Hi all,

Wondering if this might be because of the recent UK cold snap (and so will improve when it warms up a little!) - couldn't find any exact posts with these symptoms.

Car is a 2006my with the 4.2NA, just under 100,000 miles. I purchased the car in the summer and had the gearbox oil and diff oil replaced since both were original. Car has been fine since then. In November I replaced the engine oil, filters and spark plugs myself - I can't remember the plugs that came out, the code came up online for an XK8, but I replaced with the NGK BKR6EIX-11. No issues in the aftermath of that. (I mention this as some threads reported spark plugs as the cause of gearbox issues!)

In the last fortnight or so (ie since we've had low temperatures) three things I've noticed, one is that it can sometimes slam into drive from the first selection - after this is fine. From cold also, when you stop at a junction on the brakes you can feel the gearbox 'pulse' every few seconds, like it's trying to engage gear but can't - pulling away it's absolutely fine. Changing gear and driving etc all fine, except for occasionally when going uphill and the gearbox kicks down (so around that 1,500 - 2,000 rev mark) it will shift down it feels like twice, so the revs go up to 3,000 or so, a very momentary loss of drive while it works out what to do then it comes back down to the normal 2,000 ish rev range and drives as normal. All of these things seem to disappear or become much less obvious when I've been driving for a while (so I presume the trans fluid is warm). No issues using the flappy paddles to change manually at any temperature.

Is this a cold weather thing I can just live with, or should I be looking elsewhere for the source of a problem, and preparing to spend some money?

 

To start show us the bottle of trans fluid you used to put in the tranny. What technic did you use to change the tranny fluid? Drop and replace? How many times? Via the tranny cooler?

 

Had it done at a Jaguar specialist, the invoice doesn't name it but it was £70 for the fluid alone. I have confidence in their work (or at least, no reason to doubt they didn't do it correctly). They have everything in from E types to F Paces, not the first XK they've seen etc.

 

So much to say here.
The ZF 6HP28 transmission has been the target of such complaints since its inception (an inheritance from the 1st generation 6HP26??). Known cures are the filter and fluid change, a valve body rebuild, a TCM reflash.
The valve body rebuild can be completed at a ZF service facility. An in and out procedure. If your trusted shop has a Jaguar Service subscription, they can perform the TCM reflash.

As my colleague suggests, ZF publishes the precise procedure that must be followed in the filter and fluid change.
Also many purport that there are “suitable” alternative fluids (that are cheaper) then the ZF6 Lifeguard fluid that Spec’d for the transmission. At 70 pounds, the jury is out as to whether you have the proper fluid or not. Whether you “trust” the shop, or not.
Ditto for the differential. The wrong fluid can lead to premature wear, whining, failure.

Though our cars call for conventional fluids, I converted all my fluids to synthetic at 25,000 km. I change (using the simple ZF method) transmission fluid and filter every 50,000 km. I am now at 180,000 km. The vehicle runs like new, feels like new, performs like new.

Transmission failure is an expensive situation. I’d get it looked at. NOW. Some purport that the aftermarket zipkit solves all problems… and some have lost their transmission with that solution.

Cheers

 

70 pounds is about 10 pounds a liter and is not expensive. Return to garage for an opinion. They may double check if the level of fluid s high enough. Receive non engaging solutions to think about. Ask if the cover and filter were changed. Its a one piece aftermarket?

 

Cover and filter were definitely changed.

I need them to look at a squeaky suspension arm anyway so will take it in to them and see what they say. I don't mind getting the valve body rebuilt - it's 100k miles in, 18 years old, it's definitely worn. Not expecting it to behave like a brand new car!

 

We all have different perspectives. I have the ’07 xkr. And I do expect it to behave as new.

 

Your squeaky arm may like a spray of transmission fluid on it instead of a change. I looked at the transmission additives. Hot Shot Shift Restore may be of interest to you. It is the one that claims to reduce built up gums and hard shifting, in the system. A pain with the XK is, that it has to be on the lift, engine running and tranny engaged when the filler hole is opened.

 

Just a note?
Mercon SP is EXACTLY the same as Lifeguard6 fluid. The color is red and it's made in Houston.
This has been posted many times.
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and it has a different aroma

wj

 

I assume that's meant as sarcasm as Mercon SP is, most definitely, not the same as Lifeguard 6.

Richard

 

Just to say that the car can be jacked up at the back end only to assist access and it does not have to be in gear when the filler plug is removed. Engine running is all you need.

However, any additive is going to do nothing or will positively harm the gearbox so I wouldn't advise using one.

Richard

 

Yes it is and we have had many posts on this?
Mercon SP Threads.
Mercon SP Fluid

Again Mercon SP is EXACTLY the same fluid as Lifguard6. Shell makes both. One in their Houston refinery and the other over sea's.
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But you said that Mercon SP is red. Lifeguard 6 is yellow. They cannot be the same.

Richard

 

That's just dye? They can make any fluid any color they wish? Shell decided to differentiate the two fluids and made the Houston version red.
I think it was to protect the Lifeguard6 pricing because when the 6 speed ZF first came out that darn Lifeguard6 was up and over $70 a liter! It come way down now so not nearly the same savings in cost.

The CTSC sells it for $20 a liter so not too bad.
This is a great place to get ZF service stuff too. They have it all when it comes to ZF.
The CTSC-ZF Parts
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Ah, I see what you mean. Yes, it might be the same fluid with just a different dye and that shouldn't make any difference to the way it behaves. I don't actually know but you could be right.

Richard

 

I looked into the Mercon vs ZF fluid - I used the ZF as it was on sale - chart I found:

 

Got the car booked in next week so will update what they say.

I've narrowed down the symptoms in case it does help with diagnosis - the slamming into drive has gone, might have been a one off. Still pulses in reverse or drive at idle / held on the brake. Almost feels like a slipping clutch but once you put your foot down to go, no problems at all.

The confused ratio is moving from 6 to 5, around 50mph or so, about 1250-1500 revs and on light throttle (maybe 20% or so, what I'd use for maintaining speed / cruising). You can feel it start to hesitate and think about shifting down with little blips - then it will shift to 4th and come back up to 5th. If I increase the throttle input, it changes down fine and accelerates - if I decrease it, it remains in 6th and stops hesitating (but a small loss of speed results, obviously).

Once at 60mph or above (ie closer to 2000) it doesn't seem to mind and will shift down without issue. Changing down manually (which is what I've started doing when I feel it) is fine, no issues. Driving in all other gears no issues, no strange noises etc. I feel like it's pointing to an electrical issue rather than a mechanical one.

 

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So I took it into the garage. Turned out that wishbone bush was almost totally gone so definitely due for changing.

They couldn't pull any codes out for the gearbox but checked the oil and reflashed it, basically it was OK on their road test, bring it back if any issues.

This didn't fix it, so I was getting ready to take it into a ZF specialist near me in Cannock.

Today the car finally threw a code at me and restricted performance due to a misfire. It was present at low revs but above 2000 or so it was ok.
Swapped the faulty coil pack and hey presto, not only has the misfire gone but on a brief test run, my gearbox issues too. I think for some reason the misfire was present before but only at low revs, which was probably why it was getting confused about kicking down.

I think it was an original part too, so hasn't done too badly!