Full throttle shift points?

rickinAZ

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This is my first diesel, and with a 4,500 rpm redline, it's the lowest revving vehicle I've had since my minibike at age 14. Today I noticed that, running flat out through the gears, it shifts at only 3,900 rpms. What happened to the last 600 rpms? Most vehicles tend to use everything that's on the table under full throttle conditions.

BTW, it took me 6 months to discover this; it's not like I'm revving the p*ss out of it every time I jump behind the wheel.
 

Compression-Ignition

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That's actually really late. I don't see a reason why they would set the shift points so deep into the RPM's?

The way I understand it is that if peak torque is 1850 RPM you want the shift to take place there or just beyond it at say 1900. Whatever the transmission can handle really. <<< Just my understanding mind.

Gasoline-powered vehicles usually have much more shallow torque curves, which is why they might shift further into the RPM band.

But now I'm really curious and I think sometime in the near future I'm gonna find a safe stretch a road to flog on the Jeep and see if I notice the same thing. Maybe I'll throw the Edge CTS3 in the Jeep to help pin the shift points down. I don't recall if it read any transmission related PIDs though? Although I suppose if it's that close to redline, the factory gauges should show it easy enough.
 

JDub11

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It's out of fuel and air at that rpm. Diesels make all of there power down low in the rpm range. They shift early to keep the rpms where the power is. Gas engines power is usually at the top of the rpm band, and they generally don't make as much torque so they make up for that with more gear and higher rpms. This is why the diesel dosent down shift as much on hills and with headwinds. It has a enough torque at low rpm to keep chugging along.
 
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