"jerks" in lower gears(transmission shunt?)

I've checked IMO everything related to engine management and fueling so i think it's something generated by the transmission or driveline, but that's not one of my strong points. In lower gears and speeds(up to 3'rd/25mph) when i release the throttle i feel like a "tug" back, not a smooth deceleration like it used to... and when i change gear (down 4'rth to 3'rd/3'rd to 2'nd or up from 1'st untill 4'th) and push the throttle it gives me 2 or 3 "jerks" ... then it rides normally... this "jerk" / "twitch"(it's hard with my english) is more "violent'' up or down to 2'nd (transfer box in HI)... what do you think guys? ...must i dig in my wallet for a transmission overhaul ? ...input shaft for TB maybe?
.... front diff is quite new, so are the prop's u'j's and the CVJ's ...the driveshafts and the flanges are old

I dunno if it's relevant, i've fitted a LSD on the rear few months ago but i made at least 3000 miles since without any problems, and i have solid flywheel not DMF

sierrafery said:

I've checked IMO everything related to engine management and fueling so i think it's something generated by the transmission or driveline, but that's not one of my strong points. In lower gears and speeds(up to 3'rd/25mph) when i release the throttle i feel like a "tug" back, not a smooth deceleration like it used to... and when i change gear (down 4'rth to 3'rd/3'rd to 2'nd or up from 1'st untill 4'th) and push the throttle it gives me 2 or 3 "jerks" ... then it rides normally... this "jerk" / "twitch"(it's hard with my english) is more "violent'' up or down to 2'nd (transfer box in HI)... what do you think guys? ...must i dig in my wallet for a transmission overhaul ? ...input shaft for TB maybe?
.... front diff is quite new, so are the prop's u'j's and the CVJ's ...the driveshafts and the flanges are old

I dunno if it's relevant, i've fitted a LSD on the rear few months ago but i made at least 3000 miles since without any problems, and i have solid flywheel not DMF

Click to expand...

If I suspected a transmission problem the first thing I would be doing is greasing the props/uj's, particularly the sliding telescopic bit on the props. If the front hookes joint uj's are original they won't have grease nipples, but the rest should have. Get a good squirt of grease in them and check for play at the same time. Check the tightness of the propshaft flange nuts and bolts. Also check the rubber doughnut carefully - any visible cracks in the rubber, it needs replacing.

Then I would be changing the gearbox/trans box/diff oils to a. to the condition of the old oil and b. get some new oil in.

Then see how she is.

Good luck

Dave

Thanks Dave, i'll check these out

I have recently had exactly the same issue as you describe... Mine was a few (10-15) miles after I pulled my boat out of a very muddy (cley) field it had been stored in over winter.

I had to select low ratio to get the boat out of the field, even then it was a real struggle (and with A/T tyres)... I then towed the boat on the road and felt the jerking of the transmission you describe. I resolved this by going back to field, selecting low range again, doing a few laps and also in reverse, then when I selected high range again it was cured.

I am aware of other 4x4's suffering with the diff lock winding up... don't know what happened to mine, but it's cured now.

as said above ,plus hand brake catching ,rear out put bearing worn . not in diff lock or diff seized ,lsd not seized, a caliper not grabbing ,doesnt sound like gear box fault, intermediate gear can often give issuses if they have freeplay but doesnt sound quite like yours

thanks guys...i will put my mechanic friends to work then

Guys, you will be amazed... remember what i said in my first post here: I've checked IMO everything related to engine management and fueling ... i was wrong... i checked everything i could with "non-invasive" methods, no play/backlash in the propshafts or axles, oil level in the TBox was OK(i thought maybe it's some internal wear due to low oil or something... but no, clutch and solid flywheel quite new) ... the symptom occured suddenly and there was no clunks or strange noise from outside... so it was time for parallel thinking again ... returned to management/fueling after i observed a slight improvement in the mpg too(i thought it's cos i was more gentle with accelerating to get rid of the jerks)... and guess what i found out .... the problem was the brake pedal switch ...seems unbelievable and AFAIK quite uncommon... but this might be the answer for others with strange "kangarooing" issues. ... if the car is fitted with cruise controll(mine isnt) it's easyer to rule this out cos the CC will not work in this conditions

here's the theory(and it's demonstrated cos now everything is smooth on gear changes) i'll quote from RAVE where necessary cos it's better than ruin the ideea with my english (parts in red are the gist of the issue) :
The ECM uses the signal from the brake pedal switch for the following functions:
l To activate the brake lamps.
l To limit fuelling during braking.
l To cancel cruise control if operating.
The brake pedal switch consists of two component parts, one normally open switch and one normally closed switch.With the brake pedal in the off position the two switches will give opposite signals to the ECM. When the pedal is operated the signals exchange operating state. ..then i saw this during my deep investigations :
The brake switch is set automatically during fitment.
If the setting is disturbed, the switch can be reset by
depressing the brake pedal and pulling the plunger
out of the switch body, until it contacts the pedal.

I meassured the input from the switch to the ECM and no 12V at C0658 with pedal released.... so the ECM "thought" that the pedal is pressed and limited the fueling.... and this was the cause of that jerks/kangarooing at lower speeds (cos then it needs more fuel)... i'm not a violent driver to observe that probably the kickdown wasnt as it should... the brake lamps worked normally, the switch closed the contact for lamps when the pedal was depressed and opened with the pedal released but it didnt close the other switch to send feed to the ECM(the setting was disturbed and the switch's normally closed contact was not closed)... i did the adjustment as described above(not very easy if u are not a gymnast ) and now everything's back to normal.

SO ....WARNING: THE BRAKE SWITCH COULD CAUSE FUELLING ISSUES WITH THE SYMPTOMS I DESCRIBED ...JERKING/KANGAROOING AT LOWER SPEEDS....EVEN IF THE BRAKE LAMPS ARE NORMALLY WORKING

see the diagram of the switch in the pic and u'llunderstand that if it's not set well it could not reach the upper contact to close it when the pedal is released(feed to C0075/2 is going to the ECM when pedal is not pressed ... then when pedal is pressed the feed goes to lamps through pin 3 )

case closed

Pulling the plunger out of the switch body. Where is the plunger and what is a switch body? Hope this will solve my same issue

depress the pedal with one hand and pull the plunger out to max allowed with the other