Blower motor/ 14-bolt gearset.

[tombone74]

I have some questions that have been puzzling me for a while now. Recently I purchased a 1978 Chevy Crew Cab truck, it was originally equipped with a 454 ci engine and a turbo 400 trans, both of which the previous owner kept. Anyway I counted the teeth on the ring gear and pinion and came up with a gear ratio of 3.21:1 is this correct?? Or should it be 3.23:1 or 3.42:1?? Did Chevy make a 3.21:1 ratio for the 14 bolt (10.5' ring gear)? Right now the truck is running with a 350 engine and turbo 350 transmission. Amazingly everything works except the blower motor. It only spins at a slow speed no matter which setting I have it in. I have checked the blower motor resisters, replaced the blower motor itself and I want to think that it is the blower (heater) motor switch but I'm not sure, is there anything that I am overlooking?? I have made sure that I have a good ground, as of yet the heater blower motor not speeding up when the blower motor switch is in the "high" position. Any assistance in this problem would be greatly appreciated.

[77bowtie]

Best info I can find says 73-up 3/4 & 1 ton 14 bolt 10.50" Ratios= 3.42, 3.73, 4.10, 4.56. "Thick Gears"(i don't know)= 4.56, 4.88, 5.13.
Can you checkout your blower switch with a test lite or a VOM. I had to work a bit on mine to get it to operate. Still not perfect. Good Luck..Jon

[tombone74]

Thanks, I'll check the switch.  About the gearset, I plan on switching it to either a 3.73 or 4.10 because with the gears that it has now makes it a dog. I think if Chevy did make a 14 bolt with 3.21 gears the truck must have had a 454 big block because my 350 really seems to be struggling to get this thing moving. Thanks again.

[77bowtie]

If you want a dog for getting off the line my donner 79 silverado has a 12-bolt 2.76:1 ratio rearend. I'll never understand why anyone would use this ratio on a truck!  

[tombone74]

A 2.76:1 ratio in a pickup?? My truck weighs about 8,000 lbs, or at least I think that's what it weighs. It's a 1978 Chevy crew cab. What ratio would be better to go with a 3.73:1 or 4.10:1 ?? It has a 350 engine, 350 trans, and I will be using it mostly for hauling and trailering on the highway. It has whopping 16.5 inch rims, and the tires that are on it measure about 31 inches in diameter.