I had my gearbox oil changed when i got the car at 110k. There is no concern with leakage caused by fresh oil. If you follow the factory procedure, new fluid should not cause any leaks. In fact some owners have been known to run the new fluid for a few hundred miles and then replace it again. This method removes as much as possible of the old fluid that remains in the torque converter and cooler.
What is not recommended is to have the transmission "power flushed" which could dislodge any debris which have built up.

 

Where did you get the info about new oil being thinner, therefor a problem?

 

I can't remember the post title off hand, but Brutal posted to the effect that he'd had situations where customers had come in to his work place for a gearbox oil change and/or flush, and had reported problems with their gearboxes afterwards, blaming it on the dealer that had done the oil change.
On one occasion he suspected that the car may have problems after an oil change, so he kept the old oil as a precaution.
The car refused to engage reverse afterwards, so he put the old oil back in and the car was fine.
The post may have been in a thread centred around the "sealed for life" issue, and if i can find it again i'll point it out.

Edit:
Found it, Brutal's post on first page.


Discussion of 'sealed for life' and synthetic fluids

 

None of that thread was specific to the ZF 5 speed transmissions in our XK's. Some was related to S-TYPE, others to the later ZF six speeed, and the old oil story wasn't even on a Jaguar.
I would not be happy having to put contaminated oil back in my gearbox.
What I did end up with in effect, was a partial oil change and a new filter. By only dropping the pan, fitting a new filter and replacing the fluid in the pan, all the fluid was not renewed, but maybe that's not a bad thing. It's certainly better than having badly contaminated fluid and a restricted filter, that at 110k was living on borrowed time.

 

True.

I didn't get what car or gearbox Brutal was referring to when describing replacing the old oil, i don't think he stated, or if he did i missed it.

Does the S-Type use a different box?

From my own perspective i don't see how i have much choice but to at least try a filter and oil change, as i suspect the oil may well be past or approaching it's sell by date. If that's that's case it's a kind of devil and the deep blue sea situation.
It just made me decide to be prepared by keeping the old oil in case the seals couldn't handle the fresh oil, and also be prepared for the possibility i may have to drop the gearbox, either to cure an existing leak, or in an attempt to get the box to retain new oil, by replacing the output shaft seal, if i can.

 

From 2003 the s-type used the same ZF six speed transmission as XK XJ which use Shell fluid. Early s-type used Mercon fluid and our early XK's used Esso fluid. To confuse things even further, early stype manual boxes used the same fluid as our early XK 5 SPEED auto's
Have you determined the area of the leak yet?

 

I looked at that thread on gearboxes from a general perspective, with regard to the degradation of seals and oil over time.
Obviously i hope that my gearbox doesn't give me any new issues after i cure the leak and change the oil.

No, not yet, i've got other stuff to do before i get round to the gearbox, as i mentioned earlier.
Since i intend to get the steering rack rebuilt as part of repairs to the front end, the car will be on axle stands with no front wheels on it for a week, so i figure that'll be the time to attempt the gearbox.
It could be some weeks before i get the £1000 together to do both jobs.( front end and gearbox)
I stress that i only mentioned Brutal's comments by way of considering any possible/potential problems that i may have to take in to account when attempting to do my own repairs, so i'm not disagreeing with a word you've said.
In fact you've raised my spirits, because i was much more concerned earlier than i've been since you said this:

 

I've just realised which car you're working on. I'm sure you'll get it to how you want it to be in the end, and even enjoy the process.
I'm believe you're taking the best action regarding the transmission fluid change. I wouldn't worry about it causing problems, mine is now at 130k and I plan having it changed again if it gets to 160k. I suspect the leak you have will be easilly resolved when you undertake the trans. service.

 

Thank you X100, seems i inadvertantly bought a restoration project.
Or that's what it amounts to for someone with my limited mechanical knowledge.
I hope your advice will allow jaguargary to get his car running properly, and i've certainly learned from it.
I hope he lets us know.

 

Me too, i would love to have a quick look at it, sounds like an easy fix. Also, good luck with your repairs, you'll get there and have a great car to be proud of.

 

hi the gearbox fault light will show if i select reverse and then put it in neutral before starting, but the engine failsafe does light up and the amber light stays on and it just turns over but wont fire, would you no anything about a gearbox range sensor

 

hi the car just wont start and there is no spark to the plugs

 

From the online manual:

The corroded connectors X100 mentioned may be causing an illegal code, which in turn is triggering the gearbox error message.
If the error code generated is deemed as potentially serious by the system, the car may try to protect itself from damage by switching off the current to the plugs, and refusing to start.

Hopefully X100 is still around today and can advise you better.

 

Next to each gear position on the shifter is a led indicator. This must be lit to allow starting. With the ignition on and foot on brake, moving the gear lever....have you got a red LED lighting up next to each position sellected?
*P
*R
*N
*D
If not, the rotary switch on the side of the transmission is not giving the signal to allow starting. This could be the switch itself being faulty, or as I mentioned before corrosion at it's connection to the harness near the firewall.

 

ok the light on p lights, if you put it in to r no light, and if you go in to d from r to n thats when you get the gearbox fault come up, and when you pull away it is like pulling away in forth gear, i did notice that the light would light up if you went p to d but soon has you go into r gearbox fault, so do you think this is the cause of the starting problem has well

 

Hi i will pass all this information on to the chap who is looking at my car and let you all no how we get on many thanks gary

 

I still suspect rotary switch or connector.
This is the switch which is on the side of the gearbox. You can see the plug connector which goes up to the rear of the engine bay.
JAGUAR XJ8 NEUTRAL SAFETY SWITCH ROTARY SWITCH 0501209953 BREAKING SPARES | eBay

Trace the cable to it's connection..... separate the connector and clean the pins. If this does not cure it you will need diagnostics to get a fault code.

 

hi everyone engine failsafe mode now gone problem was the rotary switch on the gearbox hope that helps anybody who has a starting poblem like i had

 

thanks x100 you no your stuff

 

Good stuff.
Glad you got it sorted, and thanks for letting us know.