That depends on the gear ratio of the truck. It is hard to answer your question with out that infomation. SORRY
1800 or so
The power of the engine of the 1975 Chevrolet Suburban automatic is 99,50 HP at 3600 rpms. The maximum speed is 102 mph.
60
It would depend on the gear ratio and transmission. stock tires 235/70r16: auto(O/D) with 3.55 gears =2160 rpms auto(O/D) with 3.73gears = 2270 rpms manual with 3.73s = 2360 rpms
You should be around 2200 - 2500 rpms.
Out 2000 Dodge Neon does 2500 rpms at 60 mph. Grace
around 5 and 6 x 1000 rpms
on the end of the shifter there is a button. while doing 50 mph in drive hit the button and watch the rpms, hit it again and check rpms again. you will be in od when the rpms are at the lowest, hope this helps
If your vehicle has an automatic transmission with overdrive, then at speeds above 45 mph, it should be in overdrive, which reduces engine RPM's to save fuel.
It sounds like your clutch is slipping.
108 mph
8 cylinder 100 mph