The 'Kickdown' only operates at Speeds up to 60 mph (UK)

If I want to change down at any Speed over that, then I have to manually Select 2nd gear Auto.

Is it possible to adjust the 'kickdown' so that I can still use it at 65 mph (UK) instead of 60 mph (UK)



Also restoring my other V12 XJS after a 14 year lay up.

https://www.jaguarforums.com/forum/x...js-v12-122634/

 

OB
Assuming you have the three speed auto, It is quite likely that the KD is not in fact working at all and the box is changing down on its own. From your pic it looks like the switch is already asking for KD, even though it should not be. The KD switch works by means of a small lump on the cable that, when the go pedal is pressed right to the floor, pulls against a spring-loaded bit in the tube attached to the switch holder and thus pulls that lump against the switch arm and trips the switch. This circuit then strips an electrical solenoid on the UK passenger side of the gearbox.Yours looks from here as though that mechanism is stuck. VERY common after a layup.

Undo that flat thing with the KD microswitch in it through which the cable runs by undoing the two nuts (one each side) that secure it to the capstan. Look at the switch which is underneath and is secured by two tiny bolts. Pull off the leads (there should be two) and test the switch with a test light and see if it works. If not buy another. Next (regardless of the outcome of the first test) you need to see if the mechanism on the cable is working. If you cannot pull the mechanism to trip the switch and letting it go does not release it, the mechanism is jammed. Souse it in the mixture for a few days and then liberally WD40 it, pull it in and out and it will free off.

Once this is OK, reinstall switch, wires (orientation does not matter), and set it up using the two fixing nuts to the capstan so ther is no slack in the cable at rest. Then get the GF to floor the throttle (ENGINE OFF) and see if the mechanism and switch trip OK.

Then test the car and see if it kicks down. If NOT, then it is either the wire to the gearbox solenoid, or the solenoid itself that is the trouble. Post again at that point, but here is a pic of the solenoid attachment to the gearbox, so you can at least check that it is attached. It is the wire going to that round thing with the terminal on it towards the rear of the lovely new deep sump pan!


Greg

 

Hi Greg Wow!

That is one Sumptuous Sump!

When I floor the Throttle at any Speed under 60 mph She takes off and goes like a Bat out of hell but if I'm already doing 60 mph She just accelerates in the normal way.

So how do I tell the difference between the Kickdown Working or the Gearbox changing down on its own? I didn't even know that it could do that!

Is the Kickdown supposed to work at any speed?

 

If the KD is working properly she will KD into 2nd at 90 or even faster! The box has a vac line and a moderator thingy that (in effect) reads the throttle opening and will adjust the gears accordingly. That is why she changes down below 60.

Greg

 

OB
Just checked mine. An easy test to see if the mechanical parts is working properly:
If you push the solid end of the cable where it goes into the KD switch holder inwards towards the capstan, it should go in about 1/4 inch and you should see the KD switch arm pop outwards a bit. If that is Ok, then it at least proves it is not stuck. Then get the GF to push the go pedal and see if it pops out as if you were doing the pushing test. If that is OK, then test the switch and check if both wires are attached to it.

Greg

 

Hi Greg

That is really interesting! I never knew that you could 'Kickdown' at speeds over 60 mph, I thought there was some sort of a limiter in place (which would not have surprised me)

So it looks like there is something wrong with my set up.

 

Hi Greg

Thanks, I will do the test and then report back on my findings.

 

When mine wouldn't kick down above 60 like yours it was the switch in the transmission. Unfortunately the pan had to come down which meant the rear mount had to be removed. Chevy car with T400 = no problem, XJS with T400 = PITA.

 

^^This. Yeah, will definitely kick down ~90MPH.

 

Thanks JT You've really Cheered me up (not!)

But you will not believe what I found underneath the Bonnet/Hood and I've got the Photo's to prove it!

 

Hi Flint@JT@Greg

Just when I thought it was Safe to go back in the Water, I was suddenly reminded that nothing should Surprise you when you drive an XJS but I'll make an exception with this!

As the Car has only been back on the road as of May this year, I've not had that much call to use the 'Kickdown' but when I did it would only work, at Speeds of 60 mph (UK) or less.

Which I thought was Normal, as I came to the wrong conclusion, that Jaguar must have fitted some sort of a limiter.

So I asked on the Forum, if this could be adjusted in some way, at which point 'Greg in France' jumped in and told me everything about it I would ever want to know! (Thanks 'Greg' you're a Trooper!)

So I got under the Bonnet/Hood to have a look around and just could not believe what I was seeing!

WTF!

A Squirrel got into the Engine and has had the 'Kickdown Switch' for breakfast! Chewing its way through the Wiring and the Vacuum Pipe!

Then just to add insult to injury, left a trail of empty Walnuts scattered down the 'Vee' which I had to get out with an extractor!

Which I bought sometime ago, thinking that one day it might be useful and it was!

This is going to be a bit of a 'Nightmare To Sort Out' So no change there then.

But looking on the Plus Side, at least it didn't follow that by chewing through the Ignition leads!

At least it hasn't done Yet!

