RPM for shifting?

[1980cdeluxe]

I put a tach in my 78 2wd today to see what I've been shifting at, and the tach is saying on my normal shift it's no more then 2,200rpm. It has a 3.40 gear ratio and a 4 speed granny. The original manual that comes with all light truck 78's says change from second to third (final gear) at 35-45mph but It feels like the engine is whining so bad although the tach is reading no higher then 3200rpm at 35-40.. Is this safe, is it the engine that is whining or is it the transmission/rear end making it sound this way?

I notice if I dont shift this way the truck has no power, and will develope a spark knock... If I wait and shift higher it's smooth and has plenty of power.

Not really a great question, I just don't feel like putting to much strain on the little 250 ... How many RPMS would be too much?

[VileZambonie]

Engine RPM/torque can all be felt by shifting when it feels right.... The grade you are on the conditions of the roads are all going to be factors too aside from final drive ratio and tire size. Just shift the way it feels most economical for the way you are driving...

[1980cdeluxe]

Been driving the truck a lot harder now, i'm just wondering if anyone has a clue to what the old 250's peak HP at lol? I can't seem to find the information anywhere, but i'm guessing around 4000-4200? I usually wind it up to 4100 between shifts..

[Leadfoot]

I don't have the specs handy,but most 6 cyl. generate max torque around 3200-3500 rpms..personally,on a stock twenty year old 250 I wouldn't take it to 4100 rpm unless I really needed to..but,

I shift my little 468 at 6800 when I feel the need

Tim

[roundedline]

Peak HP for a new 250 inline was 115hp @ 3800rpms and 195lb/ft @ 1800 if that helps.

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[1980cdeluxe]

As always, thank you roundedline for the help