Author: Ben Greene
Discovering that BMW made an AWD version of the E30 is like Christopher Columbus discovering America. He wasn't really the first to discover it, but even still he probably felt like the greatest man to ever live. So it’s no surprise that after discovering this gem you would want to run and buy one as soon as possible. But how can you make sure you’re getting the best of the best and not someone’s daily beater? Maybe the most important thing you can ask for as a buyer is proof that the AWD system is actually in working order. Don’t believe me? Head on over to Bring A Trailer and you’ll see what I mean. Hordes of bloodthirsty bidders, all demanding the same thing. A jack test.
So what is a jack test? Well, before we dive any deeper into that it's important to know the basics about the 325ix’s drivetrain so we can understand what a jack test is really telling us about the vehicle's condition.
To achieve its all wheel drive status, the 325ix utilizes the same automatic 4HP 22 or manual G260 transmission as the 325i, but with a transfer case tacked onto the back to direct power to a front differential. This is where the magic happens. Inside the transfer case a silicone filled viscous coupling splits torque front to rear, up to 90% in either direction. This coupling works by using a series of hole ridden plates that spin in a silicone filled space, some being attached to the rear driveshaft output and the other half being attached to the front driveshaft output. Normally, these plates will spin at the same speed. However, when they begin to spin at different speeds (ie: a slip situation where the rear wheels are spinning much faster than the front) the friction of the plates spinning in the silicone will cause the liquid to heat up and become extremely viscous, “locking” the plates together and effectively sending engine torque to the end of the car with the most grip. This creates an extremely simple, effective, maintenance free system that is constantly active and requires no input from outside sensors or computers.
This system was so effective in fact, that multiple car magazine reviewers preferred it over Audi’s heralded Quattro system. Here is a short excerpt from Road and Track’s November 1988 edition where they put the ix against a quattro 90 in an acceleration test…
"Our acceleration champ was the iX. The AWD BMW was a blink quicker than the Quattro to 20 mph, 4.9 sec vs. 5.1 sec."
In a hillclimb…
"Once again, the BMW AWD system proved superior to the Quattro arrangement."
And in a lane change test…
"The 325iX was the best. I've raced an M3 in the SCCA World Challenge Series and currently drive a new M3 (in good weather only). Personally, I really like a neutral handling car. I dislike the understeer characteristics of front-wheel and most AWD cars. To this end, the iX is much more neutral and handles more like a BMW than one would normally expect of an AWD car. No doubt about it, both the Quattro and the iX are incredible cars, but my choice is the iX for the above reasons.”
So, having said all of this, it is not surprising that a potential buyer would want definitive proof that the source of all the high praise of the ix’s drivetrain is in top shape. And that’s where the jack test comes in.
Stay tuned for our next blog where we explain how to perform the jack test to see if you have a working all wheel drive system.
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