Replacing the speed sensor - 93 Chimaera

[keeling54]

Has anyone successfully replaced the speed sensor that sits above the diff. Any tips or tricks to getting the bugger out.

I had it on ramps earlier and could hardly see it let alone remove it.

[Belle427]

On my 95 car it was exhaust and propshaft out of the way to get good access which is needed to set the gap.

[Classic Chim]

Start by tracing the cable from sensor to connector ( usually cable tied ) to chassis tubes around Dif, and cut it free and disconnect carefully. Then you should find a lock nut pinching sensor to Bracket. Loosen that nut off and wind sensor out until it’s free.
Probably a good idea to soak the sensors fine cut thread in penetrating oil to breakdown any crud or corrosion to aide it’s removal.
If you haven’t got one already buy a magnetic torch which is very useful when working in the confines of a Tvr.

[SwervinIrvin]

On my 93, I removed the exhaust and found it easier to remove the bracket (two bolts) that the sensor is mounted to. I was able to swap it out then. When remounting make sure to get the gap correct. Have fun with that!

[keeling54]

Thanks all, I can see the cable and feel the connections onto the back of the sensor. I've got a 4 post ramp on order, I may leave it until that arrives, it'll make it easier to get the exhaust and prop out.

I'm not even sure the sensor is faulty, I've bought a replacement speedo from ETB, the original one has a failed LCD display, unfortunately it appears the speedo isn't picking up a signal from the sensor to trigger it. It's fine with the original speedo which is a strange one.

[Dalamar]

I managed to remove it on a 95 Chimaera with a GKN diff. I went through the rear driver's wheel arch and used a wide opening stubby adjustable. You have to work pretty much blind at full arm stretch but it can be done.

You can also crudely test the functionality of the sender without a working speedo. To test the output of the speedo transducer attached to the diff use a digital voltmeter set to AC. The output from the transducer is quite low and if I remember correctly I was getting around 1.3V AC at around 30 mph.

[Englishman]

If your old speedo is working with the sensor, that suggests to me that your problem isn't the sensor.

Having said that, if you do decide to swap the sender, I changed the one on my Griff 500 reasonably easily without removing anything else by getting the rear of the car on axle stands and laying under the car from the rear, I imagine the Chim is the same? I did this outside, as daylight (or good illumination underneath), really helps seeing what you are doing, especially setting the gap on the new one!

[keeling54]

I re fitted the new speedo and took it for a spin. At around 50mph it sprung into life and has been fine since. The needle is quite lazy up to around 20 mph but other than that it's now fine.