ok i have a couple problems with my 91 240sx. it has a ka24de in it and nothing works on my gauge cluster excepts the rpms, clock and miles. and i dont know what to do there, if you have any suggestions please tell me. and my other problem is my car gets real shakey when i hit 3000 rpms. and it wont go any higher than 3 grand, has this happened to anyone else? please help.

 

check speed o cable and remove gauge cluster and check wireing.
check for vacuum leaks

 

your speedometer is most likely not working due to no speed sensor on the tranny, or its just not connected.

with the car not revving more than 3k rpms, check your MAF. either your MAF is bad, or there are some wires crossed leading to the MAF.

 

ok i know this is gonna sound stupid. where at on the tranny is the speed sensor? and also what is a MAF, where is it? and how do i know if it is bad?

 

MAF is Mass Airflow Sensor

for all your questions www.google.com can help
... try searching around some, the answers aren't always going to be handed to you

 

Well, if you don't know much about the car, and where to actually check, I'd suggest getting an FSM, or a Factory Service Manual, and studying that a bit...

It could really be a number of things, and by what you are telling us, it's very hard for us to narrow it down unless we're right there with you.

Your best bet might be to take it to a mechanic.