Offroading Subarus

Where we modify and drive flat fours

VSS (vehicle speed sensor) fix for EJ conversion

One of the things you encounter when doing an EJ conversion to your EA81 Subaru is the VSS problem. EA81’s never had speed sensors expect for in the US and some other countries, so it’s best to look at the speedo you have before worrying too much. This is just one solution to the problem, but it’s easy and I believe won’t cause a problem.

First off you need a EA82 speedo from the cluster. These have a small magnetic switch (reed switch) which gets 4 pulses a rotation of the speedo cable. The cable is geared 2 to 1 in the gearbox so it runs half speed of the output shaft on the gearbox, which is directly coupled to the propshaft. So you need 2 pulses a rotation of your propshaft. You also need 2 magnets to attach to the propshaft to give the reed switch the required magnetic pull to turn it on and off. I was in a rust so I cut up a speaker magnet (crude, but it works) and used two small chunks of it. You will want your magnets big enough to give the reed switch an open time of 1/6th to 1/4 of the rotation. Some where around 10mm x 10mm x 5mm should do it for each one.

Once you get the speed sensor from the EA82 speedo out it should look like this

VSS vehicle speed sensor - EJ conversion

Next up you need a mount to put the reed switch to that will put it right near the propshaft. You can do this is various ways but this is how I done it with a small piece or recycled piece of alloy bar.

VSS vehicle speed sensor - EJ conversion

Then you need to fit the reed switch to the bracket, I just cut off one of the original brackets on the circuit board and bent the other so it could be pop riveted to the new bracket. This also solved the connection shorting out issue as the brackets on the VSS are the “wires” so to say. I then cut a piece of gasket material to insulate the switch from the alloy bracket.

VSS vehicle speed sensor - EJ conversion

VSS vehicle speed sensor - EJ conversion

Once you’ve pop riveted the switch to the bracket solder on a couple of wires to the switch and then coat the whole lot in RTV silicone to keep it safe. Then you need to find out where the magnets need to sit to close the reed switch. Do this by holding a ohm meter on continuity test setting and move the magnet near the switch. In my case the polls on my magnets worked best when they were off to the side of the switch. Just do more testing until you know where the bracket must sit to hold the switch in the right place. Then glue the magnets to the propshaft, one of each side exactly.

VSS vehicle speed sensor - EJ conversion

Mount the reed switch about 3mm away from the magnets so it’s close enough but doesn’t touch. You then need to mount the switch and run a wire to the VSS pin on the ECU and a wire to GROUND (anywhere on your chassis will do.) This should fix the problem and you should have no problem I hope.

VSS vehicle speed sensor - EJ conversionVSS vehicle speed sensor - EJ conversion

And there you have it. Your ECU should be happy as ever with the pulse code it gets.

Just for your information if you have 3.7 diffs and near standard tyres the rotations of your output and propshaft will be around 55 a second at 100kph / 60mph And your speedo cable will be half that.



I bought my first Subaru back in 2005, it was a 89 Brumby, flair red. I lifted it, fitted Kumho 27″ MT’s. After a while I swapped the dual carb EA81 it had with an EJ22 bolted on a custom gearbox which used EJ D/R casing, EA82 5sp low range and an RX centre locking diff. Once I sold the Brumby I got a 83 Leone. Converted it to 4WD, put the Kumho’s on it, added a 5sp and drove it like I stole it. I then upgraded to a 99 Outback. It was hail damaged so I repaired it myself. I fitted it out with some storage and a mattress. I now have a 87 Brumby that I’ve resprayed with two pack urethane in Waratah Red. I am planning to fit an EJ with PT gearbox and a little bit of lift. It’s another project in progress.

Phizinza – who has written posts on Offroading Subarus.

March 8th, 2007 by Phizinza
Posted in EJ22 Conversion