boxboy Posted January 15, 2011 Report Share Posted January 15, 2011 I did a third member swap last weekend in my 520. Changed the 4.88's for some 4.374's. At first I was under the impression that it was not that much of a change. But I wasn't driving with traffic or anything, so I was trusting my speedometer like a moron. RPMs at 55 seemed the same. Duh. Driving tonight at "55" I noticed people weren't riding my bumper and wanting to pass like before. Then it hit me, my speedo is now off. Okay, so how much? How do I know how fast I am going without making my wife drive in front of me at 55 and make a mark on my dash? OR, even better, is there a way I can swap the speedo gear from a 521 tranny into my 520 tranny? I know this has probably been addressed before, but I could only find stuff referencing 620's and 720's. Thanks in advance Quote Link to comment
Jester Posted January 15, 2011 Report Share Posted January 15, 2011 MIIIIIIIIIIIIIKE!!!!!!! Your up. :D Quote Link to comment
thisismatt Posted January 15, 2011 Report Share Posted January 15, 2011 It's simple if the speedometer was accurate with the old gearing. Just figure out the change in ratio and you'll get the change in speed. 4.88/4.374 = 1.1157, that is to say the new speed is 1.1157 times faster than the old speed, assuming the old speed was accurate. So, your new "55mph" speed is 1.1157 * 55, or 61.36mph Quote Link to comment
wayno Posted January 15, 2011 Report Share Posted January 15, 2011 Lifes a bitch, huh. :lol: Quote Link to comment
datzenmike Posted January 15, 2011 Report Share Posted January 15, 2011 I agree. 11. 428% different or 61.2875 mph. (the 4.88 is really 4.875 :lol:) Quote Link to comment
boxboy Posted January 15, 2011 Author Report Share Posted January 15, 2011 Thanks guys. Can I swap a speedo gear to correct it? I have the later 520 tranny with the flat pan on the bottom. If I am correct that is the same tranny as the L16 521's. Quote Link to comment
banzai510(hainz) Posted January 15, 2011 Report Share Posted January 15, 2011 Get a GPS unit. I would think you need a 521 pinion(521 have the 4.375) with all else being the same. But mine is off 5mph also with the stock diff installed Quote Link to comment
datzenmike Posted January 15, 2011 Report Share Posted January 15, 2011 I would think you need a 521 pinion(521 have the 4.375) with all else being the same. What Hainz said plus one from a very early 620 that has the same transmission with the pan on the bottom. Quote Link to comment
boxboy Posted January 15, 2011 Author Report Share Posted January 15, 2011 Thanks. I guess I will call Nissan and see if they have the pinions. Quote Link to comment
boxboy Posted January 15, 2011 Author Report Share Posted January 15, 2011 But I switched from the 4.88's to the 4.375;s so I need the 17 tooth correct? According the carpartsmanual mine is a 19 tooth I believe. Quote Link to comment
datzenmike Posted January 15, 2011 Report Share Posted January 15, 2011 Sorry there was another thread I confused it with. Your speedo pinion in the tranny you have now is matched to the 4.88 rear end ratio and should be a WHITE 19 tooth cog. Moving from 4.88 down to 4.375 is a change of 10.34%. Changing from a 19 tooth down to a BLACK 17 tooth is a 10.52% change which is as close as you can get. I have to go out and will post a possible source for the 17 tooth or the Pt.# mike Quote Link to comment
datzenmike Posted January 16, 2011 Report Share Posted January 16, 2011 A 17 tooth pinion from a 510 F4W63 is Pt. # 32703 22001. Be sure to count the teeth to be sure. Quote Link to comment
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