Subaru Differential Installation – Write Up 3/22/04

It’s true – I can’t leave well enough alone.  I’m starting to tinker with the idea of installing the 3.9l Rover V8 I have in my garage in this car.  There is no way the stock drive train will take that much power without modifications so I’ve decided to ditch the triumph parts and go with something more modern and maintainable.  The first step in redoing the rear end is to replace the stock differential with a newer unit.  I came across a website in New Zealand with a guy who had installed a Subaru / Datsun 510 rear diff into his car without modifying the frame.  After talking to him at length I decided to copy his route.  I wanted to install the differential without making any changes to the frame whatsoever.  This meant that Mike and I had to modify the differential to get it too fit.  We fabricated an adapter plate that converted the front four differential mounting bolts into the two triumph mounting bolts:

We also machined a replacement rear differential cover plate which allowed the differential to bolt right up into the spitfire frame the same way the triumph differential did.  Finally, we welded onto the differential a mounting plate for the leaf spring.  Although I want to end up with coil over shocks, to initially test this unit – I want to keep the stock swing-spring setup.

Three axle adapter plates were machined.  Two for the output shafts and one for the input shaft.   These plates converted the Datsun / Subaru bolt pattern to the triumph bolt pattern.  The output shaft adapter plates also made the width of the differential the same as the triumph unit so the stock half axles would bolt right on.  Installation of the unit took a few hours.

An update – (March 3rd 2002)

I’ve gotten quite a few emails over the past several years from people like you that have enjoyed looking at this site.  Some are just congratulatory, some ask for advice and some others who just want a little more detail on a particular section..  I’ve enjoyed receiving the emails and hope to get more in the future.  It’s been over two years since I pretty much finished putting the car back together and I wanted to let you know how the past few years have been. 

I didn’t rebuild the engine when I first went through this process (it seemed strong when I pulled it out) and in retrospect – this came back to bite me in the rear.  I just finished doing an engine swap on the car with another used spitfire engine that I had acquired.  This one doesn’t smoke like my old one was really starting to do all the time.  I also took this opportunity to get rid of the Monza exhaust system and put in a more stock arrangement.  Although the Monza looks cool with the four tail outlets – for me, it was just too darn loud.  I’d drive the car for about an hour and have to quit and boy – it almost hurt to drive with the top up!

My rear differential has also started to go – it makes an awful whine when driving over about 35 miles an hour – So, I’ve got to get this dealt with.  I also purchased, when I did the restoration, a new rear spring – man, this thing is crap.  the rear end already has sagged and needs work.  I have purchased a performance leaf spring for autocross applications that is supposedly much more heavy duty than the stock unit that I’m hoping will last considerably longer!  I also replaced the front springs with the units out of a MKIV – they were shorter than the later 1500 series springs and the front nose doesn’t stick up as badly anymore (it’ll totally get fixed with the correct leaf spring in the rear)  I still drive the car though – it’s a lot of fun.  I just didn’t want you guys thinking it stayed in my garage for months on end!

Installing of the newer engine:

Week 42: (July 18th 1999)


Well, It’s been a long process and I hope you enjoyed looking at the web site as much as I enjoyed working on the car and keeping this site up to date for you.  This page has a lot of pictures of the finished car for you to take a look at and so depending on your internet connection, this could take quite a while to load.  Please wait and enjoy the photos, I know they are worth it.

If you have any questions regarding the spitfire, how I approached a particular problem, comments, or for any other reason, please drop me a line at


Week 41: (July 11th 1999)

I did not get the gas tank back in time for this weekend so the leaky tank is still installed.  This will have to be done during the week.   I do have new tires installed as well as the front end has been aligned.  I asked the shop to bleed the brakes and they have informed me that the master cylinder is defective.  I have ordered a new unit and will install it as soon as I get the car back!  Last Wednesday after I got the car from the tires place I took the car to the painter.  The car is having it’s paint re-done in a few places (where I chipped it) as well as being buffed and wet sanded down in a few places.  I will post some photos of this later on in the week.  All that is left to be done is install the door glass, door trim, soft top, misc capping chrome, and the speakers.

