Jaguar XJ6 Quarterbreed Conversion

John's Cars is the home of halfbreeds – those wonderfully English cars with American drivelines. While not everyone loves my V8 conversions, most loathe the Borg-Warner (BW) automatic transmission. Time for another John's Cars exclusive retrofit:

Jaguar
Body

Jaguar
Motor

GM
Transmission

Jaguar
Suspension

QUARTERBREED (QB)

Which Jaguars are compatible with this conversion?

MORE QB's

Quarterbreed for XJ12
Quarterbreed for XJS
Quarterbreed for Marks

XJ6 Quarterbreed kits are for all 68 to 87 XJ6 models (XJ6, XJ6C, XJ6L). Kits for XJ12, XJS, Mark I, II, IX or X are available too. No kits for ETypes yet. The Jaguar T400 from later V12 engines and the German ZF transmission on 1988-on XJ6's (XJ40) will not bolt to a pre-88 Jaguar 6-cylinder nor to early V12s equipped with a Borg-Warner. There's never been a GM trans behind a Jaguar 6-cylinder until John's Cars Quarterbreed.

Why should I put a GM Transmission in my XJ6?

The archaic, light duty BW (derived from a 1962 Rambler design) and its idiosyncrasies are expelled by a GM Turbo Hydra-matic (THM) transmission. Prime benefits of the Quarterbreed conversion:

Strong and reliable – Jaguar uses a GM THM in their later V12 cars, Rolls-Royce has used them since 1969.
Quarterbreed cars are quicker – less mass, better gear ratios and stall speeds. They also have consistent upshift and downshift characteristics.
Older Jaguars with a 3.08, 3.31 or 3.54 rear axle ratio really benefit from a GM overdrive, relaxing a buzzy 3000 RPM cruising speed to a calming 2100+. Lower RPM means better gas mileage and less engine wear and tear.
Years later – if your Quarterbreed needs tranny service in Bass Lake, CA., you can have it repaired for a fraction of the BW price tag, not to mention the same day.
Faster Starts – the GM flywheel-starter combination creates more torque and cranks faster... Plus you'll eliminate the death rattle flywheel and the $$$ Lucas (Prince of Darkness) starter.
Finally, when your cat finally uses up all 9 lives and it’s time for a V8 – you will already have the transmission, starter and more. I will even allow you $200.00+ for the QB kit leftovers returned when you go Chevy V8.

The Jaguar twin cam 6-cylinder is retained without modification to it or the car. The shifter retains its original appearance. Check out our Customer Testimonials.

Which transmission should I use?

T350 for 1982 to 1987 Jags (with a 2.88 differential). Inexperienced drivers can lug the Jag motor (258 CID) when combined with a T700 30% overdrive and a 2.88 rear end.
T700 overdrive for pre-1982 cars (with a 3.08, 3.31 or 3.54 differential) to reduce cruising RPM.
T400 is not recommended as it is more involved and not necessary for the horsepower/torque of a 4.2L.
Don't use a 4L60E or 4L80E on your Quarterbreed.

What is included in the kit?

SHOW ME, TELL ME

If you want to know more, an abbreviated version of the Quarterbreed installation instructions is available for $25.00 (and I’ll credit it to your kit purchase). Part # QBXJ6SHOWME

block to transmission adapter
crankshaft adapter
transmission crossmember and mount
automatic flywheel
shifter linkage
speedometer hookup and calibration
transmission cooler lines
all the hardware
my infamous instructions!
100% bolt-in, of course.

You furnish the GM transmission with torque-converter and starter (see the checklist on the next page). Modify your driveshaft or we have driveshafts ready to install. Quarterbreed installation time is 5 to 10 hours – you do not have to remove the motor. All the particulars are supplied in the instructions. Check out the particulars in the Quarterbreed Quick Start below.

You may purchase via PayPal. But you will get better customer service and sometimes lower prices by ordering via telephone at (214)426-4100.

How much is an XJ6 Quarterbreed Kit?

XJ6 Quarterbreed Conversion Kits

Jaguar Model

T350 Trans

T700 Trans³

1969 to 1982 XJ6/XJ6C/XJ6L¹

$495.00

$545.00

1982 to 1987 XJ6¹

$595.00

$645.00

Driveshafts ready to install^{1, 2}

$165.00

Highlighted cells are suggested Jaguar Model & GM Transmission combinations
1	Prices include ground freight. Hawaii freight: add $35.00 for kits, $20.00 for driveshafts. Overnite freight to all 50 states: add $40.00 for kits. Call or email for freight overseas.
2	Return your leftover front driveshaft with yoke and flange for a $40.00 credit.
3	On T700 applications, manual low is not selectable because the XJ6 shifter does not have enough travel - just like the newer XJ6, GM police cars, and all Fords.

How To Order

Please fill out the XJ6 Quarterbreed Conversion Kit Order Sheet completely, sign it, and return it with a money order or cashiers check (no personal checks and no company checks). We do not accept credit cards on kits. We do not ship kits COD nor do we accept credit cards on kits. No exceptions! Especially important are the VIN, engine number on the driver's side of the bellhousing flange, and the year of the GM transmission. KITS are in STOCK and shipped upon receipt of funds.

The XJ6 Quarterbreed Conversion Kit Order Sheet is a JPEG image (about 185K) so it will take a minute or so to load. Print it out from a Laser, LED or ink-jet printer only – dot matrix printer will be useless. Make sure your print margins are set to .50 inches or it may not fit on a page. If you have any questions, please email them to qbxj6@johnscars.com.

1969 to 1979 XJ6: Please call before ordering the T700 as slight mods are necessary on some combinations.

Also, transmissions with a lock-up torque convertor require additional attention - see Lockup Transmission opposite.

Note: Given the proprietary nature of my conversion kits, I do not allow the return of a conversion kit for any reason.

Quarterbreed Quick Start

Here is a detailed check list for the items you furnish – another 30 minutes now could save you hours later! Start gathering what you need TODAY and order your Quarterbreed kit when you’re ready to roll!!! Preparation is the key to make things flow smoothly. Knowing what you are going to get before ordering will make both our lives simpler. Note: John's Cars does not sell GM transmissions – they are readily available from your local rebuilder. Hot rod transmissions are not needed or recommended in keeping with the character of a luxury car. I do not recommend any kind of shift improver kits -- you don't want slam shifts that spill your coffee -- Stock GM is the quality you want.

Whether this is your first project or you are a seasoned professional, I wanted to make sure you understand that you don't have to remove the motor to install in your Quarterbreed. Many manuals say that pulling the motor is the only way to change the transmission! It simply isn't true – you can do a Quarterbreed in 7 to 12 hours. No modifications/machining to the block or crankshaft are required.

GM Trans:

GM Turbo Hydra-matic transmission – brief ID course:

T	Turbo Hydra-matic (THM)
T200	No separate tailhousing, light duty 3-speed, not suitable
T200-4R	No separate tailhousing, 4-speed overdrive (.67:1), no modulator
T350	Four bolt tailhousing, 3-speed, vacuum modulator at rear of case
T400	Six bolt tailhousing, super duty 3-speed, vacuum modulator near filler tube
T700-R4	Four bolt tailhousing, 4-speed overdrive (.70:1), no modulator, AKA T700, 4L60 (not Corvette)
4L60E	Electric shift version of T700, must have a computer to operate
4L80E	Six bolt tailhousing, super duty 4-speed (.75:1), no speedo, computer required

Remember that the transmission type must be the same as you originally ordered or else the shifter, mounts, speedo, etc. are not going to work properly. The adaptor plate is drilled for Chevrolet or BOP (Buick, Olds, Pontiac) transmission cases. Inspect the GM bellhousing for cracks around bolt mounting holes and for damaged dowel pin holes. Inspect shift shaft where the shift lever attaches (make sure you have the shift shaft nut). Check the threads where the transmission mount bolts to the bottom of the case for damage. Make sure the transmission oil cooler fittings are in the GM case and are tight. Check case vent, modulator and modulator line as applicable. Note: The T700/4L60 Corvette trans does not have a transmission mount on the case – not suitable.

Lockup Transmissions: Transmissions that come with the torque-convertor lockup feature must be hooked up to prevent damage to the transmission. All T700 have torque-convertor lockup. Late model T350 transmissions were available with lockup torque convertors and can be identified by a blue 2 terminal connector on the left hand side of the case. John's Cars offers ELECTROLOCK™, the simple set-up to lock-up a T700 torque convertor for maximum fuel economy. Easy to install - no drilling, tapping or machining required. For T700 trans 82 to 92 (not 4L60E). The kit can be installed with the trans in the car. ELECTROLOCK™ is 85.00. If you are buying a rebuilt transmission with torque convertor lockup, tell them you want the trans to lockup on it own and they will do it (and you won't need Electrolock™).

Tailhousing: Inspect your tailhousing for wear inside the speedo gear hole – it should be polished but it must not be grooved or the speedo gears will fail. You'll need the matching speedo sleeve retainer.

T350 with 6" Tailhousing Notes: You must have the tailhousing with the small (13/16") speedometer gear hole GM #464193 to use the speedometer gears furnished in the kit. Exchange a tailhousing with large speedo hole for one with a small hole when buying your transmission or I can supply a refurbished tailhousing with new bushing and seal for $25.00, JCI Part #6"TAIL.

Torque-convertor and bolts: I recommend a torque-convertor with a higher stall speed (from a fuel injected Camaro or Trans Am). The torque-convertor should be a balanced unit when you buy a rebuilt. Not all companies balance them. Be sure! Get the proper hardware (3 bolts) to attach the convertor to the flywheel – bolts are either 3/8 NC #3987930 or metric #1261968.

Misc: When buying your trans, make sure you get a speedo clip (#6261781). If you use a T700, you also need a holddown yoke (#1254856).

