Converting a Short Wheel Base Series Land Rover to Volvo C303 Portal Axles
By: Rickard Reavey
Portal axles are becoming increasingly hot in the offroad community. In the US this is largely driven by the ground clearance benefits for rock-crawling while with the Series Land Rover community portal axles (mainly of Volvo C303 origin) offer those same benefits, plus significantly lower gearing and more beef axle than the Rover axle casing and 10 spline half-shafts - all this with front and rear diff-locks. Contrary to the many statements and claims that I have seen on the internet, Volvo C303 Portal axles are NOT "virtually bolt-on" at least not if you want them to work properly. If you want portal axles bolted onto your vehicle, they will "bolt on" with re-fabrication of the spring-mounts, relocation of shock mounts, and some upgrading of the brake system. If you want the full benefits of the portal diff clearance and you would like these axles to articulate, it will take some work. Although this article will specifically reference putting C303 axles on an 88" Series Land Rover, it will have obvious applications for both 109" Series Land Rovers and other similarly designed leaf-sprung vehicles.
Firstly, where do these axles come from? The C3 generation of Volvo light-duty trucks were forward control vehicles, driven by the B30A in-line six petrol engine generating 125 HP (same as the Volvo 164). Transmission was through a ZF 4 speed manual gearbox, two speed transfer case to Eaton made portal axles -designated EV11 (the same maker of the Land Rover ENV axles) with a 2.91:1 differential and a further hub reduction gear of 2.06:1 for axle gearing of 5.99:1 in most 4x4 applications. The Volvo C3 generation of vehicles began production in both 2 and 3 axle (all driven) format as a light duty cross-country vehicle for both civilian and (Swedish) military use. They were also assembled under license in right hand drive version in Malaysia where they had a wide variety of civilian uses. In 1983 a C303 won the light duty truck entry in the Paris-Dakar Rally. For more information on the history of the C303, please visit : http://www.volvo.com/trucks/global/en-gb/aboutus/history/1970s/C3.htm
Civilian Hard Top C303
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TGB 11-11 Swedish Army Anti-tank vehicle
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C306 - the 6x6 version in rare Mobile Command Center hard-top (lower geared axles giving a final ratio of 7.14:1)
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As far as I know, the original conversions using Volvo C303 portal axles on Series Land Rovers were done by members of the Land Rover Owners of Malaysia Club led by then President, K. Vigneswaran "Vicky" who built a number of 109" Series Land Rovers at his garage, Rainforest Auto, in Kuala Lumpur to serve as Marshal vehicles for the (2000?) Rainforest Challenge. These 20+ year old 2.25 litre petrol engined vehicles were regarded with bemused skepticism by competitors in modern diesel and V8 engined Japanese and European vehicles - until they were regularly being rescued by LROM members in these "dinosaurs". The trucks were written about by a number of journalists at the event, and it soon became a popular conversion not only in Malaysia, but also in the UK. In fact, the conversion became so popular that when I lived in Malaysia (2003 - 2004), there were virtually no 5.99:1 ratio axles available and while the 7.14:1 ratio may be great for rock-crawling, with a top speed of about 50 kph, they don't leave your rig good for much else!
After much searching and some set-backs that need no further discussion, I located a set of 5.99 ratio C303 axles at http://www.xtremevehicles.com/index.html. David is a nice guy and very easy to deal with. His real interest is in selling whole vehicles rather than parts so he may not have any available when you call, but he is reliable and honest - unlike some others in the game! Here are the axles as they arrived from a nearly 30 year old Volvo C303:
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Typical for an ex-Sweden 30 year old C303 axle. It was mostly surface rust though and there was no real deep pitting. These are pretty tough items.
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Front and rear axles - a bit beefier than the Rover axles!
Open knuckle front portal axle
One immediate piece of advice: Try to get the steering link (the piece between the pitman arm and the drag link) when buying the axles. It makes it easier to modify than trying to fabricate the whole link.
