hey all kinda new to the forum i have a 94 z28 just bought it recently havent had much time till now to look into it.

the cars speedometer doesnt work and it does not shift properly first gear goes to 5000rpm b4 shift to second then doesnt down shift until i do it with the shifter.

i just replaced the speed sensor and it made no differenct at all.

any ideas whats going on here??? any help appreciated

 

you have speed sensors at the front wheels and at the center off the rear defferential in addition to the one at the rear of the trans. which did you replace

 

The wheel sensor are just for the ABS, If a scan tool is picking up the right speed the issues are two different problems.

 

ok so update. the speed sensor i replaced was the one on the rear of the trans cause i had found out the previous owner put a new trans in... i also had read the the instrument cluster has often been to blame for the same symptoms so i now today changed the cluster and still no change.

when i first start the car no issues begin driving doesnt shift to second till about 5000 rpm then doesnt down shift until shifted with the shifter. no check engine light until the car shift to second.... one code was a speed sensor code anothe was a tans temp code...

 

the computer uses the speed sensor and the engine rpms and the throttle postion sensor to decide when to shift. be best to get it hooked up to a good scanner that can see if the computer is getting the info that it needs and if not what is not providing info.

 

Does the speedometer work now that you changes the cluster? High shift points can be cause by issues with the trans itself. I it is kind of a normal failure point. Your speedo not working is the only odd ball factor.

 

no speedo still not working nothing has changed since ive done the 2 part changes... i have a good computer coming tomorrow so ill hook it up and see if i find any answers. very puzzling

 

do you know what year the trans came from, i am wondering if this trans is outa a 95 or 96,

 

no i dont know where the trans came from but it still has all the jasper stickers on it...

update: got the computer hooked up to it. pulled 10 codes in which 75 percent are ecu and prom related... ordered new ecu thru chevy 255 plus 150 to program idc the cost but this is my next fix attempt based on the codes i pulled from the computer.

i will update after ecu install.