Last modified: 20-March-2003
Has anyone done this? Yes, Mitsubishi have the 4 door Lancer GSR and GSR EVO series, with 4G93T and 4G63T engines respectively, so yes, it can be done.
Can this be done by a private citizen? Yes, but its a MAJOR undertaking requiring all sorts of fabrication and welding. Let me repeat that another way: CONVERTING A FRONT WHEEL DRIVE CAR INTO ALL WHEEL DRIVE REQUIRES AN EXPERT LEVEL OF MECHANICAL KNOWLEDGE AND ABILITY, A GARAGE TO DO IT IN, A MIG WELDER, SHEET METAL FABRICATION EQUIPMENT, AND A BIG CHUNK OF MONEY.
IT'S ABSOLUTELY NOT A "BOLT-ON" UPGRADE.
Here's the URL of someone in Australia thats doing exactly this, including using 2.0L 24-valve quad cam V6: http://evocoupe.20m.com/lancer.htm
I've reproduced portions of some of his photos here with permission. Let's explore this a bit ...
88-91 Eagle Vista 4WD KM182 transmission. Not usable because the transfer case output shaft is above the front axle line, which would require major structural changes to the Colt center tunnel. I'd expect that all registration authorities would reject a vehicle modified to this extent without an engineers certificate, if you could even get one. The front and rear track is also smaller by about 2". It would be usable only if the car ends up jacked about 2 inches. This is how the 4WD Vista vs the 2WD model is built. I suppose that since the suspension has to be redone anyway, the car could be lowered to compensate somewhat. Gear ratios of the KM182 transmission, actually a 4-speed with low and high ratios set up as low ratio for 1st to 4th, then switch to high ratio for 5th, are not ideal for the Colt project car, as 1st is very low. Up to 89 the Vista was driver selectable 4WD, while the 90 and 91 models still used the KM182 transmission, a three piece tail shaft with a viscous coupler was added to simulate the AWD operation. These parts (in fact an entire Vista) can be had quite cheaply. The KM182 will mate to the G64B, 4G64 and 4G63 DOHC engine, but I would hesitate to use it with a 4G63T. The downside it that the VC type "AWD" achieved only works when there's front-rear slip, whereas the 4WD when selected splits torque 50/50, and the Talon/Eclipse AWD is far superior to both.
92-95 Mitsubishi Expo, Expo LRV AWD W5M33 transmission, Galant VR4 / Eagle 2000 GTX W5M31 transmission: these mechanical parts are VERY similar. Certainly the gear ratios and other specs are identical for the 91 Talon AWD and the Expo AWD. The Expo W5M33 has roll stopper mounts on the bell housing, while the Talon / Eclipse version does not.
90-95 Talon / Eclipse TSi AWD. Probably easiest to get in USA / Canada. Most wreckers seem to want to separate the transmission from the front-rear transfer case, as there is often a problem with a brass filler point leaking and causing transfer case gear failure. Based on the prices I've been quoted, it could be cheaper to buy a complete 90/91 AWD Talon in rough condition as the donor car. Note that the 5-speed Eclipse AWD diff (3.545) is NOT the same ratio as the automatic AWD diff (3.308), so if buying from a wrecker, be absolutely certain what you are getting, because using an automatic diff with a manual transmission WILL fry the very expensive viscous coupling inside the transmission. Some Talon diffs are limited slip viscous-coupler (VCD) models too.
Import 90-95 Lancer GSR parts from Japan may be a cost effective solution. The GSR uses a gearbox SIMILAR to the W5M33, but it requires a rear diff ratio of 3.909 (same as the Vista), which means that at least the final drive ratio and some gear ratios are different to the Eclipse.
You might also come across a Galant / Eagle 2000 GTX W5M31 AWD manual transmission. These use a 2.846 rear differential, which means that the front diff ratio is similar.
What would the conversion entail? Do you know how to use a MIG or TIG welder? Got LOTS of time and money?
New front crossmember that allows for the transfer case to fit. The
Talon / Eclipse transfer case outputs UNDER the front axle line, as
shown above. It is possible to import a used GSR (not EVO, as these
can be expected to be unobtainable used) front crossmember from
Japan, else it has to be fabricated by modifying and strengthening
the original unit.
To give you an idea of the scope of the modifications, here's some editted views of the standard rear suspension area, looking towards the rear and the front respectively.
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Rearward view of the standard rear suspension mounting points, showing the tubbed floor of the trunk that houses the spare wheel, and the box section L-R frame on which the lower control arm brackets are mounted. Together these form an exceptionally strong structure that MUST be restored. Its not just the vertical and horizontal loads supported by the crossmember that matters, but the structure's longitudinal rigidity as well. The bulging tub-like area to the car front (top and center left) and above the cross member box section has to be partially cut away and replaced to provide space for the rear differential. It's uncertain at present how much the box section between the lower control arm mounts would have to be cut away.
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Here's some pictures of what is required to install Lancer GSR rear crossmembers. The chap in Australia who did this acquired a complete front damaged GSR from Japan.
