I'm confused. Some places I read that the 2003 was the first year for the 4.2 and 6 speed. But other sites say 2002 on. I've always thought 2003 was the first upgrade year?

 

as far as I know 2003 is the first year for the 4.2 and the 6sp auto trans. maybe some late production 2002 were but as far as I know 2003 is first official year for the bigger motor (4hp) and the trans. I have to wonder though, WHY just 4 mor HP. Why not beef her up a little.

 

The 4.2 6 speed was released in 2002 in the UK.

 

A few more HP would have been sweet but I'm thinking they were trying to put out fires. ie cylinders,tensioners etc.
Actually I thought they were 300 hp? Now if I could change rear gears I'd be a very happy camper.

 

Ahh,that makes sense.

 

I read that the 4.2 was 294 HP.

 

Just read it went from 294 to 298. Just went for a ride. Played with a Porsche

 

edmunds, motortrend all say 294 HP, pre 2003 was 290 HP

 

Hmm, well I guess it not worth talking about then. 4hp 8 hp really it's boring

 

2003 began the much faster downshifting 6 speed ZF transmission. Used on both XK and XKR. No difference for accelerating off the line though.

Before that the XKR had the stout Mercedes Benz transmission that can be upgraded with blue top solinoids for faster shifting
BUT
the XK 2002 and earlier had a ZF 5 speed that was not nearly as stout and reliable

 

But the 5 speed can be reprogrammed for different rear gears.

 

changing rear gears is a big deal, you better love the car and plan to keep it if you plan to go there.

Make sure that tranny gets a thorough inspection by a shop that is very, very familiar with it. Place here in Denver that has seen hundreds as the tranny was in other cars too.

 

It's my understanding that with the six speed you can't change rear gears. No way to reprogram the computer for shift points. If I could I'd do it in a heart beat. I'm an ex drag racer changing rear gears doesn't bother me.

 

Several XKR owners here have done different rear ratio in conjunction with LSD install. White XKR advised me that rear ratio would probably provide more acceleration fun than either supercharger pulley upgrade but I found costs were at least twice as much. There was a different rear ratio for the Mexican market cars. I kept notes but don't have them at moment...