speedo issue defender 110

[phibbzy]

Hi guys,

I'm having a curious issue with the speedo in my '95 300tdi 110.

I acquired it with the 7.50 R16 standard tyres and noted the speedo was out to the tune of 20km over at 110kmph, so the speedo reads 130km when I'm doing 110...

I fitted 33x12.5R15 tyres and it went down to about 125km for 110 actual. At this rate I'll need 38's to make the speedo match!

Is there any way to change the speedo?? I did a bit of a check on the forum and otherwise but could not find much..

[steveG]

That's a long way out!
Almost sounds like someone has messed with the speedo drive gear in the transfer case.
Depending on what is in there currently, you may be able to swap to a different tooth count gear and sort out the speedo that way.

From what others have posted, generally 33's bring the speedo back to spot on.

I'm assuming you're running standard diffs??

Steve

[Drover]

From what others have posted, generally 33's bring the speedo back to spot on.

Steve

Yep, 33's brought my speedo / road speed to near perfect match.

[zwitter]

I have 235/85 Bridgestone MTs and spedo reads about 10% low.
So at 110km/h it shows 120!

I use GPS as speedo when it matters.
James

[phibbzy]

Thanks for the replies guys, I thought it was interesting what SteveG said about the worm gear in the transfer remembering the discovery transfer cases are lower geared than the defender (1.210 as apposed to the 1.410 in defers) so I did an experiment this morning on the way into work with the iphone...
actual = speedo
40 = 46/47
50 = 58
60 = was bang on 70
70 = 81/82
80 = 93
100 = 116/117
110 = 128

Does this mean someone has replaced the worm gear in my defender box with a discovery one?

[steveG]

The ratio doesn't affect the speedo, as the speedo drive is on the output shaft, but its possible someone has messed with it in the past. Easiest way to confirm 100% would be to pull the speedo drive gear out and check it.

I haven't pulled the speedo gear out of a LT230, but the LT95 uses the same gears and once the speedo cable is disconnected its a simple case of taking off a small retaining plate and gently levering the cylindrical carrier out of the housing. The LT230 may have a different retaining method eg circlip etc.
The cylinder you remove has an o-ring on the outside so will have a bit of drag as you lever it out (ie it won't just flick out).

Once out you can check the plastic gear colour and compare to what should be in there. There are different colours for different tooth counts.
Pretty sure all LT230's have the same tooth count steel gear on the output shaft itself, so the only thing to change is the plastic drive gear.

There's a few posts around here with more details on the colours.

Steve