I notice there are two speedometers, one goes to 160mph snd the other to 140mph. I'm suspect that the wrong one is in my car. Mine has the 140 and it reads high on both speed and odometer. Stock 3.something rear end. If i look at the dial in pictures of the 160 amd compare where my 60mph needle underway is on my 140, its in the right spot for the 160.

Any thoughts gang?

 

The "160" version was used in the V12 cars. Six cylinder cars got the "140" and, on some very early USA Series III cars, an "85" version.

I have the both the 140 and 160 versions as well at the V12 KPH version (which reads to 280 KHM as I recall) and they all read the same; that is, all of them are equally inaccurate, reading about 5% too high.

What car do you have?

Cheers
DD

 

I see you'd already had a go at editing the thread title Soeedometet. I tried too but it was totally locked so I copied your thread, renamed it Speedometer and deleted the original.

Now I've done that, I'm half expecting you to come back and say the original thread title was deliberate!

Graham

 

Yep. First. As Doug suggests. Which car ? Early enough for a cable
driven speedo?


Or late enough for the transducer off the BW transmission.


My lump' speedo is a bit nuts. I did it as I did not understand the mating of GM pulses to Jaguar pulse needs. So mine reads fast.


Over the years, I've measured its inaccuracy.


1. Drive at an indicated 60 mph and time how long it takes me from mile marker to mile marker. Erratic results at best.


2. Compare my speedo readings to the occasional radar trailer as I drive in my community. At an indicated 40 the radar says 25.


3. I compared the speedo numbers to my ancient Tomtom GPS. I forgot it's difference, but less error than the trailer method,


I know how to fix it and have the part, Someday, perhaps,.


Market in a bit. Early in the non AC Jaguar. Tired of being cold. Quite opposite for today.


Much house electrics yesterday. Part of the house went dark. After much jury rigging and travail, the local utility solved it. Just reset the master breaker. Still don't get it ? But, it is all back. Whee.
Jury rigs to undo. Fussiest is reseting my ancient answering machine!!!




Carl

 

No the misspelling comes from me posting from my Android phone. I corrected all the other fat finger nuances that always seem to happen when I email or text or whatever, but didn't see in time that SPEEDOMETER was spelled wrong in the title. When I did, which was almost immediately I tried to edit it, but maybe you can only edit the body of text and not the title?


Anyway... it's a 1975 XJ6C with 4.2l engine with a cable driven speedometer. And it reads a good 15% over consistently.

 

If the speedo is otherwise working OK then the error can be corrected by installing different drive and/or driven gears at the transmission or with a ratio adapter

See post #25 here:

https://www.jaguarforums.com/forum/x...-177670/page2/

I reckon the problem could be within the speedo itself but that's beyond my pay grade.

A change in tire size (smaller diameter) can also cause a too-high reading although 15% would require a radical change in size

A change a axle ratio will also change the speedo reading. For example, going from a 3.31 ratio to a 3.54 will make the speedo read too high, and vice-versa

Cheers
DD

 

I am not familiar with the cable driven speedometers on the earlier Jaguars, so my input is naught.
@JAGCAD:
On my lump I am using a new GM/Jag transducer from Andrew and had to play with different gears at the tail end of the 700R4. It took about 6 tries with different speedometer gears to get it where it is today. I am 2 mph off. When I am doing 80 mph the speedmeter reads 82.
Checked the correct speed by comparing actual speedometer reading and the reading on my GPS.
That is as close to perfect as I can get it. I am happy with it as it is.
Pic is the proper gear for closest speedometer reading. I broke this one due to improper installation and had to get another. Each speed gear is of a different color and come in pairs (drive and driven).

 

mine is and has always been 2.5 mph under the actual mph. No matter what size tires.

 

Sanchez:


I have the device to fix mine. Also sourced from Jaguar-Specialties.
but, done differently, to be spliced in to the wire from the PCM to the speedo.


But, I don't knw if my after market harness maker included that wire.
I do have instructions and the pin to do it, if it is missing,


But. as the car is running so nicely, not going to mess it up!!!


Carl

 

@ Jose: Are you saying that even the Jag OEM equipment(transducer and speedometer gauge) is off a little?

 

A 100% dead-nuts accurate speedometer on any car would probably be the exception rather than the rule.

Cheers
DD

 

I just put in a GPS speedometer from Speedhut, it fits the original Jaguar housing and is 100% accurate. I took new photos today of it installed in my S1 Jaguar.. has 0-60 timer, 1/4 mile timer, altimeter and odometer. The remote cable allows the selection of the choice of features and fits the same holder as the Jaguar speedo..

I took out the cable completely and the 90 degree adapter. After changing gears in the trans, changing the inside of the speedo to S3 stuff along with the odometer pieces, I gave up. The S1 speedos were never sold with heads for 2:88 gears..hence all the problems with Turns Per Mile (TPM).

It is a pleasure to have one that works perfectly.

 

Good solution, Roger.

Doesn't it make you a little crazy, though, that the tach and speedo are mis-matched? It would be an unbearable itch for me!

(Not a criticism. Just musing on a Sunday morning )

Cheers
DD

 

Not I ! On the freeway, I merely watch the tach and do not exceed
2K RPM and I seem to fit the moving traffic.


As for the speedo in the same traffic, just keep it at 80 or close.


So far so good, no speeding tickets !!!


Now, CA is on a mileage kick as to determining insurance premiums. So far OK, nuts Odometer reads have not hurt my wallet.


Getting hot. But I've set up my cool used zones system .


Out a bit ago to refresh Billy's water bucket. He is grazing away happily. Good goat, better lawn mower!!!


Guest cats got their kibble. Wet later by their cat lady mama !!


Carl

 

Yes, my insurance company accepts a photo annually..they know mine is correct.

Doug

No, not being the same is OK..I would rather have a good working speedo instead of an identical one that is a moron. I am going to take off the Green hoods on the tach lights (it has modern internals).

 

In Europe, all speedometers read 5% or more too high by default.
This safety margin is built in on purpose, to avoid claims on speeding tickets or to prevent that the speedo would read too low at any point.

 

Whew, I can just imagine a traffic magistrate or speed cop's reaction to a plea of innocence based on speedometer error. $$$$$$ coming out!!!


Carl

 

https://www.thecarexpert.co.uk/how-a...r-speedometer/