gearing questions on v6 manual

grntrdtaco

Adventurer
hello, sorry if this is a repeat thread, the only other similar setups that i have found have been people with automatics.

i switched to 33" km2s a few weeks ago and have now gone on a few trips with them. I am pretty sure i need to re-gear at this point. I have to drop into 4th gear on any slight incline on the highway and have to drop into 3rd when hitting any hills and it feels like i should go to 2nd on the steep ones (i havent gone into 2nd on the highway yet). the truck seems like its seriously bogged down most of the time. no engine mods, have a snorkel and that's about it.

after reading as much as i could find on the subject i am seriously leaning to 5.29 gears

1. i live at about 9000', i usually air down in my driveway and drive up from there to 12,000+ feet.
2. my truck is extremely heavy (full underbelly skids, winch, dual batteries, aux gas tank (25 gal but i never fill it all the way), front bumper and soon rear bumper/tire carrier, roof rack with a few 10gal water cans, shell, bed storage compartment, tools, spares, co2 tank, etc)
3. truck is not a daily driver, its a 2000 with about 90k miles on it.
4. i dont drive fast on the highway, 75 tops (seems dangerous as my truck does not stop real fast and is rather tippy)
5. i break out the hiking boots or mountain bike when the trail gets really nasty.

i am currently getting about 200 miles a tank with an uncorrected speedo, but its within a few mph when compared to my GPS so its really not that far off (my 33" km2's are not 33" tall).

I am also on the fence about a front locker. I rarely use my rear locker now, I have probably needed it 10 times in the past ten years. but could have made it without by taking my time and driving smart. I plan on getting the gears from east coast gear. is it really a big deal to put in an ARB locker in a few years if i find that i need it? I basically need to spend as little as possible to get this thing driving normally again and i cant justify another 900 bucks + compressor or parts for my co2 to run it, just dropped a ton of $ for a rear bumper/carrier.

so basically what are the negatives if i choose 5.29 gears? seems like i get better gas mileage, better gears for offroading, and they will prevent me from driving like a maniac in an overloaded truck on the highway.

thanks
t
 

grntrdtaco

Adventurer
as far as i have read for non high elevation and an unloaded truck that would be the way to go. i hardly ever drive my truck at anything less than 9000 feet
 

grntrdtaco

Adventurer
i have also never read of anyone that got better gas mileage from 4.88's and nearly every account of 5.29's people say thay get signifigant improvements in mileage. i need all the help in that area as i can get
 

Martinjmpr

Wiffleball Batter
i have also never read of anyone that got better gas mileage from 4.88's and nearly every account of 5.29's people say thay get signifigant improvements in mileage. i need all the help in that area as i can get

I don't understand how going to super-low gearing will improve your gas mileage. Power? yes. But how does making your engine spin faster for the same speed improve fuel consumption? 33" tires are not that much bigger than stock tires on a Tacoma (IIRC stock tires on a TRD are 265/70/16 which are 30.5", or 265/75/16 which are 31".) An increase of 2" diameter = 1" radius and I can't see how that would make any significant difference in gearing.

So you have a 25 gallon tank and you get 200 miles on the tank? That's horrible - less than 10mpg. For that kind of MPG you might as well be driving a full sized rig. FWIW on my 2004 Taco (also a V6/5 speed) I got ~325 miles on the stock 18.5 gallon tank with 32" tires (235/85/16.)

I don't think your problem is gearing, I think the problem is weight. If you don't do extreme trails, why are you hauling around all that armor?

For a lot less than the cost of new gears (what, $500 to do front and back?) I think you can shed a lot of unneccessary weight. You also might consider going back to a smaller tire, not just smaller in diameter, but thinner too because thinner tires = less weight.

In terms of fuel economy or speed, weight is the enemy. Try to minimize it as much as you can.
 

