Ok so I just bought a 91 RS with a 305 tbi 5 speed. One thing that is wrong with it is the tachometer doesn't work. It stays all the way to the right all the time. But the upshift light still works.

So what i'm wondering is how reliable the upshift light is. When i'm driving the car normally i can tell when to shift by listening and feeling. But when i want to go full throttle i dont want to over rev it.

What i've seen it do so far is tell me to shift depending on how hard im pressing the gas. So my question is, when my foot is all the way down, will it tell me to shift when i've reached the redline? Because i have no way of knowing.

If i go by the upshift light, i can hit almost 60 in second gear. Does that seem right?

 

you should never base your shifts off that light, get the tach working accuratly. theres many threads on here about getting it reading right. if it just doestn work at all id get it replaced. or you can get an aftermarket tach that will be accurate.