FL1 TD4 Auto - Transmission whine after cold start

So I'm after a couple of pointers of things to check. On the first start of the day after the car has stood overnight, I'm getting a transmission noise for the first few hendred metres, when accelerating. It's a whine that sounds very much like an original mini transmission. I suspect the autobox, but wondered if it could be the IRD? The whine does dissappear fairly soon after driving off, but there is something definitely not right.

Both have had the fluids changed recently, and shortly after the fluids were changed I did a day's laning where I did go through a few fords, although none were overly deep. I'm not sure if either some water may have got into the auto box (possible but highly unlikely), or the fluids in either the IRD or autobox are either the wrong spec, or the levels are not right. The garage receipt shows the correct spec fluids.

Before I go back to the garage to get them to check levels etc I was wondering if anyone had any thoughts on possible issues or whether my couple of theories above might be likely reasons for the noise?

I'm going to do a OWUT this weekend too to check the VCU.

There is a breather on the IRD that should be connected to a pipe that raises the vent up.

I'd go for VCU bearings have been washed dry of lubrication. They have little protection from ingress.

I have a pair on the bench looking to remove the useless flange collars and fit oil seals each side of the bearing so that the smooth part of the prop can run in it. Experimental stage at present.

Did the noise start after last weekend's off roading? Did you go through deap water?

Nodge68 said:

Did the noise start after last weekend's off roading? Did you go through deap water?

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I've had the noise for about a month. I had the fluids changed about six weeks ago and did some laning about a week after. I first noticed the noise shortly after that. We did go through some water but not very deep. Only a very very remote chance of water getting into the auto box. No chance of it getting into the ird.

andyfreelandy said:

I'd go for VCU bearings have been washed dry of lubrication. They have little protection from ingress.

I have a pair on the bench looking to remove the useless flange collars and fit oil seals each side of the bearing so that the smooth part of the prop can run in it. Experimental stage at present.

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One of my VCU bearings does have some play in it. They are going to be replaced imminently.

GrumpyGel said:

There is a breather on the IRD that should be connected to a pipe that raises the vent up.

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That's present and correct.

kernowsvenski said:

I've had the noise for about a month. I had the fluids changed about six weeks ago and did some laning about a week after. I first noticed the noise shortly after that. We did go through some water but not very deep. Only a very very remote chance of water getting into the auto box. No chance of it getting into the ird.

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Does you box have an extended breather tube, or just the factory stubby pipe?

Nodge68 said:

Does you box have an extended breather tube, or just the factory stubby pipe?

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Recently extended, but not before the first laning day

kernowsvenski said:

Recently extended, but not before the first laning day

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You could try sucking some fluid out the filler hole to look at the colour of it. Water has a cooling effect on drive line components, which cause the air and fluid inside to contract. If this contraction happens and the breather is under water, it will be drawn in, contaminating the fluid.
Water contamination will be visible as it'll make the fluid look milky, hence drawing some out for a look.

Nodge68 said:

You could try sucking some fluid out the filler hole to look at the colour of it. Water has a cooling effect on drive line components, which cause the air and fluid inside to contract. If this contraction happens and the breather is under water, it will be drawn in, contaminating the fluid.
Water contamination will be visible as it'll make the fluid look milky, hence drawing some out for a look.

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I will check, but I think the water ingress theory is probably a red herring as none of it was particularly deep. This was the deepest, and most exuberant water section we did.

If you are going to change the VCU bearings give them a soak with WD40 and see if noise changes.

andyfreelandy said:

If you are going to change the VCU bearings give them a soak with WD40 and see if noise changes.

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Good idea. I'm not so sure it's those though as my gut feeling is that it's too heavy a sound for bearings. I shall find out soon though

You would be surprised what the sound transmitted up the hollow propshaft can be like. Took me ages to find cause but I agree it was more of a groan than a whine. Another test is to change the load by turning tight circles and listen for noise changes.

So with a slightly tightening VCU I'm wondering if that is the reason for this issue. I shall be taking the prop off this weekend so will see if that makes a difference, although having said that, the car hasn't made the noise for a few days now.

Water in VCU bearings, surface rust making noise, cleaned after use. Just a theory.....

andyfreelandy said:

Water in VCU bearings, surface rust making noise, cleaned after use. Just a theory.....

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I would also suggest the VCU bearings.

@kernowsvenski
I have a press which would make changing the VCU bearings easier, if that helps.

Nodge68 said:

I would also suggest the VCU bearings.

@kernowsvenski
I have a press which would make changing the VCU bearings easier, if that helps.

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Thanks John. I shall report back after a re-test of the VCU. If it's kaput I'll get anoth recon one from Bell, with bearings fitted.

So the whine is still present from time to time after the car has stood over night. Today I've whipped off the prop so will see if that has changed things tomorrow morning. The more I think about it though I'm wondering about the auto box fluid level. My gut feeling is that it will still have the whine with the prop removed but time will tell. I should have mentioned that the whine occurs in sync with engine speed, rather than road speed. It is only ever for about 15-20 seconds though and then disappears until the car is started again the next day or so.

A few days driving has revealed that without the prop fitted, the whine is still present. Same symptoms as before the prop removal - it only occurs after the car has stood over night (but not everytime) - and only lasts for a short while. It sometimes takes a minute or two before it occurs, and on other occasions it starts immediately after moving off. Next step, auto box and IRD fluid checks.