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space.gif (49 bytes) Mark Quarterbreed           John's Cars, Inc. space.gif (49 bytes)
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mark2bw.gif (7383 bytes) John's Cars is the home of half-breeds – 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 conversion:
+ Jag
+ GM T700
+ Jaguar
Which Marks are compatible with this conversion?

The Mark conversion kit is compatible with ALL Jaguar Mark Sedans.  This includes the Mark I, II, VII, IX, X, S-types, 420 and 420G.  This conversion kit will not fit any E-Type nor early Sedans.  Look closely at your car before you call.  I’ve seen many Mark cars retrofitted with another Mark series motor or an XJ series motor.  A little care goes a long way to making the job flow smoothly.

Why should I put a GM Transmission in my Mark?

Now that the 420 is back in Rockport after getting some minor tuning details attended to in Houston, I have had a chance to drive it at length. I can't begin to tell you what a difference the transmission swap out has made in that car. It no longer sounds like a horse shoe in the Liberty Bell when starting (ring gear engagement) and it lets the whole car feel like its breathing as it should. Had Jaguar put this 4sp in the car when new, they would have sold a million of them. It gets off the line much quicker than with the old B.W. 8 3sp. It cruises at 2400rpm at 70mph now instead or thrashing its guts out turning 3000rpm at 70mph. Instead of slamming the whole car with every shift, you can now barely feel the shifts. You have to really pay attention to what gear you are in. Its really a nice modification. I sure wish we had done it 25yrs ago. My wife loves it so we are now fighting to see who gets to drive it. I used to hate to drive it but not now. Many thanks. I wish you a lot of success with this new transplant.

Terry Brigham, 1999

The old Borg Warner DG (Detroit Gear) and its idiosyncrasies left a lot to be desired. A modern transmission with overdrive will amaze you. Prime benefits of the Quarterbreed conversion:

  • Strong and reliable – Jaguar started using a GM transmission in late 70's and Rolls-Royce has used them since 1969.
  • Quarterbreed cars are quicker – they have less mass, better gear ratios and stall speeds. They also have consistent upshift and downshift characteristics. The Mark's 3.54, 3.77, etc rear axle ratio greatly benefits from a GM overdrive, relaxing a buzzy 3000 RPM cruising speed to a calming 2100+.
  • Lower RPMs mean better gas mileage, less engine wear and tear, and a tremendously quieter car.
  • 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.
  • Your Quarterbreed will start faster too – the GM flywheel-starter combo produces more torque and faster cranking speeds. You'll eliminate the death-rattle flywheel and that $$$ Lucas starter.

Your Jaguar twin cam 6-cylinder is retained without mods to it or the car and the shifter retains its original appearance. I only recommend an overdrive transmission. This kit is for the T700R4, a.k.a T700 and 4L60. It will cost you 20% more but you will not regret the investment.

What else do I need to know?
The Mark Quarterbreed is more involved than a XJ6 because there is less space to work in.  Known peculiarities of the Mark Series and how they affect the installation are noted belowLook closely at your car before you call. I’ve seen many Mark cars retrofitted with another Mark series motor or an XJ series motor.  A little care goes a long way to making the job flow smoothly. Additional items not supplied in the kit that you have to think about:
Trans Cooler: You will need a remote transmission oil cooler (often called an auxiliary cooler). There is plenty of room behind the grille. The GM transmission must have a fluid cooler. We offer a universal transmission cooler kit. Universal means you fabricate the mounting brackets.
Oil Filter: If your oil filter assembly angles rearward (towards 8 o’clock) it will need to be changed. It will not clear the GM starter. I suggest using a 76-77 upright XJ6 assembly. It is a direct bolt on and it uses a spin on filter for easier oil changes.
Note: A small dent (about the diameter of a silver dollar and 1/2" deep) is required for speedometer angle drive. It is not visible or unsightly, even from under the car.
Manual to
If your Mark is a manual transmission and you are converting it to an automatic, you may need to widen the right hand side of the tunnel approximately 2 inches.
Cosmetics: Mark shifters were commonly Park-Neutral-Drive-Reverse !?   GM’s T700 trans has the familiar Park-Reverse-Neutral-Overdrive-Drive-Two-One pattern. I’ll also need to know if your car is column shift or dash mounted (Fan switch) style. A new gate for the fan style shifter is available with Park-Reverse-Neutral-______-______. Then use white 5/16" stick on letters to mark the new positions. The original shifter gate mechanism can be retained but the detents (pattern) will not match.  Later column shift models used the conventional pattern and I’ve been told they will interchange with the early column covers. I do not have any shifter/column parts -- you have to chase them.

This should cover the surprises, but please feel free to ask any questions I haven’t clarified here.

What is included in the Quarterbreed Kit and how much does it cost?
The Mark Quarterbreed Kit includes:
Mark QB Kit & Goodies
Mark Quarterbreed Kit $745.00
Oil filter adapter (w/new filter) 125.00
Trans cooler (w/hardware hose) 58.00
Driveshaft - ready to install 165.00
Gear Reduction Starter - faster cranking speed, less battery drag. 195.00
Electrolock Torque convertor lock up kit. 95.00
  • Block to transmission aluminum adapter plate
  • Crankshaft Adapter Flywheel (automatic)
  • Trans Crossmember and Mount
  • Cooler lines (automatic)
  • New Speedometer Cable (early models)
  • Angle Drive (early models)
  • Shifter Linkage/Cable (automatic)
  • Detent Cable Linkage (automatic)
  • Hardware and Brace for starter
  • Detailed step by step instructions
  • Lots of nuts, bolts, clamps and...

