Bucking In 4WD

[base camp [OP]]

I've got a 2006 automatic transmission FJ. In 4 WD, when I'm reversing or moving forward without stepping on the gas the truck lurches or bucks gently. Usually happens in the parking lot. When I'm on the road, no problem. Can anyone figure it out? Thanks.

[FredtheFJ]

There's no such thing as a 2006 Fj....

But also why do u have it on in a parking lot? You shouldn't have it on 4 wheel unless ur on dirt or loose gravle it will mess up your 4x4

[FJX2000]

I think i'm having trouble understanding what "bucking" is. Is it like a sudden jump in speed without your foot on the pedal instead of a gradual increase in speed??

P.S.- your FJ may have been made on 06 but technically it's known as an 07 just FYI

[base camp [OP]]

Hayden, with the foot off the accelerator (at very low speed) the truck moves in short lurches.

[stringmachine]

Really, I thought they were supposed to be bucking since they are so Awesome!

Really, When you are in 4WD and 4L be off road, and in this position it is not a normal driving vehicle. but care, safe gas pedal levels and finesse is the key . this thing has a lot of torque in this range. not a hot rod or something you want to be racing around in. let the gears do the work and help control the vehicle. (Slow) and easy is the key..

[FJX2000]

base camp previously said:

Hayden, with the foot off the accelerator (at very low speed) the truck moves in short lurches.

Hmmm... that is interesting. But what Fred says does make me wonder. Do you drive around on dry pavement in 4wd often? Because in the vehicle manual it strongly advises against driving in 4WD on hard surfaces, it could mess stuff up and is not good for the car. Or are you just driving in a straight line on the pavement in 4WD just to test it out?

[tanyasparky75]

My manual recommends putting it 4wd at least once a month to lubricate parts but it's specific about only driving in a straight line on hard pavement.

[jasonfjc]

do not use 4WD on hard surface unless you are going absolutely straight.
whats causing the "bucking" is tires getting dragged across the surface due to locked front and rear diffs trying to turn at different speed.
its called binding.

[Winterpeg]

jasonfjc previously said:

do not use 4WD on hard surface unless you are going absolutely straight.
whats causing the "bucking" is tires getting dragged across the surface due to locked front and rear diffs trying to turn at different speed.
its called binding.

x2
Driveline bind. This happens when you are turning. The outside wheel has to travel a greater distance than the inside tire. This causes the bucking.
It shouldn't explode but the above advice about being on a surface where your wheels can slip a bit is a good rule of thumb.

[base camp [OP]]

Hayden,
No, I don't ride on dry pavement in 4wd. Today I was on asphalt, but it was slushy, icy and I had it on H4. (manual says "use H4 for normal driving on wet, icy or snow-covered roads") Didn't switch back to 2wd before going into the garage, because I needed the traction to get up the ramp.