Hi Bro

Tell me about it, I'm psyching myself up to Spend £800 on 4 New Pirelli as soon as I get 'Cherry Blossom' through the MOT.

 

OB, being retired, cost is a serious consideration for me. I have 16 inch "modern starfish" rims, as fitted to many facelift XJSs and I have Kumho Ecstas (225/15/60, V rated) all round. Under half the price of Pirellis, handling and grip just as good, good in the wet, ride quality slightly (say 10 to 15% max) les compliant. Good compromise for me. But if you have 15 inch rims, nowadays tyres are a big problem outside the Pirellis.
Greg

 

Well guys, I swapped out the Speedo Transducer...but didn't fix the problem.

It was easy enough. Just un-plugged and un-bolted. No goo gushing out.

Placed the new sensor in and gave her a test drive. Still dead. Bugga.

Can anybody tell me if this wiring goes back to the engine bay or does it go straight inside the cabin to the gauge cluster harness? Maybe I have a loose wire somewhere?

The reason I say that is I now have a new transducer and the speedo gauge isn't that old as it was re-conditioned with new PCB by an instrument specialist that is local.

The only saving grace is it probably wasn't a complete waste of time. My speedo, since getting it re-conditioned, never activated until the first gear change. As Greg pointed out this is probably due to a dodgy transducer. So when I finally get the needle going again, I reckon it should work as soon as I take off.

I was also going to pull out the instrument cluster tomorrow and have a bit of a once over but I think it will be fine.

Any other ideas?

The old transducer in situ


With the old transducer pulled off. What remains is a little yellow plug.


New transducer installed. Easiest job I have done in a while!


Tied back the wiring so it is out of the way:

 

It sounds like you did not remove the driven unit??????

That driven unit has a nylon gear that meshes with the drive worm on the trans mainshaft.

That nylon gear can loose its teeth, and hence NO drive.

The trans governor, on the other side, and driven by the same worm gear also can loose its teeth, and the trans stops shifting.

The speedo driven gear is a GM item, and colour related, soooo, if it is the issue, take it to any half decent transmission repair mob, and get one the same colour.

Failing that, look at the trip computer, and note if it is changing ANY numbers after a 10km run, it is IS, then the transducer and adaptor ARE working. It its the same as when you left home, then that gear is suspect.

BUT.

The Yellow wire that goes through that grommet in the tunnel, splits off somewhere near the console front lip, near the whole bunch of wires for the climate system. 1 wire goes to speedo, 1 wire goes the trip computer, 1 wire goes to the cruise control, and they are British, and I have had 2 cars with that split broken, so maybe.

 

Hi Grant,

Not sure what you meant about the driven unit. The transducer only came with like this:


Is this the driven unit you refer to?


It had a yellow looking nylon piece thatprotudes out of it. I understand what you are saying though I think. If the piece that I left alone today has teeth shredded then it won't mesh with the tranducer.

i'll do that trip computer test tomorrow and see if she is changing however I am pretty sure she isn't.

To be continued.

 

These may help you get a general idea of what can go wrong with the nylon gear that drives the transducer Paul, and how to change it:


And this shows what they look like new
https://www.summitracing.com/int/sea...ion-type/th400


Greg

 

Found what I was looking for earlier.



#2 is the nylon driven gear.

#1 is the alloy housing, with the o/ring on the outer rim.

#7 is the seal inside that housing.

#8 is the retainer ring for said seal.

39 teeth Jag part @ is C46070, but that may be NLA.

I got mine from a Trans Parts mob near me, but they are long gone.

 

And a snip at 22pence from JCP !
Part no. C46070 | Speedometer driven gear parts from Jaguar Classic Parts UK
Greg

 

Guys thanks a bunch for the info. I am tied up now until the weekend so will get back onto this later in the week.

Got a drive into the city early tomorrow morning for an overnight stay so will have to use the ole' GPS to gauge my speed. I can then look at the Revs and get a rough estimate. That and driving behind other cars on the left lane will work..

 

Ok just came back from my mini road trip (Training course for work with overnight stay).

I can confirm, no change to the trip computer.

Also yes, I only swapped out the speedo transducer itself, I didn't order the rest of the mechanisim that was left:





So I am guessing that swapping out the nylon gear will mean trans fluid out correct?

Also would I swap out the nylon gear on its own (typically) or is it best to order the seal ( part # 7) to swap out when I do the job also? I am assuming part # 1 (housing) will be fine.

If this is the case then it so happens I am due to replace that fluid anyway so might be best to do it at the same time.



Guys thank you again for all your help above

 

Can't hurt to replace seal #6 and #7. They're probably leaking a bit....as they almost always do.

The housing should be fine

A small amount of fluid will typically dribble out....a couple ounces or so. Could be more or less depending on the fluid level and angle of car

Cheers
DD

 

Update:

Just ordered Nylon Driven gear and O-ring # 6 off Doug from Jagdaim.

