OK, I don't really care about the gas mileage of my XJ-SC. Who cares if the girl you love drinks a little too much. :-) But this is a nice surprise. 15.9 mpg after a four hour cruise to get ice cream.

Happy cruising!

 

Some ice cream! Four hours to get...

 

The ice cream parlor is just an excuse to drive my Jaguar. :-)

 

After I installed the 4 speed auto I went into town which is about 50km each way, trip computer said 10l/100km which is 20.8mpg US.

4L60e and 3.58 rear end. Cruise 100km/h is 2000rpm.

The 4 speed auto is great.

 

The three speed automatic transmission definitely feels like there is a gear missing. I am still thinking about the $5k manual transmission that would make my XJ-SC go like an XK8.

 

You know, I've heard no end of praise for Nelsons, and it's definitely closer haha.

Seriously though, solid number for a hard drinking V12! Makes me wish my trip computer worked consistently!

 

Sure wish my XJS had a 4th or 5th gear. The TH 400 is a great and nearly bullet proof transmission but overdrive would help its drinking manners. I'd consider a TH 700 but have never heard it the swap is compatible.

 

Definite sign there is something wrong.





[kidding!]

 

That's not really that far off my three-speed. I get 2000 rpm at about 90 kph. I would have thought that the extra gearing would help more with lower speeds, getting up and moving. At least that's what I've read....

 

Warren is running a 3.58 diff.
I have a 4L80E in my 89 but stayed with the 2.88 diff giving me about 1800 rpm at 100 kph and average consumption figure of 10.4 litres per 100km.
My days of traction breaking take offs are over so don't tend to notice the down side to diff ratio.

 

So keeping the same diff and adding a gear drops the revs at higher speeds for better cruising economy, while changing the diff and adding a gear improves in-town performance?

 

I had a nice cruise this afternoon to take the wife to buy some dried firefly squid - using the expressway at between 110 kph and 120 kph on the way out, and normal roads on the way back, I managed about 16 mpg too, which pleased me. Especially as the expressway leg was actually 17 mpg, which is not too shabby, I think.

And talking of revs, at 120 kph my car was at 3,000 rpm bang on. 2,500 rpm is good for 110 kph. So they do climb faster once you're into three figures....

And sure, she drinks a bit much, but she is so smooth and sweet you forgive her....

 

Had to look that up. Looks Yummy

 

For her, not me....

 

Yes it is!
http://www.johnscars.com/qb/v12qb.html


I have consider it myself...
even not changing the rear from2.88 to 3.54
you still get a better 1st gear...
I did a speed in gears graph with the two plotted.. (I really did a Bunch of them with different transmissions selected, best way to make a decision, and I need to do a verses cost) I will see if I can find it...

 

In case you have not seen this yet, try this link https://www.jaguarhunter.org.au/Tech...00_gearboc.htm

 

I've decided to go back to the 2.88 rear as all of my driving is highway. That will have the engine at 1700rpm at 100km/h

 

Jonathon, Thanks. Very helpful. I think this is going to be added to my "to do" list. maybe not right away but at some point in the not indefinite future. For about $1000 it seems like there is nothing but huge upside in both performance and fuel economy. Lower rpms at highway speeds also means reduced engine wear.

 

I'm really glad I swapped to the 4L60e, makes the XJS a really relaxed cruiser.

Went into town today about 100km round trip and TC says 9.2L/100km which is US27mpg.