You furnish the GM transmission with torque-converter and starter (see the checklist below). Modify your driveshaft or we have driveshafts ready to install.  Check out the particulars in the Mark 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 To Order
Please fill out the Mark Quarterbreed Kit Order Sheet completely, sign it, and return it with a money order or cashiers check. Especially important is the engine number on the driver side bellhousing flange and the year of the GM transmission. We do not ship kits COD or accept credit cards on kits – plan ahead.  Please call before you order so we can go over the paperwork. Kits are in stock.

The Mark Quarterbreed 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.

Read our Customer Testimonials to hear what our customers think about us and our products.

If you have any questions about the conversion kit, please call or email markv6@johnscars.com.  Prices and kit contents are subject to change without notice.

Mark Quarterbreed Quick Start
Want to get ahead of the game?  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 for your transmission conversion 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.  Look closely at your Mark before you call. I’ve seen many Mark cars retrofitted with another Mark series motor or an XJ series motor.  A little care goes a long way to making the job flow smoothly.

Note:  John's Cars does not sell GM transmissions, you can find them readily at a local rebuilder. 

jrtip.jpg (3920 bytes) Whether this is your first Jaguar project or you are a seasoned professional, I wanted to make sure you understand that you don't have to remove the motor to put 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 Mark Quarterbreed in 10 to 14 hours.
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
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, you must use the T700R4 or else the shifter, mounts, speedo, etc. are not going to work properly.  Inspect the GM bellhousing for cracks around bolt mounting holes and for damaged/worn-out dowel pin holes.  Inspect shift shaft where the shift lever attaches.  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.  Don't worry about the year of the transmission as all are suitable for the power of your XK motor.

Lockup Transmission:   All T700's have torque-convertor lockup and it must be hooked up to prevent damage to the transmission.  John's Cars offers ELECTROLOCK™, the simple set-up to lock-up a T700 torque convertor for maximum fuel economy. Very easy to install – no drilling, tapping or machining required.  For T700 transmission to 1992 (not 4L60E).  The kit can be installed with the transmission in the car.

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.

jrtip.jpg (3920 bytes) 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 Holddown Yoke #1254856, but you’ve got to ASK!  Take your rebuilder a copy of this document so he will have a better idea on how to build your transmission.
And three matching bolts! The torque-convertor should be a balanced unit when you buy a rebuilt. Not all companies balance them. Be sure! Get the proper metric hardware to attach the convertor to flywheel – GM#1261968. We suggest a torque-convertor with an 1800 RPM stall speed (common in FI Camaro’s or Trans Am’s) to match your XK engine.
GM Metric
qbstarter.gif (1787 bytes)
Back of GM Starter

GM Metric Starter: Use a starter (with solenoid) for a 1982 Camaro 305 V8: GM S3553MS, S3502 or Delco #323-294 or 1109534 – it is 4" in diameter and has a straight across bolt pattern (not staggered).  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 #1978850.

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. 

Trans filler
tube and stick:
You need a dipstick and matching tube.  Universal tubes work in most applications.   For T700 use #T44494U.  Note:  Due to the many changes of carbs and throttle linkage over the years, you may have to bend/reshape the filler tube to clean.
Flywheel cover
and four bolts:
You need a flywheel cover and bolts.  T700 use #15650700.  Plastic covers are quieter and easier to trim, universal cover #K35803U.
Detent cable: Use: GM cable #25515598 with Seal #25518260.  
A one piece driveshaft is fine for your Mark. I suggest you wait until the transmission is in the car to measure the length of your driveshaft – use the sketch below. I can provide a driveshaft but I want the measurement from your installation. Usually it is easiest to get your own done locally.
markqbdriveshaft2.gif (3178 bytes)
Quick-Start Quarterbreed Hardware List
Item Qty T700
Starter 1
GM 1109524
Autozone 3602
Car Quest 03-846
Chief 3502
Delco 323-73
Lester 3502
NAPA 246-4813
Pep Boys 3602
Torque Convertor Bolts 3 Metric #1261968.
Filler tube and stick 1 T44494U
Flywheel cover 4 15650700
Detent Cable 1 25515598
Detent Cable Seal 1 25518260
Speedo Sleeve Retainer 1 1254856
Speedo gear clip 1 6261781
Detent/Speedo Cable Hardware 2 6mm 1.00 x 10mm
Mark Parts and Spares
John's Cars does not stock parts for the Mark Series except suspension and brake parts that are common with the later XJ Sedans and that giant leaping kitty on the bonnet.  Check out our XJ parts page for more details.
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Phone: (214) 426-4101
Fax: (214) 426-3116
800 Jaguar Lane
Dallas, TX 75226

2004 John's Cars, Inc.  All Rights Reserved.  Prices subject to change without notice.