Hardcore Offroading

[HARDTRAILZ]

I was wondering if anyone other than me was serious about wanting/needing a functional upgrade to our suspension and front end?

We have multiple weak links in the front end area and the suspension is fairly pathetic for real wheeling. We have minimal travel. We cant get enough lift to use any tires tht would allow for the ground needed for tougher trails.

I dont see the coilovers floating around as anything that would do me any good. i am trying to work with the stock or close to stock as are a couple other people to push that envelope, but it seems to not be working all that well.

I am looking for some suspension travel, some axle strength and the ability to run a 35-40 inch tire. Is anyone really wanting this or is everyone fine with the little travel and strength we have? I know it depends on your mission and thats why I am asking. My mission is to travel the country to wheel different areas and terrain. Large boulders, paved and dirt roads, drop offs, creekbeds, difficult to extreme trails and still drive it home.

I believe Guy drove his Explorer to Moab and had a great adventure while enjoying the strength of a solid axle and pretty custom rig. I want to do that, not struggle with 33's and maxxed out angles and lift and strength. I want to be limited by ability not by the rig like it currently is.

So Basically, is anyone else serious about a sas for trail use or does anyone have another way/ideas/concepts to beef up strength, add travel and fit tires for ground clearance?

[janesy86]

I do see this as somethin I'm looking to do in the future, not soon maybe 2 years or so away.

But that is what limits me at a lot of the trails I run, more geard toward rock crawling, so I would really like to get atleast a 35" tire under there and better gearing for sure.

My buddy has a cpl 70's laying around.

[MrSmithsTB]

My post from the OS. Mike brought up a good point about the transfer case. It's something I haven't attempted before, so try to remember to read my posts with an implied learning curve. I didn't really think about the angle coming out of the case, but my logic told me there will be some allowance with that as long as the axles are set to a proper angle before the suspension mounting locations are determined.


I have a serious interest in SAS. Soon, this truck will be one of two vehicles I drive, so that it can spend some time under the knife if needed. I have some ideas bouncing around in my head, and have no reason to believe that they will not work. Converting to a 2wd setup(to prevent pcm complications), a manual xfer case, a modified TB rear to use as the front axle, and 4-link front and rear suspension w/coilovers are where my interests are taking me right now. I don't know where your head is, but if it is anywhere close to this, I think we can probably benefit from picking each others brains.

[HARDTRAILZ]

Life has upped my rush and I am hoping for about a 6 month time frame to get the plan finalized and started so it can be done within a couple months of that.

70's are pretty heavy, but plenty strong.

[MrSmithsTB]

Life has upped my rush and I am hoping for about a 6 month time frame to get the plan finalized and started so it can be done within a couple months of that.

70's are pretty heavy, but plenty strong.

I hear ya. If this is something I want to do, it either needs to be soon or not at all. The woman has been on me about planning the wedding. Your little find at the swap meet this weekend didn't help, Kyle. Now she really wants to turn me into a family man.

[bartonmd]

My post from the OS. Mike brought up a good point about the transfer case. It's something I haven't attempted before, so try to remember to read my posts with an implied learning curve. I didn't really think about the angle coming out of the case, but my logic told me there will be some allowance with that as long as the axles are set to a proper angle before the suspension mounting locations are determined.

Even if you tip the axle back, you're still looking at the angle coming out of the T-case, and the shorter the prop shaft, the more splined length adjustment you have to have for suspension travel. You could do like Jeeps do and split and angle 3 ways by using a double cardon joint at the rear of the T-case, but then that's more expense that's not really needed, and a divorced T-cases are getting more expensive and harder to find, not to mention having 2 more cardon joints to take care of and worry about popping...

It should be pretty easy to get our T-case to work with a SAS, as I stated on the OS (leave the splined disconnect actuator plugged into the wiring, and up out of the way, so the computer gets the feedback)... If our T-case ends up not being strong enough, the 3/4 ton Autotrac T-case has been retrofitted to our platform, and IIRC, it's pretty much a drop-in...

Mike

[Trail X]

State of the art these days are minimal lift with big ol tires.

Maybe the focus should be on moving the front suspension forward a bit, rear suspension back a bit, and fitting 37s.

That could be almost as easy as new upper and lower control arms front and rear. Almost.

[HARDTRAILZ]

State of the art these days are minimal lift with big ol tires.

Maybe the focus should be on moving the front suspension forward a bit, rear suspension back a bit, and fitting 37s.

That could be almost as easy as new upper and lower control arms front and rear. Almost.

I been debating similar to that, but steering and shaft strength are very questionable then. I plan to cut sheetmetal to keep it as little lift as possible as well.

[HARDTRAILZ]

One big thing...

GEARS

We have almost no options that would support 37's. 4.56's would be ok, but I was think in the 5 range since the t-case is 2.7, but if there is a doubler or something floating around that would give 5.4 t-case and then 4.56 would be ok.

I know lower gears would have helped in TN. I spent 18 hours in first or second and 4lo in one weekend. I never had a use for 4high and 2wd was just from parking lot to camp.

[janesy86]

Yep I'll agree with low COG but big meats and then like Hardtrailz is sayin, regearing is definately needed. Heck I'd even like a better gear ratio than I have with my 32's now. 3.42's aint really cutting it for me on the trails.

[glfredrick]

State of the art these days are minimal lift with big ol tires.

