Possible driveline backlash?

[edproccia]

Hi everybody,

I have one doubt that is really gonna drive me crazy.

As my forma mentis imposes me, I will try to be as clear as possible - also because English is not my mother tongue - and with the risk of becoming boring. I will accept it.

Since the beginning of my ownership of my Toy (which has a 6speed manual gearbox, with low gear insertable without locking the center diff) I can hear a sort of noise (more or less like a knock, or hit) coming from the driveline when: a)transiting from gas-pedal released to acceleration; b) passing from R to 1st gear or from one gear to the other

Might be a sensation , but I feel that this phenomenon comes more evident when the driveline is somewhat hot.

I do not use my Toy to tow anything and neither I have ever used it with the central differential locked on the asphalt, but only in some passages in snow/glawed ice on the road or steep inconsistent ground (gravel).

I have already bringed the car to a mechanics, with the result that "this is quite normal, and if you change gear gently the phenomenon almost cannot be perceived. Anyway, this is because this is a real full-time 4WD, and some backlash is voluntarily given to the driveline".

Notwithstanding this, I have made a visual control being under the vehicle, while another person was very slowly passing from the R to the 1st and vice versa, moving on a plane asphalt for not more than half a meter forward and backward. Briefly, the result is that when inversing the gear and the motion of the Toy, the front shaft exiting the central differential turns a little with respect to the back shaft exiting the diff, that for a moment rests motionless. Vice-versa inverting the motion of the vehicle.

At this point, my question is:
a) is there anyone of you with the same phenomenon? And if yes, do you consider it overall normal?
b) on the contrary, if it a symptom of something going wrong, what has been the cause for you.

I really thank you in advance and I look forward to hear a response.

Emanuele

 

[Crispin]

Hi,

I have the 5sp manual and don't have anything like that which is noticeable while driving or changing gears.
There is some slop on the rear propshaft, you can wiggle it by hand.

Not ever watched the propshaft while changing gear though. Could it be your clutch that is not disengaged enough and causes truck to try and move?





Sent from TapaTalk

 

[edproccia]

Hi, thanks, it may be so. Anyway I cannot rotate the shaft by hands, and the relative motion within the front and back shafts is (approximately) a couple of degrees.

Anyway, this implies that is not normal; I think it might be better to "convince" the mechanics to further investigate the problem before it becomes (hoping that it is not already that...) too expensive.

 

[Crispin]

There are people far cleverer than I on here, maybe someone else has a better idea but could it not be clutch related? i.e. the clutch is dragging when you changing gears which causes things to "not happen smoothly" Just thinking out loud...

 

[Jon Wildsmith]

There are all sorts of things to check that could be causing excessive slop in the drive train. Your noise might not even be in the drive train, it could be a loose bolt on a bush holding an axle control arm on, front diff bush, shock absorbers, all sorts of things can go clonk in those circumstances so I would first check that all the connecting points between the axles and the chassis are tight, so that's the front diff mounting points, front and rear control arms, front and rear shock absorbers mountings etc. Those are all cheap / easy to check. Next job would be to remove the front prop shaft and see how much backlash there is in the front pinion flange movement. There could be excessive backlash between the ring and pinion inside the diff, or slop in the CV joints or sometimes there's play in the drive flange splines, you mechanic should be able to detect any of those.

 

[edproccia]

Thank you Jon, I think you have actually explained to me all the steps that my mechanic should perform to verify.

I will try the way to suggest this.

Thanks again.