Roamerdrive SS
Roamerdrive SS
Suitable for use in Land Rover Series vehicles
The SS ROAMERDRIVE is a modern overdrive designed for Land Rover Series models, providing smoother and quieter highway driving. Using advanced planetary gear technology, it delivers efficient lubrication even at high speeds and on steep inclines. The unit shares oil with the transfer case, ensuring long-term reliability with minimal maintenance.
What's Included
What's Included
- Overdrive unit with a stainless steel shift lever
- Dipstick assembly for monitoring transfer case oil levels
- Alternative filler plug in a new top cover plate
- Comprehensive installation instructions
Which models is this typically for?
Which models is this typically for?
The SS Overdrive has been designed for use in Land Rover Series vehicles and is generally compatible with the following models. However compatibility depends on your vehicles specific gearbox and transfer case. Contact us for assistance if you are unsure.
- Series 1 1946 - 1959
- Series 2 1958 - 1961
- Series 2A 1961 - 1971
- Series 3 1971 - 1985 (four and six-cylinder)
It will not fit the Series 1 V8 Models or those fitted with one-ton transfer cases.
Installation
Installation
Installing the SS Overdrive is straightforward and can be completed in approximately three hours with basic automotive tools such as a socket set, spanners, and a torque wrench. The unit is attached to the transfer case using the provided gasket and bolts, with the shift lever mounted on the right-hand side of the transmission tunnel. A dipstick assembly is included to monitor oil levels, ensuring your overdrive remains well-lubricated for long-term reliability.
Note: Some modification of the dipstick elbow may be required for Land Rover models prior to the Series IIA.
Important Installation Note
If you are using the SS Overdrive with a non-standard engine, you must install the SX-COV oil cooling transfer case cover to ensure proper cooling.
Download the full installation instructions below:
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ROAMERDRIVE Technology
All Garage Therapy overdrives utilize Global Roamer Corporation’s epicyclic gear train technology, also known as planetary gears, providing strength, silent operation, and proven reliability. This technology has been used in thousands of overdrive units worldwide, making it the gold standard for performance and durability.
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Fuel Efficiency & Reduced Engine Wear
By reducing engine RPM, Garage Therapy overdrives help you achieve better fuel economy while minimizing wear on your engine and drivetrain components. This results in lower maintenance costs and longer-lasting engine performance.
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Smooth, Quiet, and Reliable Performance
Garage Therapy overdrives are designed to deliver a quieter, more comfortable driving experience by reducing engine noise and vibrations. Built to handle both on-road cruising and off-road adventures, they provide reliable performance for years to come.
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All-Range Overdrive (Any Gear, High or Low Range)
Garage Therapy overdrives can be engaged in any gear, including reverse, and operate in both high and low range. This makes them an ideal solution for cruising on highways or tackling challenging off-road terrain.
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Precision Engineering
Each overdrive is precision-engineered using the latest manufacturing techniques to ensure durability and silent operation. High-quality bearings, retaining rings, and tightly machined components guarantee that every unit performs flawlessly under demanding conditions.
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Advanced design simulations
Nothing was left to chance in our pursuit of the most durable LT95 overdrive gearbox. The very latest analysis software was used to accurately predict thermal load sand component stresses. What we learn here is applied in the machine shop, so you’re not stuck on a mountain trying to guess what went wrong.
Frequently Asked Questions
Where are Garage Therapy Overdrives manufactured?
Our overdrives are manufactured in British Columbia, Canada and Perth, Australia.
Which Land Rover models can use a Garage Therapy Overdrive?
Garage Therapy Overdrives fit most Series and Defender models as well as some Range Rover and Discovery models with an integrated, LT230 or LT230Q transfer case. This includes:
- Series I, II, IIA, and III
- Stage One V8 (including ex-military models)
- Defender 90, 110, 127, and 130
- Perentie (ex-Australian Army)
- Range Rover Classic
- Discovery 1 and 2
- 101 Forward Control
If you’re unsure about compatibility, contact us for more details.
What are the benefits of installing a Garage Therapy Overdrive?
