A new knocking...

Post by **GeorgeHurst** » Mon Nov 16, 2009 10:28 pm

Hi there,

Having recently replaced my prop shaft following worn UJ's, a knocking noise has developed.

It is a loud knock or 'clunk', that happens predominately when changing up a gear. Occasionally it also occurs when accelerating sharply, though generally it is only when changing up.

It happens ever so slightly after changing gear, rather than during or directly after engaging the gear.

Thinking about it leads me to think it might be a worn diff, and the knock is caused by backlash in the diff. Though sometimes it sounds like it doesn't come from the back, and I'm thinking perhaps it could be a knock in the gearbox, the vibrations/sound of which are getting conveyed up the prop and sounding from the rear.

Any thoughts?

Cheers,
George

Post by **bmcecosse** » Mon Nov 16, 2009 10:32 pm

Loose prop shaft bolts ?

Post by **ssnjimb** » Mon Nov 16, 2009 10:35 pm

did it knock before uj replacement

Post by **GeorgeHurst** » Mon Nov 16, 2009 10:43 pm

The prop shaft bolts are all nipped up good and tight...
There was a knocking before prop replacement but, it was a different one... it was basically from play in the UJ's causing a speed related knocking, this is definitely a different one (unfortunately!)

Post by **ssnjimb** » Mon Nov 16, 2009 10:49 pm

does the car vibrate really bad when the engine rev's increase through the gears.

Post by **bmcecosse** » Mon Nov 16, 2009 10:53 pm

U/J coming loose ?

Post by **GeorgeHurst** » Mon Nov 16, 2009 11:03 pm

ssnjimb: No vibration at all really, other than at very high revs in 4th...

BM: The UJs are all fine... I bought a second hand prop after finding it literally IMPOSSIBLE to replace the UJ's in my old prop, and all the UJ's have no play. One is slightly stiff on one of the axis but not drastically.

Post by **bmcecosse** » Mon Nov 16, 2009 11:05 pm

Well - that prop must be suspect!

Post by **ssnjimb** » Mon Nov 16, 2009 11:05 pm

stiffness in the uj's can cause the symptoms you describe there should be no stiffness at all. have you worked it in with lots of grease

Jamie

Post by **GeorgeHurst** » Mon Nov 16, 2009 11:25 pm

Yeah, have given it a very good greasing, I suppose it is worth unbolting it from the diff flange and then seeing if the stiffness has gone with the grease worked in.

So neither of you think it could be the gearbox or diff?

Thanks for the comments thusfar

Post by **ssnjimb** » Mon Nov 16, 2009 11:30 pm

My diff only knocks when i engage second when slowing down to quickly select first.

Now i may have a worn diff but when i sharply release the throttle and slap it back on again the diff is really jumpy and knocky

When moving along its fine and smooth with a gentle wine

Jamie

Post by **GeorgeHurst** » Mon Nov 16, 2009 11:45 pm

hmmm, ok perhaps not out of the ordinary then.

When I am next in front of some car ramps I'll disconnect the prop and see if the stiffness is still in the joints...