AlexJet

Explorer
Agree on weight.
I have 35s and 4.56 on mine and I d still feel all that weight. I was thinking of 4.88s, but then mileage would be gone, especially on highway. (buddy of mine drives Jeep TJ with 5.something and he gets about 5mpg on the highway)
 

grntrdtaco

Adventurer
i have an aux 25 gallon tank. the 200 miles per tank is the stock tank. i generally only put 15 in the aux when i use it to keep the weight down.

i dont really know how it works but just about every person that i have read about that has changed to 5.29 gears with a heavy/expedition type tacoma reports a fairly good sized improvement in gas mileage (2-3mpg better than before the gear change). i would think its from freeing up the engine from bogging down so much in 1st through 4th gears, im sure it uses more gas in 5th on the highway.

i use the skids so there is no way they are coming off. the tires i have now are 33x10.5. i had a set of 32x11.5 tires on before these and didnt have the problems of having to shift into 3rd on the highway. i regularly drive roads that are as or slightly more difficult than pearl pass in colorado, i dont consider that extreme but not having armor or going to a smaller tire would be really asking for trouble.

are there any other downsides to 5.56 gears other than not being able to drive much above 70-75mph? the seem like they they are better in every aspect but that one point.
 

tacollie

Glamper
As long as you are ok limiting you speed I would say go with 5.29s. The 3.4 does really well in the mid 3k rpm range. 5.29s will put you on the high end of that. The pedal barely pressed down at 3500 rpms will yield better milage than it floored at 2800 rpms. I don't see 5.29s doing any better than 4.88s mpg but I could be wrong.
 
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grntrdtaco

Adventurer
thanks, i guess all of the reports of better mileage are with the auto tranny. but it seems to make sense that i wouldn't have to have the gas pedal pressed to the floor like i do now while still bogging the engine down
 

blakeape

Adventurer
I have a 1996 Tacoma V6 5spd and used to have 4.88's with 33's and loved it. The truck had an ARB bumper, winch, topper, ladder rack, and usually a bed full of either tools or toys depending on what I was doing that day. I eventually SAS'ed it and ran both 35's and 37's with the 4.88's. When I got up to 37's I was wishing for 5.29's but the 33's and 35's were great with the 4.88's.
 

CJCA

Adventurer
I seem to remember that Scott Brady did a very good, in depth write up on this subject of differential gearing effects on driveability and fuel economy. You might do a search for his postings. It's worthwhile reading.
 

grntrdtaco

Adventurer
I have a 1996 Tacoma V6 5spd and used to have 4.88's with 33's and loved it. The truck had an ARB bumper, winch, topper, ladder rack, and usually a bed full of either tools or toys depending on what I was doing that day. I eventually SAS'ed it and ran both 35's and 37's with the 4.88's. When I got up to 37's I was wishing for 5.29's but the 33's and 35's were great with the 4.88's.

thanks for the info. what elevation did you generally run the truck at?
 

grntrdtaco

Adventurer
I seem to remember that Scott Brady did a very good, in depth write up on this subject of differential gearing effects on driveability and fuel economy. You might do a search for his postings. It's worthwhile reading.

yes he did but it was an automatic and i think there are differences between the 2 trannys when it comes to gear ratios etc.
 

CJCA

Adventurer
yes he did but it was an automatic and i think there are differences between the 2 trannys when it comes to gear ratios etc.

Comparing autos to manual transmissions, there will be differences on the under driven gear ratios since the 340 has two under-driven gears vs. the 5 speed which has three under-driven gears. First gear in the auto Trans is usually lower than the typical manual Trans. But for the sake of an apples to apples comparison, both the automatic and the standard manual trans have a direct 1:1 gear ratio in their respective high gear ratios (this does not apply to the overdriven gear ratio in either transmission. In both transmissions high gear (not the overdriven gear ratio in overdrive) is basically a solid direct 1:1 connection between the input and output shafts. All the rotating internal components of either the auto or standard Trans just go along for a free ride, rotating freely under no load and unengaged from any underdriven or overdriven gear ratio power transfer. No practical differences there.

I'm not interested enough to research what the overdriven gear ratio in either Trans is. I'll leave that chore to you to research. But I doubt there is a huge discrepancy between the manual vs. automatic transmission overdriven ratios. All going by my aging memory, but I suspect the difference in ratios probably doesn't differ by more than 10%, between auto vs. manual trans, if that much. And climbing steep grades with a significant cargo weight at high altitude is generally a job for high gear (1:1), not overdrive. Scott's article should be relevant to your questions, regardless of transmission type.
 
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tacollie

Glamper
My buddys taco with and auto is a good 300rpm lower at 75 than my manual when the trucks were stock if that helps. An auto with 5.29s should be closed to a manual with 4.88s from what I understand from researching the same topic. The OD in the auto is really tall. A lot of guys on cottora are running 4.88s and 5.29 with 33s. That may be a good place to find some info.
 

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