Garage Therapy Overdrives reduce engine RPM by 28%, making highway driving quieter and more fuel-efficient. They also reduce engine and drivetrain wear, act as a splitter gear for better performance on hills, and improve low-range capabilities in off-road conditions like sand and desert terrain.
What is the Power Capacity of the LT95 Overdrive?
The LT95 overdrive’s power-handling capability is governed primarily by torque rather than outright power. Its planetary gear assembly is designed to manage torque levels on par with those of the LT95 main gearbox. Planetary systems distribute loads over multiple gear teeth, resulting in notable strength and durability for their size. Nevertheless, the limiting factor in overall drivetrain integrity remains the main output shaft of the gearbox.
Under high-torque conditions, lateral forces produced by the transfer gears can cause excessive main shaft deflection. This deflection leads to uneven loading across the transfer gears, potentially resulting in gear tooth surface damage and, in the case of LT95A gearboxes, may cause failure of the intermediate transfer shaft retaining bolt.
To counteract these issues, this LT95 overdrive design includes an additional main bearing on the output shaft and an extra needle roller bearing in the coupling assembly, both of which mitigate shaft flex and enhance the rigidity of the transfer gear assembly.
Despite these reinforcements, shock loading—rather than peak engine torque—remains the primary cause of drivetrain failure. Consequently, proper driving technique is crucial in preserving drivetrain longevity under off-road conditions.
Large four-cylinder diesel engines such as the Isuzu 4BD1 frequently impose higher stresses on drivetrain components than high-torque gasoline V8s, due to their non-overlapping power strokes that generate higher peak torque. Engine manufacturers partially address this by increasing flywheel and clutch assembly inertia. However, adding an aftermarket turbocharger without a corresponding increase in flywheel inertia can intensify stress on drivetrain components.
Operating Temperatures and Cooling Considerations
Aside from ultimate strength concerns, elevated operating temperatures are commonplace due to the overdrive’s position behind the engine and main gearbox, where airflow is restricted. The LT95 transfer case itself is known to operate at high temperatures, often exceeding 100°C. With increased power demands, prolonged high-speed operation, and high ambient temperatures, the additional heat generated by the overdrive can push operating temperatures beyond the design limits of standard gear oil, leading to lubrication failure.
Even installing a finned transfer case cover may be insufficient to maintain safe oil temperatures in these conditions. In such scenarios, an external oil cooling circuit is recommended. Failures resulting from lubrication breakdown are not covered under our warranty.
How does a Garage Therapy Overdrive compare to a high-ratio transfer case?
Unlike a high-ratio transfer case, a Garage Therapy Overdrive can be engaged or disengaged at any time, reducing RPM by 28% without affecting low-range performance. High-ratio transfer cases make permanent changes to your gear ratios and often reduce off-road capability. They typically reduce RPM by only 15% or less and can make it harder to climb hills or handle heavy loads. Our overdrives are also easier to install and can be moved between vehicles if needed.
How easy is it to install a Garage Therapy Overdrive?
Most owners can install the overdrive in about 3 hours using standard tools.
- On Series models, a small hole must be drilled in the transmission tunnel for the shift lever.
- On Defenders, installation is a bolt-in job with no modifications to the bodywork.
What about servicing and maintenance?
Garage Therapy Overdrives are designed to be low-maintenance. They use transfer case oil, so there’s no separate oil reservoir to maintain. There are no dynamic seals, minimizing leaks, and they can be disassembled with common workshop tools. Parts like bearings and synchros are standard Land Rover components, making repairs simple and affordable.
Only use API GL4 75W90 oil in the transfer. Do not use GL5 or GL4/5 oils as these are designed for hypoid gear sets and often contain additives which may be corrosive to the internal bronze components used.
What oil can I use in the transfer case?
Only use API GL4 75W90 oil in the transfer. We recommend fully synthetic oil for high temperature climates or where high loads and extended high speeds are anticipated.
Do not use GL5 or GL4/5 oils as these are designed for hypoid gear sets and often contain additives which may be corrosive to the internal bronze components used.
For a comprehensive list of oils please see this document.
