Possible upgrades to 5-6-8 speed auto

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alia176 said:
are you affiliated with the above company with cool parts? Other than the cost of a Toy 8sp, is there any advantage over the 8HP trans?
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I am not affiliated with any company, just enthusiastic about the prospect of having a better and more modern transmission in our 80's.
I have been chasing this dream for many years and it looks like it is turning into reality.
 
OGBeno said:
My interest would be in seeing how a 1FZ power bands match with this many gears….

I can see a 5speed being optimal for 1FZ power.

What would 8 gears do to useable power and torque?

I’m not an automotive engineer so I’m genuinely interested.
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The way the original transmission is geared in our 80's is not optimal. The torque and RPM drops significantly from first to second gear. If anyone is towing with an 80 knows that getting up to speed is painful. If feels like there is a missing gear between the first and second gear.

Also due to Toyota trying to improve gas mileage they designed the shifting patter to upshift as soon as possible and keep the revs down.
It is a painful experience to get out of a low speed turn in third gear and wait and wait for the engine to finally rev up and catch some speed.
Yes you can floor it and have it kick down, but that's not the way it is supposed to be.

More gears in between will make our driving experience much more pleasurable.

Not to mention the very low first gear in any towing or offroad situation.
 
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Dragos80 said:
The way the original transmission is geared in our 80's is not optimal. The torque and RPM drops significantly from first to second gear. If anyone is towing with an 80 knows that getting up to speed is painful. If feels like there is a missing gear between the first and second gear.

Also due to Toyota trying to improve gas mileage they designed the shifting patter to upshift as soon as possible and keep the revs down.
It is a painful experience to get out of a low speed turn in third gear and wait and wait for the engine to finally rev up and catch some speed.
Yes you can floor it and have it kick down, but that's not the way it is supposed to be.

More gears in between will make our driving experience much more pleasurable.

Not to mention the very low first gear in any towing or offroad situation.
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Your points are excellent, and I'll add mine. I used to hate the 343F in my bloated phat NA rig, but when I got in a 2000 100 series with the V8, that tranny wasn't so bad. It shifted normally-ish, held the gears appropriately on the uphills, and cruise control actually did a decent job with the V8. After adding the turbo on my 80, that 343F tranny no longer pissed me off. So, what I deduced was that an extra 100 (or more) hp makes that antiquated tranny behave more or less decently from my limited experience.

I have the A750 on the V8 4runner and the steps between the shifts is beautiful. Like some folks, I too am hoarding an extra A750 to stick into the 80 series, but this 8HP is giving me some seriously dirty thoughts. The conversion cost of approx $8k is quite daunting at this stage but it'll come down eventually, I hope!

I think that 8HP will definitely help the NA fellas but an additional 100+hp would really help with that many extra gears. Of course, there are myriad of other factors that contribute to the whole thing as we all know. I have 4.56s with 315 tires.
 
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When my old 80 was supercharged, with meth injection, intercooler and small pulley all on 4.88's- the a343 was a perfect combo- for a 4 speed.

After the supercharger came off, I shifted that thing manually to get more revs and it was still really good with 4.88's. The other huge help was doing the free transmission mod that tools R us (RIP) came up with the tighten the shifts up.

Back on topic, the 1fz starts to wake up above 3000 rpm so that 8 speed might be amazing in there if it kept the revs going.

Hell, the owners manual in the glovebox says to shift to second on steep mountain grades and hold 4500 rpm. I did it, and it was great. Took a bit to get used to the idea, but was great.
 
I forgot to mention the transmission losses on the 4 speed. They are great. Well that's not great, be the losses are large.
The newer transmissions tend to have less loses therefore more power will be at the wheel.
Not to be confused with the (wrong) idea that a new transmission somehow will miraculously add more power.
But losing less power through the transmission, more will get to the wheels.
 
alia176 said:
are you affiliated with the above company with cool parts? Other than the cost of a Toy 8sp, is there any advantage over the 8HP trans?
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Sorry, got carried away and pretty much did not answer the second part of your question.

Gearing is slightly different. On paper I think I prefer the ZF over the Toyota transmission is I just look at how the ratios are.
However, I am not so sure in real life I can tell the difference in driving identical 80's with different 8-speed transmissions.
Maybe drag racing, but who cares at that point. 6000 lbs of steel racing down the street. I don't think 0.02 sec difference is enough to make a difference.


Anyway here are the ratios for the two transmissions.

Toyota 4.79......... 2.81.... 1.84... 1.43... 1.21... 1.00.... 0.82... 0.67
8HP70.. 4.714...3.143...2.10... 1.667...1.285....1.00...0.839...0.667


I tried to place the ratio in such a manner so one can easily see how they stack one over the other.

Also Toyota's 8-speed transmission's second gear almost matches the 80's first gear on the 4-speed.
Essentially you could start in second gear (2.81) and and it feels the same as the original transmission but what follows after will be totally different.
On the 4 speed it drops from 2.804 to 1.53 whereas on the 8-speed the drop is not that sharp.

You can see why on paper I prefer the ZF since you could start in second gear (3.143) then third at 2.10 and the fourth gear still lower than on the Toyota keeping the engine rev'd up in the powerband really nicely.

Again this is all speculation on paper.
I have no idea how they will behave in real life. It may all be totally different then my theoretical scenario.
 
Used shifter.

Screen Shot 2025-11-23 at 8.55.41 AM.webp
 
So everything in parts alone could be just over $5000.
Labor costs? Not sure.

I gotta talk to my mechanic who is also interested in a 8-speed swap.

*Note to self*
Wait till the Toyota 8-speed kit comes up t compare the two.
 
@scottryana
Would you consider changing the title of this thread to 5 or 8 speed auto since there was so much more development in the 8-speed tranny swap and it seems to be available vs the 5-speed?
 
Corbet said:
I’d be so much happier with 1 more gear but 4 more…. 😎 switching between the 80 and 250 really makes it obvious the advantage would be.
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With the original 4 speed it feels like you are changing gears on a manual transmission from first to third. It falls out of the powerband quickly.
Having more gears in between will also keep the revs flatter which is a positive too.
 
Dragos80 said:
@scottryana
Would you consider changing the title of this thread to 5 or 8 speed auto since there was so much more development in the 8-speed tranny swap and it seems to be available vs the 5-speed?
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Done
 
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