gearing and 255/85 tires

steve103

Observer
any one have 255/85/16 tires and manual trany. if any problems with shifting to 5th with out regearing. 07 tacoma v6 4x4
 
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Andy@AAV

Old Marine
I'm running that combo. I have the six speed and only need to down shift when going up long steep grades. Around town I've lost 1 MPG but gained 1 on the highway at 70 MPH. I would imagine the 5 speed would be similar. I love these tires BTW!
 

downhill

Adventurer
I really disliked the 3.73 gears and swaped them out for 4.56. IMO any increase in tire size just makes a bad situation worse. I'm running a 32" tire which is shorter than the 255, but I like the new gearing much better. It is more in line with what I use a truck for. If you plan on adding weight to the truck I think the gearing may become more of an issue. It all depends on what you want though. My truck is an 07 6spd access cab. I use it for long distance travel, towing, hauling gear.
 

Applejack

Explorer
I wouldn't imagine you having any problems at all. I'm not sure what specific tire you want to run but for example, a BFG KM2 in the 265/75 size is 53lbs and the same tire in a 255/85 is only 2lbs heavier weighing in at 55lbs, or so says Tire Rack.
If you are stepping up from the stock tires though, I'm sure you are going to notice the power loss but still have the guts to move them.
 

downhill

Adventurer
i thought that the 07 acc cab v6 4x4 has 410 gears,am i wrong?

Nope, they come with 3.73. The 4.56 gears are a tad low for my tires on the road, but IMO would be perfect for the 255s. Mostly my highway driving is 65 or less, so no worries for me. Offroad the difference was dramatic. I've actually got a crawl gear now that I can use for some technical work. The stock gearing works for things that require maintaining speed like sand and mud. I don't do any serious rock crawling with this truck, but sometimes you need to pick your way over something and that is where the gears make a big difference. Reverse gear in these trucks is too tall as well, and the lower gears improved that. With the 32s and 4.56 gears I lost about 1.5 MPG on the highway. With 255s you would probably lose less (if any). The 4.0 is turning faster but is operating farther up the torque curve. It's pretty flat at 2000 or less. At 2400-2500 it starts to come alive. I rarely have to downshift on hills unless I'm towing or hauling.

One more thing to consider. Toyota used a crush spacer in the pinion gear to make factory set-up faster. Under normal loads the pinion doesn't see enough pressure to further crush the spacer and alter the gear mesh. If you go to a tall tire and get too excited offroad, you could cause that to happen. When I replaced my gears I installed solid spacers, like most diffs run to prevent the problem.

You may not need gears for mild adventuring, that's your call. These are just things I've experienced for reference.
 

mvbeggs

Adventurer
I've been discussing this same issue over in TACODOC's 2005 Tacoma build thread. Here's some numbers I posted over there regarding gearing, tire size. Most of these numbers were calculated for the auto tranny, but may have some relevance here.

These numbers led me to think that 4.10 is the correct gearing for me. I want/need my max cruise to be about 85mph without the engine screaming down the highway. (No heavy crawling, ability to pull the AT Chaser trailer, and probably nothing more than a 4 rated trail.)

Tacoma Auto vs Manual Gearing.jpgTacoma Engine RPM vs Gearing Chart.jpg

I couldn't find a dyno curve specific to the Tacoma, but this is one from an FJ with the same engine. I'm assuming this discussion is about the 4.0L.
Tacoma '07 Dyno Curve.jpg
 

downhill

Adventurer
MVbeggs,
That's a great reference. Look at the difference in torque from 2000 to 2500. That is why I set mine up for cruising around 2400-2500 most of the time. Of course that was assuming a lower cruise speed and a manual gear box. I do alot of towing with a 2500 lb trailer, and I can tell you it makes a huge difference staying in that range. Typically, when I tow I also have 300-400 pounds of gear in the truck as well, and I lose 2 to 2.5 MPG which includes lots of grades. If you have a stock truck running mostly empty, you can afford the lower rpm and lower torque, but loaded you end up in a lower gear anyway on any incline. Heavier tires are also part of the load.

Regarding gear selection, last time I checked nobody offers an aftermarket gear set in 4.10. It is Toyota only and very expensive. I think it is really unfortunate that nobody offers 4.30. That would put alot of people right with the world that are not going to extremes. I would have chosen 4.30 if it were offered.

just reading off that graph:
At 2000 RPM = roughly 85 ft/lbs = 23.5 RPM per ft/lb
at 2500 RPM = roughly 185 ft/lbs = 13.5 RPM per ft/lb
More than double the torque for just 500 RPM is a pretty good bargain.

I think Doc's gearing is spot on.
 
