depends on alot of variables. Like tire hight, and gear ratios(rear end). More information should help solve this problem. From there you could use a gear ratio calculator. Do you happen to know the final output ratio for your final drive gear?
I was un-aware that such an animal existed. The IDI turbo was a 1 year only deal, 1993, and to the best of my knowledge, 1992 was the last year of the C6. I thought only the E4OD was available behind the 7.3 "non-PS" turbo diesel. If it's a F-250 with a 3.56 Dana-70, and a C6, your gonna bump redline at about 78 mph. If it's a F-350 with a 4.10 Dana-70, and a C6, redline comes at about 70 mph. With an E4OD, those figures go up to roughly 85 and 92 mph. Running a diesel @ redline will not harm it. Overspeeding it will cause the valves to float, and power will drop off........ "Will not harm it" is a relative term, however...... Abuse it and it will break.
What is redline for a 7.3? This is a modified jalopy hauler. The drivetrain was originally a 6.9 which has been replaced with a 7.3 and Banks turbo. At 65mph it is now turning 2800rpm and getting 11 mpg. Been told, 1800 is a good rpm for 65 mph and should get 20mpg at this rpm/speed. Did the 6.9 like higher rpm's?
3400 is the "redline". 2800 @ 65 sounds like 3.56 gears to me. F-250 I presume? 11 mpg is ****-*** poor mileage... Have you had your injectors pop-tested? Has someone "cranked up" the smoke screw on the IP? That combo should be getting 16-18 mpg... 20 is not an unreasonable expectation if you drive it easy. I'd go ask these questions on the diesel-place, or another diesel web site. Sounds like you have some issues.
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