skirkland1980 Posted February 7, 2013 Share Posted February 7, 2013 The car is a 1983 280ZX turbo with a digital speedo. It has a 700r4 transmission. I may have found a way to have a fairly accurate speedo that should reach 130+ mph. The first thing I had to do was make the 280zx speedo cable fit the 700r4. That was simple. I just had to grind the cable to a square on the end. Now my speedo reads 85 mph at about 65 mph. So I disassembled a spare gauge cluster that I have. I removed the odometer assembly from the cluster. I removed 5 screws, removed the optical sensor and exposed the trigger wheel (pictured). If I switch the speedo to read km/h, when the speedo reads 85 mph It will then read 137 km/h. I need to slow the speedometer down by about 50% to get a semi correct reading. So if I divide 137 by 2= 68.5. To slow the speedo down by 1/2: If you look at the trigger wheel there are 24 slots. I just filled 1/2 the slots with silicone and reassembled. This is still pending to be functional. I will update once the modified speedo is installed. What do you all think? Should it work? Quote Link to comment Share on other sites More sharing options...
Domzs Posted February 7, 2013 Share Posted February 7, 2013 (edited) Good job . Looking forward to your progress . I'm kinda doing the same . Running LS1 w 6 spd. trans. . I bought Dakota Digital converter but i just can't slow down the pulse enough to get a correct reading . I'm getting about 40 to 50 % off . I'll try it your way to see if i can get it to work . Edited February 7, 2013 by Domzs Quote Link to comment Share on other sites More sharing options...
skirkland1980 Posted February 7, 2013 Author Share Posted February 7, 2013 The silicone didn't hold so I'm trying jb weld to modify the trigger wheel. It shouldn't be raining tomorrow so I should be able to test it then. Quote Link to comment Share on other sites More sharing options...
Domzs Posted February 8, 2013 Share Posted February 8, 2013 Oh , I forgot , I didn't use OE sensor . I just used signal wire to the speedo and GM sensor . Nissan sensor is a photo sensor , you can make your own reluctor wheel out of whatever . Quote Link to comment Share on other sites More sharing options...
skirkland1980 Posted February 8, 2013 Author Share Posted February 8, 2013 UPDATE: This does work. My speedo is still a little off but I should be able to get it closer with different speedo gears. This mod will not effect the odometer. Quote Link to comment Share on other sites More sharing options...
skirkland1980 Posted February 8, 2013 Author Share Posted February 8, 2013 Even better news: Since my speedo was still too fast, I did some more calculations and it appears that 10 slots in the trigger wheel would be ideal. So...I made a 10 slot wheel from an Ace rewards card. Thanks for looking. Quote Link to comment Share on other sites More sharing options...
Domzs Posted February 8, 2013 Share Posted February 8, 2013 Good deal . Odometer reading will be different , accumulates more miles than actual . Quote Link to comment Share on other sites More sharing options...
skirkland1980 Posted February 8, 2013 Author Share Posted February 8, 2013 Yes. I pulled out the worm gear so now the odometer does not work. I figured this mod was worth doing because is was completely free. The best way to do this, to keep the odometer accurate, is to adjust the speed of the speedo cable before the gauge cluster. For that you would need a reduction box. (about $80) Quote Link to comment Share on other sites More sharing options...
Domzs Posted February 9, 2013 Share Posted February 9, 2013 Who needs odometer . Just change your oil every 3 to 5 months. LOL . Quote Link to comment Share on other sites More sharing options...
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