||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:
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. Ive 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
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
- 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
- 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 below. Look closely at
your car before you call. Ive 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
||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.
||If your oil filter assembly angles rearward (towards 8 oclock) 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.
||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
|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.
||Mark shifters were commonly Park-Neutral-Drive-Reverse !?
GMs T700 trans has the familiar Park-Reverse-Neutral-Overdrive-Drive-Two-One
pattern. Ill 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 Ive 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
havent clarified here.
What is included in the Quarterbreed Kit and how much does it cost?
|The Mark Quarterbreed Kit includes:
QB Kit & Goodies
|Mark Quarterbreed Kit
|Oil filter adapter
|Trans cooler (w/hardware hose)
|Driveshaft - ready to install
|Gear Reduction Starter - faster cranking speed, less battery drag.
|Electrolock Torque convertor lock up kit.
- 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
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
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
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 firstname.lastname@example.org.
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 youre 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. Ive 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.
John's Cars does not sell GM transmissions, you can find them readily at a local
||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 Turbo Hydra-matic transmission brief ID course:
||Turbo Hydra-matic (THM)
||No separate tailhousing, light duty
3-speed, not suitable
||No separate tailhousing, 4-speed
overdrive (.67:1), no modulator
||Four bolt tailhousing, 3-speed,
vacuum modulator at rear of case
||Six bolt tailhousing, super duty
3-speed, vacuum modulator near filler tube
tailhousing, 4-speed overdrive (.70:1), no modulator, AKA T700, 4L60
||Electric shift version of T700, must
have a computer to operate
||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.
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.
||When you buy a rebuilt transmission,
youll get the case and guts only cables, bolts, etc. will be up to you.
Ive listed most items here but Im not there to know every detail. Most
often they will give you things like the speedo clip #6261781 or Holddown Yoke #1254856,
but youve 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 Camaros or Trans
Ams) to match your XK engine.
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
oclock 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.
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
and four bolts:
|You need a flywheel cover and bolts. T700 use #15650700.
Plastic covers are quieter and easier to trim, universal cover #K35803U.
||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.
Quarterbreed Hardware List
Car Quest 03-846
Pep Boys 3602
|Torque Convertor Bolts
|Filler tube and stick
|Detent Cable Seal
|Speedo Sleeve Retainer
|Speedo gear clip
|Detent/Speedo Cable Hardware
||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.