Can the overdrive handle upgraded engines?
Yes. On Series vehicles, the SS model can handle popular upgrades like the 200Tdi engine. In these cases, the SX-COV transfer case oil cooler is required. On Defenders, the DS model can handle up to 380 Nm of torque. For higher power outputs, it’s essential to install the DS-COV oil cooler and monitor oil temperatures to prevent overheating.
How reliable is a Garage Therapy Overdrive for expeditions?
Garage Therapy Overdrives are highly reliable for demanding expeditions. We recommend packing a basic seal and gasket set and your original drive gear and cover in your spares kit. Failures are extremely rare, but seal kits are available from our distributors if needed.
How does the shift mechanism work?
The shift mechanism is fully mechanical and easy to use.
- To engage: Press the clutch and move the lever forward.
- To disengage: Press the clutch and move the lever back.
The lever is mounted on the transmission tunnel for easy access.
Quality product, very well packaged. Excellent service and communication from Garage Therapy. The overdrive has transformed my Series Land Rover. Will recommend to a friend. Many thanks.
I've installed a Roamerdrive SS to my '69 109" Series 2A, and it has transformed the vehicle, much more relaxed driveability and will happily bowl along at 55 - 60mph with little more than a burble from the engine, infact the tyres are more noisy than anything! My Land Rover has the 2.5NA engine which drives the higher ratio with no bother. Fitting was straight forward, everything is very nicely engineered and it's evident that a lot of thought has gone into the design. Instructions are clear and concise, I did a couple of things "my way" as it worked better for me. I bent the operating lever so that it falls more conveniently to hand and it's a joy to use.
The Roamerdrive unit finally arrived in its little wooden box, giving the whole thing a touch of handmade quality. This impression is confirmed when opening the box and having a closer look at the unit itself, very clean and solid work.
The step-by-step fitting instruction makes the process of installing it an easy and straight forward operation. It's done and the unit is working. The reduction in RPM is immense and in the long run there will hopefully be a surprise when driving to the gas station.
This is a picture of my Series III which I own since 2005 when a good friend and very skilled (Landy) mechanic called me one evening asking: "Would you have some money for a car you actually don't need " (This was the night before I went to sea for six months.) The first two years my new car, (not having T V which is the German MOT) stayed in a friend's garage with its worn diesel engine, two broken windows and about two hundred other "diseases" on the to-do-list. After a long and even colder winter in our unheated workshop we finally went off on our first adventure trip. With new seats, canvas hood, parabolic springs and of course the 2.5 litre diesel engine providing enough power for the 4.7 to 1 Range differentials. Snow (canvas hood - do you remember ) and heavy traffic together with a broken alternator brought us close to giving up. But we finally managed the whole 450 kilometres to my father's garage, where the necessary repairs were made and the next day we received the certificate making my Landy a historic vehicle (over thirty years old and in more or less original condition).
I have been using the Series as an everyday drive for the last 15 months and every morning a little smile runs over my face when I see her parked next to all the family vans and far-east micro cars. In addition she carried my wife and me 1800 kilometres to our holiday destination and back with only one minor roadside repair last summer. Several long-distance runs and off-road tours with Defender driving friends were accomplished without any trouble.
The Roamerdrive has added a little comfort and we are looking forward to new adventures! Best regards from sunny Berlin!
On a recent trip to New Zealand's South Island. I covered about 5,000 kms both on and off road in 7 days of driving in my '96 300Tdi 90 truck cab, and it would have seemed a lot further without the overdrive!
The focus of my trip was to visit some of the old gold workings around Queenstown and Central Otago, but this photo was taken further North at dawn in the bed of the Wairau River near the Marlborough wine region (liquid gold!).
The Global Roamer overdrive has transformed the 90 into a viable choice for a trip like this!
"Finally got round to fitting the ROAMERDRIVE. A brilliant success thanks to your great engineering and clear fitting instructions! You might be interested to know, I fitted the ROAMERDRIVE to my 1991 Santana 2.5B DL. There are a number of differences but these ultimately made fitting the ROAMERDRIVE a breeze. Thanks once again to the whole team!"