Adding a Toyota 5-speed to a Triumph TR6

[Editor's Note: This article originally appeared in the March 2014 issue of Classic Motorsports.]

In the world of ’60s British roadsters, the Triumph TR is a standout. However, even a well-sorted TR6 has a few weak spots, and the transmission is one of them. The four-speed box is nice, but the car really needs an overdrive or fifth gear to purr instead of howl at highway speeds. Our 1969 Triumph TR6 would definitely benefit from that extra cog.

Sure, a Laycock de Normanville overdrive unit was a factory option when these cars were new, but it was rare then and is even rarer today. Finding one that isn’t worn out is rarer still. This overdrive unit can be made to work, but it’s also heavy, expensive to restore, and a bit cantankerous to maintain.

Through the years, enthusiasts have figured out how to install any number of five-speed transmissions into a Triumph TR. They’ve used everything from Ford T-5s to units from Ford Sierras, Nissans and Toyotas, but these swaps have had varying levels of success.

Swapping a five-speed into an old TR is rather tough. In addition to simply finding the space for the new transmission, you have to figure out how to mate it to your engine, clutch and driveshaft. Then you have to get the shifter to appear in the right location. As you can imagine, compromises are common.

Herman Had a Better Idea

Retired machinist and Triumph enthusiast Herman van den Akker decided this swap didn’t have to be so difficult. He designed a kit for installing an ’80s or ’90s Toyota five-speed transmission into a TR, and it has really set the Triumph world on its ear.

The HVDA Triumph Transmission Conversion Kit offers everything you need to make this swap, including a 32-page booklet and instructional DVD explaining the process in uncanny detail. Designed for all TRs–from the first TR2 to the last TR6–this kit comes in different variations depending on the car.

The kit doesn’t include the actual transmission, but HVDA can refer you to a couple of suppliers of rebuilt transmissions that include a one-year warranty. You can easily source one for less via eBay Motors or your local junkyard, but we decided to take up HVDA on their offer. Their transmissions carry a warranty, and we figured that using one would ensure we didn’t run into fitment issues.

The installation itself is very straightforward. First, you yank your old transmission–you can do this from inside the car once you remove the transmission cover and some interior pieces. Just disconnect the bolts at the bell housing, unhook the hydraulic clutch, undo the driveshaft and transmission mounts, and remove your original transmission.

Here’s a trick that can help. Before unhooking the transmission, stick a block of wood behind the engine. Unless you have a jack under the back of the engine, it will fall backward once the transmission is unhooked.

With the driveshaft removed, move the transmission back–a floor jack underneath it makes this easier–then up and out of the car.

The HVDA five-speed swap doesn’t require a lift, as the gearbox can be accessed from inside the car–just remove the transmission cover and a few small interior pieces.

Prepping for Transplant

Now you can prep the Toyota transmission for installation. First, remove its original bell housing and install the one supplied with the HDVA kit.

Next, the shifter adaptor–another piece supplied with the kit. Van den Akker came up with a solution that retains the original Triumph shift lever and even places it in the proper spot. The conversion is imperceptible unless you crawl underneath the car.

The conversion retains the original Triumph clutch master cylinder, but it eliminates the slave cylinder, cross shaft and throw out arm.

A supplied adaptor connects the new Quarter Master hydraulic throwout bearing to the rest of the system. This step takes some careful measurements, but the instructions fully explain the process.

The kit uses the stock TR pressure plate and includes a new pilot bushing. If you have a four-cylinder TR, you’ll need to purchase a TR6 pressure plate. You’ll also need to get your flywheel machined to accept the TR6 pressure plate.

HVDA includes all of the required extras, too, like this aluminum block that positions the Toyota shift lever in the proper spot.

They even include the pilot bushing needed to mate the Toyota input shaft to the Triumph engine.

More details: A clamping ring keeps the driveshaft at the proper length, while the swap retains the original Triumph rubber mounts.

The HDVA conversion kit includes a new Quarter Master throw-out bearing, and some simple measurements will tell you how many shims to install.

Next, install your new transmission using the included mounts. From there, adjust the driveshaft length using the supplied tightening ring. Once everything is back together, install the speedometer cable, calibrate the speedometer, and hook up the backup light switch.

At this stage, we filled the transmission with Red Line manual transmission oil. We’ve had very good luck with Red Line oils and transmission products in our TR race car, and more often than not, we use their manual transmission oil in our project cars.

Five Speeds for Fun

Before attempting this swap, we took our car for some baseline runs on its stock-sized 185R15 Vredestein Classic tires.

We turned 3500 rpm at 70 mph, and our 103.3-mile test loop yielded 22.4 mpg. After the swap–no other changes were made–we got 25.7 mpg on the same loop. Our engine speed at 70 mph dropped to 2800 rpm.

The swap saves some weight, too, as the Triumph transmission is about 10 pounds heavier than the Toyota unit. Then there’s the extra weight of the Triumph overdrive–about another 50 pounds.

Perhaps more important than the numbers is the feel. Though our Triumph four-speed unit was recently rebuilt, it was still a bit notchy. The Toyota transmission, on the other hand, simply shifts beautifully. The gear spacing is perfect for the Triumph–much nicer than the stock ratios.

It took a couple of days, but we solved one of the Triumph TR’s main weaknesses. We can now take this car on the highway or on a 1000-mile tour effortlessly.

Sources:

One More Thing

After the transmission swap was tested and in the books, we had a little more work planned for our 1969 Triumph TR6: swapping out the stock exhaust for a Tourist Trophy system. We’ll cut to the chase: This polished stainless steel exhaust system is a work of art. The build quality is excellent.

It’s technically designed for the 1972-and-newer TR6, but we’d already converted our car to the later, dual-exhaust setup. We haven’t dynoed the new system, but it does sound tough–a bit throatier than the Moss stock system previously on the car. Tourist Trophy systems for other popular British sports cars are also available through Moss Motors.

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Comments

Gary SuperDork
9/26/18 9:34 p.m.

Well, I have a terminally garage-bound '68 Spitfire. But I have learned a lot from it. And that's why I bought it originally. I definitely learned a lot. One of my desires is a roadworthy TR6, and my budget definitely permits this. I would definitely go for a 5-speed conversion. Then again, how do I want to maximize my available capital? I saw a beautiful 912 for sale in LA selling for about as much as I'd have to put into a TR6 to make it as nice. I'm not bragging, but it's good to have the financial resources to make these choices. I will have a great car.

wspohn Dork
10/2/18 11:06 a.m.

Seems a retrograde step to take a car that had an optional 7 speed gearbox (or 'only' 6 speed, if you have the later J type OD unit) and putting a 5 speed box in it, although I agree about the scarcity factor.

Personally I much prefer OD stock box - if you are driving along a winding road in Autumn enjoying Fall colours, you can flip back and forth between 3rd and 3rd OD by flicking a switch, without touching the gearshift.

I've done both, and have a T5 in my rebodied MGA with V6 - the shifter ended up located just right; not sure how that would work out on a TR.

Tim Suddard Publisher
10/8/18 7:17 a.m.

The shifter does come out in the right place and our TR6 did not have the overdrive. While I like the overdrives, they are delicate, heavy, and getting harder and harder to find and rebuild. When we moved our TR3 from overdrive to T5 five-speed, we knocked over 50 pounds out of the car.

eastlex91 New Reader
1/15/24 10:32 a.m.

Great article on the HVDA 5-speed conversion. I have a '73 with no overdrive and the Toyota trans made my car much more enjoyable to drive. The gear selection is more precise and slightly shorter, so even around town, it's much better. While it is an expensive upgrade, you will never regret the HVDA conversion. I am still considering the Nissan LSD swap - do you have any thoughts on that?

Rayt53 New Reader
4/5/24 2:15 p.m.

In reply to eastlex91 :

I need help in finding a replacement speedo cable for my HDVA tr6 to Toyota conversion. Any help would be much appreciated.

rayt@supplysourceinc.com

wspohn UltraDork
4/7/24 6:14 p.m.

Tim Suddard said:
The shifter does come out in the right place and our TR6 did not have the overdrive. While I like the overdrives, they are delicate, heavy, and getting harder and harder to find and rebuild. When we moved our TR3 from overdrive to T5 five-speed, we knocked over 50 pounds out of the car.

I haven't found the ODs to be delicate at all if treated the way they should be - I even raced with them in two of my MG based race cars (they use the smaller and theoretically more delicate Laycock). Definitely avoid holding your foot to the floor when you flick the OD switch, though. Have also used them on my TR2 through 4As and in my MGC.

No argument about either weight or using the T5 - I used that trans in another of my sports cars and it is smooth and deals well with a couple of hundred BHP - you want the later World Class version and you have to carefully pick your gear ratios - many cars that came with them had stupidly low gear ratios,