Alright you guys so I kow ive asked this question before but I ditn really get an answer...

The thing is this..When I am on the freeway going at about 70-75 MPH....my RPM'S are at 4000...I know for a fact that I have a stop non posi rear end and that my tach is wired up correctly and everything...becuase I rev it to 4000 and it sure sounds like it.....so I more than sure that the tach is not off. So I am really not sure my car is reving so high...The base timing is advanced by 12 degrees, My car is literally reving at 5000RPM'S if I wanna even go 80MPH on the freeway it sucks because I wanna go fast but Im afraid Ima "blow" the engine....

 

I have this same issue I put a new ATK motor into the car and it does this. I usually cruise at 72

 

What ar your RPMS at 72?

 

These "tach"s are notorious for failing; after all they're not an "instrument", they're just a "trim package". Their usual failure mode is to read WAY high. I have one in my pile that reads almost twice what it should, and others here have reported them reading 3 times reality. So yours fits right in; sounds like it reads between 1½ and 2 times actual engine RPM.

Check it against a piece of actual test equipment.

 

My aftermarket tach shows 3000 when my stock shows 4500ish.

 

My stock tach is way off i knwo that part but I wires an aftermarket tach and it showing 4000RPM and its wired correctly...

 

3000 @ 72pmg mine easiyl goes over 4000 at 70

 

Set to 8 cyl, not 6 or 4 cyl?

 

I checked and it was set to 4...I set it back to 8 and when I drive it wont pass 3000RPMS...?? if it does the engine sounds over reved....

 

Are you shifting into 4th gear? Can you feel it going through all the gears? it might be staying in 3rd gear if the rpms are as you say.

 

His info says he has a 5 speed...

 

reading comprehension ftf. OK, then either his clutch is slipping mad, or he has a tach issue for reals.....Or he hasn't learned o shift past 3rd gear

The 5 speeds are like 3.08 rears correct? My 3.73 rear with 24" tires and my 700r4 spins 2500 at 70. I would think a 5 speed should be turning 2000+- , half of what his tach says

 

Either the tach is off or you are geared differently then you think.

 

Well I am still confused onto what can be going on whats a normal RPM range when driving down the freeway at 75PMH in 5th gear?

 

For a typical LG4/T-5 car w 2.73 or 3.23 gears, around 2200 - 2400 RPM

 

Are you sure the previous owner didnt swap a lower gear into the rear? An easy way to check is jack up the back of your car and mark your driveshaft and a tire, then rotate the tire a full turn and have some one count the drive shaft rotations. This will give you your ratio. Im pretty sure lol, hope this helps.

 

Stop asking questions. Go determine what rear gear is in the car.

Then measure the diameter of your rear tire. Take that information and plug it into an rpm calculator. (google search)

Then you will know.

 

You guys are right that the only way I will knwo....I know for sure thats its a non-posi, but lets say I do have higher gears..will that explain the high rpms?

 

are you running 12 inch trailer tires in the back?

you either have 4.xx gear ratio or a bad/incorrectly installed tach

my money is on the latter

 

I wanna say that its the tach thats wrong but When Im driving the engine even sounds/feels liek its at 4000RPMs..So I am not to sure that the tach is wrong....

 

Agreed even with different rear gears you shouldn't be turning anywhere near 4000 rpm. Unless you have some crazy rear end ratio like 5.xx:1 or really smalll tires. What size are your rear tires? Need to verify correct tach operation first Engine will really be screaming at 4k rpm Do the test to determine your rear end ratio then by jacking it up and seeing how many revolutions the drive shaft turns with one rev of tire

 

Like ive said I really hope its the tach that I wired wrong but....Ima do lift up the rear and do th test either way.

 

get a timing light with integrated tach. Have someone tell you what the tach shows in the cluster and then compare with the timing light

you're going to be shocked

 

If I was the betting kind, I'd bet that a tach that says your motor is doing low 2000s on the freeway, is substantially accurate.

I think you're wasting your time and effort carrying the matter any further.