2003 XJ8 Sport LS2 Swap

Figured I should start a build thread for my project before it gets much further along - hopefully some of you find it interesting, and perhaps it can answer questions for anyone curious about such a swap.

Specifics so far: 2003 XJ8 Sport, Jaguar Specialties LS swap kit, 2006 GTO LS2, leaning heavily towards a T56 over the 4L60E at this point, limited slip 3.58 rear end, also weighing options on brake upgrades (Silverline vs. C5/6 vs. CTS-V or other).

Basic plan: 100% integrated, 100% functionality - OE at a glance utilizing the best blend of GM, Jaguar, and strategically selected aftermarket parts.

Progress to date: Old drivetrain out, LSD swapped in, engine bay prepped, just getting started with the harness in the car, JS mounts in the car and on the engine, waiting for oil pan modifications, reworking engine harness currently, and taking measurements for brake options.

In the time before I had purchased the kit or engine I figured I may as well detail the car: all seats and console removed, carpet shampooed, all leather scrubbed and cleaned, various repairs made throughout the interior. Exterior halfway through process of compound, polish, glaze, and wax, lenses polished and sealed, wheels cleaned and waxed, etc, etc, etc.

Fresh off the trailer after sitting a year (trans failure);


In the wash bay;








Tucked into the lab next to the ragamuffin XJ6;


About to pull a perfectly good engine;










Minimal cleaning in the engine bay required - very clean;




Diff stuff;


LSD 3.58;


X marks the spot;


Comparison of differentials and associated bracket (centered and offset);


Diff swapped and cleaned;




Camber shims between the axle and diff - 6mm for XJ40/X300 and 4mm for X308;


Cleaned all this like an insane person would;


Installed;


Observation; Jag coupler looks suspiciously like almost current GM coupler - DAMN, bolt pattern almost lined up…


Interior stuff - nothing too remarkable, lots of cleaning needed;






Baby steps in the brake department;


And the business;




For the coil covers I have considered Corvette, CTS-V, none, etc… but I think the GTO covers match the exterior paint well enough to leave alone.


Wiring - thank goodness for JTIS;


No wonder people put LS engines into anything - incredibly simple and standalone;


That’s all for now, folks. Progress to come...

 

Very nice. I look forward to following your build. I've built LS motors before (500rwhp in an '04 GTO and 720rwhp in a '11 Camaro SS), so this is something I'm considering for my "new" '94 XJS. In fact, that's why I chose an XJS with a high mileage 4.0 I6 - I think Jaguar fans would crucify me if I molested a V12.

If you don't mind, allow me to pick your brain:

1. I love the 6L80E and would love a 6-speed in the XJS. These are easy to find behind the G8 GT L76. So, what issues would there be in choosing a 6L over a 4L65E? Mainly concerned about mounting and driveshaft. Shifter can be figured out.

2. I haven't contacted Jaguar Specialties yet, but what exactly is involved the the GTO oil pan modifications?

I have lots more questions, but I'd also like to hear more about the brake and diff upgrade options. Mine has the 3.58 LSD, but I know it and the driveshaft/half-shafts won't hold the power I plan.

Meanwhile, I'll be working on getting my XJS up to spec on all maintenance and repairs, especially suspension. I look forward to enjoying it as is before I go crazy in it.

Padre

 

Definitely subscribed and looking forward to your progress! If you decide to go T56, please detail the installation steps, parts needed, etc..

Is it a bad thing I'm looking forward to an imminent trans failure in my superbly running, 75k mile, '02 VDP, just so I have an excuse to do the exact same swap??

 

Cool build! Looking forward to seeing your updates and how you overcome any difficulties you have along the way. I posted a thread of a really cool LS3 swapped XJ8 a while back but I think I will prefer the final product of yours as it will retain a stock sleeper look while still having a beast under the bonnet. How much power do you expect to be running when it's all done?

 

Outstanding! The 350 Chevy (GM) power-plant with a TH350 or 400 was a popular swap here in California. We even had a shop that specialized in that up in Orange County. You have taken it a millennium further. Thanks for the pics.

 

1: Assuming you mean "choosing a 6sp" not "6L", the T56 mount being further back is the primary concern. The JS AT adapter plate is pretty basic, but it may will go unused for the T56. I'm also not sure how the T56 will clear the OE trans crossmember. A conversation took place between Andrew at JS and I the other night, and he didn't make it sound like it would be too drastic, however didn't disclose any more information at that time.

As for the driveshaft, it isn't as simple as a coupler; anticipate working with a competent shop to build one for your application using parts of your old one.

2: Out of respect to Andrew's R&D, his provided manual is labeled "confidential". However I feel I can share that it's a pretty typical notch in the sump you'd see with any minor "crossmember meets oil pan" encounter.

Andrew is a great guy to work with - keep in mind this is his business. Part of the cost of the kit is his support, which is there for you the moment you become a customer.

The diff I used was just a low mile factory limited slip from an older model I had, all I did was swap the center diff and front bracket out and used the rest of the X308 rear end. The two lower bolts that secure the diff to the wishbone need to be swapped also and are a royal pain.

