Car identification help plz

Hi all,
I have an XJ6 S1 i’m working on the get running, i have basic information about the series 1 numbers but these i don’t have so if anyone can fill in the blanks it would be greatly appreciated, the reason for this request is the car has a manual transmission (jaguar motor) but has an auto transmission console. Can’t find a year stamp anywhere.were there any manuals built around 1969 to 1970? i’m guessing that this S1 is about a 1970 and the manual was added in later as well the engine may be a reco as it’s been painted red, i’m hoping it’s a 4.2.
INFO> Car # 1L 12280 BW
Body # 4L 17811
Engine # 7L 23420-S (matches plate)
Gear Box # 15762

Jaguar heritage trust is your best bet.
I think it will cost you somewhere between 8 and 10 US dollars.
They’ll look it up and tell you what the car was new
what engine, transmission, and color. based upon the VIN.(you supply).

The BW in the car number would be for Borg Warner, i.e. automatic.

They did make manuals around this time, my car is manual from that period.

My car is 1L 25669BW - a 1972 original auto. My original engine has a 7L prefix and is a 4.2 litre. The “S” denotes 9:1 compression. Some were changed back on rebuild to allow for poorer fuels (post lead).

This may help.



Low, Standard, High?

Alle Jaguar Modelle wurden wurden auf verschiedenen Märkten mit verschienden Kompressionsverhältnissen angeboten. Die Regel war ein Kompressionsverhältnis von 8:1. 7:1 und 9:1 betrafen die frühen Mk 1. Das Suffix /7 /8 or /9 in der Motornummer gibt Rückschluss auf de Kompressionsverhältnis des jeweiligen Motors. Nach Dezember 1970 wurden die Suffixe -9 -8 oder -7 durch H (High), S (Standard), or L (Low).
Source, Sorry, German.

According to this you would have 8:1. correct?
Same as per Crespins‘ buying advice book: the 4.2 S1 XJ is 8:1.
So it’s a 4.2 manual conversion then. Lucky you I guess!


your manual tranny is certainly not original, as per the VIN.

It would be interesting to hear about the conversion: what kind of box do you have? Is it the car specific 4sp, 4sp/OD or the later (SIII) 5sp, or even different? Manuals were produced from the very beginning and quite popular in the low-specced 2.8 l cars, partly because these cars were designed to enter the volume selling fleet market and needed to be downgraded, partly because the anaemic engine was not the best candidate to feed the auto box enough power and torque. I doubt whether a register for the gearboxes exists.

If the ID plate is original and the engine no. is stamped on, you have “matching numbers” and the original engine. Of course, someone also may have fabricated the plate …

In any case, “7L” engines are 4.2 litre engines. They started with “1001” the first Jaguar SI car in September 1968. Numbers were used for all relevant cars (Jaguar and Daimler SWB or LWB) and carried over to SII. In September 1973 SII numbers started with 7L 74000. So 23420 could well be around 1970 - it is almost certainly not much younger than your car. The red color might be just a tell-tale sign for a later restoration.

Good luck


75 XJ6L 4.2 auto (UK spec)

Thanks everyone for your comments & i’ll respond to you all here in one swoop, the engine is a match to the car but has been a later reco, as for the manual gear box i’ve yet to determine what make & model it is, so if anyone knows where i should look on the box for this info let me know…i’m not familiar with the jag manual versions, we were led to believe it’s a 4 sp/OD…i’ll be under the car today & will know more…i’ll agree it’s more likely a 70’s build. i had a chat with our JDC registrar last night & he has plenty of book info to refer to…fingers crossed…lesson learnt:i was a bit too trusting that the owner was giving my friend (who secured the purchase) honest information about the car which is now turning out to be a bit of a dud but as i’ve been saying to many people over the decades “it’s not dead till “I” say it’s dead” so i’ll forge on and make it into something that some will want to have as a project…i’ll keep you all up to date…Tom @

The overdrive has the switch on the shift knob. The tail end of the gearbox is bigger as this is the bolted on overdrive unit.


both 4sp and 4sp/OD were used ex-factory. Different from later gearboxes and auto-boxes of the time I’d guess they were made by Jaguar, so there should not be any sign on them other than part numbers. The originals should look somewhat like these (you can even see the different lever knobs for standard and overdrive boxes.

Frankly, decades ago these Jaguar 4sp boxes were widely available. Nobody would have bothered to make do with a lumped gearbox. Only much later, when people wanted the benefit of an extra gear Getrag or ZF conversions for XK engines became popular. Maybe the job was done when the engine was reconditioned.

Good luck


75 XJ6L 4.2 auto (UK spec)

Nope. My car is a 9:1, same high domed pistons as my 3.8 E Type. Source English.

1 Like

Hi all,
thanks again for responses & i’ll reply to all in this post, the motor is a 4.2 Lt 9;1, i lifted the car yesterday & could see the extra extension on the back so it appears to be an O/D, will check the stick for switch again, still sorting out the carbs & ignition, finally have spark at points, disconnected choke as it’s flooding, got a new battery for it so hoping today is a better outcome…will give you update tomorrow…thanks.tom

Hi all, well this car keeps giving me curve balls that for sure, this switch is in the ski slope, appears to be a switch from a MK11 for auto & may be used as an OD switch for thus S1…yet to determine what’s it connected to…can’t drive the car yet - disc brakes binding up…


It is indeed a switch used with DG series automatic transmissions made by Borg Warner. Gives a hint as to the source of the gearbox? I guess repurposed as an O/D switch. Should be ideal as both control solenoids. The “real” switch position is in the middle of the shifter. Paul.

Paul is right for the XJ by which time they had dropped 7:1 versions of the XK. Prior to that the /7/8/9 and L/S/H suffixes were used. The engine size is of course cast very prominently into the RHS of the block. That’s RHS as in right hand side, not Racing/High/Standard, or Royal Horticultural Society :slight_smile:

However, like-for-like ratio, the piston crowns are always markedly higher on 3.8s, which is why they are more prone to pinking.

Hi all,
quick update about this XJ6 S1, i discover that the pass/side rear end has broken away from the mount rubbers so after some “friendly” conversation with the guy i got the car from he agreed to take the car back & full refund, i have lost a couple of hundred dollars & labor on it but better than a couple of $k…better luck next time i hope…