Interdasting Ratios

King TChalla (wakanada forever) got me thinking about why they haven’t put the Toyota 8 speed, what toyota calls the worlds first 8 speed auto, into the tacoma where 8 and 10 speed autos are the norm. They even already have a version that mates up to the tacoma engine in the AA81...so why don’t they? I think I figured out why.

The 8 speed has a strange ratio spread. here

4.596 - .685 vs the 6 speed 3.52 - .586

The key takeaway is the overdrive ratios, .685 being the tallest vs .586 being the tallest.

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Toyota uses this transmission in the land cruiser alone right now for 4wd applications and in that application it uses a 3.3:1 axle ratio which is way low for a Toyota truck. Normally they are in the 3.9-4.3:1 ratio I think because their transmissions give them very tall overdrives and big ratios mean strong gears and less transmission strain.

The Tacoma has a 3.909:1 axle for example in auto form (4.3:1 in manual)

If you took the Tacoma axle ratio and put the 8 speed in front of it it would have amazing low end torque, nearly 18:1 first gear crawl alone is nutty and it would take off like a rocket...but...at .686:1 and 3.909 its only 2.67:1 vs 2.29 for the 6 speed. So it would get worse economy both on the highway and city cycles because it would be in shorter ratios pretty much all the time.

Im guessing they don’t have a 3.3:1 ring that can fit the Tacoma’s carrier. Seems like a problem they can and NEED to solve. if you had a 3.3:1 ratio in the Tacoma like the land cruiser with the same transmission you would get better acceleration in all ratios and SLIGHTLY better overdriver at 2.27:1 It would actually make that high strung 3.5 feel pretty perky and they could relax the shift logic a little to allow it to stay in gear longer.

I personally wouldn’t mind the overdrive penalty on the Tacoma as it would be a killer towing machine even with that 3.5 and it would crawl like nobodies business.

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Granted Toyota also has a new FR - 10 speed that is supposed to solve that issue

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So...GET ON TOYOTA!

UPDATE: found the ratios for the AGA0 (10 speed) here is a comparison

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Good gads that 10 speed 1st gear ratio is hot. Too bad overdriver is still less than the 6 speed. Still, with the new transmission you could easily get a 3.73 ring on that axle and be perfect.

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Okay, thats pretty great.  Even with the wimpy 3.5 I think the 10 speed would transform the Tacoma.  DO IT!

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