JagSTR2004, for now I want to leave the engine stock just to keep the swap simple. Once it's up and running and the kinks are ironed out, I'll certainly consider making some changes, or even build a different engine altogether to swap in. In the meantime, the factory numbers on the LS2 are 400HP and 400TQ - that's par with a 2004 XJR - I can live with that.

 

Nope. I meant 6L80E. Always been an automatic guy. I haven't seen anyone else do a 6L80E with the JS kit. Lucky me I have an axle shop up the road.

Nothing but respect for Andrew as I intend to buy the kit. Just need to know if the GTO pan is the only one that works so I can plan which motor/parts to buy. GM, Holley and some others offer aftermarket ones for swaps, and they may be just as easy to modify as the GTO, or they may fit outright.

Padre

 

Oh I see, I'm not familiar enough with the 6L80E to know why it couldn't be used; it's girth vs. the floorpan perhaps? Nothing a cut and reweld couldn't cure.

I waited until I had the kit to make an educated decision on the engine selection.......

 

Not a real technical post, just a glimpse into the complexity of the wiring. The JS swap manual points out the key wires needed which is literally less than a dozen in all this. I have two objectives in dismantling the harness; first is to not leave a huge mass of dead wiring in the car, and second is to re-purpose as many as I can such as battery positives, switched positives, grounds, and utilize existing Jaguar relays rather than wire in GM or aftermarket ones to support the LS system. The GM harness will be routed where the stock Jag harness was in the channel along the firewall, and the PCM will reside where the Jag unit once was.

Here's one example of a benefit to this approach; my application requires the use of a fuel tank pressure sensor, so rather than add a GM unit in somewhere (which JS suggests a simple solution to), I studied the operating voltage between the Jag and GM units (equivalent), and found the the corresponding wires to use the existing Jag FTP sensor with the GM PCM.

Small victories such as this will result in a better end product I believe. Progress is slow when you want it to work right.

 

Can hardly wait for the next installment!

 

Once again not a tech heavy post, just further down the wiring rabbit hole. All unused Jag wiring out, re-purposing what is left in the engine bay, and finally ready to integrate the GM harness(es). Modified the GTO PCM bracket and mounted it in the Jag "bucket-o-wires and relays". Yes, that's a level in the pic - don't judge me. Do it once, do it right.

 

Sweet

 

Ah! That was what I was going to ask.

Royal pain ... how so?

 

Looking great buddy, you won't regret taking the time to do it right keep it up!

 

There's some form of green Loctite on them making them extremely challenging to remove. I had to bolt the diff back on to the lower wishbone just to stand on it for leverage, and use the biggest pipe wrench I had to break them loose. Once removed I used a bench grinder and a file to smooth out the marring from the wrench.

Thanks, I feel overwhelmed every now and then, but it's all part of the journey of a project like this I suppose. I'd like to think I'm nearing the crest of the hump for the electrical work, sorting out the car side harness and making strategic removals was very time consuming. The GM side is pretty standalone only requiring a few connections that are now laid out.

 

Notes on brakes; while re-plumbing the hoses from rubber to stainless on my '69 Nova with C5 brakes I took the opportunity to see how the Jag penta wheel cleared the C5 calipers:


The clearance is good, though I know the rotor offset is different which will affect clearance between the caliper and wheel - I have a dimension comparison on my work computer I will check out tomorrow, my recollection is that is wasn't much. C5 brakes are big, cheap, and work exceptionally well on a street car. I haven't ruled out CTS-V calipers or current Cadillac Brembos:


Pedal assembly out; 2 out, 3 in - details on that may be a while:


Pulled the oil pan for modification, the bottom end looks great:


That's all for now, haven't had a lot of time to get anything real technical to post, just slowly chugging along.

 

I'm curious about the brake setup that you're planning.. Now you say that the C5 brakes are cheap, but what about the Cadillac Brembos? Those look fairly similar to the Brembos that came on the XJR 100/R1 package cars. I'm guessing the rotor size is different though. It would be cool to find an aftermarket or other brand caliper that could use the factory x308 big-brake rotors.

 

I've done some rotor comparisons and it's looking like a current model ATS Brembo Calipers would be a good match for the 325mm Jaguar rotors. The bolt spacing on the Cad calipers is 5" so it's not a bolt it, a custom bracket would be required. This may be a simpler route than the C5 stuff. I was going to attempt C5 calipers with modified GTO brackets, and modified C5 rotors (enlarge the center hole), but I think the Cad units are the way to go.

On a side note, I do know the C5 brake hoses work great because they are a metric bubble flare just just the Jag. When I put C5 brakes on my Nova I reflared the the standard lines using spare Jag tube nuts from an XJ40 I parted out.

 

More on brakes once parts are in, in the meantime the oil pan it out for modification, and back to wiring. LS2 harness sorted out and simplified, Jag harness stripped and labeled, Jaguar Specialties CAN module and voltage converter mounted - the ECU box will be crowded but all the business is in one place, and that means less clutter elsewhere.


More tomorrow! Cheers.

 

Good times