Gearing confusion

[Pathrat]

Surprise, I know, there is something technical I don't get.

I am sitting here with no work to do so I got back on the Toyota site and was making the attempt to educate myself about truck stuff.

I came across this press release statement about the FJC:

The front/rear differential gear ratio is 3.727:1 (5 A/T)

then a few paragraphs down, I read this:

With automatic-transmission models, FJ Cruiser gets a part-time transfer case. When the transfer cases are in high range, their output ratio is 1:1. When shifted into low range, their gear ratio is 2.566:1. With the automatic transmission, the FJ Cruiser's crawl ratio is 33.76:1

I do not understand how that double digit number 33.76 fits in.

Question two: I think my FJC feel geared a bit high unless I am in 4L. Does my gearing ratio kind of suck, according to the numbers?

Thanks

[gragravar]

I'll take a stab at this for you.

your engine spins are shown as RPMs on your tach. those revolutions go through 3 sets of gears to get to your wheels/axles.

the first set of gears you encounter is in the transmission. I looked up the FJC and most of them seemed to use a first gear ratio of about 3.5:1. this means that the engine output needs to spin 3.5 times to get the transmission output to spin once.

the transmission output then turns the transfer case. it further reduces the spin 2.556 times in low range. so for every spin of transfer case output the transmission must spin 2.556 times and for each of thoes 2.556 revolutions the engine must spin 3.5 times. that means 2.556 * 3.5 = 8.9 turns of the motor for every turn of the transfer case output.

from there it is on to the differentials and one last 3.727 reduction. so to turn your axle (and thus your wheel) once you will have to spin the input to the diff (output from the transfer case) 3.727 times, and the engine will have to spin 3.5*2.556*3.727 = 33.76 times. thats where your 33.76 came from. your engine spins 33.76 times for every one time your wheel goes around when you are in 1st gear low.

to take that a step further each of those axle revolutions will move the vehicle forward ~9 feet with a 33" tire. that means that at 1500 engine RPM your wheels will rotate 1500/33.76 or 44.4 times. that means you'll move forward 399 feet per minute. thats 4.5mph.

it is a little fast for low range, but not too bad.

if you replaced the 3.727 diff gear with say a 4.556, then your final crawl ratio would become 3.5*2.556*4.556=40.75. that same 1500 rpms would then rotate the wheels 36.8 times, and you'd move forward only 331 feet in the same minute. your pace would have dropped to 3.7 mph.

clear as mud?

[BLOODBANE]

Here ya go pathrat, straight from wild horses website........
Gear Ratio Calculation

How low can you go? Take the lowest gear in your transmission and multiply that by the low gear in your t-case and then by your ring and pinion gear.

Example 1: NP 435 first gear is 6.69 x 2.34 in your T-case x 4.11 ring and pinion = 64.34 which we would call 64 to 1. Not bad.

Example 2: Now let's throw in a Dual T-case. NP 435 first gear is 6.69 x 2 in your Super Crawler x 2.34 in your T-case x 4.11 ring and pinion = 128.68 or 128 to 1.

[Brody]

Your gearing isn't bad for stock gearing. If you went lower (higher numerically) at some point, you would find an improvement in both off and on road performance. The posts to this thread regarding gearing sum it up very nicely. My crawl ratio with my gearing, tires, manual tranny, dual transfer cases with lower gears, gives me a 233:1 crawl ratio which is pretty sick, but it is a compromise vehicle, too. It also doesn't do badly on the road, either in mileage or performance. It did cost a lot to do all the differential regearing because this is something that I can't do. It also cost to regear the transfer cases, upgrade the output shafts, upgrade the internals gears, even though I did this work.

As Nay said-install a hand throttle for the moment, especially with your auto trans, and call it good enough for awhile. These can be done in about 45 minutes for the price of a bike shifter and some long cable. Save your money for something like a new front bumper and a used winch. You already have a very capable off road rig as it is...

[Pathrat]

Everyone, it was not overly confusing to read your replies! :D THANKS! :clap: Great answers.

I found a great explanation, with pictures, on Bill Burke's site that gave me some good, simple background on gearing. This coupled with what you all wrote gives me a better understanding of the whole gearing issue.

Nay and Brody, I am going to have to google how a hand throttle would work with my auto trans. I don't quite get it so I need to find a picture.

And yep, I have 33s on there now. If (ok, maybe when) I do the bumper and the suspension changes I am considering, maybe going down to 32s instead of the 33s would be more suitable overall.

[Brody]

Hey Pathrat

Check out the 'hand throttle' link I posted in here on this site (tech/ cheap tricks/how to-I forget which section). It cost me $15 and 45 minutes to do mine and I helped Dave Pritchett do his. Really not a big deal and very effective, too. Everything is available through your local bike shop. The shifter is something that they will have extras of kicking around in their shop. Get the absolute longest brake/shifter cable they sell, about 105 inches long.

[Brody]

Ahhh...tain't no function like dat dysfunction.....I, alas, can't resist the temptation of bigger tires and lowers gears, etc....

Kinda penile envy, you know....big gun, big tires, little ....

So I got a lot of issues....including anger management....so what?

Just kiddin'.....

[Pathrat]

I wouldn't go down a tire size, it won't make any difference with your transmission and you'll have smaller tires in the rocks.

Do you think gaining some of my articulation back and is more useful than more tire? I have thought about that option as a way to coordinate a 2" lift overall and still be able to use my garage, besides getting more of the wheel travel I used to have.

What the hand throttle will do is allow you to engage throttle extremely slowly and deliberating and then lock it in.

