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I own a 90 base coup L98, 6spd, last year I upgraded my gear ratio from 3:33 to 4:11 and also picked up a electronic ratio adapter from Zip corvette, does anyone here have experience with installation of these, I have it installed but speedometer is still too fast as per actual speed. I talked to someone from zip and he did a calculation for me but that didn't change anything, but today I just realized I may have it wired in wrong. Instructions come with wire directions but not a schematic. I have factory manual's and have located wires to use, power, volt12 ignition, ground, signal from VSS,
And VSS out from ECM to CCM
Any one using this mod please let me know 🙄
I solved the same problem by just swapping out the gears driving the VSS to the correct ones for 4:11s. Haiback over on the ZR1 section sells them. Much easier and correct mod for the car.
So I drove over to Chicago area from Springfield and picked up these transmission gears for 4:11 changeover from Haiback technology's he does ZR1 mods and such they came with instructions and some advice from mark as well made this a 2 hour installation. Other wise I would have pulled the extension housing like the manual says got it on the road and speedometer is nearly spot on. Now since everything works good, but since I fixed the tach the engine won't rev high and now speedometer is working cars seems slower! WTF,,
What did you have to do to the tach? Often on a 1990 (I have one of those also) it is either the capacitor or the circuit board that causes the tach to malfunction. Neither should create a limiting factor for the engine.
Sorry my post didn't come off more humorous, but now that my tach works I pay attention to my revs and now that my speedometer is accurate I mind my speed so the car really is slower lol thanks for reference to the ZR1 shop! He sure does love them ZR 1s, not much for base coup L98 trash like me lol
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Speedometer ratio adapter