These are pretty beefy items designed to push 3.5 - 5.5 ton (GVW) vehicles through the Swedish snow and Malaysian mud generally on 9.00 x 16 tyres. Some scraping, blasting, and grinding, revealed that the rust hadn't really set in and a Rustoleum treatment sorted them out pretty well. The wheels were in somewhat worse shape and needed restoring as both the negative offset (compensating somewhat for an otherwise much wider than LR track width and protecting the reduction hubs) and 8 on 8.75 lug pattern do not allow many options for aftermarket wheels! The wheels came out rather nice in Land Rover Limestone.
Rear axle blasted and treated with Rustoleum
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Land Rover Limestone - nice!
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With the 5.99 gearing and the portal axle effectively reducing topside wheel clearance problems, the opportunity to put some more rubber under the Tonka while running the same springs and without a lot of body trimming was too good to pass up. The decision was for TSL Super Swampers in Q78/16 (35.5" x 9.5"). While not as aggressive as the Simex Extreme Trekker Centipedes that I brought from Malaysia, those were in 32" x 10.5" 15R, and the only importer of Simex that I found in the US wanted silly money for 35 x 11.5 16R. In any event, as you can see, the @ 23" under the diff is what these axles are all about. While looking at the axles, it is worth noting that the EV11 axles share certain brake components with the Rover axle on the six cylinder Series 109 Land Rover, namely:
Part number front shoes RTC3424 (full set for complete front axle)
Part number rear shoes STC2797 (full set for complete front axle)
Part number wheel cylinder rear right 243296
Part number wheel cylinder rear left 243297
The Tonka ready to accept the rear portal
The brakes are 11" twin leading shoe all around and to work on a Series Land Rover require both the big bore 109 M/C and servo assistance. Optimally, in addition to a Series or Defender Servo - I used a remote Servo because the LHD pedal box does not accommodate the LR Servo on M/C well - a vacuum reserve tank would really help. On an 88", these brakes are going to give the vehicle plenty of stopping power - except when they're wet, covered in mud, etc... Disc conversions are available but at @ USD 750 an axle, it will have to wait until at least next Christmas!
While on the subject of vacuum, it is also worth noting that these axles are equipped with vacuum actuated difflocks. While I gave serious consideration to cable operation (Oxlocker cables or any high quality cable and a pair of scrappy parking brake levers will do), on the SWB Land Rover at least, the diff is so close to the chassis rail on the "short side" where the difflock actuator is located (exacerbated by the fact that the actuator lift is angled in that direction - see first picture above) that it makes for a very awkward angle to operate the cable and could potentially foul, making it difficult to lock and unlock. The C303 used vacuum to actuate the difflock and there's no good reason (or so I thought) not to use vaccum on the Land Rover. The problem is that 2.25 isn't producing a lot of vacuum at idle/low revs, i.e. crawling speed, and drawing it off to the lockers would roughen it up at a time when off-camber operation already has the carb complaining and sputtering. In other words: not so good an idea. The solution came from Anthony at Simmonites in Bradford (since moved on I understand) who suggested using the vacuum pump from a Land Rover 300 tdi that bolts up directly in place of the 2.25 petrol mechanical fuel pump. I replaced the Series mechanical fuel pump with a Range Rover Classic electric pump and it now produces enough vacuum to suck a golf ball through 30 feet of garden hose. (Tip - if you are doing this in the US, buy the pump from the UK as any tdi components are super expensive this side of the pond!)
The key issues that arise and that refute the claim that C303 portal axles are "bolt-on" become apparent when offering up the axles. First, the axle casing is square unlike the round Rover axle. After grinding off the spring mounts (the C303 ran SOA in front and SUA at the rear) you have to position the new spring mounts and saddles. You could weld on half moon shapes, or full circles, and mount the springs as if on a Rover axle, but the C303 axles are already much beefier so adding diameter becomes a problem. Besides which, the full benefit of the portal clearance comes when the reduction hubs are perpendicular to the ground and the pinion parallel (also correct castor on the C303) to the ground. The best result came from welding the spring saddles to the axles such that the hubs remain perpendicular and pinion horizontal:
Prepping the axle for welding
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Welding on the spring saddles
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Spring saddle with U-Bolts in place (Difflock actuator to left top of u-bolts under duct tape)
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Custom fabbed U-bolts, spring mounts and adjustable shackles for mocking up various angles and ride heights.
