Lunging/Bucking in 4lo

[kabookie10]

I swear I’m beginning to think this JT is a pile of garbage. Finally figured out the popping noise and I have new rear control arms coming in to be replaced. Now I have a couple new problems I discovered while figuring out the popping noise.

First is when in 4 low. In drive or reverse the problem happens. It’s most pronounced in drive and first and second gear. If I am in drive and in 2nd gear and accelerate forward to about 2000 rpms then let off the gas and coast. The Jeep slows normally and rpms drop. Then the issue arises. Once it hits 1000 rpm it starts lunging forward and the rpms jumpup to 1500 then back down. It does this cycle 3 times one after another. Does this sound normal? I also noticed that when I hit the brake too to stop it lunges forward a bit. I know the rubicon has some really low gearing but this just doesn’t seem normal or safe to drive off-road. I was on a flat straight in my yard.

next issue is still in 4 low. When I shift from drive to park it shifts extremely loud. It almost sounds like the shift levers are under an extreme bind making it shift loud.

any help would be appreciated.

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[kabookie10]

OK so more on this and hopefully someone can chime in and give me some feedback. I had the dealer test drive a rubicon JT and a Sport S JT to determine if the lunging/throttle surge is normal. The SPort S did not lunge forward when in 4 low and in 1st or second gear. The rubicon did. I know with the rubicon transfer case and 8 speed tranny that its an extremely low gearing, but if I decide to go wheeling and i have to crawl over a rock or obsticle and the jeep is in 4 low and in 2nd gear i'm afraid that its going to lunge forward.

My question is for those with a rubicon JT. When your in 4 low and in 2nd gear. If you drive forward keeping it in 2nd gear then let off the gas at 2000 rpm's and let it coast, do you also get a lunging/throttle surge? I haven't had the jeep offroad to test it out on an obsticle or anything but it just really concerns me. If i offroad this, i'm going to have to limit 4 low to 4th gear or higher to keep things smooth.

It almost makes me look like i'm learning how to drive a manual in 1st gear and your lunging or bucking the vehicle.

If you have been offroad in your rubicon jt, do you notice alot of issues in lower transmission gears when in 4 low or do you keep it in a higher gear by manually shifting it there. Sorry for the newbie questions but i'm use to my old 09 sport wrangler that had a 6 speed auto and standard transfer case.

 

[j.o.y.ride]

Is this on dry pavement by any chance? When you say the dealer test drove it did they have a dirt area to do this in or just on the lot?

Sounds like maybe you're not getting it properly into gear.

 

[kabookie10]

Is this on dry pavement by any chance? When you say the dealer test drove it did they have a dirt area to do this in or just on the lot?

Sounds like maybe you're not getting it properly into gear.

I"m not sure what the dealer did. I tested mine in my yard and on my drive. I do know not to do that on pavement or hard surfaces. I just stumbled on the lunging/throttle surge trying to figure out the problem i have with the rear control arms. I was trying to get them to act up so i could pin point where my sound was comming from.

I have it in gear right. Its almost like there is an extreme amount of slop somewhere in the driveline and the lower the gear is, it just magnifies it that much. If you think about the steering box issues and having to much play in the steering, it almost reacts like that. Its like the teeth on the pinion are not wide enough to make proper engagement allowing alot of slop or the chain or belt drive in the transfer case is stretched. Thats what it reminds me of.

Does anyone even really wheel their jeep in 4 low and in 2nd gear. Mine starts out in 2nd when it automatically shifts. If i want 1st gear i have to put it in manual and shift it to 1st. I'm almost considering if i wheel at all in 4 low, i'm going to have to shift the transmission manually. IF i'm crawling i'm going to have to stick o 4th gear or higher. But to me, that defeats the purpose of me having a rubicon.

 

[bastage]

So I have a Sport S so the other transfer case obviously. I would honestly with as low geared as you start with put it into manual shift mode & keep it in a higher gear. If that resolves it then its because the thing is just tooooo low for the task at hand.

 

[j.o.y.ride]

Are doing this sequence for 4lo? Just to rule out sequence error that may keep it from engaging correctly.

Roll at walking speed
Put transmission into N
Firmly pull transfer case all the way down into 4lo, all the way and making sure it's engaged.
Put transmission back into D

I also have the 2.7:1 box like bastage above, not the Rubicon 4:1, but I have had zero issues with 4lo on the trail.

 

[morejeepsthanicancount]

Are doing this sequence for 4lo? Just to rule out sequence error that may keep it from engaging correctly.

Roll at walking speed
Put transmission into N
Firmly pull transfer case all the way down into 4lo, all the way and making sure it's engaged.
Put transmission back into D

I also have the 2.7:1 box like bastage above, not the Rubicon 4:1, but I have had zero issues with 4lo on the trail.

