Topic: Ultimate Dual - what gear to use when?

[Cyberman]

I thought I would create this post to get a feel how the rest of you use your dual cases.  With the possibility of 20 forward gears and 5 reverse I find it hard to figure out sometimes which one to use.

I've had mine for almost a year now and love it.  I mainly wheel rock gardens, rocky forest trails, muddy creek beds and the occasional hill climb.  My driving style leans to the side of caution, which means I tend to not use the skinny pedal unless absolutely necessary.  I probably overuse the low gears, mainly because I can.

I started wheeling my rig when it had stock gearing on ifs and 33s.  I went with a single 4.7 case just so I didn't have to bounce around so much.

 Now I'm SAS'd with 5.29s locked front and rear with chromo front shafts and duals.

I know there are times when wheel speed is needed, but most of the time I've seen people use it, they tend to break stuff.  Those are also the times when it looks better to crawl than to go all out.

So what is your opinion?  I know most of you guys have been wheeling with duals or even triple cases for years.  Is there any advice on when to use a particular gear?

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[Steve92yota]

It all comes down to what you're comfortable with. Whatever works for you works, and what doesn't doesn't. Obviously in some deep mud you're not going to want to be in low low in 1st trying to idle through it. And over rocks that don't need wheel speed, low low 1st gear is fine if you want to go that slow. You go at your own pace and do what makes you happy any comfortable.

Maybe I'm not really getting the question, but that's what I came up with.

[Cyberman [OP]]

Well, even I f don't know what I'm asking for lol. 

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[jtaco1]

We wheel the same trails have have similar setups, with the exception of I'm still IFS and run 4.10 gears. For the most part I will tool around in single low on the access roads due to my axle gearing. When we hit the rocks, I'll see how it is going, if I want to go slower, put in the front case, if too slow then, shift up with the transmission. I do run around with just the front case in as well, but not too often as I don't want to blow the input on the rear case. Go with the speed you feel comfortable with and your suspension can handle. I have done full throttle assaults with the engine bouncing off the rev limiter and two tires off the ground before without issue to the cases. I tend to get mad at the IFS on the upper blacks and reds at Rausch and use the throttle.

[Cyberman [OP]]

JT,

Thanks for the info.  Maybe I should have asked from locals first.  So, my real question I guess is what parts may be affected by duals?  You mention not running the front tcase in low too often and affecting the input of the rear case.  If the rear won't hold up to the setup, then how do you do it right?  I have already gone from lifted ifs to SAS.  If chromo shafts are needed to do it right, it should just be part of the kit.

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[Rocksurfer]

Here's the best advice that I can give on which gear to use....  the one that pisses off the guy in the Jeep behind you.

[jtaco1]

Well I run a 21 spline input on the rear case with the 4.7 gears. I have read that you can snap the input running around with just the crawl box in low range. It happened to my buddy Andy in his IFS 4Runner. He has since gotten a new 4.7 input gear and had it cryogenic treated.

Big thing is don't run the front case in low and the rear in high and get bound up, things will break. Typically I run the front case in low on the access roads and blues since I am moving at a decent speed and not getting bound up. Once things need to slow down, shift the front case to high and the rear case to low. If too slow, upshift the transmission, if not slow enough, put the front case in low.

I also tend to not run in first gear since it pops out, so I run in second and up. If I need to go that slow, I have a bungee cord that holds it in place. Ultimate low is generally to low and I end up up shifting to get some wheel speed, not easy to do when the transmission shifter is essentially locked into first gear by the bungee.

To my knowledge, no one makes a chromo front input, just 21 versus 23 spline. So far I, along with a number of others haven't had any issues. Anything can break though.

[Cyberman [OP]]

With the v6, I have 23 spline all the way through.

So, after thinking about it, the front case in low is basically applying 2.28 times the torque to the input of the rear case.  So the argument then is, if you put an engine in front of that case with twice as much torque, will it handle it.

I haven't had anything in the driveline break (yet).  I did have 5 out of 6 studs and one dowel snap on my locking hub (not cool), after crawling down Rock Creek in double low 1st gear.  Ironically, I still need to put chromo gears in those hubs.

I guess the thing is, the truck crawls so well, I start to wonder whether using all that torque might do something bad.

Here's the best advice that I can give on which gear to use....  the one that pisses off the guy in the Jeep behind you.

Best advice yet.  I have about half a dozen gears that will do that lol.

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[Cheesemaker]

The reason I want duals is for the fact that you can split gears better.  I don't have a dual case setup yet, maybe in June when I'm in Fresno!!  But there are alot of times I'm in low, and 2nd is too high, and 3rd is too low in the RPM range I like to be in.  By running another 2.28 case, I'll be able to get the right RPM I want for the situation I'm in.   I do alot of Firebreaks, that aren't maintained, and fairly steep.  There is a road I take that is called the Incline Road.  It's a 4Lo, 1st gear show for 1 mile straight up the side of a mountain.   The only place the road levels out, is at the switch backs, and the top of the mountain. 

[THEMAN]

 "I do run around with just the front case in as well, but not too often as I don't want to blow the input on the rear case."

I am considering duals and also have some questions.  I currently have a 4.70tcase and 4.88's locked front and rear.  I have to say I miss the 2.28 in the snow.  I do as others have stated and shift the tranny to get the rpms I want but have often wondered that if I had duals, I could just run the front 2.28 and be good.  According to the above post this may not be such a good idea.  Or "Big thing is don't run the front case in low and the rear in high and get bound up, things will break."

So my question is, what should you NOT do with duals?

[OOPS]

On most of the trails I run (Con, 4-Dice and Dusy) I run with the front box in hi and the rear in low (4.7's) in 2nd gear in the tranny. As a lot have said, what ever you are comfortable is what I tell people. A lot depends on your axle gearing and tire size also.