Oh, not hand-eye coordination! I need to start playing video games. Thanks for the simplification.

I'd suggest a run on Old Chinaman's as a perfect test since you can pick your difficulty. If you find you'd always take the bypasses, leave it alone. If you find you want to play...then that will be another story :cool:.

After seeing what SCRubicon did to his gas tank?
I would like to try more things, with assistance and with minimal damage to parts I care about. Shelling out a couple hundred for those tail lights that stick out past the body (as Brody pointed out last weekend) would upset the balance of the Almighty Cash Flow. I intend to continue to determine what I can do and what the FJC can accomodate.

The bottom line when you are with a good group is that it is ok to learn your limits by getting stuck, and I always suggest (safely) learning the limits in a group (FR4x4 :D) environment before spending money or even deciding what to spend on

This has been an excellent, patient group and the willingness to assist and educate is most appreciated!

Now if you are a guy, and you have body dysmorphic dysfunction in relation to your truck, then you are going always want bigger tires, lower gears, more strength, and all the fine tuning goodies. I resist all such notions :D

I would like a set of All-Pro adjustable coilovers, OME rear springs and a bumper. This set up is one of many I have considered and discarded (more research!) over the last few months and I find that I have ideas for the bumper that might be socially unacceptable. Occasionally, I find myself wanting to give the car in front of me a little 'bump'. :D

Thank you for the detailed posts. I enjoy reading your concise and literate responses and am looking forward to meeting up off pavement.

I'll try not to have my hood higher than the top of head. Maybe if I moved the ladder to the front though...:rolleyes:

[Chris]

The bottom line when you are with a good group is that it is ok to learn your limits by getting stuck, and I always suggest (safely) learning the limits in a group (FR4x4 :D) environment before spending money or even deciding what to spend on

This is so true and something to always consider. I'm very conservative if wheeling alone. Watching others do obstacles gives you a chance to see how they pick their line and how it relates to your truck. If things go wrong you know you can get a tug and be fine. I drove my truck stock with sliders for a year before making any changes because I wanted to get familiar with the truck, learn what it could do and what I could do. There's a lot more value in knowing the techniques than throwing money at something and assuming that you can anything. I think we've all seen people who throw a ton of money in a truck and haven't a clue how to drive it.


(unless you are Chris, who needs to do 4.88's and 35's right now :lol:).

Hey now Dave, my 33's rub when stuffed already!


Now if you are a guy, and you have body dysmorphic dysfunction in relation to your truck, then you are going always want bigger tires, lower gears, more strength, and all the fine tuning goodies. I resist all such notions :D

I'm not sure how I feel about this comment right on the heels of my needing bigger tires and lower gears! :lol:

[Pathrat]

Echo on the immense benefit of having you guys around to test out my truck with. :bow:

As far as dysmorphic disorders, there are so many fun ways to go with this, but don't forget that another criteria that must be included in our own little Diagnostic Statistical Manual for disorders is the envy which prompts full grown men to hang plasticized testicles off those bumpers. But they look so small next to those tires and the big spaces the body lifts create. Don't even start me in on impulse control deficiencies...

[Brody]

Well, now I know where to hang those testicles thingies I bought! I rigged an under garment garter belt to hang them inside my pants....What the hey....they didn't come with instructions....

BTW, I wouldn't be looking at ARB bumpers. I don't think too much of them and there are other bumpers out there that offer much more bang for the same price. Offer to help with any install still stands when you get around to it. Ditto hand throttle. I'll try to post some pictures of mine soon.

[Pathrat]

....Add lightest winch you can get away with. Buy spares. Done. Wheel. Wheel. Wheel. Attend friend's wrenching party who didn't follow this advice. Wheel. Attend friend's next wrenching party who didn't follow this advice. Wheel. Pick sides in friend's divorce. Wheel. You see where I am going with this :D

As for plastic testes, I think you can call up Bobby Long and order a Super Set of something, I've thought those should be named the Big Ballz Super Set just to be clear :lol:


OWW OWW OWW :lol::lol: my sides hurt! Steel ones that clank audibly to remind the driver of his prowess. You know how much money we could rake in if we opened a shop called OverCompensator4x4??? The ones who would buy would not understand the inherent slap upside the head giving money to us would be. % of profits to Blue Ribbon or something.

I have been reading up on upgrades to parts like upper control arms. And, I will have to admit, when I bought the FJC, a month later I bough a big old BentUp bumper. Close to the ARB design, but lighter. I thought the ARB too heavy, didn't want 100lbs hanging off my front end. I didn't know jack about suspensions, and only realized my mistakes after I got the thing. :o It was sold a few months later. I agree...light. I have not checked out what is out there now, a year later. As far as winches, I am looking at Superwinch (2 year warranty, @ $499) or maybe the Warn not branded as Warn, starts with a V.

I want some increased load bearing in the rear, looking at the Toytec "stock ride rears" and possibly the coil overs. My goal is a two inch lift, enough flexibility to add weight to the front and the ability to carry all my gear for the vacations. So many options out there!

I was kind of disappointed that my front skid had no marks or gouges. My old one has multiple marrings labelled with the trail of origin. My new one has not a mark for me to Sharpie label!

Nay, again, thank you for your detailed and informative input. :clap:

[Pathrat]

Brody, how much tissue glue am I into you for, as at least some payment for your genuine offers of help and instruction? :)
Yes, I will need help with whatever I do. The Bilsteins were installed up in Thornton my a Toyota employed mechanic for a few hundred. If I can get some help when I actually do alter my set up, it would be great to be able to learn and watch. Once I get the cash...stupid economy.

And LaDawn let you out like that????