Dual Case driveing techniques

[Machete]

Just got my dual cases in my truck and was wondering if anyone has experience and wisdom to share. I've got an '80 with 5-speed manual and 4.7 in the rear case.  :turtle:Thanks! 8)

[FIREBALL]

Everybody has there own driving style, but I usually use just my 4.70's in the rocks until I get into something knarly, then i'll shift in both cases, and find a happy gear. In the snow it depends on the conditions, but when I get into a situation where I have to rock out of a hole, i'll use my front case, because the 4.70's are too low to get any momentum in reverse.
What ever you do, you'll love em, and you have plenty of gear options to choose from for any situaiton.
Have fun.

[CruzrDave]

I use mine simalar to Jason. I've found 470:1 with the trans in 3rd gear is close to first gear with a stock low range. Both case's in low range with the trans in 3rd gear is simalar to 4.70:1 low range with the trans in first gear.

Instead of shifting back and forth I'll run both cases in low and use 3rd or 4th gear in the trans. I would not use 5th gear, you can but if you need more speed shift the t-case to a higher ratio.

[KYOTA]

Same here lo lo and shift tranny between 1 2 3, need more then shift a case.

[Hyena]

For me it depends on what i feel like doing.

[BigMike]

What ever you do, some wise advice would be to leave 5th gear alone if your moving about more than 4,000 rpm. It would be a wise idea to shift out of Crawl, and use stock low range range 3rd or 4th instead of Crawler 5th. Just think about it, if you were doing 4,000 rpm in 5th gear in high range on the freeway, what speed would you be at? Uh-huh, and do you think its even possible? No. So go easy on 5th (the weakest gear in the tranny) and your trans will reward you with many years of service.

Another wise thing is to be very careful if you are in Crawl in first gear and you push the clutch in and allow the vehicle to free-roll. This is even more dangerous with Dual, Ultimate, Tripple, Overkill, and Ridiculous gearing. If you are, lets say 100:1 in Crawl, and you push the clutch in while moving downhill and your vehicle speeds up to, oh lets just say to a meager 10 MPH, then here is what will happen:

10 MPH = about 96 tire revolutions per min (if using 35" tires)
96 tire RPM = 9,600 Transmission input shaft RPM at 10 MPH (if final drive is 100:1)

So if you could imagine for a second, when you press your clutch pedal with it in gear at 100:1 and let the vehicle gain momentum to just 10 MPH, your clutch disk will be spinning at almost 10,000 RPM. Now obviously this cant be good since your engine redlines at somewhere closer to 6000 rpm and the clutch is basically only designed for those speeds.

And while 100:1 may not blow apart your clutch if you are lucky, then 223:1 (Ultimate) will sure make some noise!
96 tire RPM = 21,408 Transmission input shaft RPM at 10 MPH (if final drive is 223:1)

Well Im sure no clutch disk this side of F1 technology will hold together at over 21,000 rpm!!

So just be careful with free-rolls in Crawl + low range 1st gear. And to be honest, we are very surprised that we dont hear from people completely grenading their clutches. I mean if you are in Crawl, 100:1 or what ever, and you're about to go over, some people will instinctively press in the clutch in and try to hit the brakes, but this doesnt really work. Usually the vehicle will roll either into the roll-over or out of it, and that poor poor clutch disk will almost always get sped upwards to 10,000+ rpm. I've accidently let this happen (the free-rolls, not the roll-overs!) in Marlins truck while engaged in Double Ultimate (Overkill), which is two cases with two sets of 4.70:1 gear sets. His final drive is 454:1 in this gear, and I've heard his clutch sound like a Turbo!!

Love em Crawlers-
BigMike

[Prismo]

I use both cases on rock. 4.7 case a lot on the trail. I use 2w low more than anything else. You would be amazed at how far you can go in 2w low with a locker & 529 gears.

[Skinny_Pedal]

ive driven a truck with duals once. i put it double low up and downhill. regualar on the flats. there way to much fun

[Hyena]

I grenaded my clutch.  but the clutch was crap anyways.  It still was fun driving on the road going like 10 mph at 4000 rpms.

[jvministries]

I never thought of that. I will have to be very careful about that.

I wonder how fast that clutch was going with the double 4.7's it's a wonder it didn't grenade on you.

could you imagine a clutch disk going 40,000 rpms???

and to think it is sitting right below your legs isn't this why they use scatter sheilds on drag cars for that exact reason.

[mudguts]

What ever you do, some wise advice would be to leave 5th gear alone if your moving about more than 4,000 rpm. It would be a wise idea to shift out of Crawl, and use stock low range range 3rd or 4th instead of Crawler 5th. Just think about it, if you were doing 4,000 rpm in 5th gear in high range on the freeway, what speed would you be at? Uh-huh, and do you think its even possible? No. So go easy on 5th (the weakest gear in the tranny) and your trans will reward you with many years of service.

Another wise thing is to be very careful if you are in Crawl in first gear and you push the clutch in and allow the vehicle to free-roll. This is even more dangerous with Dual, Ultimate, Tripple, Overkill, and Ridiculous gearing. If you are, lets say 100:1 in Crawl, and you push the clutch in while moving downhill and your vehicle speeds up to, oh lets just say to a meager 10 MPH, then here is what will happen:

10 MPH = about 96 tire revolutions per min (if using 35" tires)
96 tire RPM = 9,600 Transmission input shaft RPM at 10 MPH (if final drive is 100:1)

So if you could imagine for a second, when you press your clutch pedal with it in gear at 100:1 and let the vehicle gain momentum to just 10 MPH, your clutch disk will be spinning at almost 10,000 RPM. Now obviously this cant be good since your engine redlines at somewhere closer to 6000 rpm and the clutch is basically only designed for those speeds.