The existing Colt welded in crossmember (left) has been removed and the GSR crossmember(outlined in yellow) that supports the rear diff front support (outlined in blue) is to be welded in. The GSR crossmember (outlined in green) that supports the rear suspension lower arms is a removable item, and fits in about the same place as the original Colt welded in section. Note the four captive bolt pieces in the chassis rail. Note also how this crossmember angles towards the rear of the car to accomodate the diff. The cast iron piece outlined in orange is the rear support for the diff. It is attatched to the diff by three bolts rather than the two found in the Eclipse. |
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Forward looking view of the standard rear suspension. Note that the original gas tank has been removed from its standard position between the center and rear crossmember. In the AWD conversion, either a bisected or two piece tank (hence double fuel pumps) has to be used, or else the tank moved to behind the rear axle line.
The lowest part of the modified rear crossmember and the rear differential itself will result in somewhat reduced ground clearance. It's very likely that a skid plate to protect the differential would be a good idea.
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Here's what a Lancer GSR rear crossmember looks like:
You can see the standard lower control arms are pressed U sections. It would be a good idea to box these in with 1.5mm steel for extra strength for the AWD . The trailing arms are also pressed assemblies that would benefit being boxed as well. In addition, the current trailing arm bushes and mounting points are designed for tension loads (i.e. the biggest load occurs during braking). This crossmember is a pressed steel part, and importing a whole used assembly from Japan would seem to be the most cost effective solution, rather than trying to fabricate something similar. This would leave only the creation of a GSR-type crossmember to weld in place. The GSR diff ratio is 3.909 or 2.846, not the same as the Eclipse. |
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Above is a cross-section view of the rear floor of the standard Colt and the modified version that provides space for the rear differential, and repositions the fuel tank. The fuel filler neck has to be rerouted, and the three pressurized fuel delivery and recovery lines have to be extended or preferably replaced entirely. Not shown here is the mounting bracket assembly that attatches to the upper rear of the diff (see the image above) and connects to the crossmember (or body frame) with large rubber bushes. The fuel pump and gauge sender are an integral unit that has to be accessible from a port in the new floor plate, shown in red.
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A shot of the GSR floor pan from underneath. While the floor shape is quite similar to the Colt, the image center area shown here provides clearance for the diff and suspension parts. Unknown is whether the tail shaft will even fit without modifications to the central tunnel once the AWD transfer case is fitted. The Talon also has a central carrier bearing (i.e. a two piece propeller shaft), and this should be retained. A welded-in front diff support crossmember would not be hard to fabricate to produce the EQUIVALENT structural supports and clearances. It just would not look the same as the pressed steel original. The GSR uses a double frame system to support the diff, because the fuel tank, while different to the coupe, is still in the same place under the rear seat floor. With the fuel tank repositioned at the rear, there are more creative options available to mount the diff, as shown left. In fact, while the welded-in front diff support crossmember is required, its not essential that the diff be mounted on to it if other parts are fabricated. |
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The handbrake cables are different for the disk brakes compared to the drums, and quite likely the Colt / Mirage disk cables can be used. Rear disks also require installation of a proportioning valve that is not present in the drum brake models. The Lancer GSR is not the same as the Eclipse, and does not use the spindle/cup system above. The outer CV has splines and bearings similar to the front axle shafts. It also has the 4x100 stud pattern.
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There's also the issue of the rear drive hub: the existing trailing arm has to be modified by carefully removing the standard axle stub welds (shown in magenta), and inserting the Talon AWD spindle and a bearing carrier. Machining this carrier up from stock is probably easier than trying to cut the Talon part out of its trailing arm to fit. The bearing carrier has to be expertly fitted and welded into the Colt trailing arm (if you are not an expert welder, pay one to do the job properly). While the axle spindles are the same, the cup (see below) comes in either 3-bolt (small) or 4-bolt (bigger and stronger from the 92-95 Talon AWD) types. Vista 4WD spindles and 3-bolt cups are the same dimensions as the 90-91 AWD Talon, but have 4 wheel studs rather than 5. Vista and 1G AWD Talon have the same length axles too, but according to the workshop manual, the joint to joint length is 30mm longer on the Talon. Reason is unclear as the joint carriers appear to be very similar, though the I suspect that the Talon outer stubs are longer than the Vista. If GSR / EVO3 rear trailing arms can be located, these use a hub similar to and perhaps the same as the front hubs. The bearing inner diameter is the standard 40mm, outer is 70mm. |
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1G and 2G AWD Talon rear diffs are not the same, and the axles are different. The latter model with thicker axles and 4 bolt outer CV carriers is shown left, with the early model on the right. These appear to be the same as the 87-91 Vista 4WD units. Note that the Talon diff ratios are the same (Manual transmission 3.545:1) and the Vista / GSR diff is 3.909:1. You cannot use the Automatic transmission diff (3.308:1) or the Vista diff with the Talon W5M33 manual transmission. If you do, it WILL fry the vi$cou$ coupler in the transmission.
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4 Bolt cups vs. 3 bolt cups. Note the differences in the axle shaft and inner and outer CV cariers. The later model has a thicker axle, and the inner CV carrier axle stub is a larger diameter as well. Put another way, a 4 bolt axle won't fit the 3 bolt differential. The mounting bolt circle diameter is the same for both the 3 and 4 bolt models. Hence, when locating the parts, ensure that you get all the necessary parts. 3 bolt diff / axle sets should be less expensive that the 4 bolt bits, as the 4 bolt is both newer and a popular upgrade.
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Copyright © 2003 Stewart DIBBS
