Hi Guys,

Fairly new 1997 XK8 4.0 owner here.

I have had the car a month now, and am having some issues with the gearbox.

My problem is that if you take off from a standstill with more than a light throttle, there is a delay, and to the driver it almost feels like the car is wheelpinning then there is a slight jolt and away you go, I was living with this, and babied the throttle i.e letting the car creep ever so slightly before giving it throttle, but yesterday my girlfriend (who is heavier footed than I am) drove the car and this morning as I drove out 'Gearbox fault' popped up. Since stopping and restarting, car is same as before so still going for now...

Once moving, the car changes perfectly, and is smooth, and goes into all gears including reverse smoothly without complaint.

I notice in the service history no transmission work has ever been done, is it worth trying a fluid change before writing off the gearbox? or could it be another problem?

I appreciate your responses.

 

How many miles on the vehicle?

 

Car has done 103,000 miles.

 

I'd like to hear thoughts about this too as it is virtually identical to what I'm experiencing with my one week old (to me) '97 XK8 with ~98K miles

 

When I hear about a transmission allowing the engine to rev and then suddenly "catch", my first thought is low transmission fluid. When the fluid is low, it allows air to get into the torque converter. Then the inner part of the TC, which is connected to the engine, can spin freely without load because the fluid isn't being forced through it. Then some fluid finally gets drawn into it, and you feel the jolt as the non-compressible fluid suddenly causes the TC to "catch".

However, in your case I don't think that's the case. If the fluid was low, it would probably allow the engine to rev up at other times, too, not just when accelerating from a standing start. But, it's free to check your fluid level, and cheap to add another liter if that's the problem. I'd probably start there. Heck... I might even try just adding a quarter to half liter through the transmission cooler hose, just to see what happens. You're not going to overfill your transmission by adding a quarter liter of fluid unless it's already filled to the limit of the "normal" range. If the transmission has never been serviced, then it still has the factory fluid in it. I would GUESS that the factory fills the transmission to the middle of the normal range. That's what they tell the dealership to do when doing transmission work. So if you add a few ounces of fluid you're not going to do any harm. And even if the transmission is already filled to the top of the normal range, I'm sure there's an allowance in there to allow the transmission to be overfilled slightly before the extra fluid starts blowing out seals.

I know this is a long winded response, but I'm just thinking through things as I type them. To summarize, if I owned your car I'd probably add a half liter of fluid just to see if it changes anything. If the lurch goes away, then you know you were low on fluid and you need to go through the laborious process of measuring your fluid level. If it doesn't go away, then you have a different problem.

 

I thought of something else. This might be completely ridiculous, so someone correct me if I'm being stupid here...

Let's say the filter has gotten clogged. When the TC is spinning slowly, it doesn't have much suction to pull fluid up out of the pan. When you rev the engine, the TC has more suction and more fluid flows through the TC. Maybe there's enough suction there to cause the fluid downstream of the filter to cavitate, which then allows the TC to spin without resistance momentarily. Maybe you just have a severely clogged filter. If so, you probably have other problems, too, because the only thing that's going to clog the filter is metal particles.

But like I said... This guess is a complete "pie-in-the-sky" guess. Don't take it seriously.

 

Oh yeah... the moral of this story is DON'T LET YOUR GIRLFRIENDS DRIVE YOUR CARS!

 

On page two of the thread below there's a couple of pictures which shows where the transmission cooler hose is. My car is a 2003, but I assume it's in the same place on a 97. Make sure you put a couple of rags under the connection because an ounce or two will drain out when you pull the hose away from the connector.

https://www.jaguarforums.com/forum/x...k-sound-50852/

 

I could have said all of that stuff in a single post, but by dividing it up into four posts it improves my post count and newbies will think I know what I'm talking about.

 

Sam, I just watched your changing the trans fluid/filter vid and was both entertained and enlightened, thanks. I will probably go though that process in the next couple weeks.

However, to add to the description of my tranny's malady, it shifts fine into reverse without lag, just the one from park to drive is problematic, not sure that helps isolate the issue?

 

Nope! Not for me at least. It just confirms I don't know what I'm talking about.

 

Reverend Sam,

I appreciate your responses, I feel honoured that you have responded after watching some of your legendary youtube videos in the past few weeks!

I will try the top up route and report back, my only question is regarding the type of oil - can you guys advise if this would be suitable -

ATF MV LT71141 Synthetic 1 lt | eBay

 

I hate to be a poop, but the symptom of delayed drive can be related to a common problem with the 5HP24 gearbox....the failure of the A drum due to cracking of the retainer ring groove. The A drum is essentially 1st gear drive and holds a group of multiplate clutches. But I suggest taking it to a ZF expert and let them run some tests to see what's going on, there are other possibilities such as a bad shift solenoid in the valve body. Once you determine the fluid level is okay, you're done...you need help from a guy with the tools and skills to analyze the problem.

 

This is the insight I suspected would eventually surface. Taking the Eight to a local indy shop on Thursday, ex factory guys should be able to verify where the problem is.

 

ive read that jaguar used to replace the transmissions when xk8s were in for service because they were prone to failure. would be nice if thats still in effect. i think my 2000 has original trans. just hit 66,666 miles.

 

late to the party, but the first gear jump made me think of the a-drum immediately. When it gets to the point it breaks, more parts will be damaged...think of tripling your repair cost. If you can get the a-drum replaced with the new-n-improved unit (and they DO make refurbished, 'beefier' drums out there that won't fall apart again, just google it) you'll save yourself a full rebuild later on, and alot of grief.

 

I did take my 8 to a indy shop Wedneday and the tech didn't think the prob was the a-drum, saying that when it fails it goes completely. But, he didn't have any other insight as to what it could be. Though based on your post and other that I've run across, it seems more likely to be the case and maybe I'm in that just about to destroy itself period. Any other way to evaluate short of pulling the trans and taking a look?

 

From your description, mine ('99 XK8) has the same symptoms, been that way for awhile. I think the drum is OK, but the actual problem may be a worn pressure regulator or a defective solenoid. I have (possibly erroneously) deduced this from other threads on this and other forums. I also think that this symptom may be the cause of the A drum failure, as the force applied to it is a tremendous jolt when the pressure is applied at a higher rpm, such as when normally accelerating from a stop, the car acts as though it is in neutral, and then drops into gear.

 

I might try a fluid change with a new filter and presure regulator (which I think is pretty cheap).

As I recall, Reverend Sam posted a link a few weeks ago to a great 5HP and 6HP mantenence parts site. That's where I saw the pressure regulator...

 

hello, could you describe the "squeal bark sound"?