Hi Everyone,

This is an extension of the thread I started about running my JK on the dunes of Silverlake. The question I have here is a little more specific.

I'm not sure if I have a problem, if I don't understand what I am doing with the ESP (which I already know is part of the problem), or if I am trying to get the JK to do something that's not possible.

The basic problem I have is getting the RPMs up in a lower gear before upshifting to build a little more speed.

In 4-Lo, I can start out in 1st or 2nd and get the RPMs up to 2,500 or 3,000 before upshifting to build some speed, and then downshift for more power as I climb toward the top of a dune.

In 4-Hi, however, I couldn't get the RPM up with the amount of distance I had to build speed.

I'm not sure if the 4.10 gearing, the larger tires, and 4-Hi at the approach speed were keeping me from seeing any RPM above 2,000 RPM, or if it was a matter of not having the traction control completely off. (I thought I had it off; but, thanks to planman and a few others, I will use the detailed approach to make sure it is off in the future.)

Is there anything in the traction control system that would prevent the JK from starting out in 1st or 2nd? Or, is it just a case where I wasn't running fast enough? (I really think I was; but, maybe it was deceiving.) I should have taken the time to play with 4-Hi on some of the less agressive hills, or flat runs to see if I could start out in 1st or 2nd in 4-Hi and get the RPMs up. I'm just curious if anyone else has experienced anything similar.

On another note... A few times I had difficulties getting into reverse on a hill after I got stuck. I would shift from drive to reverse and it was as if I was in neutral. If I shifted back into drive, touched the accelerator enough to feel the transmission grab, and then shift back into reverse everything was good. I'm not sure if it had to do with packing sand on the underside of the JK, or something else. Any ideas?

Thanks

Jeff

 

You simply do not have enough time/power to get to the shift RPM in 4HI.

4HI is a 1:1 (read one to one) 4LO is 4:1 on a rubi (2.73:1 on other models)

Meaning in 4HI one revolution of the input shaft of the tranfercase equals to one rotation of the output shaft.

Meaning in 4LO four revolution of the input shaft of the tranfercase equals to one rotation of the output shaft.

Also, the auto trans will shift at different RPMs according to the position of the throttle. If you have the skinny pedal to the floor it will shift close to the red line. If you are stopped the trans will start in 1st gear.

In your auto you have has 4 gears, it just shifts through them with out driver input. If you select any gear shifter positions below "D" you are simply asking the transmission to stay in that gear or below. "D" is allowing the trans to shift through the gears including over-drive. If you press the "OD" button you are placing the trans in over-drive lock-out so it will only shift up to 3rd gear.

If you are going past a certain speed and move the selector from a higher gear to a lower setting the trans will not shift down. This would cause damage to the trans and/or motor and a face imprint on the windshield.

 

Hi toymaster,

I should have done my homework on the transfer case output before posting. I knew 4-Lo was 1:1; but, I thought 4-Hi was something other than 1:1.

It is pretty clear now that even in 1st gear in 4-Hi I would have to have some pretty significant approach speed to get the RPMs up to a point at which they would have the engine closer to its power band. Regearing from 4.10s to 5.13 )or even 5.38) wouldn't make enough difference for this type of run to justify the switch. (Contrary to what others have experienced, I am not really disappointed by the 4.10 gearing with the larger tires. Around town it can hold its own, and on the highway it generally does okay (although in the strong headwinds I experienced coming home over the weekend, I did need to take it out of overdrive).)

At the dunes I was getting a lot of advice... mainly about starting out in 4-Hi, 2nd gear, before we hit on the right combination of 4-Lo, 1st or 2nd gear. Everyone was trying to be helpful, it was just a difference in equipment (mainly manual versus automatic transmission and gearing).

Thanks for taking the time to post the details that you did.

Take Care

Jeff

 

You can't use ESP in sand

4wd Hi= Press and hold esp off button for 7 seconds to turn off esp completely, it comes back on if you travel over 40 MPG

 

Interrupt switch on the esp wire, kills all that crap, resets when you turn off the engine. Search toggle switch mod. No stopping ya then.

 

I konw siverlake very well.....

Simply not enough power....you are running 35's with 4:10's.....I'd move that to 4:88's with a manual tranny...

FYI - that place (being almost all deep sand) will tear up your drive train....especically your gears... Most folks just chase the top of a hill in the sand. I'd stick to watching or crusing thorugh some of the mud areas.... unless of course you put a hemi in?

those buggy's and old jeeps with 350's in them do great out there, but the name of the game in sand is power & gears.

 

The ESP doesn't come on again above 40mph, we regularily travel in 4Hi with ESP off in the desert at up to 60mph on the flat stuff. With regards to getting the revs up on an auto sahara 4 door I normally use 4Hi and just switch between 1 and 2 but when we are on the really steep stuff that we don't get a run at then 4Lo is the one and generally stay in 2 or 3 and keep the revs at about 5000 for the peak power.

 

That is a great point. I was out there last year, and after taking my JK around a bit, I decided the best bet was to rent a buggy to save some real damage. The JK, especially with 35s now just won't be able to cut it on the deep sand out there. And the first incline to your right is near impossible unless you are willing to risk some real damage. Whenever an ATV struggles going up a hill that is that steep, you know it's gunna be tough going. If you're gunna run 5.13s or 5.38s and a hemi, you might be able to get some air!!!!