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keating

New member
I've got a stock V6/Auto with the stock 245/75R16 Dunlop tires and the thing feels like it could use more gear. I'm going to 265s, since they're stock size on the TRDs it should be deemed "acceptable", but I'm dreading it. I can't imagine running 255/85R16 on 3.73s. For anyone who doesn't have the TRD OffRoad with E-Locker, wouldn't you have the 8" front and 8.4" rear, same as a 4 banger? There should be some 4 banger 3rd-members with 4.10s in junkyards by now?
 

mvbeggs

Adventurer
... Look at the difference in torque from 2000 to 2500. That is why I set mine up for cruising around 2400-2500 most of the time.... I do alot of towing with a 2500 lb trailer, and I can tell you it makes a huge difference staying in that range. Typically, when I tow I also have 300-400 pounds of gear in the truck as well, and I lose 2 to 2.5 MPG which includes lots of grades. If you have a stock truck running mostly empty, you can afford the lower rpm and lower torque, but loaded you end up in a lower gear anyway on any incline. Heavier tires are also part of the load....

Regarding gear selection, last time I checked nobody offers an aftermarket gear set in 4.10. It is Toyota only and very expensive. I think it is really unfortunate that nobody offers 4.30. That would put alot of people right with the world that are not going to extremes. I would have chosen 4.30 if it were offered......

Downhill,

Thanks for the response.

Have to agree with about everything you say. The 4.0L just doesn't have a lot of low end torque. Also agree with what you said about the 4.30 gears. I'm looking pretty seriously at a Tacoma build for the trips I don't need the rock crawling abilities of the Jeep. (mostly the hunting trips) I believe there is someone now offering a 4.10 ring and pinion set for the Taco.

I'm really interested in the experiences folks have had pulling trailers. (I'll be pulling my Chaser on most trips) I worry very little about the Tacoma's performance when lightly loaded. I'm not so sure how it will perform when loaded and pulling a trailer. I'm sure lower gearing would make towing a "non issue". My fear is that the low gearing will make her a bit obnoxious as a daily driver on the highway. (i.e. high rpms at 70mph-85mph) Compromises, compromises, compromises. :-(

What kinds of grades do you drive? Do you ever drive in Colorado, on I-70, up to the Eisenhower Tunnel? (that's a pretty good grade if you're not familiar with it) I'd be interested, if anyone would care to share, what kind of engine rpms are required to pull a 2,500lb trailer at 65mph up a similar grade.

Also, what are you driving auto or manual, what tires are you running, and how are you currently geared?
 

downhill

Adventurer
Mvbeggs,
I spend half the year or more traveling, mostly the western states. I'm familiar with virtually all the rocky mountain grades. My trailer weighs 2350 on the axle with 225 on the tongue for a combined truck load of around 600 pounds with gear. I have the 4.56 gears with 235/85-16 E rated tires (approx 32"). My unloaded truck weight is 5350 with a full tank, me and 2 dogs. I also towed this combination with stock gears prior to the switch. At 65 I'm turning 2550 RPM in high gear (manual 6 spd). With the 255s you would need the 4.88 gears to approximately match what I have.

With regards to daily driving: I love the lower gears around town. The only downside was that they produced even more axle wrap than I had with the 3.73. That was eliminated with the installation of All-Pro expedition springs.

With regards to highway driving: The 4.0 does not produce much power below 2400, but the good news is that the engine purrs right along at the higher speeds. My highway speeds are never above 70 and usually around 65. That keeps me under 3000 RPM.


With regards to towing: While the 3.73 gears did work, I found the 4.56 much more enjoyable to drive. Launching and accellerating through the gears is much easier, especially loaded on a hill. Down the road the difference is about one gear. With the 3.73 I would be one gear lower for the same incline than I would be with 4.56. Moderate grades require no downshift. I just lean into the gas a bit and it rolls on. Steeper grades like the I70 climb, the Siskyou pass etc, I take in 5th gear running I think around 2850 RPM. The only climbs that get me into 4th and down to 55 are like the climb into the Tetons out of Jackson Hole. On alot of these passes altitude also takes it's toll, but I can't recall ever hitting 3rd unless for traffic or corners.

There is one issue though that is probably not common knowledge. The weak link in the towing ability of the 4.0s is the rear diff. Both the 8" and the so called
"8.4" measure 8". That is a really marginal gear size for the power of the 4.0 under high loads. When I swapped gears after just 20K of combined towing my carrier bearings were already showing evidence of spinning. To monitor the situation I installed a temperature probe in the rear diff during the gear change. My typical unloaded diff temp running mostly flat or rolling hills is between 125 and 165 degrees. The same run with the trailer and weight runs 150 to 185. When I start climbing hard the heat builds fast and often runs 200 to 220 degrees. I don't let the temp ever exceed 225 degrees. If I approach that I get a lower gear and slow down. Above 225 the rate of viscosity breakdown accelerates and at 250 it is cooking the oil. The point is, the truck has the power to cook the diff under these conditions and I would never know it without the gauge. No doubt I had done that before the gear swap which resulted in the spun bearings. I would advise anyone towing under similar conditions to take it easy up steep sustained grades, especialy in the summer. I change my rear diff oil every year and I'm currently running Amsoil Severe Gear 75/140. At the last change out the oil looked just fine after running all over Wyoming, Montana, Idaho, Washington, Oregon, and Northern California. The trick is not overheating it. I could probably go longer on a fill, but I know the gears are working at their limit at times so I spend the bucks and change it out.

Hope that helps....
 

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