Shifting point

[mr_speed77]

What do you guys shift at? I shift at like 2500-3000. Is over 3k too much to rev to all the time?

 

[MAKG]

Not really. It depends more on throttle position than on RPM (so it's different on hills). The only thing to avoid is getting the computer into "passing mode" continuously. I doubt you'll do that cruising on level ground at 3000 RPM. If you did, you would notice it in the fuel mileage.

The question is not where you shift, but rather where you shift INTO. Always over 2000 RPM on a 4.0L (higher on 2.9L and especially 3.0L). That's for economy. For acceleration, shift at the power peak (I believe 4700 RPM).

 

[Donnie strickland]

Depends on the situation , but sometimes it might be as high as 3500-4000 rpm. Why?

 

[AllanD]

Power peak on a 4.0 of thatvintage is 4200rpm

Revving as high as 4400-4600 is OK.
the rev limiter should stop you from going past 4950.

3000rpm is fine for every day casual driving.
If you are accelerating out into traffic 4500 or so can be fun.

AD

 

[NVR2FST]

If you're going for speed, rule of thumb is usually around 600 rpm or so above peak power. That way you sweep back through the power band without falling to far out of it.

Good to know on the economy. I've wondered the same thing since I bought mine a few months ago. I'll give it a try once it's back together.

 

[4.0LRanger]

Power peak on a 4.0 of thatvintage is 4200rpm

Revving as high as 4400-4600 is OK.
the rev limiter should stop you from going past 4950.

3000rpm is fine for every day casual driving.
If you are accelerating out into traffic 4500 or so can be fun.

AD

So there is a rev limiter on the 4.0 then? I know when I rev it pretty high the thing starts popping. Is that the limiter coming on?

 

[AllanD]

Yes, the "popping" is the rev limiter.

The actual ideal shift point is a carefully considered compromise.

what you need to know is the torque curve of the engine with a fair degree of accuracy and know your gear ratios.

And the idea is to maintain maximum torque to the
wheels (or ore precicely at the driveshaft flange)
without hitting the rev limiter or Red-Line.

Basically it's playing to the "magic of gearing" or if you
prefer "torque multiplication" from the gears.

You basically want to rev it until the point to where when you upshift
you shift into a situation where you get more torque in the taller gear
because torque was falling off in the lower gear you just shifted out of.

Between each gear there is a tradeoff point where revving further in the
low gear become pointless, so you shift the instant it gains you something
to do so...

These points occour as a matter of the interaction between the engine's torque curve
and the actual specific (transmission) gearing.

It's also why a "close ratio" transmission is generally
prefered for performance applications, because it narrows
the jump between gears making it easier to keep the engine
near the power peak.

AD

 

[mr_speed77]

Interesting, Well i just think my engine at 3k is reved too high. I have 3.27's also so im not sure. Since replacing all the bulbs in my gauge i can see the tach at night. I have been keeping an eye on it more throughout the day.

 

[MAKG]

If you're doing 3000 RPM in 5th with 3.27s, you're speeding ridiculously fast.

But I think the real problem is that you have an ignition problem. Tachs can read high with noisy ignition primaries.

 

[AllanD]

I agree with MAKG, if you are reading 3000rpm in 5th
with 3.27's you are either going 95mph or your tach needs to have an exorcisim performed on it.

My truck with 4,10's is doing >75-ish at 3000rpm.