Is this possible? I thought when engines moved from 4ltr to 4.2, gearboxes moved to 6spd auto? Or was there a period with 4.2 and 5spd auto?

Thanks!!

 

My understanding is that the 4.2 engines were mated to the ZF 6HP26 transmission from day one of production....

 

^^ +1
The 4.2 motor may mechanically fit the Merc. transmission, but I suspect you would run into comms issues between engine & trans control modules

 

The 2002 XKR has the 4.0 engine with the Mercedes 5spd transmission I believe.

 

Hi!

In the United States, a 2002 model year XKR will have a 4.0L from the factory, not a 4.2L, It should have the Mercedes 722.6 aka W5A580 5 speed. The 5 speed Mercedes unit was/is one of the most robust transmissions coming out of europe.

If I owned a 2002 XKR, I wouldn't bother trying to fit a 4.2L engine in it. If power is concern, do some pulley swaps, improve the cooling, upgrade the intercooler pump, and have fun. If it's because mechanical failure, the older 4L lump should be cheaper anyway.

 

Don't be confused by the number on the shift bezel. This number is for the max gear you want the transmission not to go above, so it is a "5" for the 6 speed 6HP26, and a "4" for the 5 speed 5HP24. If you want the max gear to be the top gear, then you simply put it in "D". Hope this helps.

 

I was given wrong info. It was in fact a 4.0 after all.

Thinking of swapping my '98 xk8 4.0 for this '02 xkr 4.0

Worth the hassle?

Thanks guys!!

 

Everything else being equal the XKR is going to be the faster, more reliable car - how much is that worth to you? Once the tensioners have been upgraded (and the very last of the 4.0 cars had the latest versions) your 4.0 XKR is going to be every bit as reliable as the later 4.2 cars.

 

And given my own experience with both 5HP24 (4L N/A cars had these) and the 6HP26 (03+ all cars had) transmissions, the 5HP24 falls dead last as a terrible unit (have had one fail in a BMW 740i, one AWD variant fail in an Audi A4; both with only like 100k ish miles and service histories). The 6HP26 is a much improved unit, but still a little less robust than the W5A580/722.6 Mercedes unit in the 4L XKRs. Both the 6HP26 and Mercedes unit are great and with maintenance will likely last longer than you will keep the car, but the 722.6 is cheaper for parts, less likely to have issues, cheaper if you pay for a rebuild, and really a ROCK solid unit.

Really the complications you get from an R car combined with the overall improvements make it hard for me to recommend a XK8 4L car since the reliability improvements in the near same price range used 4L XKR make the car cheaper to own long term overall. They are just too close in price right now. On top of that, the R model has significantly more scoot.