FAQ's
Following are some questions that our customers ask
We hope our answers are helpful to you.
Q: Where are ROVERDRIVES manufactured?
A: In British Columbia on the Pacific Coast of Canada.
Q: What Models of Land Rover can be fitted with a ROVERDRIVE?
A: The following Land Rover models can be fitted with a ROVERDRIVE:
- Series I, II, IIA and III models with four and six cylinder engines
- Five speed Defender 90, 110 and 130 models with C suffix or later transfer cases
Q: What Models of Land Rover can not be fitted with a ROVERDRIVE?
A: At present we do not make an overdrive to fit the four speed LT95 gearbox. This means you cannot fit a ROVERDRIVE to a 90, 109 or 110 model with a V8 motor or an early Australian ISUZU MD11B motor.
Q: What are the benefits of fitting a ROVERDRIVE to a Land Rover?
A: The ROVERDRIVE will give you the following advantages:
- When engaged, the ROVERDRIVE reduces engine RPM by 28% in any gear
- Used in top gear on the highway, fuel consumption is reduced and the vehicle is quieter and more fun to drive
- The ROVERDRIVE also reduces wear on the engine and drive components
- It can be used as a splitter gear between the standard gears when climbing long hills
- When engaged in low range, it increases ground speed which can be useful in sand conditions such as deserts
Q: Can a ROVERDRIVE be compared to a high ratio transfer case? (see discussion below)
A: No, a ROVERDRIVE cannot be compared to a high ratio transfer case.
Unlike the high ratio transfer case, the ROVERDRIVE does not permanently alter the gear ratios on the gearbox, so overall vehicle capabilities are not compromised.
The usual high ratio transfer case offered on Series vehicles raises all the gear ratios 32% making the standard engine too weak to pull the vehicle up a hill in fourth gear. On 90,110 and 130 models the high ratio transfer case not only degrades lower gear performance but decreases engine RPM on the highway by only 15%, versus 28% with the ROVERDRIVE.
The ROVERDRIVE is also considerably easier to fit than a high ratio transfer case and can easily be moved between vehicles if required.
In our opinion, a high ratio transfer case is only viable on Land Rovers used primarily on motorways.
Q: Is the ROVERDRIVE similar to the SANTANA, BEARMACH or FAIREY units?
A: No, the ROVERDRIVE is very different than these older units.
-
The above named units use spur gear trains that become very noisy as they wear
-
They have separate oil reservoirs which are prone to leaks and fine tooth couplings with needle thrust bearings which are prone to failure
-
These older generation overdrives do not have the power transmission capability of the ROVERDRIVE which employs an epicyclical gear train similar to an automatic transmission
Q: Is the ROVERDRIVE similar to the now discontinued GKN overdrive unit?
A. The only similarity between the GKN and the ROVERDRIVE is in the use of an epicyclical gear train which reduces engine RPM by 28%.
However, the ROVERDRIVE is a more robust unit than the GKN with stronger gearing.
Another significant difference is that the ROVERDRIVE has no complicated electronic or hydraulic controls and no slip clutches. To engage the ROVERDRIVE you move a neat lever in the cab and the action is purely mechanical.
Another feature that sets the ROVERDRIVE apart is that it does not have a dedicated oil reservoir like the GKN does. The ROVERDRIVE is lubricated by oil from the vehicle transfer case. This simple concept eliminates the need for dynamic seals and breathers.
The ROVERDRIVE requires no service except to check the transfer case oil level at the recommended service intervals.
Q: Does not having a dedicated oil reservoir make the unit more compact?
A: Yes, the ROVERDRIVE is a very compact unit.
At only seven inches in diameter (much smaller than other overdrives), the conical castings are easy to produce which keeps costs down. Unlike some of the other overdrives, you do not need to move the exhaust pipe or other vehicle components during installation.
Q: How does the shift mechanism operate?
A: In exactly the same way as other mechanical overdrives. The engagement lever is situated on the transmission tunnel.
To engage the ROVERDRIVE you depress your clutch and move the lever forward. To disengage the ROVERDRIVE you depress the clutch and move the lever back.
The latest model ROVERDRIVE uses a modern compact syncromesh assembly so the movement is very short and light.
Q: I have difficulty understanding how the epicyclical unit works. Can you explain this to me?
A: It is not very complicated. The drawing here shows a cross section of the unit.
Inside the ROVERDRIVE is a rotating planet carrier (E) which is driven by the gearbox output shaft. Three shafts (G) are held in the planet carrier and rotate with it. Three planet gears (H) rotate about the shafts (G) on bearings (I). Sun gear (J) is placed in the centre of the three gears (H) and annulus gear (L) is placed on the outside of gears (H). Annulus gear (L) is connected directly to the output shaft of the overdrive on which is machined a large gear to replace the topmost gear in the transfer case. Bolts (FF) hold the overdrive together inside casing (U).
