325iX

The 325iX was BMW's first foray in four-wheel drive,

History

In the wake of the Audi Quattro and its rally success, many manufacturers adopted four-wheel drive to its models. BMW was not interested in AudiÂ’s progress in the rally scene, but when the press and the public cried out for more, BMW changed their mind.

BMW used a 4x4 system from Ferguson, which was made available for mass production through an Anglo-German motor industry cooperative. The system BMW used included Viscous Couplings, one in the rear differential, and one in the central differential gear set. The power to the front wheels was fed forward by an external shaft from that central differential gear set. The system was a permanent 4x4 layout, rather than the then popular part time 4x4, which had to be engaged by a lever.

To maintain the rear drive handling characteristics of any BMW, the power split between front and rear was 37 % at the front, and 63 % at the rear. But in slippery conditions, as rear wheels start to spin, the Viscous Couplings start to work, and shifts power to the wheels with the best grip. The front suspension had to be reworked to give room to the front differential and shafts. The standard anti-roll bar and power steering was repositioned. Also the aluminum sump pan was reworked. It had a passageway, to allow for the shaft feeding power to the front wheels.

Compared to the 325i, the iX has a wider track. At the front there were added 13mm, but at the rear end, only 1mm. All in all, this gives the iX a steady feel. Even though the iX rides about 20mm higher than a standard 325i, the road holding is excellent due to stiffer springs, twin tube gas dampers and of course, the added traction.

Performance wise, BMW had always been conservative with the numbers. Because of the extra weight the 4x4 system added (90kg/198lb), BMW claimed a sprint from 0-62mph (0-100km/t) in 9 seconds. But everyone who has driven a 325iX, or any other BMW for that matter, knows that BMW is rather careful. One Scandinavian magazine, named AUTOMOBILE, took the iX from the 0-62mph sprint in only 6.8 seconds! This was done rather brutally with high rpms before take off, but still. They never managed to accelerate as slow as 9seconds, to use their own words.

The BMW 325iX is a rare automobile, and perhaps it lives in the shadow of its rarer sibling, the E30 M3. But still it deserves attention from the car-enthusiast community. They were expensive in its time, and gives a lot of driving pleasure. Everyone who owns one should take good care of it, and keep it original. This is going to be a classic!

It's permanent 4WD, power is transmitted to the front diff via a viscous coupling; rear diff is a viscous LSD.

Weighs only 80 kg more than a standard 325 touring.

Up to twelve of these cars are known to have been professionally converted to RHD by BMW dealers within the UK. However, all were recalled to BMW for a steering issue and two were ultimately dismantled. Only one 325iX in the UK is an officially registered BMW-approved RHD car.

Alpina made an ix-based E30, which is known as the B3 ALLRAD.

Technical

Overview

Drivetrain

Despite the beefy requirements of powering all four wheels, the iX was fitted with the exact same 2.5 litre M20 engine as the 325i, mated to the same family of manual or automatic gearboxes. But that's where the similarities end.

From the end of the gearbox, a small transfer box splits the output to two prop shafts; one forward, one rear. This transfer box is a relatively simple design made by Ferguson, and employs gears and a chain to split the power with a rear bias; 37:63%.

The rear end is similar to the E30, but the differential is a specific viscous limited slip differential with a 3.73 ratio. The front end is a completely different kettle of fish; it employs a differential inside the engine sump before sending power through the drive shafts to the hubs.

Sump and diff

Because of the design, the iX's drive is a permanent All-Wheel Drive system rather than four-wheel drive. There is no option to lock either the front or rear differential, although the viscous nature of the rear diff means it can lock between 10-100%. However, the viscous coupling inside these differentials are known weak points, and almost all require a long-overdue rebuild by now.

The drivetrain layout means that all the mechanicals at the front of the car are custom-made for the iX, in order to squeeze everything into the relatively small space. The subframe is unique to carry both the engine and front differential, as are the wishbones and hubs. There's even a custom steering rack, which is mounted behind the front cross-member instead of in front, like other E30s. Most of these components (including the subframe) are aluminium, making repairs or modifications difficult.

To accommodate all this, the 325iX bodyshell is fundamentally different to standard E30s in almost every aspect. From the outside, you can clearly distinguish the wider arches both front and rear, which are to accommodate the wider track that the iX employs. And there are differences underneath too. The transmission tunnel is significantly wider (far wider than a simple lump hammer can achieve) to the point where the seats rub against the centre console. Open the bonnet and you'll see similar differences, with the suspension turrets moved farther forward to change the suspension geometry, which also affects the inner wings and chassis legs. Since all 325iX models are LHD, there are also bulkhead differences to UK cars.

It's fair to say that, forward of the windscreen, the 325iX is a completely different car to every other E30.

Wheels

Because of the wider track of the 325iX, special wheels were fitted with the correct offset to compensate. Frustratingly, this means that the iX cannot use standard E30 wheels as they will scrub the arches. The correct offset for 325iX wheels is .

Conversion

A lot of people, upon hearing of the existence of the 325iX, entertain daydreams of grabbing the mechanicals and fitting them to their own car. If you're one of these dreamers, give it up now; it's not going to happen.

As explained earlier, the bodyshell of the 325iX is unique. The all-wheel-drive mechanicals will not bolt up to a standard chassis, and the changes required to do so are so involved that it is dramatically easier to restore a rusted 325iX shell rather than adapt a standard one.

There is also the issue of the steering rack. The 325iX unit is specific to that model to fit inside the subframe. Its location within the subframe makes it almost impossible to access for RHD cars, which is why no RHD versions were produced, meaning no racks are available. If you manage source a compatible rack from another non-E30 vehicle, then there's the problem of getting the linkage past the exhaust pipes.

That's not to say it's impossible given enough time, talent and cash, but it is an immense project that has not yet been done, for very good reasons.

Common Problems

The drive train on the iX appears to be pretty bulletproof, with only a few known problems. Of course, fluid changes are required every 36K miles to keep things running smoothly; ATF in the transfer case and hypoid SAE90 (GL-5) gear oil in the front and rear differential. The viscous coupling units do not require any service but can fail with age and require a rebuild. The transfer case only holds about 1.5 pint of ATF, so be sure to check the fluid regularly. However, the transfer case on an automatic can leak into the transmission with no visible sign of a leak.

Viscous Coupling

Viscous coupling failure. See this video: http://www.youtube.com/watch?v=a4exvt2_Yjc

Front Prop Shaft

The weak link on the iX drivetrain seems to be the splines on the front driveshaft which mate with the chain-driven gear in the transfer case. These splines have stripped on several iX cars which are owned by members in the iX Registry (now with about 1100+ members.) Apparently, the moly grease which lubricates these splines dries out or becomes contaminated with water and allows the splines to wear down. The only way to check the condition of the grease is to remove the front driveshaft (not a complicated procedure and is covered in one of the Registry newsletters.) If the splines strip, the front driveshaft must be replaced. If the female mating gear is ruined, the transfer case will need to be removed and the gear replaced.

Transfer case

Regularly falls apart.

General Info

Please also see the E30 325ix Register