Speedo drive

[George1511]

Need help,  Spitfire mkIV the speed was playing up, reading below the speed and distance it should, the engine has been changed to a 1500, but still has the original gearbox (I think). I’ve had the car resprayed, but somehow they seem to have blown all the gauges and radio. I had brought some second hand gauges so replaced them easily. The originals were jaegar which I’m planning to get refurbished, the speedo is now seized. So the new gauges are smiths, when I connect the speedo I get no reading at all, I checked everything was ok at the speedo end, which it was, I managed to get the gearbox end off ok but the thread is stripped on the gearbox so I don’t think it was engaging properly. Is this easy to change on the car with the gear box tunnel removed? And is it ok to drive the car with nothing plugged into the gearbox? (I have a gps speedo).  Thanks

[Pete Lewis]

The speedo pinion hsg. Is held in place with a simple locking screw,   thays a bolt with a spigot end , remove the bolt and the housing pulls out  part number is 144621  £6.40  3 rail.  Easy to replace on car  once the tunnel is removed 

Single rail box is very different and hsg is held in with a plate

As for speedo calibration you need a speedo with the correct turns per mile  the TPM is the printed number on the face under the oddometer (mileometer)  rolls 

I take it this is a std 3 rail gearbox  and not  with  overdrive  to work out is thisn3 rail or a 1500 single rail

3 rail reverse is to the left of 1sts       single rail is to  the right of 3rd

Do not understand how they can blow all the instruments ,  just what doesnt work 

Pete

[George1511]

Yes, it’s a 3 rail without overdrive. Can I still drive it without the cable plugged in?  

‘The fuel gauge and temperature gauge stopped working, and Speedo had seized, the radio and speakers were also knackered, think it was water damage. Thought it was the voltage regulator at first, but tested everything and there was power to everything. The tachometer I had converted to electric, because it was mechanical still works, but it has new seals and is connected directly to the coil. 

[Pete Lewis]

this could be the result of the  dreaded fuse box  , the cap of the fuse connects un fused circuits , the  contact clips need to make good contact with the fuse end caps as they act as a bridge between the terminal clips .  renowned for causing odd failures on certain circuits

you can drive without a speedo but its not legal 

if the speedo seized i would fit a new cable anyway as it gets torn when one end stops and the rest keeps turning

temp and fuel gauges the common is the stabiliser  or its feed form the back of the  fuse box 

Pete

[George1511]

Thanks Pete, was just worried I may lose oil out of the gearbox. I have a gps speedo, I know it’s not legal, just in case I had to take it somewhere 

[Pete Lewis]

you may get a cup full out the drive when removed but the tunnels got to come off so refilling is easier

Pete

[George1511]

Right got the speedo drive out, when it came out a load of what looked like water came out and the cog was thick with brown sludge, is it knackered? TIA

[Pete Lewis]

hows the water got in , certainly an oil change but some areas  prone to fail could be suffering from poor oil quality

only use EP80/90 GL4 oil

pete

[George1511]

Don’t know where the waters got in, was going to remove top of gearbox and flush out the box and replace the gasket.  Do I have to remove the extension top cover separately or will it come away as one?

[Pete Lewis]

you can leave it on or remove it ,   select 1st gear first to remove the top cover and its forks  same for refitting

in fact to give it a flush just remove the remote unless you need to peer inside 

 

Pete

[Clive]

You can use some diesel to flush the box. Leave for a while to soak. Then Jack the rear wheels up, and run the box in gear with the diesel to get it everywhere and warm. Drain and bobs your uncle. 

This is what a friend uses at work for industrial stuff, both engines and boxes. (engines he just lets tick over with some of the old oil in there, not thrashed on the rev-limiter!)