldn't a taller gear upset the steps on the way up?

As mine isn't shown in your list I'm guessing the boxes work differently.
 
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My box is a 3 speed + overdrive, so basically 4 speed. I only count 4 actual changes. Overdrive gear (4th) seems to kick in around 55-60mph.

Maybe those 6 changes you count is when you feel the torque converter locking up? I'm not sure. I'm not very familiar with how these boxes work, never opened one up or anything! I think Bob on the forum is the expert with these.

I basically want a taller 4th gear (overdrive), for example now overdrive can kick in slightly higher at 65-70mph and my RPM's would be a lot lower.
 
Yes, you could be right Beau, I'm not certain if it is 5 or 6 changes I can hear. It's news to me if the TC does in fact lock up.
 
The petrol models (5VZ-FE) have the same autobox (A343F) and therefore share the same characteristics; sitting at 2700rpm around 80mph, which is really annoying as the 5VZ-FE has a definite hole in its power and torque delivery around that rpm! Either side of that and it's fine.

Really wish it was a 5 speeder, it would transform high speed cruising IMHO!
 
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The petrol models (5VZ-FE) have the same autobox (A343F) and therefore share the same characteristics; sitting at 2700rpm around 80mph, which is really annoying as the 5VZ-FE has a definite hole in its power and torque delivery around that rpm! Either side of that and it's fine.

Really wish it was a 5 speeder, it would transform high speed cruising IMHO!

Yeah, would make cruising at higher speeds more pleasant and would also save a few on the fuel. Judging by the lack of responses I'm guessing no one on the forum knows if this is possible...
 
I'm not very familiar with how these boxes work, never opened one up or anything! I think Bob on the forum is the expert with these.

If you mean me I'm afraid I can't help much. My '100' is the first Auto I've owned and I've never been inside it (I prefer manual boxes :icon-rolleyes:).

On my 3+OD box the torque Converter only locks when it gets to the highest gear possibly - usually 4th, but if running in "O/D Off" it locks in third and when in "2nd" it locks there.

One day I'll have to get to understand the insides but until then I'll keep feeding Raspberry Juice to the Gremlins :lol:.

Bob.
 
If you mean me I'm afraid I can't help much. My '100' is the first Auto I've owned and I've never been inside it (I prefer manual boxes :icon-rolleyes:).

On my 3+OD box the torque Converter only locks when it gets to the highest gear possibly - usually 4th, but if running in "O/D Off" it locks in third and when in "2nd" it locks there.

One day I'll have to get to understand the insides but until then I'll keep feeding Raspberry Juice to the Gremlins :lol:.

Bob.

Yeah the manual boxes are a lot easier to work with. And so far these are the boxes people have successfully installed a taller 5th/6th gear in, however nothing with a auto. I believe the Auto in your 100 series (4 speed) is the same in the colorado? That's what I've been reading anyway...
 
What about the possibility in swapping the entire box out for a newer one? Some never 100 series run the 5 speed A750F box. How would things work with ECU's, any idea anyone?
 
Sure i read somewhere our engines peak at 3600 rpm .
 
A343F specs -
1st 2.804:1
2nd 1.531:1
3rd 1.000:1
OD .753:1
R 2.393:1


The A340E box which is very similar has the same gear ratios except overdrive is .705. I'm wondering if I'll be able to use the overdrive gears and swap them on my box. Now I need to just figure out the difference and do some maths...Making a little progress
 
Can't remember it was a long time ago i asked myself similar questions about revs at that speed , off the top of my head i would guess 4000 is redline and 3600 is max power output .

The self preservation society starts singing in my head before i get to 3000 rpm in top gear on a motorway :icon-smile:
 
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Can't remember it was a long time ago i asked myself similar questions about revs at that speed , off the top of my head i would guess 4000 is redline and 3600 is max power output .

The self preservation society starts singing in my head before i get to 3000 rpm in top gear on a motorway :icon-smile:

I believe 4200 is red line on the tach, but the auto always changes at 4000. I've never free-revved it at standstill to check although that's what the manual says to do when adjusting/setting max RPM.

Max top speed run for me was 110mph down a slight incline (private - road/runway/motorway). There was actually a little bit more left but I was a little worried about pushing the engine at those extreme RPM's for a long period of time.
 
5000 miles in a fortnight while pulling a trailer mostly at 2700 rpm suggests its nothing to be concerned about is what i'm saying , i think your money would be better spent on an exhaust .

As a side note my truck as it is now could do with a slightly taller gearing throughout but i reckon the final weight when a winch bumper and other bits will balance thing out .

But if its a modification that you want i can only suggest you look at old TVR's i vaguely recall they have something of an open final gear , its way out of my depth but maybe if you can find out how that works it might spark some ideas ?
 
I know what you mean Shayne, these motors can handle the long distance high rpm runs, but with a taller gear they can relax a bit on the revs, and fuel consumption should improve as well. From 2200-3000rpm there is a good amount of torque.

I'll be looking into the A340E final .705 overdrive gear and comparing it to my A343F 0.753 OD gear. If they're similar I'll then source the parts and do the swap.
 
Just did some quick maths. With my current tire height, if I change out the gearing to the .705, my RPM's will drop by 200RPM in 4th gear.
 
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