Likely gear ratio?

[436'd skylark]

Ok, I bought a rolling '88 3/4 ton chevy. ITs a six lugger with a 14 bolt rear. 350 truck, short cab long box 4x4. any guess on what the likely ratio is? I'm hoping 3.73s or 4.10s, but I know the chances. thanks!

[75K30]

Joe:
I am willing to bet a cold beer that it has a 3.73:1.
These 14B's that were six lug, semi-floating 9 1/2" ring gear with 1.370" diameter 33 spline axles were mostly 3.73's.
The heavier duty 14b full floaters were 4.10's.

[436'd skylark]

cool. I was worried about 3.42s. I didn't want to lose the gear. it was really more of a headache anyway. changing speedo gears and what not. This whole project is borderline assine. How hard could it be to swap the frame. I'm thinking that I'll leave the fenders and core support bolted up, and pull the cab and nose as a unit. Then I'll pull the motor, finally ditch the wee, and bolt up the 350 Buick motor. Then I'll drop the motor/trans into the 3/4 frame, hook up the driveshafts. and the other undercarriage stuff. should be easy with no carriage on top.

I'm trying to list the stuff I'll need to pull to lift the cab off..

E-brake cable
Steering column/shift linkage
Transfer case linkage
speedo linkage
The computer harness, and engine harness
radiator, and the lower shroud


Anything I'm missing? any tips?

[pbouffard]

my 88 3/4 had a 410 14": ring gear, so its 50 50, i needed another rear end pulled it from another 88 and that one is a 373 14" ring from a 3/4 ton also, im running it now, im getting better gas milage now, just dont have as much pull, i dont need it.

[75K30]

Might remember heater core stuff. Those hoses will have to come off to free up the cab. There are some fuel vapor and return lines that are attached to the cab. There are probably a small handfull of things to still remember, but you will find out when you start to pull it.

pbuffard:
Not sure what the 14" refers to in your reply. The 14b's had two different size ring gears. The 6 lug semi floating 9.5" ring, and the 8 lug full floating 10.5" ring gear.

[436'd skylark]

heater core, thats a good call. might have looked pretty silly with a couple of hoses so tight I could play them like a guitar.. I'm sure there will be a bunch of things I forgot..

[Hayden]

Look for any grounding strips from engine to firewall

[pbouffard]

Originally Posted by 75K30

Might remember heater core stuff. Those hoses will have to come off to free up the cab. There are some fuel vapor and return lines that are attached to the cab. There are probably a small handfull of things to still remember, but you will find out when you start to pull it.

pbuffard:
Not sure what the 14" refers to in your reply. The 14b's had two different size ring gears. The 6 lug semi floating 9.5" ring, and the 8 lug full floating 10.5" ring gear.

sorry that 14" is a type "o" dam i hate when i do that meant 14 bolt

[75K30]

Originally Posted by pbouffard

sorry that 14" is a type "o" dam i hate when i do that meant 14 bolt

I knew that, it was no biggie, I was just being a wise guy. Lol.

[J Long]

The most accurate way to find out gear ratio is to pull the cover and count gear teeth. Divide the number of ring gear teeth by the number of pinion teeth and that will give you the ratio to the decimal. It means changing gear oil. If you don't want to change it, the second but less accurate way is to lift the truck on one side if it is a non posi and put in neutral. Mark the drive shaft at top with chalk (12 clock). Mark and rotate the tire exactly one revolution. Note the number of full drive shaft revolutions while you do this. The mark on the driveshaft will probably land at some odd angle like say 9 clock which works out to .75 turns plus the number of full revs. If it made 3 full revs, it works out to 3.75 turns which is very close to 3.73.