The speedometer O-ring kit was replaced on our 240z not too long ago, and now it's leaking transmission fluid from that same area again. Any idea why it's leaking again so fast? It's only been about 5 months since the new o-ring kit was installed.

Might be just a junk quality o ring or wrong size. Might have had an edge crushed during installation. Replace with a new one and put some vaseline on it so it slides in easily and allows for good fit. Other than that, one guess is as good as another.

O-ring kit? How (other than price) would that differ from the O-ring at the hardware store for $.39.

What Leonard said, go buy a new O-ring and gently intall paying particular attention to avoiding those sharp edge.

Cheers

It's not always the o-ring. Don't forget to replace the tiny oil seal, down inside the cast housing, that the pinion shaft slides into.

Take out the speedo drive unit, punch out the tiny split pin, slide out the gear and shaft, use a drill bit that fits loosely into the housing. Insert the drill bit while twisting it hard by hand. The sharp tip will bite into the oil seal. Then yank it out. Hopefully the old seal comes up with the bit. Assembly is reverse of removal. I like to use a tiny bit of RTV on the outside of the new seal as a lube and sealant. Use the butt end of a snug fitting drill bit to press the new seal down.

It's a bit confusing at MSA:

Speedo Pinion O-Ring, Large, 70-83 Z/ZX All, 84-89 ZX Manual

Code:20-1552

Price: $1.27

Speedometer Pinion O-Ring, Small, 70-86 Z/ZX

Code:20-1550

Price: $3.38

One is an O-Ring and one is an oil seal. You need both when you try to fix the leak.

Edited February 2, 201114 yr by cygnusx1

On the small o-ring/seal.....  does the grooved side face in or out??   My original was pretty roached so it was hard to tell, but it looked like groove out.

The open side always faces toward the fluid.