Metallic Rattle only in 3rd & 4th??

LeftFoot · Sep 7, 2014

DEF 110 300tdi R380

I've been trying to find the source of an annoying metallic rattle for a while now and have not been successful.

It occurs only when I come off of the gas pedal while driving at a moderate speed. It never occurs in 1st or 2nd gear but always only in 3rd and very seldom in 4th. Never happens when idling.

When it does happen in 3rd or 4th after I lift the gas pedal, I just apply the gas again it goes away. Is it a coincidence that this happen only in 3rd and 4th gear while coasting the vehicle?

Gearbox related?

Any opinions would be appreciated as usual.

Cheers

West Slope Rover · Sep 7, 2014

I'd check out the UJs.

LeftFoot · Sep 7, 2014

West Slope Rover said:
I'd check out the UJs.

Thanks. This was my next course of action (already have the rear pair and acquiring the front pair soon) but I'm curious as to why I hear this only in 3rd & 4th.

West Slope Rover · Sep 7, 2014

The engine torque forces the uj to firm up against the worn bits, usually the bearings and cup (or whatever you call it) while it's powering. When you let your foot of the pedal, that torque diminishes and the play becomes apparent. Once the engine speed slows enough that compression starts slowing the car down or you give it gas again, it will tighten up again.

Take it out on the road and when driving at speed, back of the throttle enough to get the motor to sort of coast-no power to speed it up, but not enought deceleration to get the car to slow down and if it's the ujs, you'll here nad feel them.

I hope my attempt to describe it isn't jibberish

Shifty1962 · Sep 7, 2014

I'd check the prop UJs. This happened to me just yesterday.

http://www.landyzone.co.uk/lz/f7/lucky-escape-265711.html

LeftFoot · Sep 8, 2014

West Slope Rover said:
The engine torque forces the uj to firm up against the worn bits, usually the bearings and cup (or whatever you call it) while it's powering. When you let your foot of the pedal, that torque diminishes and the play becomes apparent. Once the engine speed slows enough that compression starts slowing the car down or you give it gas again, it will tighten up again.

Take it out on the road and when driving at speed, back of the throttle enough to get the motor to sort of coast-no power to speed it up, but not enought deceleration to get the car to slow down and if it's the ujs, you'll here nad feel them.

I hope my attempt to describe it isn't jibberish

No, you're making sense. I'll change the 2 fronts with some GKNs as soon as I possibly can then monitor and update. I'm aware that the symptoms of worn UJs can be very diverse and I'd actually be very happy if this was indeed the UJs.

LeftFoot · Sep 28, 2014

Ok as an update:

Removed front prop only to find that the UJs appear to be in fine condition. No play what-so ever and well lubricated.
What I did find however is that the angle of the spiders cannot be changed on this propshaft. They seem to be phased by 2 spines and when I separate them and try to increase or reduce the number of splines it is not possible. The two ends of the shaft come together in one position only (45 degrees).
I thought these propshafts can be adjusted at the splines? Has anyone else has this experience?

Metallic Rattle only in 3rd & 4th??

LeftFoot

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West Slope Rover

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LeftFoot

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West Slope Rover

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Shifty1962

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LeftFoot

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LeftFoot

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