Dawgz83948 Posted September 11, 2011 Report Share Posted September 11, 2011 Any way to find out what the ratio is of the rear end in my 620? I need to replace the speedo gear since the speedo doesn't work. (I've already replaced the cable) Quote Link to comment
flatcat19 Posted September 11, 2011 Report Share Posted September 11, 2011 It's on the firewall. A search will tell tell you which of the 2 different rear ends yours has. Quote Link to comment
Laecaon Posted September 11, 2011 Report Share Posted September 11, 2011 It's on the firewall. A search will tell tell you which of the 2 different rear ends yours has. assuming it hasnt been changed... Quote Link to comment
datzenmike Posted September 11, 2011 Report Share Posted September 11, 2011 Fatcat I think you are thinking of the 720 engine tag. The 620 doesn't have one that lists the rear ratio for the differential. The '72-'78 standard transmission 620s had a 4.375 ratio. The '79 had a 4.11 The '72-Sept '73 automatic had a 4.625 and 4.375 from Oct '73 through '79. Have you had the speedo pinion out? Any reason it would be damaged? Be sure the transmission cable end is properly fitted and locked into the transmission drive pinion. Now pull the dash end off and drive or push the vehicle several feet. Does the cable turn??? If so either the gauge end isn't properly seating or the gauge is not working for some reason. . Quote Link to comment
flatcat19 Posted September 12, 2011 Report Share Posted September 12, 2011 Fatcat I think you are thinking of the 720 engine tag. The 620 doesn't have one that lists the rear ratio for the differential. Touche. I know nothing of the 620's. Hell, I know nothing about any of these things. :D Quote Link to comment
datzenmike Posted September 12, 2011 Report Share Posted September 12, 2011 Touche. I know nothing of the 620's. Hell, I know nothing about any of these things. :D The know nothing is the true beginning of knowledge grasshopper. (did I sat fatcat in my post? Likely a Freudian slip.) Quote Link to comment
flatcat19 Posted September 12, 2011 Report Share Posted September 12, 2011 (did I sat fatcat in my post? Likely a Freudian slip.) Many factors have led to the flatcat being quite round. I'll accept it. :D Quote Link to comment
Dawgz83948 Posted September 13, 2011 Author Report Share Posted September 13, 2011 The diff seems to have junk yard tags on it (paint pen). Any physical way of verifying it? The cable is nex and installed correctly. I think I figured out the problem though. The transmission in the car is a 280zx transmission so it's probably the upside down speedo gear issue I was reading about. Quote Link to comment
datzenmike Posted September 13, 2011 Report Share Posted September 13, 2011 Yes, '80 and on transmissions will not work with pre '80s speedo pinions. There is a way around this. Take the pinion out and with an angle grinder and a cut off blade, (about $5) carefully cut a notch for the key as close to 180 from the one on there now. This is what I did on my 710 5 speed install. I was getting desperate to get it working and should have taken pictures but once installed and working I wasn't going to take it out again. :P I have an early '79 zx but put a '85 720 diesel tailstock on it and didn't have the proper pinion for it. Here's picture (not mine) of what I mean ... Cheaper than a rear end. Quote Link to comment
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