So, unable to put up with it any longer, I got a new speedo cable and spent 30mins replacing it last week. When it didn't fix the problem (speedo was still not reading), I had to delve a little deeper to find what the problem was.
It turns out it was the speedo drive gear in the transfer gearbox that was worn and not turning the speedo cable. So it was back to the Landy shop to get a replacement drive gear.
This is how I replaced it.
Important note on the speedo cable: If your speedo has stopped working, 9 times out of 10 it's the speedo cable that is at fault. This is what I replaced first, and I would urge you to do the same. If it doesn't fix your problem, (like on mine) then you need to check the speedo drive gear is actually turning the inside of the new cable.
To do this you disconnect it at the speedo end and just secure it in view. Then drive the Land Rover for a few yards down the road. If you can see it turning, your speedo is knackered, if it doesn't turn, then its time to replace the drive gear.
Land Rover Defender Speedo Drive Gear Overview
Land Rover made the speedo drive gear interchangeable to allow for different size tyres to be used on the vehicles. If you fit larger (or smaller) diameter tyres, your speedo will not read correctly, so you have to swap the speedo drive gear for another one with a different number of teeth to make it accurate again.
Land Rover colour coded the speedo gears for easy reference. So here is the list of speedo drive gears and their relevant part numbers. The speedo drive gears aren't expensive, I paid £7 for mine.
Land Rover 90/110 speedo drive gears
- Colour: blue/20 teeth - Part number: FRC3310 - Tyres: 7.50/16 or 235/85/16
- Colour: green/21 teeth - Part number: FRC3311
- Colour: yellow/22 teeth - Part number: FRC3312 - Tyres: 205/16 tyres
- Colour: red/24 teeth - Part number: FRC3313
How to change the speedo drive gear on a Land Rover
The job isn't all that difficult, but you can have complications if the speedo gear housing is corroded in the transfer gearbox casing. Its advisable to soak the area in a penetrating oil a day before you plan on doing the job.
So for this job you will need:
- Sturdy screwdriver or chisel
- WD40 or other penetrating oil
- 10mm spanner/socket
- Copper grease
Access: The speedo drive gear is located at the back of the transfer gearbox in front of the handbrake drum. You can access it from underneath the vehicle, but it is easier to remove the middle seat (or cubby box) and get to it by removing the cover from inside the car.
2: Undo the 2 10mm nuts which hold the speedo cable in place. I choose to nip them up together and then undo the stud from the gearbox, as it gives better access to the area when working from above. (you can see the 2 nuts/stud circled in the pic above)
3: With the nuts/stud removed you can just pull the speedo cable out and secure it off to one side out of the way.
There is a little recess in the housing which allows you to get a srewdriver/chiesel in it to start levering it out. (see pic on right) Once you have got it so far, you can get the screwdriver behind the bigger flange and get some more leverage on it.
It took about 10 minutes of levering, and plenty of WD40 to make the housing pop out. I would spray some WD40, then knock the housing back in again slightly to make sure the lube got to all parts. This made it progressively easier to work the housing out of the transfer box.
Once you have removed the housing, the speedo drive gear will pop out with it, and you will see what colour gear you have been running - in my case, blue - which is correct for the 110.
As you can see from the photos below, the problem for me was a worn drive gear - the teeth were square, not pointed, so they weren't engaging properly, hence not spinning the speedo cable.
I chose to buy a whole new housing assembly and oil seals. The new drive gear, housing and oil seals came to £21, so it won't break the bank.
Reassembly is the reverse of removal, and is straight forward, especially if using new parts.
5: Put a small smear of copper grease on the drive gear shaft and the housing. This means it all slots back into the transfer box without a problem. It also means it shouldn't seize should you need to remove it in the future.
6: Tap the housing home using a screwdriver and hammer.
7: Replace the speedo cable and secure it in place with the retainer and do up the 10mm bolts/stud.
That's it - job done. If you want to go that little bit further, you can check the accuracy against a GPS speed reading on a straight road.
I can report the speedo now works, and is reading just under the GPS reading, which is right. Happy days!