 

OB,

Welcome to the club that most us have joined when re-commissioning a car after a layup - the "Rodent Hidden Damage Club!" I'm surprised it's taken you so long to join it! The Squirrel section usually have it easier than the Mice Section as Squirrel habitation is easier to see (larger foodstuffs /bedding etc). I think the Mice section have a more difficult time as it's harder to find the damage and often involves wiring damage and upholstery damage. As you can see, you've got off remarkably easy!

"Full-throttle Kickdown" is often confused with "Part-throttle Changedown" I bet your changedown at under 60 was happening without you having to put your foot ALL the way to the floor? If you look through the owners handbook or the service manual I'm sure you'll find the speed parameters within which 3 to 2, 3 to 1 and 2 to 1 changes will happen under Changedown & Kickdown.

I suspect at 50mph, you were getting a 3 to 2 changedown, rather than a 3 to 1 kickdown. It's not just the speed at which kickdown can operate, it's also the ability to drop 2 gears in the right conditions. Try it in your 4 litre and also see the difference if you put it in Sport Mode which you gives a better ability to get a 2-gear dropdown for acceleration in full throttle.

And don't worry, there are limits under which Kickdown will operate! If you drive at 130, I guarantee it won't drop into 2nd under Kickdown!

Paul

 

Hi Paul

You have really Cheered me up! (yes!)

And there was I just thinking that I was the only one!

So as You say I got off very lightly, though its never nice when Cars like this go wrong.

Also Thanks for explaining about the gear changes, I never knew any of that and Yes! you were right, She sometimes changed down, without putting my foot to the floor.

Thank Goodness it didn't develop a taste for the Marelli ignition, or that would have been very expensive to put right.

So all I really have to do is pull it all to bits and see what this young Varmint got his teeth into.

It could have been worse it could have been the Seats or even the Soft Top!

 

When I bought my coupe the engine was covered in empty shells. I had to use the shop vac to clean up. after driving home 3 hours they were nicely roasted.

 

When that Squirrel got in there, that has to be the only time my Car Alarm didn't go off!

 

This reminds me of something I've never understood. If I press the accelerator lightly to the floor, she'll stay in 1st gear until 50 mph; if I hold it down hard, she won't shift until 62 mph. Every other car I've ever driven, "on the floor" didn't make a difference, it was all she had. Not with this baby, though. Gotta love those British engineers.

 

Good to hear from you Hank

That is something else I never knew but as the moment I am not able to try this out for myself, until I get this 'Kickdown' problem sorted.

 

Thanks for the kudos but I am afraid that you are mistaken; the autobox is an American lump.

The GM HydraMatic TH400 Transmission - Novak Conversions

 

I've had to start a new Thread on this, as someone marked it RESOLVED

But it's still giving me a problem at the moment.

If you look at the (First Photo) with the Throttle at rest, you can see a very Small Spring in the Sleeve.

If I push the Sleeve towards The Capstan a quarter of an inch, it Trips the 'Kickdown' but this little Spring is so strong that I have to use mole wrenches in order to do so.

The Spring isn't jammed or anything but it is a very Strong Spring.

If you look at the (Second Photo) with the Accelerator pressed to the Floor, the Throttle is open but the Spring in the Sleeve hasn't moved to Trip the 'Kickdown'

There isn't a lot of Tension in the Capstan, just enough to close the Throttle when you lift off.

It looks like an internal spring as its not visible.

So this is the bit I don't get.

Which part of the Sleeve set up, pulls that strong little Spring to Trip the 'Kickdown'

Has something broken in the Sleeve or am I missing a Big External Spring on the Capstan?

I just don't get what pulls this Strong Little Spring.

Help needed please Guys.





Photo 3 is a normal overall shot of the Capstan

 

OB

The setup may be jamming a bit, even though you do not think it is. First now you have unjammed it, lube it with some engine oil and work it in and out a few times. You should be able to push it in by hand relatively easily.

The thing is activated as follows:
When you floor the throttle pedal, first the capstan winds up and opens the butterflies. At this point the inner cable of the throttle should be tight. Then you push a bit harder on the throttle pedal, and as the cable inner is tight, a force is being applied to the outer - effectively the inner is trying to squeeze the ends of the outer together.

Normally this is impossible, BUT the cunning design of the Jaguar V12 kickdown actually ALLOWS the ends of the outer to be squeezed together by allowing the outer to go into the tube against the spring. Clear so far?

Normally, to adjust the system, you loosen the two nuts that hold the cable/switch setup to the capstan frame and (effectively) move the outer AWAY from the capstan casting it is fixed to, thereby taking up the slack. The trouble is, in your pic, the adjustment looks completely used up.

So first try a little test: undo the two nuts which hold the thing to the capstan frame and pull the inner tight. Then clamp your Mole wrench on the inner and ask the GF to push the throttle to the floor. See if the switch/spring system then works and pops the microswitch. Remove carpet and any stuff below the pedal before trying this.

If this makes it work, then reinstall onto the capstan frame, getting the inner as tense as you can using the adjuster nut. Then try again and see if it trips when installed.

BAD NEWS if not. This means the inner has stretched and that is not adjustable, and you need a new or decent second hand, cable. bad news not because of the cost, but because of the total PIA that installing it might be!

Post back when you know what's what!
Good luck
Greg