Calibrating S3 speedo

[jagwit]

My car has the 3.31 diff and BW 3-sp auto gearbox.

Speedo reads 135km/h when doing 120km/h(GPS). What is the most cost effective method of fixing this? (I saw a thread which talks about different speedo's for different diff ratios but that solution would be too expensive.)

On my Jensen Interceptor with the Chrysler A727 3-sp auto, I have a similar problem but various "speedo drive pinion gears" are available (around $25) that can be fitted to the transmission to correct the speedo reading. Are such gears available for the BW?

[jagwit]

Just after typing the previous message, it occurred to me that another diff ratio might be a solution.

A 2.88 diff would give me 117km/h on the speedo for a true 120km/h... That also has the benefit of dropping cruising rpms by 400rpm, from 3300 to 2900 (still not enough IMO, but its something)

[MLBS3V12]

Hi Philip
You may discuss with
http://www.speedograph-richfield.com/
they look like to be a good way to get something accurate after your IRS modification with the 2.88 diff.
They have a specific service to calibrate the speedo at tour spec.
I use the same ratio on my car but a manual gearbox.
Michel

[jagwit]

Hi Philip
You may discuss with
http://www.speedograph-richfield.com/
they look like to be a good way to get something accurate after your IRS modification with the 2.88 diff.
They have a specific service to calibrate the speedo at tour spec.
I use the same ratio on my car but a manual gearbox.
Michel

Thank you Michel, I wrote to them.

[jagwit]

Thank you Michel, I wrote to them.

I received a reply from them stating that their RGB4604 box could do the trick @ GBP95.00. Trouble is that by the time I have it in my hands, freight, duties and VAT has been added and the cost has doubled. Still, good to know.

[abowie]

I stopped bothering.
Using a GPS and Tippex I have made 3 dots on the speedo glass in each of my cars, corresponding to 60, 100 and 110kph.

[AussieEtype]

If you give any decent instrument (speedo) repairer your wheel size, diff ratio etc that will be able to recalibrate the speedo - should even be able to redo it on the information you have - shows 135kph when doing 120kph.

My hand book indicates that it was only Canadian cars with had an auto had the 3.31 diff ratios and autos everywhere else has 3.07. So if originally a Canadian car has the speedo been changed or vice versa if it was not originally a Canadian car has the diff ratio been changed from 3.07 to what you have now and the speedo has not been changed.

So a bit more investigation/research is needed on your part.

Garry

[jagwit]

My hand book indicates that it was only Canadian cars with had an auto had the 3.31 diff ratios and autos everywhere else has 3.07.

Very interesting. This car is RHD. If it was a Canadian car, one wonders if perhaps somewhere along the line its been converted to RHD????

I'll try do some research as you suggest Gary.

[angelw]

Hello Jagwit,
3.31:1 ratio with auto transmission applied to early cars delivered to USA and Canada. However, all late model cars were 3.31:1 irrespective of destination.

Typical of E Type production, there will be smudging of that line during the transition, or perhaps even what was available when the car was coming down the line. For example, although not as significant as a transmission, I've seen numerous RHD, Australian delivered cars that have LHD wiper arms and wiper arm park position.

Regards,

Bill

[jagwit]

However, all late model cars were 3.31:1 irrespective of destination.

Hi Bill

Since mine is an Oct '71, I presume it does not qualify as "late", therefore it must be on of those that got what came down the line?

[angelw]

Hello Philip,
Your car definitely qualifies as an early car. Given that it is now RHD, the options are:
1. It started life as a manual car and somewhere in time it was converted to Auto. I don't believe many would do that, but who knows. You can determine the original transmission type from the VIN, the Auto cars are suffixed with BW. Interestingly, there is no difference in the transmission tunnel of Auto and Manual transmission S3 E-Types except for the removable top through which the gear lever passes. With S1 - S2 cars the tunnels are completely different.

2. It started life as a LHD USA/Canada delivered car and has been converted to RHD. If your car was originally RHD, the VIN will be in the range of 1S/50065 and 1S/52116. LHD Coupe VINs started at 1S/70524. From 1972 on, US delivered cars' VIN were prefixed with U.

3. It was a USA/Canada delivered car, ordered with RHD by a client working in these countries but knowing they will be returning to countries that drive on the Left side of the road. I've seen quite a few that fit this category over the years.

With regards to your question in another Thread, asking if the differential from an XJS can be swapped into an E-Type, I believe it will. I've not actually carried out this swap before, but we have an S3 E Type currently in work where the client has an XJS diff he wants installed in the car. In this case, the client wants the original diff centre from the E Type installed in the XJS diff housing and the assembly installed in the E Type. Accordingly, I'll be able to answer that question accurately in a couple of weeks. The advantage of this swap (although a lot of effort to do so) is the far better output shaft bearing system of the XJS.

