Auto transmission 'woof'!

[new2jags]

Hi everyone. I occasionally get a strange sound, I can only describe as a sort of soft 'woof', when the auto box changes up on my 53 plated XK8. This only happens when accelerating 'quickly'. I seem to remember reading/someone saying that it could be a lack of transmission gearbox oil, but I may be mistaken. Is not the gearbox a 'sealed for life' unit? Any advice would be be appreciated. Thanks.

[mike020150]

'Sealed for life' is a misleading marketing misnomer. Any gearbox can develop a leak from one of its seals and hence lose fluid. A physical inspection on a ramp or similar should allow you to check for leaks. However, for good service life a more important point is that the gearbox oil should be changed regularly refilling with the correct fluid. The change point used to be quoted by Jaguar as every 30,000 miles and with today's improved (definitely more expensive) oils, it could be argued that the change point can be extended to 50,000 maybe 60,000 miles. Without a change of oil (following slavishly the Jaguar sealed for life recommendation) a high percentage of these gearboxes fail after not much more than 100,000 miles. The gearboxes are expensive to replace so, by comparison, fresh lubricant is cheap maintenance. The ZF gearbox requires careful filling according to a set procedure which has been listed previously in the bulletin board archive. If the box is under or over filled, it can make unusual noises which may be the source of your car's problem. Mike.

[J44EAG]

I`ve heard of the ZF "Lurch" but not the "Woof"! There is a dedicated web site to "The Lurch".

My first indications of gearbox failure was red transmission oil leaking from the gearbox to prop shaft oil seal. When the box later blew up, we found the tail shaft bearing (amongst other component part failures) had completely collapsed. Apparently, it is a classic tell tale sign.

Mike H and I co wrote a lengthy oil article in our JEC magazine some time back. I think it was the November 2010 edition. In that we explored the reasons for oil break down. Heat, pressure, age, oxidisation and contamination were primary causes for lubrication losing its effective protection properties. Oxidisation is probably the biggest factor in oil longevity.

There is no such thing as sealed for life where oil is concerned. All things in this world have a life expectancy and oil, whether mineral or synthetic , does, can and will eventually expire. To expect oil to last indefinitely in engineering terms is plain crazy. Any self respecting and qualified engineer in this field would tell you the same. Sadly, Jaguar chose to ignore this engineering fact of life.

Our gearboxes run in synthetic oil. Synthetics are a designer type oil. The chemical engineers who design those oils, work to a specification for life expectancy in service. If that life expectancy is exceeded, then as my learned friend Mike suggests, the gearbox will expire at a later date. No doubt about it.

Bristol Transmissions who rebuilt my gearbox, recommend an oil change at 24k miles or two year intervals. Some may see that as over kill servicing and perhaps go for a slightly longer renewal period. BT say that if the 24k intervals are adhered to, then the transmission should live to a ripe old age.

BT refilled my box using OBD11 software plugged into the socket of the car. The car was run up to a specified transmission temperature having been cycled through the gears. A final top off then took place through the transmission breather orifice. Unless the car is on a level ramp and the technician able to stand directly under the transmission, topping up with transmission fluid is extremely difficult.

I can also tell you from experience of one of the effects of an overfilled Jaguar transmission. On a motorway, oil is forced past the torque converter oil seal, is flung over the converted casing, which then exits out of the bottom of the bell housing. The oil then drops onto a hot exhaust down pipe and gets burnt off. The net effect is that you progress like an RN destroyer laying a smoke screen! This can spoil your day.

Mike K

[Nik]

Hi Guys ,
Have to agree with all that has been said , think it's important to use the correct oil and not an equivalent , got to be worth it in the long run ,

Nik

[new2jags]

Thanks to the two Mikes and Nik for your respective responses. The car has done nearly 40k miles, so taking everything into account, it's probably due for an ATF change. Previous posts have recommended using Esso ATF LT 71141, (which has apparently been rebranded as Mobil ATF LT 71141), and to source the filter, gasket and 'o' ring from a main dealer. On my travels looking for info, I came across the following, which although specifically refers to the S-Type, describes my problem - even though it's a squeal/squeak rather than a 'woof'!
http://www.jaguarforums.com/forum/xk8-x ... ise-38805/
It may be of interest to other members. Thanks again. Leighton.

[J44EAG]

This link from another posting may be useful.

Note my comments on the wisdom of DIY oil changing in these Jaguar gearboxes. Changing oil in just the gearbox is only half the job done.

http://www.jec.org.uk/forums/viewtopic. ... +questions

Mike K

[new2jags]

Thanks for that advice Mike K. No, I'm not going to attempt the job myself due to lack of facilities and, more obviously, lack of knowledge! I appreciate everyone's comments.