hey i just swapped my 96 lx y8 tranny on my zc with a z6 tranny everything mounted up fine but im having issues with the speedometer not reading the correct speed example it shows me going 50mph when im doing 40-45mph am i going to have to get a new guage cluster or ecu or what to get it to read the correct speed (im a noob to this still but im learning)

thanks

p.s. im having a very slight 3rd gear grind guessing its the synchro so i had the fluid swapped with synchro mesh but the guy at the shop added a quart of ATF too im thinking i should swap the fluid myself and use just gm synchromesh fm only

 

Drain whatever concoction you have in there and put some 10w30 in it (a lot of guys find MTF too thin for older D-series transmissions)

As far as the speedometer what makes you think it's off?

 

yeah i planned on it i knew they were retarted for adding the atf but i wasnt charged so the money i saved will go to the right fluid change!!! besides feeling like 40 when it says im going 50 and having to get the speedometer upto 37-40 in a 30mph speed zone to keep pace with traffic happens in school zones im going 35 by what the speedometer say and keeping a 25mph pace with traffic giving me the feeling the speedometer is off...wow i went a long way to explain that sorry!!!

 

Was the gear ratio different between the two trannys, tire size? If so you will have to change the gear out in the speedo meter to match the new output.

Try running a GPS while driving to see how far you really are off...