6 speeds, can we drop out interstate rpm's with differential gearing ???

Swapping for a higher-ratio 6th gear may be possible, and a reasonable option. The Aisin AY-6 transmission is used in a bunch of vehicles, some (FJ Cruiser, Cadillac CTS, etc.) with higher (numerically lower than the stock 0.85) 6th gear ratios. Any transmission shop that rebuilds Toyota manuals should be able to tell you about availability and cost with minimal research.

With regard to the potential loss of 6th gear usability while towing, I really don't see that as a consideration. Gearing down to 5th is the solution, and it is direct-drive to boot. This places all of the load on the main shaft, which is the strongest component of the transmission. Under heavy load, this should be the preferred method. Nobody should be towing at 80 MPH.

Mike

 

Im not sure if its been discused but city will suffer with higher gears. Just like bigger tires, imagine a 10 speed bike, starting from a stop is much harder in a higher gear, just as it will be harder on ur truck to start with higher gears.

 

yep, I was lookin to pay for parts and get help with installation. You have a good point




Now Im googlin about re gearing the 6th gear, this seems more of an answer. At some point I will have to replace the brass on 3rd gear anyway...

 

I think ya mean I higher ratio. Lower would be like .95:1


Overdrive gears shouldn't be used when towing anyway. Wouldn't be going higher than 5th (direct drive 1:1) unless it's a light load.

 

That was a question as to how in the hell would any one tell him some thing like that.

 

Care to site any incidences of 6th gear failure from towing? Granted 5 is direct drive (head gear locked to the output shaft) but the O/D gearing is more than strong enough to handle the load. Most trailer tires are rated 65 MPH so it's probably better to keep the speeds subsonic any way.

 

Seems the ratios are all the same for the AY-6 guess the gearing is all final drive. http://en.wikipedia.org/wiki/Aisin_AY_transmission I guess I was right there is no optional gearing out there.

 

By that logic, the 4.17:1 first gear is a higher gear ratio than any of the rest. Conventional usage says that if a vehicle travels farther per engine revolution in gear A than in gear B, then gear A is the higher gear. A 6th gear ratio of 0.70:1 is a higher gear than 0.85:1. Math...

 

4:71 is the lowest gear ratio in our transmission.


Higher would be 3:1.


Lower would be 6:1.

Math.

 

I think he has it right if I understood him correctly. Looks like he said, a 0.95 ratio is lower than a 0.85.

 

http://www.cadillacfaq.com/faq/answers/transmissionspecs.html

This is the first example I found of an AY-6 with a 6th gear that is not 0.85:1. This data could be incorrect, for all I know, but I think that digging deeper than the Wikipedia page will probably find more examples. I also have a hard time believing that any manufacturer would be so shortsighted as to make a transmission with only one possible gearing configuration. It's much more likely that there are three or more different 6th gear sets. A transmission shop with the full Aisin parts catalog should have access to an exhaustive list of compatible gear sets.

Mike

 

I haven't check my owners manual, but I have checked a dodge owners manual. Dodge says don't use overdrive for their manual transmission when towing. I have seen one instance of the main shaft over drive gear driven gear splitting. From towing in overdrive. And if you saw that transmission I posted photos of on the last page, those gears are big and heavy. Probably significantly larger than the tacoma 6 speed gears.

 

I don't know of any 6th gear towing failures at all. I also don't know of any transmission that can withstand a higher load on a secondary gear shaft than on the direct-drive main shaft. Do you?

I'm not saying that 6th gear isn't strong enough. I'm saying that 5th gear is stronger. Additionally, an altered 6th gear ratio may not be able to handle the same load as well as the stock 0.85:1 gear set. At the extreme end of gear fitment, the strength of the individual gear teeth can become critical. A larger quantity of smaller teeth will not handle the same stress as a smaller quantity of larger teeth. Vehicle engineers have powerful computer modeling systems to help figure out what will meet the design parameters. We can speak about it in relative terms, but at the OEM level, giving the thumbs-up or down to a given configuration requires stuff like metallurgy and component failure testing. I'm happy to just ask the transmission shop. Knowing the GVWR and engine power specs of any production car that uses a particular gear set is a good starting point for educated guessing.