This.

I had an issue where the tcase was partially engaged when it was new. I had to "help" it into 4Low when I realized the issue, and it hasn't happened since. My JKU and TJs could just neutral, pull into 4Low and drive. This one likes to be slightly moving to get into 4Low

 

[j.o.y.ride]

This.

I had an issue where the tcase was partially engaged when it was new. I had to "help" it into 4Low when I realized the issue, and it hasn't happened since. My JKU and TJs could just neutral, pull into 4Low and drive. This one likes to be slightly moving to get into 4Low

Yeah I have read the first few 4lo shifts can be clunky, and if he is doing it standing still even more so.

 

[bastage]

I wouldnt call the first few shifts clunky... I thought I was going to break my damn truck when I first tried. Its much easier now, but at first holy shit it was hard.

 

[kabookie10]

Are doing this sequence for 4lo? Just to rule out sequence error that may keep it from engaging correctly.

Roll at walking speed
Put transmission into N
Firmly pull transfer case all the way down into 4lo, all the way and making sure it's engaged.
Put transmission back into D

I also have the 2.7:1 box like bastage above, not the Rubicon 4:1, but I have had zero issues with 4lo on the trail.

I shifted in 4 low at a stop. I wasn't rolling. My 09 JK, as morejeepsthanicancount stated, could be put in 4 lo at a stop. These new ones i'm learning still.

 

[kabookie10]

I wouldnt call the first few shifts clunky... I thought I was going to break my damn truck when I first tried. Its much easier now, but at first holy shit it was hard.

Are you talking about it shifting when its moving or actually shifting it into 4 lo? I can get it to shift into 4 lo with no issues. Its pretty smooth actually. Its when i'm actually in 4 lo and the transmission is in 2nd gear and then start moving. If i give it gas to get up to 2000 rpm's and let off to coast, the rpm's drop to about 1000 then it starts surging. You can see the rpm's surging to 1500 then back down to 1000. It does this cycle a few times and pretty rapidly. I feel like i'm just starting to learn how to drive a manual and learning how to work the clutch and gas from a stop.

 

[brianinca]

Yeah that surging is not right. My JTR drives like any other 4x4 in 4Lo, just with STEEP gears, I love it!

Driveline slop is a thing, I replaced the intermediate and final driveshaft on my old Ranger to get the factory clunk out (the clunk when it catches up to the slop). Bummer to spend the money, since I eventually went to a one piece driveshaft. The Ford dealer did the "totally normal" dance, maybe try a different dealership?

Are you talking about it shifting when its moving or actually shifting it into 4 lo? I can get it to shift into 4 lo with no issues. Its pretty smooth actually. Its when i'm actually in 4 lo and the transmission is in 2nd gear and then start moving. If i give it gas to get up to 2000 rpm's and let off to coast, the rpm's drop to about 1000 then it starts surging. You can see the rpm's surging to 1500 then back down to 1000. It does this cycle a few times and pretty rapidly. I feel like i'm just starting to learn how to drive a manual and learning how to work the clutch and gas from a stop.

 

[j.o.y.ride]

I shifted in 4 low at a stop. I wasn't rolling. My 09 JK, as morejeepsthanicancount stated, could be put in 4 lo at a stop. These new ones i'm learning still.

It's just easier to get the proper and full engagement when rolling. At least when it's brand new.

Try the sequence I mentioned and see what happens

 

[kabookie10]

Yeah that surging is not right. My JTR drives like any other 4x4 in 4Lo, just with STEEP gears, I love it!

Driveline slop is a thing, I replaced the intermediate and final driveshaft on my old Ranger to get the factory clunk out (the clunk when it catches up to the slop). Bummer to spend the money, since I eventually went to a one piece driveshaft. The Ford dealer did the "totally normal" dance, maybe try a different dealership?

It's just easier to get the proper and full engagement when rolling. At least when it's brand new.

Try the sequence I mentioned and see what happens

brianinca, i know it doesn't seem right but i haven't owned a Rubicon before and want to make sure its normal or if something is truly wrong. In my opinion, it doesn't seem right. I just feel it defeats a little of the purpose of me buying a Rubicon. I am getting a little dance from the dealer. He "said" he test drove a rubicon and it did the surge, but the sport s didn't do it.

j.o.y.ride, i'm going to try the rolling engagement tonight to see if it helps.

Thanks for everyone chiming in on it.

 

[kabookie10]

It's just easier to get the proper and full engagement when rolling. At least when it's brand new.

Try the sequence I mentioned and see what happens

Tried it. Still lunges.....‍

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