Quick Zzzsscchh Noise On Accelerating - Auto 4.2

[richard10002]

We have a 2005 XTR 2.0 Auto. Bought in 2011, it's only needed a few Wiper Blades and a Battery since purchase, so a great car. About 70k miles to date.

Just recently my wife noticed a very quick noise on accelerating from very slow speed... I can only describe it as a zzzsscchh type noise, which lasts for less than a second. We don't hear it every time we accelerate, but most times.

It might be on a gear change, but I wouldn't know, and am fearful of letting a garage suggest several solutions, which would all cost, but might not work.

Any ideas what it might be?

[firemac]

I'm willing to bet that it's the heat shield on the middle silencer box. Eventually this rusts out around one or other of the holes that mount them to the box; the shield then begins to vibrate against the box at certain frequencies.

Our previous 4.2 auto started producing exactly that sort of noise but only when starting up/pulling away and my local Mr. T suggested simply taking it off and binning it. Others have refitted the shield with new bolts and a suitably sized washer to trap the shield firmly between the bolt head and the silencer box.

[richard10002]

Good call!

Took it for a service this week and asked them to check the heat shields... One was loose!

Also had the gearbox oil changed.

Wife says it drives like a new car!

[firemac]

Good call!

Took it for a service this week and asked them to check the heat shields... One was loose!

Also had the gearbox oil changed.

Wife says it drives like a new car!

Interesting that you had the ATF changed, Richard. When we had our 4.2 autos, they were always serviced by our local Toyota dealer and he was never able to find any Toyota schedule that indicated that the ATF should be changed (conversely, on our current 4.3 auto there is an ATF inspection at 40K miles).

Presumably it is filled for life although there have been several debates on this forum about whether it is advisable, or not, to change it. Those in favour very reasonably point out that it is only common sense to change hard-working fluids like ATF regularly whereas the "nays" suggest that there is a great risk of dislodging sediment, etc. within the oilways in the box by draining and refilling, which then risks serious blockages that could lead to other failures.

In the end we always went with Mr.T's schedule and our 02 car left us after 11 years' sterling service with nearly 90K miles up and the box performing just as it did the day we bought it. Ditto, our 54-reg 3-dr with nearly 60K miles.

I assume that your service was carried out by an independent?

[richard10002]

Local garage did the service. They rate highly on the Good Garage Scheme, so would expect them to decline unnecessary jobs - they have before.

So far so good. I thought there was a magnet in most gearboxes to catch any stray bits. My X Type had the gearbox oil changed at 104k miles.... Jaguar recommend 150k miles. I cant believe you would "never" change gearbox oil, so their is always a day when it needs doing, and I chose 72k miles.

Given that we change our engine oil very regularly, I cant really see much difference between engine and gearbox ..... but i'm no expert.

[crofter]

An auto box is a different kind of animal to a manual gearbox as it does not have the gears that slide against each other upon moving the gear stick. The gear oil is picked by the gears and transferred by contact with each other and the metal worn away by that contact stays suspended in the oil until it passes close enough to any magnet to be attracted to it

An auto is operated by the movement of smooth friction plates caused by the oil passing through various valves and this means that the oil suffers less from contamination. There are a few gears in there as well but they are protected from any stresses that are sometimes placed on a manual by .harsh treatment or heavy handedness on the gear stick.

Hope that helps a bit

Del

As an aside to this I think the Good Garage Scheme is something that is sold to garages as advertising.

I don't think any serious testing is carried out as to the proficiency of the places