 

Every reference I see to the RA60F variant of the AY-6, including here on TacomaWorld, says that 1st gear is 4.17:1 (or 4.171:1).

http://www.tacomaworld.com/forum/2nd-gen-tacomas/226076-6spd-manual-transmission-differences.html

If they are all wrong, please provide some authoritative reference that says otherwise. I can't find any documentation from Toyota.

 

It's far easier to tailor the final drive than the gear box. Feel free to check it out I don't think it will be any easy search if there were parts out there I would think the Chevy guys would be all over it they can't leave any thing alone. Regardless I would also believe that the gear set would be a good bit more expensive than a ring and pinion not to mention the labor involved. I also think that the gear box was chosen for the car applications because of it's tight ratios.

 

Stock configuration for a V6 Camaro. Wider gear spread that the RA60/RA60F produces the equivalent of a tire size increase without the adverse steering and braking effects. I can't guess what external differences there may be with the Toyota and GM variants of this transmission, but it seems likely that the internals are identical.

http://www.camaro5.com/forums/showthread.php?t=206840&highlight=AY6
Aisin Warner AY6 six-speed manual (LS, LT)
Gear ratios 1):
First: 4.48
Second: 2.58
Third: 1.63
Fourth: 1.19
Fifth: 1.00
Sixth: 0.75
Reverse: 3.67

 

Part of the problem is that GM is replacing the entire transmission when it has problems. They send the complete transmission to Aisin for diagnosis and future improvement. BamaToy posted about this somewhere. Because of this, I suspect that there is not a large supply of repair parts in the USA. When I look at the Camaro forum, I see more questions about suitable replacements for the AY-6 than I do about potential repairs/upgrades.

If you look at my previous post, you can see that the gear spread is actually wider on the Camaro variant than on the Tacoma, the exact opposite of your supposition. This works on the Camaro and CTS because of the small tires. I'd like to see how it drives with the stock Tacoma tires. It should feel more "truck-ish" with the wider gear spread.

 

*** SUMMARY SO FAR ****

oK, come to some possible solutions so far.

-2WD taco's, just change the Rear Differential! plenty of options from other models of taco

-4x4 Tacos, changing the front diff DOES NOT seem to be an option.

- Drive slower (Fk that)

-Taller wheels and tires may make a difference, but the taller wheels and tires MUST BE LIGHTER than the ones being replaced. Otherwise the excess rotationg mass canceles out the advantages of the larger diameter. some of us would do this anyway. below is different stock tire sizes based on different model taco (olathetoyota.com).
2005-2013215/70 R15245/75 R16265/70 R16265/65 R17255/45 R18

-Over drive additional gear box- seems to be a good answer, but at $2k plus labor, it would take forever to "pay for itself" in any fuel saving advantage

-Re-gearing 6th gear with a gear from a different variant of the RA60F (FJcruiser?) transmission. This looks feasable, needs more research... http://www.tacomaworld.com/forum/2nd-gen-tacomas/226076-6spd-manual-transmission-differences.html

doing any of this will effect your speedomoter readings?

 

FWIW ...

At steady-state highway cruising, a vehicle's mass doesn't come into play at all when it comes to fuel use. That includes the mass of any of its parts. Highway fuel use depends on:

• Tuning (how rich or lean)
• Gearing (what speed is the engine running at)
• Tire diameter (see: Gearing)
• Aero

That's pretty much it. Rolling resistance, mass, etc are all major concerns for city fuel use, where you're slowing, stopping, re-accelerating, etc. But at a steady speed on the highway, the above list is it.

The thing with bigger tires: you have to balance the reduction in RPMs with the reduction in aerodynamics. Increasing the tire diameter will, by definition, increase the truck's frontal area, and thereby reduce it's aerodynamic efficiency. Now, trucks are rolling boxes anyway, so it may not have as much of a negative effect. But, that's how larger tires can negatively affect mileage on the highway. Again: it has nothing to do with their mass.