Week 40: (July 5th 1999):

I do not have any photographs this week, sorry.  Anyhow, I noticed some gear grease on the floor underneath the rear differential this weekend as I was checking under the car.  The front pinion seal needs to be replaced.  Damn!  Why didn’t I do this when the differential was out of the car?  Now it’s all installed with the propeller shaft bolted up to it..  Crap…  Anyhow, I ordered a new pinion seal and unbolted the propeller shaft, followed the instructions in the Bentley manual and replaced the seal.  It is not leaking anymore!  This week I also had the windscreen professionally installed by the local speedy auto glass place.  They did quite a good job!  Other little tidbits were done like the sun visors, side view and rear view mirrors.  Another exciting thing happened and that is I drove the car for the first time.  Oh, this is going to be a lot of fun when it’s finished :).  However, The gas tank that is installed currently (the second one I have put in I might add)  has a leak around the seam where the float sensor is installed.  I have taken my spare fuel tank down to a local business that also refurbished my radiator.  I hope I can get the refurbished tank next week so I can install it.  Other things planned for next week include getting new tires installed and having the front end aligned.

Week 39: (June 27th 1999):

Man, it’s all the little things that take all of the time, let’s see if I can tell you what all happened this weekend.  I installed the hood, front headlights, headlight rims, side lights, hood support bar, wiper bezels, washer nozzles & associated hoses, handbrake console, knee pads, center support arch, radio, vented gas cap, rear vent line, aluminum valve cover (replaces the old orange metal one), brake and clutch rubber boots, handbrake grip, front foot carpets, tunnel cover carpet, recovered the metal glove box covers (w/ black vinyl).  From the top of my head, the following still needs to be done:

Front alignment, windscreen needs to be installed (it’s just sitting there right now), finish supporting the exhaust, grease two rear u-joints, install glove boxes, get the paint retouched where I’ve chipped it, install door glass, inner and outer glass scrapers, door panels, outer door handle, black trim, side and rear view mirrors, sun visors, glass handles, interior door handle bezel, and bleed the brakes.  Probably another weeks worth of work.  We’ll see.

Here are the photos, what do you think? Let me know!

Hood installed w/ headlights:

Steering wheel, handbrake cover, knee pads etc..:

Rear deck w/ seatbelts (and some speaker wires):

Radio installed:

Week 38: (June 20th 1999):

Slowly but surely, the car is starting to take shape. This week saw the installation of the hand brake, most of the carpet, the rear and side interior panels, seatbelts, and seats. The doors (which were installed last week) are shown in the following photos, the door handles have not yet been returned from the painter so I will wait until all that is installed before putting in the door glass and the door panels.

Here are the photos, what do you think? Let me know!!

Front image w/ grille, spoiler, front lights:

Picture of the seats installed:

Front dashboard finished w/ border trim, you can also see the handbrake and choke cable:

Rear trunk lid installed:

Week 37: (June 13th 1999):

Nothing really exciting happened this weekend and there are no photos. I managed to install the doors and the brake and clutch. I used DOT 5 Silicone fluid so when the fluid leaks (it’s a British car, it’s not a question of if, but when) the paint won’t be destroyed.

Week 36: (June 6th 1999):

Working on the electrical system this week, I installed the dashboard and all connections including heater, tach, gauges, lights, hazard switch, tail lights, indicators. I built a new wiring harness for the overdrive transmission. The rebuilt unit I bought did not come with one and so I used my other overdrive as a guide. The control switch has also been installed on the shift lever. Special thanks to Sam Gentry who did the walnut veneer on the dashboard. It looks VERY nice.


Dashboard & crash pad:

Another shot of the dash w/ overdrive switch visible: