New on the market are valve bodies that make the overdrive work on the lower gears giving a broader shift range.

4L80E 6 Speed Valve Body?? - The BangShift.com Forums

I do not know if they will work on an XJR6 yet.

Richard Wright
96 XJR
3 XKE's
52 years of Jaguars

 

I've read up on these as well, and it does sound "interesting". There are a lot of more modern cars with similar HP as the X300 XJR but much quicker 0-60 times, and I have to think part of that is due to better transmission gearing that keeps the engine in its sweet spot.

But the kits I've seen need their own specialized controller, and I'm not sure how that would mate with already electronically controlled 4L80E in the XJR. Plus these kits aren't cheap.

Now if you already needed a rebuild, maybe worth toying with?

Would definitely be interesting to hear about anyone using one of these kits on the X300 XJR transmission, how they integrated it with the OEM transmission controls, and how it performed of course.

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Exactly.

But the kit being discussed splits the ratios.....which would be most useful if the 4L80 had deep transmission ratios to begin with. Which it doesn't.

Seems to me that a kit like this would help 0-60 times if the 1st and 2nd gear ratios were changed from the existing (and tall) 2.48 and 1.48 to something more like 3.25 and 2.00.

Cheers
DD

 

Curious: Not knowing enough about transmission building/rebuilding myself, can the 4L80E be rebuilt with different ratios, or is that not really changeable?

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Some specialty outfits offer alternate ratios for the old 400. TCI transmissions, for example. I strongly suspect they'd work in the 4L80 as well.

Cheers
DD