|The MGA With An Attitude
MGA SPEEDOMETER DRIVE FAILURE - GT-103
At 06:32 PM 7/14/02 -0600, Phil Bates wrote:
>"My speedometer ceased to function. .... Took the cable out, and it is good .... So, it must be the drive in the transmission. Has anyone had to replace this part, and how difficult was it?"
Quite easy to R&R the speedo drive spindle from the gearbox. Just disconnect the cable and use the appropriately large socket to remove the big brass fitting from the gearbox tail housing. Do expect some oil to run out, have a pan ready. The speedometer drive output spindle is below normal oil level, so you may want to drain the oil first.
The driven gear is nylon and is a press fit on the spindle. If this gear comes loose from the spindle it can slip, and drive to the cable will be lost or intermittent. Cure is to replace the spindle with the press fit nylon gear.
Now if you're less lucky it may be a different problem inside the gearbox which may require R&R of the gearbox and disassembly.
The driving gear is on the output shaft of the gearbox. There is a key to prevent rotation of this gear on the shaft, but if the retaining nut was left loose the key might be sheared.
For the early and mid 1500 gearboxes with the sliding spline coupling at the rear end, there is a large nut on the output shaft immediately behind the speedo driving gear. This nut should be quite tight and should be retained by a locktab. If for any reason this nut is not tight you would have to remove the tail housing to get to the big nut to tighten it. Bummer, big job.
For the late 1500 and all 1600 units with the flanged output coupling at the rear, the news is much better. Here the speedo driving gear is retained with a long tubular spacer to be clamped securely in place with the rear flange fitting and the large nut on the back end of the output shaft. If this one gets loose all you have to do is to disconnect the front of the propshaft and torque up the big nut on the gearbox rear coupling.