Ahoy gents,
I’m playing around w idea of fitting another auto box to a 73’ E for better efficiency. I don’t wish to hack up the tunnel so can someone suggest a gearbox with a similar size as the original BW12?
I can make an adapter plate so I’m not concerned about that.
I fit a 4L60e in my 73’ XJ6 with little effort however I’m not sure if the 73’ E tunnel is smaller?
Would be nice to hear from those who have already done so.
Consider a TH400 that was fitted after the BW12 in many V12 jags - you get a 4 speed with 4th an overdrive and the torque converter is lockup so better fuel consumption. Fits an XJ that has had BW12 so should fit a Series 3 Etype. I have not done it though.
Fitting kit here https://www.johnscars.com/qb/v12qb.html (does say the Etype does require modification)
Garry
These TH 400 trannies you speak of, were they more talented outside of North America?
A TH400 transmission is a three speed transmission, not a four speed. A 4L80E would be a four speed transmission with an overdrive fourth gear but you need an electronic transmission shift computer to control it.
That John’s cars webpage you have referenced is for fitting a GM 700R4 transmission. The problem with a 700R4 is that it has strange gear ratios from what I have heard.
A few yrs back, 1 or 2, there was an article in Jaguar World magazine about replacing three speed auto transmissions with modern 6 speeds… can’t remember what brand, I assumed they were from Jags… I think it was a pricey option…
I wouldn’t even dream of it: I’d put in a more modern American gearbox, even if it meant putting in some kind of computer to control it. There just simply is no need for six speed anybox for a Jaguar.
I sure love the 6 speeds I have in my 2006 XK8 and my 2008 XJ8 1800 RPM at 65 mph
It may make for more efficiency, but the way my X100 is always changing up and down at normal cruising speeds is a PITA. My S1 XJ would pop into top at about 20mph, and there it would stay, the torque of the 4.2 took care of the rest, much more relaxing, and, seat of the pants, I think the XJ was quicker in those normal speed ranges. That said, I think the XK was better in that range than a V12 as well; I converted my S1 XJ12 to 4.2 power, so can make a reasonable assessment.
But, what’s the extra efficiency break even point with fitting a 4, 5 or 6 speed trans. How many miles, at a few mpg , at best, improvement in economy, will it take to pay for the cost of the “upgrade”? WOFTAM IMO, ( waste of F time and money)
Steven - yes you are quite right - I did mean to type T700. My bad - thanks for correcting.
At 3000+ rpm despite all the torque……
You‘ll save a bit of petrol money with overdrive and make as many miles, just at lower rpm.
I could take another gear for sure. Or a higher 3rd!
Thank you gents. I have decided to make another 4l60e work.
I installed one in my series 1 xj6 a few months ago and it really turned out great.
I agree wigs, having any more than 4-5 gears is ridiculous I think….
Fairly sure I seen people shoe horn 6-8 speed gearboxes in their e types via the internet. 
