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521 4.88 speedo gear

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So my 521 has had the rearend replaced at some point in its life. My speedo always reads 10mph or so faster than what I am doing. Checked this against gps lots of different times.


It may be a shot in the dark but does anyone have the plastic speedo gear that bolts into the side of the tranny for a 488 rearend?? I would like my speedo to work properly, at least till i put 411s or 437s in the back.


Thank you!!

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That would be a 19 tooth pinion.... probably white plastic but count the teeth to be sure. The 4.875 axle uses #32703-78600 about $16 from the dealer if still available.


The 4.375 is likely a 17 tooth and black #32703-22001

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What kind of trans does this have to come out of ??  does a stock 4speed one fit in the 5speed you have?,,,, I'm not saying i have one but don't want to pull them all out to look if they don't fit anyways.. 

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Yes I assumed it was a PL521 with L16. This would have had a 4.375 ratio. Putting a 4.875 from a J13 4.875 rear in it would throw the speedometer out by about 11.4%. You would read faster than you are going. To slow the pinion gear down you get one with more teeth on it. You have the 17 tooth L16 gear in it and going to a 19 tooth is about an 11.7% change. Pretty close.

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  • 4 weeks later...

If Jayden got his part, I'd like to jump in on here. I'm in the same boat.


Dogleg in my 70 521 (P.O.). Rear end is unknown posi (P.O.). I think I'm even higher than 10 mph with my 15" low profile tires.


Any direction, help? At least get me close.



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