1) Buy the torque convertor from the same guy as your transmission. 2) If you are buying a rebuilt transmission with torque convertor lockup, tell them you want the transmission to lockup on its own. 3) When you buy a rebuilt transmission, you'll get the case and guts only – cables, bolts, etc. will be up to you. I've listed most items here but I'm not there to know every detail. Most often they will give you things like the speedo clip #6261781 or T700 holddown yoke #1254856, but you've got to ASK! Most 1980 trans are metric – all T700 are metric.

Torque
Converter:

I recommend a torque-convertor with a higher stall speed (from a fuel injected Camaro or Trans Am). The torque-convertor should be a balanced unit when you buy a rebuilt. Not all companies balance them. Be sure! Get the proper hardware to attach the convertor to flywheel – 3/8 NC #3987930 or metric #1261968.

GM Metric
Starter:

Back of GM Starter

Use a starter (with solenoid) for a 1982 Camaro 305 V8, S3502MS or Delco Metric #1261968 – it is 4" in diameter and has a straight across bolt pattern (not staggered). Some people won’t like this starter, but be assured it is more than adequate to turn over a Jaguar six cylinder. A big case GM starter will not clear the oil pan.

Starter Nose: Be sure the kit starter bolts fit the nose properly. Drill or ream the holes in the nose if necessary. If you already have a metric starter but it has a staggered nose, the correct nose is GM #1986096.

Starter Stud: The starter should have a stud extending from it (at the 4 o’clock position) for the "L" brace to attach to. Part number for the stud if it is missing or damaged is GM #1979441. The nut is supplied with the kit. This brace is very important – you cannot install the stud with the starter in the car – do it now! Verify the back of the starter has the bolt and stud at the same locations as illustrated.

Filler Tube
and stick:

You need a dipstick and matching tube. Universal tubes work in most applications. For T350 use #K35999U, for T700 use #T44494U.

Flywheel cover
and four bolts:

You need a flywheel cover and bolts. T350 use GM#14038632, T700 use #15650700. Replacement plastic covers are quieter and easier to trim, universal cover #K35803U.

Detent cable:

These instructions use the following names interchangeably: Kickdown/KD, downshift, throttle pressure, detent, and TV (throttle valve) cable. If you don’t have a cable:

T350: GM cable #25507541 with Seal #1262475
T700: GM cable #25515598 with Seal #25518260

AND

matching bolt, either
1/4" NC x .5" or 6mm 1.00 x 10mm

Modified
Driveshaft:

I prefer to modify the front half of the Jaguar 2 piece driveshaft assembly and replace the Jaguar slip yoke with a GM one. Any driveshaft shop can do this for you. They’ll cut off the STUB of the shaft and fit a new weld yoke at the dimension specified. I suggest you use a Spicer slip yoke 2-3-6361X. Length provided when you order the kit.

Quick-Start Quarterbreed Hardware List

Item

Qty

T350

T700

Starter

GM 1977194
Autozone 3602
Car Quest 03-846
Chief 3502

Delco 323-73
Lester 3502
NAPA 246-4813
Pep Boys 3602

Torque Convertor Bolts

3/8" NC #3987930 or metric #1261968.

Filler tube and stick

K35999U

T44494U

Flywheel cover bolts

14038632

15650700

Detent Cable

25507541

25515598

Detent Cable Seal

1262475

25518260

Speedo Sleeve Retainer

3708148

1254856

Speedo gear clip

6261781

Detent/Speedo Cable Hardware

1/4" NC x .5" or 6mm 1.00 x 10mm

Other Look Fors

Here are items you might find while doing the Quarterbreed Conversion... better to check them out now than have them "find" you later.

Catalytic Convertor Cracks:	The forward catalytic convertor (at the manifold) has a history of cracking. Listen for exhaust leaks before you start – it is no fun to have to pull it off when you thought you were finished, besides the customer expecting you to PAY FOR IT! We have replacements for $285.00.
Shift Cable Failure:	Series 3 cars have a history of shift cable failure. The cable was downsized and will kink if forced. Parking against curb stops and on an incline are the usual cause of kinking when pulling the transmission out of park. Use the hand brake and don’t force the shifter. The kink will occur inside the console at the shift lever.
Cruise Control Operation:	On Series 3 models, take a drive (if the vehicle still drives) and test the cruise control before you start – about 50% of the units DO NOT work. Cruise only functions in the "D" position.
Center Support Bearing Wear:	If you have time before starting this project, pry on the center support bearing to see if it is shot. Usually 75,000 miles or that THUMP, THUMP on acceleration is a sure sign. Jaguar Part # EBC9040 at $64.95 from JCI with the purchase of your QB kit.
Shifter Position on Overdrives:	Park, Reverse, and Neutral positions stay the same as before. Overdrive position of the T700 will be the "D" (drive) position on the shifter, direct drive is "2" (second) on the shifter, while second gear is 1 (first) on the shifter. The shifter does not go far enough to "hold" 1^st gear. You can modify your shifter if this is a must for you. I do not offer a modified shift mechanism nor a modified shift indicator plate.

Jaguar Parts and Spares

John's Cars is more than Jaguar conversions, we also stock a full line of Jaguar Part and Spares (new, used, rebuilt and aftermarket), available on our on-line catalog.