When the overdrive is not in use a clutch locks sun gear (J) to the three planet gears (H) and as a result the annulus gear (L) is forced to rotate at the same speed as planet carrier (E) and there is no overdrive effect. Note that in this mode none of the gears is actually working - all the components are rotating at the same speed about the centre.
When the overdrive is in use a clutch locks the sun gear (J) to housing (U) and the sun gear can no longer rotate. As planet carrier (E) rotates about sun gear (J), planet gears (H) are forced to rotate about shafts (I) and the effect is to cause annulus gear (L) to rotate 28% faster than planet carrier (E) thus giving an overdrive effect.
Q: Are the gears and clutches very highly stressed?
A: No, the gears and clutches are not highly stressed.
As the torque is divided among the three gears the stresses are much lower than would be the case with a single gear train. And, as the three gears are placed 120 degrees apart all side stresses in the assembly are contained. The whole overdrive assembly rotates supported by one large deep groove ball bearing. It is a very simple concept.
Epicyclical overdrives are not new of course. Many British cars in the sixties were fitted with them. However, the ROVERDRIVE is the first epicyclical overdrive for a Land Rover that employs a simple mechanical shift mechanism. There are no electrical solenoids, relays or microprocessors. A lot of thought and testing have gone into the design and we have patented the concept.
Q: How difficult is it to install a ROVERDRIVE? Can I install it myself?
A. A ROVERDRIVE is not difficult to install. Most owners find they can do the job in about two hours using normal shop tools.
On Series vehicles a hole has to be drilled in the transmission tunnel to accommodate the shift lever.
On Defenders it is a straight bolt in job and no modification is made to any bodywork.
Q: What about service and maintenance?
A: We have put a lot of thought and effort into making this product as simple as possible. Anyone with a good mechanical aptitude can install and service the ROVERDRIVE.
It is lubricated with transfer case oil so there is no independent oil level to maintain and no drain plug or breather to leak.
It has no dynamic seals. It can be dismantled using common workshop tools.
If you ever have to repair your ROVERDRIVE, you will note that we have used simple metric ball bearings that can be purchased from regular bearing suppliers. Many of the internal components are stock Land Rover parts.
The ROVERDRIVE was made in the tradition of the older Land Rovers. It is virtually indestructible!
Q: How reliable is a ROVERDRIVE in an expedition environment?
A: Your ROVERDRIVE can be used with confidence on the most demanding expeditions and will greatly reduce the cost of fuel. We suggest you take a basic seal and gasket set with you. Such kits can be obtained from any ROVERDRIVE distributor. Our experience shows that no other parts need be carried.
The ROVERDRIVE vs HIGH RATIO TRANSFER CASE Debate
For some years now Land Rover drivers have been offered higher ratio transfer cases (HRTC) as an alternative to overdrives in both Series and Defender models. The vendors of these products make claims like ‘eliminate the need for an overdrive’ or ‘a stronger alternative to an overdrive’.
In our opinion, these claims are misleading and do not give the whole truth about the products sold.
In a question and answer format, we state our case below.
Q: How does a HRTC work?
A: What a HRTC does is permanently alter the ratio between the engine RPM and the speed of rotation of the vehicle wheels. This is done by dismantling the transfer case and substituting a new set of drive gears. The cost of the new gears themselves is cheap but the cost of fitting is expensive.
Q: What is the change in ratio offered.
A: In the case of a Series Land Rover it is 31% In a Defender it is 16%.
Q: If I put a HRTC in my Series what will it be like to drive?
A: If you have a standard Land Rover engine you will find that the altered ratio makes it possible to drive in fourth gear on the flat with reduced RPM (similar in effect to driving with an overdrive engaged). However, on even a slight incline you will find you have to drop back into third gear. There is no splitter gear available between third and fourth, as there is with an overdrive fitted. If your vehicle is loaded you will also find that it is difficult to pull off on a hill without starting in low range.
If you like to use your vehicle off road you will find that you have to drop down into low range to climb obstacles that could easily be surmounted in high range before the HRTC modification was made.
Q: If I put a HRTC in my Defender what will it be like to drive?
A: You will notice that engine RPM drops somewhat on the highway making the vehicle quieter. However the 16% drop in RPM has nothing like the effect of an overdrive which drops the engine RPM by 28%. You may notice that your ability to pull off on hills has been compromised. If you like to use your vehicle off road you will find that you have to drop down into low range to climb obstacles that could easily be surmounted in high range before the modification was made.
Q: Is it easy to take a HRTC out of my vehicle?
A: No. You have to remove and refit the transfer case with the original gearing. Compare this to a Roverdrive that can be removed (and refitted into another vehicle) with ease.
Q: Can a case be made where a HRTC has advantages over a Roverdrive?
A: No. Manufacturers of the HRTC emphasize the simplicity and reliability of their modification but the Roverdrive is a robust well proven design which offers multiple advantages to the owner without compromising vehicle performance.
You can take the ROVERDRIVE anywhere with confidence !