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With the axles ready to mount up with the springs, issues became evident. At the rear, with longer than standard shackles (in my case I will continue to use Revolver Shackles) the longer spring makes for less of an issue and the pinion (almost exactly the same length as a Rover axle and with the same propshaft flange pattern) angle is minimal while still allowing an acceptable propshaft/u-joint angle. I have custom wide angle yolks on mine (similar ones can be had from Gon2far Suspensions in the UK, along with C303 axles and other cool parts for Series Land Rovers and Defenders http://www.gon2far.co.uk/) and this certainly helps, as does the added length in the slip joint necessary for full articulation with the Revolver Shackles. On the front axle, the geometry with the short springs is a problem.
If bolted straight up, the pinion would face down to the ground at an unacceptable angle. Tilting the pinion up would diminish ground clearance and inhibit non-adjustable castor.
The solution is to lengthen the front spring hangers, run longer shackles (Revolvers for me even though Rover geometry will never let them fully open), and make some compromises. Initial testing suggested that to get the pinion angle and geometry right (where the Revolvers would really open) meant an extension to the front hangers of at least 6" The result would have been a truly outrageous lift with the top of the wing sitting almost 4'11" off the ground! Not only is this ugly and ridiculous, it would create a top heavy and unstable vehicle:
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This kind of lift might be okay in the Pine Barrens but it's not okay elsewhere (and yes, Jake is that short!)
4'11" Way too much lift. Back to the drawing board...
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The pinion angle is good but the gap to the hangers is extreme.
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On the other hand, cut of the ends of that bumper and that's quite an approach angle!
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Back at the drawing board, we made some compromises. Simple fact: there's just not much you can do with the front end of a Series Land Rover. We decided to notch the front cross member to give it a few more inches of articulation (but it will still need wire rope check straps to stop it fouling) diminish the length of the extension to the spring hangers, angle the pinion somewhat and accept that while the Revolvers will never fully open at the front, the lateral flex allowed to the springs, combined with the maximum articulation possible and three locking diffs are good enough. As you can see in the pictures below, the ride height is much better - the sills are about the same height as my Dodge Ram 2500. The diffs are about the same height as the bottom of the rock-sliders and everything else is above that, so clearance is pretty good.
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No, Paul is not a giant, ride height is much more acceptable and a set of arch spats will clean up the wheel wells. The way the Revolvers work will mean that on extension, the rear wheels will move back (away from the vehicle centre) where they have plenty of room while the fronts will move towards the vehicle centre (where they also have room).
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Black strips at the bottom of the fender designate area that needs a trim.
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Looks good from the rear, sitting pretty level and doesn't look all that remarkable - until you realize that you can't see an axle.
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After making the compromises and readjusting ride heights, while there is a considerable overall lift vs a stock Series 88", the overall look is not unpleasantly out of character. The fender trimming is minimal and with the wheelarch spats, it should look quite good. We have lowered the upper front shock mount and used the stock lower mount - which needs further study under field testing to see if it's the right set-up. The final step is to now fab up the steering link (no pictures yet available). The power steering box is a Toyota model and it will need a new pitman arm. The stock C303 steering link comes up off the drag link pretty sharply and it needs to be reformed flatter at the top and extended. All the brake piping needs fabbing up and needs to be pretty flexy! We also need to plumb in the vacuum lines for the difflocks. The final plan is a truck cab soft top and tonneau cover but that may wait for the Spring. More pictures when it's "finished".
Lowered front shock mount
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Stock C303 lower mount
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Fenders trimmed - it'll run out Hi-lift before they get the tyres off the ground!
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The Evolution of the Tonka
Dubai 2002
Malaysia 2004
USA 2004
2005???
Photos courtesy of Robison Service http://robisonservice.com/default.asp
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