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"D" vs "L" on Steep Hill Climbs - A question for FDII drivers

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Sandstone

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Discussion starter · #1 ·
In my off-road travels I noticed that for some reason my FDII tends to do better on steep hill climbs if I leave it in "D" or "D" 4Lock rather than "L" or "L" 4Lock. In "L"'or "L" 4Lock it seems to give up faster on steep inclines, and the engine RPM seems to be held slightly lower than if left in "D" or "D" 4Lock.

Earlier this year, I was on a trail run with another FDII and they had seen the same thing happen.

So I'm curious, has anyone else with an FDII had this experience?

Thanks!
 
#2 ·
I haven't been on any hills steep enough yet to find out the limits of Low with 4 lock... its pretty flat here and the off road Parks are closed on my days off

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#3 ·
I would imagine that it seems that way due to being a crawl ratio.,. I don't know. Guess that's why you put the title as you did


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#4 ·
Sandstone said:
In my off-road travels I noticed that for some reason my FDII tends to do better on steep hill climbs if I leave it in "D" or "D" 4Lock rather than "L" or "L" 4Lock. In "L"'or "L" 4Lock it seems to give up faster on steep inclines, and the engine RPM seems to be held slightly lower than if left in "D" or "D" 4Lock.

Earlier this year, I was on a trail run with another FDII and they had seen the same thing happen.

So I'm curious, has anyone else with an FDII had this experience?

Thanks!
Click to expand...
Well, not many guys will experience the grades you do in Colorado. I never really noticed this in my FDII. One possible explanation would be the engagement of the off-road programming in the FDII. The BLD's engaging would tend to hold back the rpm, unless you put your foot into it. Also, L-Lock doesnt HOLD the 19:1 gear ratio. The CVT will build speed.
 
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#6 ·
Afmcronnie said:
Well, not many guys will experience the grades you do in Colorado. I never really noticed this in my FDII. One possible explanation would be the engagement of the off-road programming in the FDII. The BLD's engaging would tend to hold back the rpm, unless you put your foot into it. Also, L-Lock doesnt HOLD the 19:1 gear ratio. The CVT will build speed.
Click to expand...
You nailed it any wheel slip and the bld's tend to bog the pat (or compass) down in FDII mode, i only use the low locked when im real stuck and also in the winter on super slick surfaces
 
Discussion starter · #7 ·
Afmcronnie said:
Well, not many guys will experience the grades you do in Colorado. I never really noticed this in my FDII. One possible explanation would be the engagement of the off-road programming in the FDII. The BLD's engaging would tend to hold back the rpm, unless you put your foot into it. Also, L-Lock doesnt HOLD the 19:1 gear ratio. The CVT will build speed.
Click to expand...
Tyler-98-W68 said:
You nailed it any wheel slip and the bld's tend to bog the pat (or compass) down in FDII mode, i only use the low locked when im real stuck and also in the winter on super slick surfaces
Click to expand...
I hear what you guys are saying. But sometimes there isn't any wheel spin for the BLD to act on, you just roll to a stop with the RPM stuck at about 1800-1900. Once you come to a stop, put it in "D", floor it, and you start to slooooowly move forward with the RPM around 2100-2200.

I thought it was just my Jeep until I talked to the other guy on that trail run.

Now I'm thinking maybe it's to do with torque management in the software.
And if so the question is why. IIRC the motor is rated at a max of 165ft-lbs @ 3300 rpm, the transmission is rated max at about 183 ft-lbs. If torque management is involved, why couldn't it be tweeked to allow higher RPM while in "L"?
 
#8 ·
I'd agree. If it's loose traction, the BLD will kick in.
I will use "L" and make sure I turn off all of the traction control.
The BLD is still there, but is much less invasive.
 
#9 ·
Sandstone said:
Now I'm thinking maybe it's to do with torque management in the software.
And if so the question is why. IIRC the motor is rated at a max of 165ft-lbs @ 3300 rpm, the transmission is rated max at about 183 ft-lbs. If torque management is involved, why couldn't it be tweeked to allow higher RPM while in "L"?
Click to expand...
I could rev my FDII as high as I wanted in "L". It just kept building speed. I dont think I ever took it over 4000 rpm in low, but if you hold the rpm, the speed slowly rises. Sounds more like you were running up against the ETC programming. Switching from "L" to "D", did you have the ETC ALL the way off? My Wrangler eliminates the need to do this by automatically killing the ETC when in low range, my Pats didnt...
 
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#10 ·
It could just be the speed you are carrying into the hill while in D vs L. Don't get me wrong. The Pat does tend to bog down. It always seemed to me to be a software issue. In my opinion it shouldn't bog down at all. It should just keep clawing, or slipping whatever. But something restricts the rpm and it bogs. ETC I think. But I haven't noticed a difference between D and L In that sense...
 
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#15 ·
Earthworm51 said:
What happens when you put it in R for Reverse ? Does it bog down in R low ?
Click to expand...
I never got it stuck or bogged down in reverse.

I remember one incident where going up a rocky hill in 2 high it bogged. So I threw it into 4. Still bogs. 4 low, bog. ESP partial , bog. ESP Full Off, bog. I gave up and rolled back down the hill and drove around and hit it again with no problem and couldn't replicate it. Even stopping in every awkward position I could find half way up the hill it would just start clawing and go. It seems as though the ESP needed some tire rotation to activate it. So it wouldn't activate while bogged down.