$5 for the gear which I should get tomorrow.

#7 seal is NLA. Doug says the XJS uses a Jag brand for that seal but the XJ uses a pretty generic seal.

Hopefully I won't need it however I was going to swap it out as a matter of maintenance whilst I was already in there.

To be continued...

 

#7 was used on millions of GM cars

Google "1240382 Speedo Seal"

(I remember that part number from my days as a GM parts guy decades ago!)

Cheers
DD

 

Made some progress today whilst underneath changing my trans fluid.

Ok so swapping out the speedo sensor made no change. Time to swap out the nylon gear.

Un bolted the speedo sensor and moved out the way.


Next took off the retaining bracket with a 13mm socket. Why are 80% of bolts on my car 13mm?


And then...I couldn't get the housing out. Watched a You Tube video and they simply just yanked it out....ok doesn't work for me. So I screwed the speed tranducer back in and used some multi grips around the sensor nut to gently lever it out a bit. Then I took off the speedo sensor again and pulled out the housing by hand.

Thar she be, housing and nylon gear.


The nylon gear actually looked ok:


Nevertheless I wanted to swap it out anyway to eliminate this and also installed a new o-ring. Getting it all back in was just a reverse of the above but easier.

Now....that all back in I noticed the wires to my speedo transducer, where I crimped them the other day, were starting to come out! What? I tug tested them when I crimped them and the were ok.

Can't have this...so I soldered and heat shrunk the connection. This is further back and not at the actual plug part. At any rate is should be more reliable.

So....could that have been the problem? I think this may have happened when I was moving the sensor around but I will have to find out tomorrow after I finish servicing my transmission.

Stay tuned....

 

Paul
if when all back together the speedo still does not go, I am sure there is a meter setting that would test if there is electrical output from the gearbox transducer. The speedo wire come up into the tunnel, but under the console, through a grommet about level with the passenger's thigh/knee area. Worth checking the signal is getting into the cabin, and the joiner plug's integrity once you have repaired the wires.
There are LOADS of dirt cheap speedos in all the breakers in the UK, if it does turn out to be the actual speedo. But could just as easily be the connectors into the binnacle, or the binnacle circuits as well, if the gearbox checks out.
Greg

 

Thank you Greg,

The moment of truth will be today.

So I am wondering...... if I take out the speedo sensor but still have it connected to the circuit, and I find a point in the circuit with my multimeter on Volts DC and I twist the speedo with my finger what voltage to expect? (if any).

I am wondering also If I would have to have the car running to liven up the Dash perhaps?

Any ideas?

 

If you turn the transducer, you should get about 5 volts AC out of it, if I remember correctly.

The yellow wire is the signal wire to both the speedometer and trip computer, you can always pull out the trip computer and test for continuity between the yellow wire at the trip computer plug and the transducer.

 

Ok finished my transmission service today. After all that it was time to test if in fact those poorly crimped wires were the source of my pain the other day....started driving and WELLA! She is working!

Explanation: I think the fault was in fact the speedo transducer. When I wired it up the other day I used cheap charlie insulated lugs. When I was underneath yesterday replacing my nylon gear I noticed that these wires were half hanging out (As mentioned previously) so this time I soldered them and heat shrunk them. This is a splice in the cable I have and not the two pin connector where the transducer connects. I left it so it can still be unplugged if necessary.

Seeing how the nylon gear looked fine I can only assume it was actually the sensor. Never mind the nylon gear is a consumable so it didn't hurt to swap out the $5 part.

My only qualm is.....my speedo will not come alive until after the first gear change. This has been like this ever since I took my dud speedo gauge to a Instrument Repair mob. He confirmed the little PCB was faulty and installed one he gets made up locally. i never complained to him though as at the time I couldn't find a speedo gauge anywhere and this is only a small little annoyance.

All in all...she is fixed....for now.

Thanks for all the help guys. I learnt heaps

 

Paul, great news. I meant to mention before, the stick end (as against the lollipop end) of the nylon gear has a square hole in it into which the transducer metal drive fits, quite often this gets rounded so it will not drive the transducer. If you still have the old one, take a look. The lazy speedo is probably a slightly iffy circuit in the instrument binnacle. I think you are VERY sensible to leave it until you feel like a w/e at the dining table with a white tablecloth and R&R-ing the entire instrument pack.
Greg

 

1. You have a bad ground in the instrument panel Or the speedometer is not making good contact at the plug. Tapping the instrument panel is the prime clue! Doug is right on target.

@. illuminating the warning lights works best the farther you get the bulb into the receptacle. I tried T10 LED's and fasten them to the outside of the entry point of the bulb opening. Good, but not a winner. I use T-5's and took them out of the wedge fitting and then soldered the led wire to the Jaguar bulb contacts. The T-5 lighting head slips into the hole and goes in about 3/4 of an inch. With this setup you get light from the original bulb and the LED. Also, there is no modification to the panel and it looks original., except you can now see the warning lights!