I’m new to the forum and I, like many others, have questions regarding a transmission swap for an XJS.
A guy mentioned he has a 4-speed gearbox from a v12 E-type (he didn’t say what year) laying around and said it should bolt right up to my 83 XJS 5,3 H.E and all I needed to do was find a clutch and flywheel. Is this true?
How long is the E-type 4-speed gearbox compared to the TH400 trans it currently has? Can I use the current propshaft and will the shifter line up properly?
Also, can the Getrag 265 from the 3,6 XJS be fitted to the bell housing of the 4-speed gearbox from the E-type?
Hopefully these aren’t silly questions. Thanks in advance.
Hi Karl-
Welcome! No silly questions. If you’re going to go to the work of doing a transmission conversion on an XJS, in my opinion, you’d want a five speed. The four-speed still gives you 1 to 1 in fourth, same as you have today with your TH 400. So you gain nothing in terms of highway cruising, although you’ll have an extra gear compared to what you have now.
The V12 e type bell housing will fit your v12.
The Getrag to eType bell housing is not a bad idea, in fact, I’m pretty sure people here have done it. You’ll need an adapter plate, but that’s not a big deal. That transmission, while not as stout as the T5 that most people use, will be just fine behind the V12 as long as you don’t beat on it.
Regardless, you’ll need a new prop shaft.
I did a five speed conversion on my XJS a little over a year ago, search for that thread for lots of detail on the minor roadblocks and headaches you are likely to discover with any manual transmission conversion. Think clutch, pilot bearing, and locator dowels for the bellhousing for starters. All will need to be figured out for your application.
I can’t speak for the TH400, but the manual box used in the LWB E Types, non o\d XJ6 and XJS is the same length as the BW Type 12, so uses the same mounts and propshaft. The V12 E box should be a straight swap onto your XJS using appropriate E Type or XJS parts as required, and IMO be a worthwhile swap. As mentioned, it won’t reduce revs at any given speed, but will make more of a driver’s car. IMO, 5 speed conversions look like more trouble than they are worth. Wouldn’t be a problem on some other cars, but it’s such a drama pulling the engine\box to rectify issues that you don’t want to do it more often than you need to.
A 5 speed conversion is no big deal. I did it last year on my 87 V12 using a Getrag gearbox. Simply Performance sells a kit with what you need. You do not have to pull the engine to do it. It is no harder than doing a swap with a Jaguar 4 speed. The conversion absolutely transforms the car. The TH400 was an awful match for the V12, whereas the 5 speed makes it a real driver’s car.
I have an XJ12 with HE and E Type 4 speed manual gearbox.
It’s way more fun than the slush box.
At first I used the 2.88 diff, but soon found it too tall. The gears the E Type 4 speed were designed to work with the 3.54 diffs they put in those cars. Once I put in a 3.54, it really moved!
Peter Crespin had some of the required parts a few years ago, maybe contact him.
Alright.
The rest of the car is far from pristine, so I want to see how cheap I could do a conversion, and many 5-speed kits are expensive. I was thinking I could get away with the 4-speed for cheap?
And do you really have to pull the whole engine to do it?
Thanks
Ok, sounds good.
What did you have to do for the prop shaft?
And did you run into problems with the bell housing dowels?
I can’t find good info on how the dowels were placed on the 83 HE and the S3 e-type?
Others can chime in, but I suspect the xjs wants to have the longer top cover (like the xj12 saloons) on the Jag box to make the gear lever come out in the right place. The etype wants the shorter top cover.
I still have the 87. The 4L80E auto transmission in the 95 is far, far better than the TH400 was in the 87. The transmission gearing and rear end ratio are much better matched to the engine characteristics. Of course the displacement increase helps some.
I changed the rear end in the 87 to the 3.54 used in the later cars. The overall gearing in 5th is almost identical to the 95. While the 4L80E is good, I may eventually convert the 95 to a manual, as the driving experience is so much better.
I understand that… I loved driving my 66 MGB back in the 60s. Then marriage and kids put me into family cars and auto trannies. A brief period in mid 70s we had a 5 speed Mercury version of the Ford Capri for about a year.
Fast forward to 2012 and I bought a 2003 Nissan 350Z. 6 speed and very nimble. Really a fun driver and the hydraulic clutch was nice and light.
I drove Skip Fritz’s 91 XJS which he had converted. Fun, but not enough to make me want to convert mine. But I admit to using S mode alot, and manually shifting. Especially gear down coming into a turn
I’m rather surprised that Jon was able to do his conversion without removing the engine; my manual states that the engine and gearbox should be removed together for both XJS manual and XJ12 auto configurations, and from my ( limited) experience, the area around the bellhousing is pretty tight in the XJ, and I assume the XJS is similar. But, if he says he did it, I have to believe him. Also says engine\box out for clutch work. Correct that XJ\XJS has different top cover to compensate for further forward location of engine compared to E Type.
This is an XJ6 box, same as V12 E, XJS, but XJ and XJS use this top cover, E Type has shorter extension. Bellhousing obviously different for V12. Overall length from front of bellhousing to rear flange the same as Type 12 BW, so rear mount goes straight into existing floor mounts on an XJ.
Yeah, getting the transmission out is pretty easy. Even the ROM says to do it without removing the engine. You need an engine support bar to hold the rear of the engine. You let the back of the engine/transmission down a bit to get the upper bellhousing bolts. I did it on my back using quickjacks to lift the car and a cheap Harbor Freight transmission jack and engine support crossbar.
Too bad you’re in the frozen north. I’ve got a 50k mile TH400 from my 87 that worked perfectly when I took it out. I’d let it go cheap to get it out of my garage.
Is the top cover somewhat easy to find and replace to fit an xjs?
Otherwise it sounds like I’m better off finding a getrag out of a 3,6 XJS (or a T5, though more expensive?) and get and adapter plate/bell for the 5,3?
And from what I’ve been able to gather, the E-type v12s had the dowels placed differently to my 83 H.E, so the bell housing wouldn’t quite fit anyways?
