Stype Clunky Gear Change

[JagPJ]

Evening all,

I've got a 99 Stype 3L auto and it's just started giving me clunky gear changes every so often. Mainly when I am gently accelerating. The best way to describe it is, if I were driving a manual then go to change up but drop the clutch quickly and get a slight jolt forward. It's just been for it's 80k service at RAcing Green and they checked out the gear change problem and confirmed it wasn't anything mechanical they could find, but unfortunatly they didn't have the gear to re-flash the gearbox. Though they suggested that a re-flash would be a good idea.

For info the car had a new gear box at about 55k and is now on 80k, so I have to strongly suspect it's not the gearbox, but perhaps that's just optimisium! Another thing that makes me think it's not the gearbox is that when it's in sport and I am having fun it changes fine......

So I have just taken it to the local dealer (Gatwick Jag) and they have told me that they can't re-flash the gearbox as it's to early a model. They want it overnight so they can check the oil level first thing when it's cold. A source on another forum suggested disconnecting the battery for an hour to reset the gearbox, this sounded plausiable so I gave it a try.

No change, so decided to change the battery as the one in the car looked pretty old. SO I changed the battery and no change, was jerky at first but then seemed to get a little better. Does this sound about right? Got a trip to Bath which will be about 300 miles this weekend, will wait and see how it goes.

one thing I did notice is that the new battery is 800mA (i think that's the right measurement) and the old was 680. Also the car seemed to start easier and quicker and bizarrely the remote central locking is working better as well, it was occasionally tempremental before but seems to be working better now.....

Does anyone have any ideas?

[Trooper2]

Definitely have the Trans fluid level checked.

[JagPJ]

Is it true that needs to be done when the car is cold, as I'd prefer to take it to Racing Green than the local Jag dealer but that's trickier if I have to leave it overnight.....

[Trooper2]

Yes, the Trans fluid temperature needs to be 86F or lower and the fluid level check needs to be done before the temp reaches 120F. The car needs to be connected to a WDS or IDS diagnostic computer to monitor the temp, with engine running and car up on a lift and the tech has to check the drizzle out of the fluid level hole in the bottom of the trans. When it turns from a drizzle to a steady drip the fluid level is considered to spec.

It's really a pain and after having done 5 or 6 checks myself I sure wish they would just bring back the dipstick....

Edited by Trooper2 on Thursday 15th March 20:10

[GavinPearson]

JagPJ said:

So I have just taken it to the local dealer (Gatwick Jag) and they have told me that they can't re-flash the gearbox as it's to early a model. They want it overnight so they can check the oil level first thing when it's cold. A source on another forum suggested disconnecting the battery for an hour to reset the gearbox, this sounded plausiable so I gave it a try.

No change, so decided to change the battery as the one in the car looked pretty old. SO I changed the battery and no change, was jerky at first but then seemed to get a little better. Does this sound about right? Got a trip to Bath which will be about 300 miles this weekend, will wait and see how it goes.

The battery disconnecting is purely about depowering the PTEC unit and having all of the 'adapt' values removed from the system. These are basically self calculated changes to the applied pressure to the clutches in the transmission that give the correct shift characteristics - not too firm and not too soft.

The adapt values are caused by the transmission learning from specific events, such as a 1-2 change at half throttle. Do 20 of these in the same way and by the end of the 20 shifts the transmission will be pretty near perfect. The issue is that doing this for all speed load points takes a long time, but the system is there basically to compensate for the transmission ageing.

So the question is what to do....

Personally I would have the oil changed, use Ford Mercon V fluid, available from your local Ford dealer. Do NOT use anything else - it WILL mess up the transmission. The torques converter DOES have a drain plug and it WILL need draining.

With the fluid changed and the level reset (after a leak check) the transmission should shift noticeably better.

As for Trooper 2's comments about the level setting being a pain, I would concede it is, but when I wrote it it was to address a number of issues found at dealerships and if it is followed to the letter it is bulletproof.

As for the dealer's comments about a reflash not being possible - they are just plain wrong. A call to the Jaguar Hotline will confirm that.

[Trooper2]

OOPs! open mouth insert foot...


Thanks for helping out Gavin....

[JagPJ]

well, just to post progress on the problem. Have been all over the south of the UK this weekend racking up over 300 miles and the gearbox seems much better, still very slightly jerky but only just noticable. Will monitor and see if this gets better or worse.

So thanks for all the advice, the replacement battery has done wonders for the gearbox and the remote. Can now lock the car from 6ft rather than 6 inchs.....

Thanks all