74 k10 going 55 mph is at 3,500 rpm

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squaredeal91

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Greg bush
Truck Year
1991 SB
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K30
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Does it run reasonably well, sluggish? How is the timing?
 
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Oregon
First Name
grant
Truck Year
1974
Truck Model
k10
Engine Size
350
Does it run reasonably well, sluggish? How is the timing?
She run’s pretty damn well, I rebuilt the engine around 300 miles ago. She’s got a stock bottom end, .30 bore, heads from a 71 camero, new edlebrock intake, 1103 summit cam, headers and a street fire msd distributor
 

JBswth

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Vallejo, California
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James
Truck Year
1973
Truck Model
C25
Engine Size
292 cubic inches
I got a 1974 k10 with a 203 transfer case, turbo 350 and a 355 sbc. The rear gear is 3.73 and at around 55 mph cruising the rpm’s are up to 3,500. That seems a bit high to me, does anyone know what I should do to the truck to get lower rpm’s at 55? I’m also getting 8mpg.
3500 at 55 MPH? You must have 4:56 gears for the engine to be revving that high. Others are saying that maybe your trans isn't upshifting into 3rd, but I have a hard time believing that you wouldn't be aware of a problem like that.

J.B.
 
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JBswth

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Location
Vallejo, California
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James
Truck Year
1973
Truck Model
C25
Engine Size
292 cubic inches
I got a 1974 k10 with a 203 transfer case, turbo 350 and a 355 sbc. The rear gear is 3.73 and at around 55 mph cruising the rpm’s are up to 3,500. That seems a bit high to me, does anyone know what I should do to the truck to get lower rpm’s at 55? I’m also getting 8mpg.
A good way to tell is to jack the rear end and have a couple of buddies turn both rear wheels together one complete revolution, and you see how many revolutions the driveshaft turns. If you have 3:73 gears, your driveshaft will make a little less than four complete revolutions, but if it makes more than four, you don't have 3:73 gears, you have something deeper.

J. B.
 

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