The only other time it happened to me was trying to climb that log. When I first tried to crawl over it, it bogged. After I got enough of a running bump it went easily. But I can't remember if I was in ESP off or not. So I'm not sure if the Pat will bog down with ESP off. When bogged down, the RPM's won't go past 2000 RPM's. I guess that's the engine power reduction system. But now I want/need to do some offroading to figure this out. My approach is probably going to be to put it into ESP Full Off and try and get it stuck...:doh:
 
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#16 ·
One other thing i've done before is pulled the abs fuse out, you can still get into the FDII mode and you have no BLD's at all, and i've found this way allows lots of wheel spin and works great if you have some deep mud or slop to get through.
 
#17 ·
ironkique said:
I never got it stuck or bogged down in reverse.

I remember one incident where going up a rocky hill in 2 high it bogged. So I threw it into 4. Still bogs. 4 low, bog. ESP partial , bog. ESP Full Off, bog. I gave up and rolled back down the hill and drove around and hit it again with no problem and couldn't replicate it. Even stopping in every awkward position I could find half way up the hill it would just start clawing and go. It seems as though the ESP needed some tire rotation to activate it. So it wouldn't activate while bogged down.

The only other time it happened to me was trying to climb that log. When I first tried to crawl over it, it bogged. After I got enough of a running bump it went easily. But I can't remember if I was in ESP off or not. So I'm not sure if the Pat will bog down with ESP off. When bogged down, the RPM's won't go past 2000 RPM's. I guess that's the engine power reduction system. But now I want/need to do some offroading to figure this out. My approach is probably going to be to put it into ESP Full Off and try and get it stuck...:doh:
Click to expand...

That's an interesting thought. With everything on the Patriots being computer controlled (instead of mechanical locks, etc.) I never thought that it would need to have a roll-in period to get everything programmed correctly.

But with that being said, the only time I have ever had the bog-down problem was when I was in deep snow, 4wd High - and I had forgotten and left ESP on. I got stuck, and I couldn't get the tires spinning even though they were all on ice/buried in snow. (trusty shovel and a 2x4 got me out).

All other times when I try to go up a loose gravel hill or hard climb, I turn ESP off and put it in Low and have had no problems. Even if, sitting on a steep incline in gravel, all 4 wheels are spinning wildly.
 
#18 ·
I've also had all four wheels lock up when in deep snow, but didn't have the Esp full off. It's on odd felling, hit the gas and nothing happens. I assume it's the BLDs locking up each wheel. And I was used to, in similar situations in the past, just spinning the wheels to dig through some snow and ice and hit stone or earth, and pull away. Or filling in the holes with brush, stone, etc. Which is what I had to do to get the Jeep out of that, that time it locked up. I always have ESP full off now when I think I might need the L off road. I'll pull off the road, stop, lock the 4x4, shift into L, and turn ESP full off, then go. Often though if things aren't real bad, I'll just let the AWD go, or just lock 4x4, but if I do go into L, I always turn off the ESP now.

Would be fun to get several FDII drivers together one winter and experiment, video tape, etc. I'd like to learn how all of this works too.

I've not yet done the "pull the fuse" trick yet. I'll have to try to remember to try that one this winter.
 
Discussion starter · #19 ·
Afmcronnie said:
Well, not many guys will experience the grades you do in Colorado. I never really noticed this in my FDII. One possible explanation would be the engagement of the off-road programming in the FDII. The BLD's engaging would tend to hold back the rpm, unless you put your foot into it. Also, L-Lock doesnt HOLD the 19:1 gear ratio. The CVT will build speed.
Click to expand...
Afmcronnie, I think the answer to all of this is in a previous post you made that I have added below. I had the great experience of running in the 25th annual Jeep Jamboree in Ouray this last week, going over several high mountain passes. What I learned through the course of this in my mind confirms what you posted, and is the reason why Drive works better than L in some cases, like steep uphill climbs.

===============================================

http://www.jeeppatriot.com/forum/showthread.php?t=23400&page=17

http://www.caliberforumz.com/archive...hp/t-1536.html

This link is to a topic about the CVT in a Caliber forum. They mention several times about the CVT having a program to limit engine power and torque at low speeds to limit "macroslip" of the belt. Apparently the belt is designed to incorporate "microslip", encountered when it rides up and down on the pullies during normal ratio changes, but any slippage of the belt at low speed, such as would occur in a situation when you have high traction and a need for maximum torque, is prevented by the systems limiting engine power. This would fit very well with what we experience with out Jeeps. When the Jeep is on a hill, or getting suction from deep mud, the engine is trying to push the belt to the point of slipping on the pullies. The CVT asks the computer to limit torque to prevent this from happening. The problem then, it would seem, is not too little power, but too much! This would also explain why pulling the ABS fuse only seems to be a partial solution. If this is, in fact, what is happening, I dont see an easy mechanical fix. Taller tires would offer some torque multiplication. I think it's still going to come down to technique. More speed. Hit the hill as fast as possible within the limits of your suspension and you wont need as much torque to get over the top, momentum would be your ally. If the hill is too long, or an obstacle prevents you from getting or keeping your speed up, you're screwed. The old off-roaders solutions apply. Stiffer shocks, more ground clearance, taller tires and pick your line.
 
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