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Wingnut · 04-08-2015, 03:33 AM

Looking for a little help from anybody that has the older Cummins 8.3 (6 CTA) mechanical fueled engine.

I have a 1996 Freightliner FL70 with the Cummins 8.3, Eaton 6306A, 4.33 rear gears and 11R-22.4 tires. Its current setup is a 26’ flatbed and GVW is 34k. It buzzes along at 2100 rpm at 60 miles per hour. To me, that just seems too high. The truck has been retired from commercial use and I am converting it to an RV tow rig and I would like to squeeze some fuel economy out of it.

I am trying to find out what the factory recommended cruising RPM should be or several people that are running the same engine to compare it to. I have found tidbits of info that it should run at 1650, 1950, 2150 rpm, or 200 rpm over max torque, or 80% of rpm window. Nothing is consistent and nothing to verify it with.

I can switch transmissions, gears and tires around but I have to find out what the actual cruising rpm should be first.

Any thoughts or ideas?

04-08-2015, 03:33 AM	#1
Wingnut Junior Member Join Date: Mar 2015 Location: seattle Posts: 3	Cummins 8.3 (6 CTA) Looking for a little help from anybody that has the older Cummins 8.3 (6 CTA) mechanical fueled engine. I have a 1996 Freightliner FL70 with the Cummins 8.3, Eaton 6306A, 4.33 rear gears and 11R-22.4 tires. Its current setup is a 26’ flatbed and GVW is 34k. It buzzes along at 2100 rpm at 60 miles per hour. To me, that just seems too high. The truck has been retired from commercial use and I am converting it to an RV tow rig and I would like to squeeze some fuel economy out of it. I am trying to find out what the factory recommended cruising RPM should be or several people that are running the same engine to compare it to. I have found tidbits of info that it should run at 1650, 1950, 2150 rpm, or 200 rpm over max torque, or 80% of rpm window. Nothing is consistent and nothing to verify it with. I can switch transmissions, gears and tires around but I have to find out what the actual cruising rpm should be first. Any thoughts or ideas?