Maybe the focus should be on moving the front suspension forward a bit, rear suspension back a bit, and fitting 37s.

That could be almost as easy as new upper and lower control arms front and rear. Almost.

Now we're talking!

[glfredrick]

Axles are just a pull-a-part visit away...

[SteveTB03]

Now you guys are talking about using the stock transfer case but I know I've seen Tcase adapters around so you can mount a stronger and better tcase to our TBs.

Now what axles were you all thinking of using if you go SAS? maybe a 14 bolt rear? Or are guys thinking some hi pinion D60 axles?

[glfredrick]

14 bolt would be overkill for a TB. A set of 60s from a Ford or Dodge pickup would be more than enough.

Out back, even the Ford 8.8 would add strength and the ability to select a host of gears and lockers. I prefer the 8.8 to the 9" unless one is going full custom with 35 spline axles (big $$$).

Rock Jock would be my choice if funds weren't an issue.

http://www.currieenterprises.com/cestor ... kjock.aspx

For 35" and up tires, gears are a must. 4.56 is barely adequate for 35s. I'm running 5.13 with 38.5" rubber, but I'm also doing a t-case doubler. My final crawl ratio will be about 92:1 (not a typo) not counting the torque converter which gives a bit of a boost.

Here is a nice calculator (use the 700R4 for the transmission ratios and 2.70 for the t-case).

http://www.4lo.com/calc/gearratio.htm

With 33" tires and a 4.10 gearset, the crawl ratio of a TB is about 34:1.

More involved calculators for those interested in really playing with the numbers:

http://www.grimmjeeper.com/gears.html

[Trail X]

Guy, maybe you can answer this for me. Why would tire diameter come into play when determining final drive ratio?

The drive ratio is how many times the engine turns over to how many times the wheel turns over, right?

Now, if we were comparing thrust output, yes, tire diameter comes into play, but not drive ratios.

[glfredrick]

The diameter of the tires is the final part of the drivetrain, and what actually places the torque of the engine on the ground. If it didn't make a difference, we could run 31s, 33s, or 40s with impunity, but we all know that is not the case. We're not talking theoretical here, we're talking power on the ground, and the tire size is part of the equation.

There are two ways to change a crawl ratio or gear ratio -- change gears or change tire diameter. Both do the same thing for ultimate ground speed and crawl ratio. The inverse is also true, change gear size and tire size has to change to keep the effective range within certain parameters, or change tires and one must change gear ratios to keep the effective range within certain parameters.

What happens if one runs 4.56 gears with 28" tall tires? The engine tachs out and a very low terminal speed is reached, albeit very quickly. Conversely, if one runs 44" tires and 2.73 gears, the engine will likely never hit its tached out rpm, the vehicle would potentially go 200+ mph, but there would not be enough horsepower to push it because of the crawl ratio (or drive ratio, if you like -- I use crawl to delineate low speed work for off-road).

That, in part, is why I keep talking "lever arm" (from physics) in conjunction with tire diameter. As the tire rolls out farther, the lever arm is increased. Tires roll out farther when they are larger in diameter.


For off-road use, one must balance the available ground clearance (which dictates very large diameter tires) and the ability of the vehicle to go both slow enough and also to have enough power to propel those large tires up obstacles. Simply raising the body off the tires only accomplishes part of the solutution for off-road use (and, perhaps the least effective part of the solutuion at that). More desirable is to increase the distance between the bottom of the suspension and the ground, which requires tires with larger sidewalls. This in turn requires the gears to turn those large tires successfully. An additional problem is ground speed, which, for true off-road use, must be very slow when working obstacles, not quite so slow when doing flat hill climbs or mud, and not slow at all for desert racing or mud bogs, where maximum tire speed is a plus. The only truly effective way to have all of the above is to incororate some form of transfer case with multiple gear selection.

[bartonmd]

Guy,

I think you pretty much just said the long version of what James said when talking about thrust, in his last sentence...

I'm also curious about if there's a number for ratio that takes tire size into account... Like the driveline ratio in shaft speed is 100:1, but since the tires are 50% bigger than factory (1.5x the size), the ____________ ratio is 67:1

Mike

[bartonmd]

It'd almost have to be calculated in a foot/lbs ratio, I would think, so you're not worried about what size stock was... Stock shaft speed ratio is a 42:1 on my truck, and with 31" tires that divides the ft/lbs by 1.29, so the ft/lbs ratio is 32.56:1 for a torque to the ground of 500 * 32.56 = 16,280 ft/lbs

If I go up to a 44" tire, half of the 44" tire is 22", or 1.83 feet; so I divide my 42:1 by 1.83, which gives me a 22.95:1 ratio, or 11,475 ft/lbs at the ground.

Mike

[Trail X]

So what's the unit of this metric? If you're bringing tire diameter into it, your unit will be something like 1/inch. When you have units in the metric, it's no longer a ratio.

Essentially the number you're calling the crawl ratio works into this equation:

[Engine Torque (Ft-lb)] x ["Crawl Ratio" (1/inch)] x [12 (in/ft)] = Thrust (lb)

A drive ratio would be purely:

[Engine speed (RPM)] / [drive ratio] = Tire speed (RPM)

Someone correct me if I'm wrong.

[glfredrick]

The calculators that I linked above will take into account tire size.