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MG MGA - Gearbox pinion leak

Hey all,

I filled the gearbox with 20W50 and discovered that there is a leak around the speedo pinion. It appears around the "outside: of the housing, not the pinion shaft. Barney and Moss show no seal or washer for the housing. Is this correct?

Also, can I just unscrew the entire assembly if necessary?

Thanks, Tom
Thomas McNamara

Moss does list the seal parts for the MGA speedometer drive. The shaft seal is a small garter spring seal 461-445. Seal between the drive housing and gearbox housing is a copper washer 321-820. See internal seal replacement here: http://mgaguru.com/mgtech/gearbox/gt106.htm

You can easily R&R the speedometer drive assembly. Drain oil from the gearbox first, because this part is below oil level. Disconnect the speedometer cable. Unscrew the drive assembly from the housing (1-5/16" socket as I recall).

The spindle sits at an inclined angle with output end lower than input end. The input end of the spindle is nested in a pilot bore in the gearbox housing. In case the spindle might stick in place, be very careful and go slow pulling it out while trying not to drop the spindle with small pinion gear into the bottom of the gearbox tail housing.

When reinstalling the assembly, put the copper washer on the drive assembly first. Be careful that the washer does not slip out of place into a leading groove to be trapped in a bad spot where it might prevent mating of the assembly with the gearbox housing (again being careful not to drop the pinion gear and spindle inside).
Barney Gaylord

Thanks Barney, you are the Guru! Would it hurt to put some "sticky" dressing on the copper washer to hold it in place? Tom
Thomas McNamara

Can do. Just don't put so much on that it gets inside the gearbox.
Barney Gaylord

Hey Barney, I got the assembly out only to find that there was no copper washer at all! Next question, does it matter which direction the flat side of the new seal goes? Tom
Thomas McNamara

Yes. Garter spring side toward the oil to stay clean, flat side toward the dirt.
Barney Gaylord

This thread was discussed between 27/02/2012 and 28/02/2012

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This thread is from the archive. The Live MG MGA BBS is active now.