Defender 110 Jerking problem

^^ what tottot said^^ Jack a front wheel up, if diff lock is disengaged you should be able to spin it freely, diff lock engaged will prevent the wheel spinning - though there may be a little movement.

Sorry to bring this up again but the problem is still there but I am going to add a few other details. The bouncing is slight but if you are going on a long downhill in the mountains, the truck just slightly bounces but not up and down, it is almost like someone is touching the brakes every half second just barely. (I have felt the handbrake case under the car after the downhill and it is not warm but I dont know if it is the problem or not. Secondly, in third gear going up hill, there is a terrible whoooommmmm in the gearbox (or something nearby) that is a low metallic grinding wommm noise and then goes away as the revs climb. I will try to post a video of this noise tomorrow. It is the most noticeable in 1st gear low range crawling downhill, it just can’t do it, it jumps and bucks like a horse until you just clutch in and use the brakes which is obviously a dangerous way of crawling downhill so I’d love for this to get diagnosed. Italian dealers say they can’t really do anything without throwing a code which it doesn’t so at this point I’m just trying to break the truck instead of replacing everything in the driveline. Any other ideas from anyone? Slowing down in 4th gear only engine brake from say 60km/hr all the way down to 0 it is a wom wom wom noise like a unbalanced tire but it still does a long low WOMMM even at 1km/hr right until 0 which I dont think tires would make any noise under say 10km/hr but again, not a mechanic, but can’t get a good one here in Italy because no one really has the experience with Defenders here. Any more help appreciated! Thanks all,