And while 100:1 may not blow apart your clutch if you are lucky, then 223:1 (Ultimate) will sure make some noise!
96 tire RPM = 21,408 Transmission input shaft RPM at 10 MPH (if final drive is 223:1)

Well Im sure no clutch disk this side of F1 technology will hold together at over 21,000 rpm!!

So just be careful with free-rolls in Crawl + low range 1st gear. And to be honest, we are very surprised that we dont hear from people completely grenading their clutches. I mean if you are in Crawl, 100:1 or what ever, and you're about to go over, some people will instinctively press in the clutch in and try to hit the brakes, but this doesnt really work. Usually the vehicle will roll either into the roll-over or out of it, and that poor poor clutch disk will almost always get sped upwards to 10,000+ rpm. I've accidently let this happen (the free-rolls, not the roll-overs!) in Marlins truck while engaged in Double Ultimate (Overkill), which is two cases with two sets of 4.70:1 gear sets. His final drive is 454:1 in this gear, and I've heard his clutch sound like a Turbo!!

Love em Crawlers-
BigMike

My runner will not free wheel with the dual ultimate engaged and the clutch disengaged  Pressing the clutch feels almost like applying the brake  MC05 #19 

[KYOTA]

ive driven a truck with duals once. i put it double low up and downhill. regualar on the flats. there way to much fun

I know what Gavin wants for X-mas

[BigMike]

My runner will not free wheel with the dual ultimate engaged and the clutch disengaged Pressing the clutch feels almost like applying the brake MC05 #19

That's because you're trying to turn your clutch into a turbo!

[Hyena]

I only have a dual t-cases, no 4.7 .  It didn't grenade all the way.  All the clutch material on the pressure plate side fell apart.  It felt a little different but not too much when i was in double low.  But i really noticed it when i put it in 2wd high and it didn't want to go anywere, even revving to 4000rpm's.

[Skinny_Pedal]

ive driven a truck with duals once. i put it double low up and downhill. regualar on the flats. there way to much fun

I know what Gavin wants for X-mas

u guys can all get me one . ill be your best friend

[mudguts]

ive driven a truck with duals once. i put it double low up and downhill. regualar on the flats. there way to much fun

I know what Gavin wants for X-mas

u guys can all get me one . ill be your best friend

How about we add it to your wish list

[mudguts]

My runner will not free wheel with the dual ultimate engaged and the clutch disengaged Pressing the clutch feels almost like applying the brake MC05 #19

That's because you're trying to turn your clutch into a turbo!

I don't understand BigMike 

[BigMike]

My runner will not free wheel with the dual ultimate engaged and the clutch disengaged Pressing the clutch feels almost like applying the brake MC05 #19

That's because you're trying to turn your clutch into a turbo!

I don't understand BigMike

It feels like brakes because of the resistence you have in (the weight of the clutch disk) x (extreme gear multiplication). Basically, if you shifted into Ultimate + 1st gear, and got out and tried to push your truck on level ground by hand, I bet it would be very very hard to move it by your self more than about 2 MPH or so.. That's because for every 1 MPH of speed you apply to your truck, you are increasing the velocity of the clutch disk by 2,230 RPM*S². Yup, so if you can push your truck consistency at the increased speed of just 1 MPH, after 4 seconds for example your clutch would be turning at 8,920 RPM with your truck just moving at a fast pushing pace of 4 MPH. So that's why it seems like the brakes are on, the clutch disk is slowing you down!


(35" tires = 10 tire rpm x 223:1 crawl ratio = 2,230 rpm per second clutch disk speed)

[FIREBALL]

Ok Mr. "Fiziks"
Translation.....lots of gear reduction in the tcases and tranny, therefor resistance, lots of it.

[mudguts]

My runner will not free wheel with the dual ultimate engaged and the clutch disengaged Pressing the clutch feels almost like applying the brake MC05 #19

That's because you're trying to turn your clutch into a turbo!

I don't understand BigMike

It feels like brakes because of the resistence you have in (the weight of the clutch disk) x (extreme gear multiplication). Basically, if you shifted into Ultimate + 1st gear, and got out and tried to push your truck on level ground by hand, I bet it would be very very hard to move it by your self more than about 2 MPH or so.. That's because for every 1 MPH of speed you apply to your truck, you are increasing the velocity of the clutch disk by 2,230 RPM*S². Yup, so if you can push your truck consistency at the increased speed of just 1 MPH, after 4 seconds for example your clutch would be turning at 8,920 RPM with your truck just moving at a fast pushing pace of 4 MPH. So that's why it seems like the brakes are on, the clutch disk is slowing you down!


(35" tires = 10 tire rpm x 223:1 crawl ratio = 2,230 rpm per second clutch disk speed)

After close examination of this post, I have concluded the facts herein. 

Ok Mr. "Fiziks"
Translation.....lots of gear reduction in the tcases and tranny, therefor resistance, lots of it.

Oh, I see 

[Machete]

Thanks for all of your input. Especially the things not to do. Keep me out of trouble. 
I'm sure I'll have lots of fun learning to drive with my new gears!

[gferris5]

Ditto on the "no 5th gear rule" I was having fun in  a parking lot with some decorative rocks and I thought it'd be a neat trick to continue showing off by putting it in fifth and driving it around. Nothing bad happened then, but when I took the tranny apart, fifth gear was missing teeth, if you've ever seen how small the 5th gear cog is, you can see how easily it is to break them. Have fun.