The original output shafts bearings of the E Type are no longer available, irrespective of how much money you care to spend. The original bearings are 29mm wide, double row, angular contact, ball bearing race bearing. They have a split centre race that when assembled onto the output shaft, pre-loads the bearing. The replacement for this bearing is a 27mm wide, double row, angular contact, ball bearing race bearing, without the split inner race. Of course, this bearing requires that it be assembled with 2mm spacers. I've seen some horrible examples of these spacers being used.

Regards,

Bill

[jagwit]

Hello Philip,
Your car definitely qualifies as an early car. Given that it is now RHD, the options are:
1.You can determine the original transmission type from the VIN, the Auto cars are suffixed with BW.

2. It started life as a LHD USA/Canada delivered car and has been converted to RHD. If your car was originally RHD, the VIN will be in the range of 1S/50065 and 1S/52116. LHD Coupe VINs started at 1S/70524. From 1972 on, US delivered cars' VIN were prefixed with U.

Thanks Bill, very interesting indeed.

VIN: 1S 50810 BW

Therefore, the car was born as Auto.
Its always been RHD.

[AussieEtype]

XKdata shows this car was a South African car from the start so it should have a 3.07 diff ratio.

I guess it has been changed at some stage to whatever they had on hand at the time. Now if you are happy with the way the car drives with the 3.31 then fine - just get the speedo recalibrated.

If you are not happy with the 3.31 then I would be looking for an original 3.08 diff - if you want to go to a higer ratio diff (lower numbers) then fine and then also get the speedo recalibrated for the new diff.

Garry

[Dave123m]

Hi Philip,

As you recognised in your first post the Speedometer should indeed be matched to the Differential as the Gearbox Speedo Gear was constant for all diff combinations.

If a 3.07 BW Car (reading mph) your car should have the same numbers on the Speedo Face as mine, just above the centre of the Dial below the Trip Mileage:-

The speedo on my car says:-
SN 6322/08 ;1120 (as it's a UK 3.07 Differential Ratio car with mph)

Other Serial Number; Diff; Calibration (unconfirmed) as below:-
SN 6322/00; 3.31; mph
SN 6322/01; 3.31; kph (not for Germany/Italy)
SN 6322/02; 3.31; kph (Germany/Italy)
SN 6322/08; 3.07; mph
SN 6322/10; 3.07; kph (not for Germany/Italy)
SN 6322/11; 3.07; kph (Germany/Italy)

If you have a 3.31 Diff with a 3.07 Speedo the speedo will over-read (as yours appears to) so this should be very easily fixed by simply changing the speedo & whilst this could be expensive it won't be as expensive as changing the diff however this needs to be traded off against the benefit of the higher cruising speed.

Whilst clearly Jaguar didn't make an E-Type Speedo with a Serial Number for a 2.88 Diff but if you are certain of your current diff ratio then checking this may give you something to quickly check to see if the diff & speedo are still paired?

Hope this helps.

Dave

[jagwit]

Very good info, thank you Dave!!

Right, my speedo reads:
SN-6332/05A 700

This no is not on your list. But it is clear to me that the speedo should have been paired with a 3.07 diff, so either the diff was replaced with incorrect ratio or the speedo was replaced incorrectly calibrated version.

Replacing the diff with a 2.88 is by far the most attractive option as this will not only make the speedo much more accurate (albeit under reading by 2%) but for me the biggest win would be the longer legs, better economy, lower cruising RPMs.

I am SOOOOOO tempted to drop a GM 4L60 transmission into this car - if only I could know up front if it would fit. With a 0.7 4th, it would transform the car's cruising ability and return unheard of economy figures. The 3.06 1st would not hurt either.

[Dave123m]

Hi Philip,

Not exactly the same as yours but the below definitely shows 3.07 so well done confirming this.

SN 6322/10 ; 700; 3.07; kph
SN 6322/11 ; 700; 3.07; kph (Germany/Italy)

With regard to the 2.88 Diff Conversion this is a really satisfying & relatively simple process as per my other reply & with a standard Auto or 4 Speed Manual this is a great solution, I would definitely recommend this.

As an alternative I am not sure how readily available they are where you are but my Laycock Compact A Overdrive (I rebuilt it & uprated it with revised Friction Cone / stronger Piston Springs, uprated Spragg Clutch) has a 28% overdrive (0.78) 5th Gear & with the 2.88 it is just a little too lazy but it certainly is an effortless cruiser & much more pleasant to drive at speed than the standard combinations.

Whilst I'm going to keep the 2.88 for the future for 2017 I'm planning to remove it & replace it with the original 3.07 as I haven't tried this combination & am thinking it will give me a little more performance but with reasonable economy due to the overdrive.

My longterm plan is a 6.0l XJS 4 Speed Autobox (with overdriven 4th) but as I think the gearbox is controlled by the engine ECU it's something I still haven't had time to solve but hope to in time.

Good luck in all you do, if I can assist don't hesitate to ask.

Dave.