Hi all,

I have a 1999 XJ8 with the 4.0L engine which I bought a month ago. Has been running well, but I've noticed a significant lurch or jolt when the car is shifted into Drive. It does not seem to matter whether I am shifting directly from park, reverse, or neutral -- there will be a noticeable 'thunk' and jerk forward.

Interestingly, the records from the seller indicate he had the transmission rebuilt two years ago, possibly for the same reason: "Several years ago I felt it was shifting a little rougher than it should, so I took it to a trans shop and they convinced me I ought to have it rebuilt. Haven’t had any issues since then."

Would appreciate any insights -- in particular, whether this is something I need addressed in the near future.

Thank you,.

 

I should also note that once in Drive, shifting is perfectly smooth.

 

When you start the engine up cold, wait 15 or so seconds for the RPM’s to come down below 1k before shifting. See if that makes a difference. Shifting into gear immediately after starting up the engine from cold is asking for trouble. The A drum is made from recycled beer cans says our now retired transmission rebuilder. The valve body can also be worn out and the pressure regulator valve can be updated for further shift improvement. Tons of posts about it.

 

Agree. I always wait for the revs to drop. Sometimes if doing a rolling stop and then gas I get a minor thunk in my XK8.
Anyone one else remember being an ignorant 16 year old and doing neutral drops in there first car (mine ‘70 Olds F85)?

 

How many miles has your car done? Do you get a gearbox fault warning on the dashboard?

I’ve had two of these gearboxes fail on me in one of my old 4.0 XJ’s, the original box failed and after going through the rigmarole of changing it for a used gearbox from a supposedly low mileage car that too failed. The 4.0 cars tended to lunch their gearboxes more readily than the 3.2 cars and they are rare in the UK these days. Many of the cars still running around these days are 3.2 models which have less power than the 4.0 and are easier on the gearboxes.

I absolutely love these cars but the gearbox is a constant worry for me. On my current car, also a 3.2, I’ve had the modified valve installed from Trans Go and the fluid has been changed twice within the last ten years; by myself in 2017 when the modified valve was installed and then again in 2022 by the guy I sold the car to before I bought her back a few weeks ago. The car has done less than 50K miles between 2017 and now but I can tell by the way it’s shifting that there isn’t enough fluid in the box and I’ll need to top up. I’ll probably try and find another gearbox to keep in stock as a spare but I’ll rebuild and strengthen that one.

There are further modifications that can be done to this gearbox to make it stronger using factory parts, Audi used the same gearbox in some of their high performance RS models which have power far in excess of that the N/A X308 has. But the best advice is to look after that gearbox, like others have said be patient with it and don’t floor it from cold.

 

Ditto on waiting for RPMs to drop below 1,000 at starting. After reading about this issue after buying my current car, beyond having the filter changed and valve upgraded at 30,000 miles five years ago, I made it a habit to just take a deep breath and let the idle come down. And I'm going to have the box fully flushed at 60K, about 6,000 miles from now.

 

Thanks to everyone for your helpful comments. I waited about a minute today for revs to fall below 1000 before shifting, and the lurch was still there but noticeably less harsh. I'll continue to try to baby it for a while.

@pcolapacker When I was learning to drive my father would gleefully recall doing neutral drops as a teenager and then warn me never to do it myself.

@Stu 1986 There's about 97k miles on the car; service records show the transmission was rebuilt around 80k. No faults appear on the dash screen.

 

If it’s been rebuilt and serviced then it may be low on fluid. Try adding half a litre of fluid and see what you get. It is possible to add fluid via the transmission cooler line in the engine bay, just be careful with the connections.

 

Those high revs may be a sign of something not quite right e.g. a sensor reading wrongly or an air leak. OBD live data can be used to check things.

 

I’m leaning towards the PRV in the valve body needs addressed. Just my opinion. You certainly don’t want the A drum to fail due to a faulty PRV.

 

He hasn’t got an issue with high revs per se, the reference to high revving relates to when you start the car from cold and it is on auto choke.

I’ve never started a vehicle from cold or even when warm and driven away immediately, I’ve always allowed a few moments for oil to circulate and reach the various components. In the case of a cold start, especially with a ZF equipped X308, I always give it a few minutes before moving and making sure the RPM has dropped to a slower idle to avoid causing issues with the gearbox.

My next door neighbour who has manual gearbox cars has this habit of putting his car in gear and dropping the hand brake before starting his car and has already begun lifting the clutch whilst cranking. This results in the car moving on the starter in gear and when it fires the already depressed accelerator kicks in. I’ve lived here 13 years and he’s on his fourth car in that time

 

I'm grateful for everyone's insights.