FJ40 2f (1976) Speedo gear keeps shredding to pieces!! help (1 Viewer)

[NathRay23]

Hi there, having troubles getting my speedo to work. I first replaced the cable and speedo gear within the transmission (which was shredded when I bought the cruiser) I replaced the gear like for like (a 16 tooth gear). Again after one drive it shredded it. Ive replaced the whole instrument cluster also aswell as replacing the trans gear again. Again, shredded it. ive now come to realise there are different gears that can be installed to match the cars speed depending on what wheel / tyre set up you have. im currently running 33 / 12.5 / 15 inch tyres. would this mean I need a 17 or 18 tooth gear for this tyre set up? and would the bigger tyres cause the gear to shred as mine has being doing? or is there something else at play that I don't know about. Any help is much appreciated.

 

[charliemeyer007]

I think tire size affects the accuracy of the gauge ie speedo will read to fast or to slow. My thought is the metal gear in the transmission that dives the plastic speedo gear that is being eaten is the issue as in it is rough or the shaft it runs on is loose/out of line and eats the plastic gear. The plastic gears could be really old and are weak from from UV/ozone break down even though they are "new".

My dad had a Rambler that ate some of the plastic speedo gear. There were no parts, so he took some brazing rod, cut into like 3/8" pieces, heated them up with a torch and inserted them in the plastic gear. After they cooled in place he used to needle file to shape them into the gear tooth profile. Put the gear back in and it ran smoothly for many years.

If you have a good tack, you can make a chart that will give you accurate speed for each gear. There are magnet sensor speedometer one you can add to a wheel and calibrate to read accuracy. Your phone GPS can provide a good speedometer.

 

[NathRay23]

yeah I suspected it be the gear driving the nylon gear, taken it apart and the gear itself looks visually ok and there wasn't any play on the shaft or gear but it has been opened up before so unsure if these washers are in the correct place? struggling to find any diagrams online. bigger washer, then gear, then a smaller washer. could anyone confirm this is the correct order? looking through the hole it seems like the gear is offset too far to the left?

 

[65swb45]

You are correct. There is only supposed to be one sleeve in there, thicker than what you have, and on the output bearing side. More like the thickness of the two sleeves you have combined.

My WAG is that someone cut your sleeve in two trying to do a work around on mismatched gears.

The steel drive gear should have a number stamped into it. And the nylon gear has to match.

www.marksoffroad.net

 

[NathRay23]

You are correct. There is only supposed to be one sleeve in there, thicker than what you have, and on the output bearing side. More like the thickness of the two sleeves you have combined.

My WAG is that someone cut your sleeve in two trying to do a work around on mismatched gears.

The steel drive gear should have a number stamped into it. And the nylon gear has to match.

www.marksoffroad.net
Top man, thank you. im really not surprised, the guy I bought it from has bodged so many things on this cruiser, fuel lines sitting on top of the exhaust pipe being just one of many. Just to clarify, it should be both washers I have and then the gear onto the shaft? my guess is the gears don't match either at this rate. Thank you again for your assistance

 

[65swb45]

Yes, but…the overall thickness has to match the original, because it is part of a system. It’s not just a matter of centering the drive gear.

The parking brake drum locks the whole assembly down…at a predetermined distance. If the combined thickness of your two spacers is not as thick as the original, the parking brake shoes will hit the flange of the drum when you tighten things up, and nothing will turn.

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