1.8 manta, speedo drive removal from gearbox

[Neilm]

I've fitted a 1.8 berlinetta engine and box in my 1951 smiley riley RMA. drives ace. But the speedo needle started wobbling then stopped. Seems to be the gearbox speedo gear at fault. (Mines the yellow 19tooth drive). Low tech question but how to remove the drive housing from the gearbox? I've removed the slot in/ bolt keeper plate, but the housing is solid in the box. Bash it? Turn it? How best to work it free so I can then replace the 19 tooth drive cog? (Speedo cable is fine, both ends, but not rotating) 

[®evo03]

Cable sounds broken in the middle! Not the first! 

8mm bolt holds a plate which holds the gear drive, push in, pull out. 

 

[Sutty2006]

If the cable is fine, it’ll be the drive gear. Not the first time I’ve had this issue. The Opel rekord (same getrag gearbox) had this issue. Only way I solved it was to buy another gearbox. 1.8 gearboxes are stupidly expensive now. If I were you I’d buy a heads up display digital speedo. My mate has one in his 1970 Fairlane cobra jet. 

[Neilm]

OK thanks. I'll get the old drive out and hope to find a stripped tooth....if not....guess ill have to go hi tech! 

2 hours ago, ®evo03 said:

Cable sounds broken in the middle! Not the first! 

8mm bolt holds a plate which holds the gear drive, push in, pull out. 

 

OK thanks...ill have a go at pulling it tomorrow....I'd taken the 8mm bolt n plate off but it still felt solid....I will thread a nut onto the unit...and pull on that unless I can jemmy it using the slot that houses the retaining plate....

[cam.in.head]

yes it should just pull out. maybee someone has used some kind of sealer but as mentioned above it may be the drive gear on the output shaft ( easier if its the yellow cog driven mechanism thou)

with gearbox in neutral if you spin the prop the end should rotate .not rotating obviously proving a problem with it rather than the cable 

[rutts]

You can buy three different coloured drive cogs with different amount of teeth to alter/correct speed shown on clock. Around £10 each on German eBay. 

[paulmanta]

The plastic speedo drive cog is held onto the output shaft by a flat spring clip, this spring clip can go a bit weak and allow the drive cog to walk backwards on the output shaft. 

The bit you connect the speedo cable to can also fail, the coloured plastic shaft with the slave cog on the end can break or wear out. 

If your slave cog/shaft holder is stuck in the gearbox after you have taken the 10mm bolt and little retaining bar out then you need a bit of twisting and light bashing with a copper or hard plastic mallet to get it out. 

 

If the slave drive is OK shine a torch up the hole and see if the drive cog has walked backwards. 

 

If it has you need to remove the prop shaft and try and find your original cog clip, it's metal and magnetic so a small telescopic ariel style magnet should fish it out. 

It will need opening back out a bit so it's able to clip again or if it's broken then you need a new clip. I have stock of these but they are rare. 

You can put the cog back into position and using a long thin steel rod with a blob of sticky blutac on push the clip back into position in its slot in the drive cog and the hole in the output shaft that the tang in the clip fits in. 

I have done this many times and it Is possible, some say its not but I have done it. 

If I get 5 mins tomorrow I will take a pic of the parts I have here out of a gearbox so you can see what I mean.