VA WTB 71-72 rearend

[panhead59]

I am looking for a 71 or 72 coil spring, 5 lug rearend to replace the 6 lug out of my '68 swb, that I now have for sale. Prefer posi but may intertain non-posi for right price. I am willing to travel from SW. Va. a resonable distance to P/U. What have u got? Thanks

[panhead59]

Wow. Not one out there for sale? There's a guy on west coast looking for one also. These things are getting very hard to come by. Only 4 (posi) on junkyard finder site in whole country and they are outrageous. $650- 850.

[GR8-68]

How far are you willing to travel ? I am near Greensboro NC, I may part out my 72 I have.

Just google mapped it from my shop to vinton is 2 hours

[flashed]

Im going to part out a 72 I have soon ,not sure what rear it has though .

[panhead59]

Greensboro is definitely not too far. Even Ga. if the gears and price were right. Please keep me in mind and let me know when/if you decide to sell. Of course my first ? will be what gear ratio. Thanks and look forward to hearing from u both.

[flashed]

How do I find out the gear ratio ?

[GR8-68]

I can check on the spid tonight and see if it is listed

[GR8-68]

I found my spid in another thread it has 3.73 gears probably not a posi though (just a guess)

[GR8-68]

How quick are you needing this ?

[67ChevyRedneck]

Originally Posted by flashed

How do I find out the gear ratio ?

I found this on another site, pretty easy:

This is easy to do. FIRST chock the front wheels in both front of the tire and rear of tires so it doesn't roll since your E brake goes to the rear wheels. Jack up the rear end with both wheels off the ground. I usually use a floor jack in the center of the axle. With both rear wheels off the ground. Spin one wheel. If the other wheel spins in opposite directions, then you likely have an Open differential without a locker or LSD, but G80 Locking Diff does also spin in opposite directions, so you could still have locking differential. That doesn't matter for figuring gear ratio though. Bottom line here, you're trying to determine if the wheels spin in opposite directions, or Not. If you go to spin the one wheel, and it doesn't turn at all, then you'll need to put the transmission in Neutral, and this is likely going to mean you have a locker, good LSD unit or welded spider gears. After the trans in N, spin the one wheel, and it's likely to have both rear wheels spinning in the same direction.

It's important to know this, if the wheels spin in opposite direction or if they spin the same direction. If they spin the same direction, then it's even easier to determine the gear ratio. If they spin in opposite directions, then you have another step of multiplication to do. So lets do the easy one first, and assume the wheels spin in the same direction.


I use the valve stem on the tire as marker and start my wheel spin count at 12, 3, 6 or 9 o'clock position. Whichever position I have the pinion yoke or U joint either straight across or straight up and down. It just makes it easier for an accurate count. Then you're off. Make 1 full tire spin by hand and count how many times the driveshaft, or the pinion yoke turns. If the driveshaft spins:


Wheels Spin in the SAME direction.

A hair over 2 1/2 times or 2.5 times, then safe to say ratio is 2.56:1
A hair under 2 3/4 times or 2.75 times, then safe to say ratio is 2.73:1
A bit over 3 times, then safe to say ratio is 3.08 or 3.07:1
A hair over 3 1/2 or 3.5 times, = 3.54 or 3.55:1
A hair under 3 1/2 or 3.5 times, = 3.42:1
A hair under 3 3/4 or 3.75 times = 3.73:1
A bit over 4 times = 4.10 or 4.11:1
A hair over 4 1/2 or 4.5 times = 4.56 or 4.57:1
A bit under 5 times = 4.88:1
A bit over 5 times = 5.13:1

You should have this by now, so that's as far as I'm going and anything else is very uncommon anyway in light duty trucks and cars for sure.

Now, if the wheels spin in opposite direction the procedure is a bit different.
You must put 1 wheel back on the ground so it stays stationary and you can get an accurate count. This is because if the wheel is moving, that means the spider gear to the that other axle shaft is moving and you don't know exactly how much and it makes your count inaccurate. So with just one wheel in the air, transmission in Neutral so that the driveshaft is able to spin, then count the pinion yoke spins to 1 full tire revolution. Now here's the difference and the added step. Take the # of spins and multiply it by 2 and that is your gear ratio. The reason you have to multiply it by 2, is because the distance you are moving the wheel, the spider gears are spinning backwards on the other stationary axle shaft gear, cutting your pinion yoke turns in half. So if you pinion yoke spins:

Wheels Spin in the OPPOSITE direction.

A hair over 1 1/4 times or 1.25 times, x2 then safe to say ratio is 2.56:1
A bit over 1 1/3 times or 1.33 times, x2 then safe to say ratio is 2.73:1
A bit over 1 1/2 or 1.5 times, x2 the safe to say ratio is 3.08 or 3.07:1
A hair over 1 3/4 or 1.75 times, x2 = 3.54 or 3.55:1
A bit under 1 3/4 or 1.75 times, x2 = 3.42:1
A heavy bit under 2 times x2 times = 3.73:1
A bit over 2 times x2= 4.10 or 4.11:1
A hair over 2 1/4 or 2.25 times x2= 4.56 or 4.57:1
A bit under 2 1/2 or 2.5 times x2 = 4.88:1
A bit over 2 1/2 or 2.5 times x2 = 5.13:1

And that's how it's done. Now noone should need to remove their diff cover, unless you're just wanting to do a differential oil change, to calculate your gear ratio. Which, if you don't know the history of your truck, it's not a bad idea to change the gear oil, and identify which carrier you might have when the cover is off. Keep in mind, some units require special oils like synthetic, or synthetic blend, some require GL4, some GL5, and some require LSD additive, so make sure you get a good ID on your carrier type if it appears to be a Locker or LSD.

They are getting a little harder to find. I went on a 6 hour round trip down into GA to get a 72 rear with a 3.73 open differential for my C10.

[southern parts]

There is a 3 letter code on the top of the pass side axle tube. Once you find it you can look up the gear ratio online. Only a 2 letter code on 67-70 rearends.

[ghalperin]

Originally Posted by southern parts

There is a 3 letter code on the top of the pass side axle tube. Once you find it you can look up the gear ratio online. Only a 2 letter code on 67-70 rearends.

I wouldn't rely on the code or SPID. My rear end with codes for 3:08, turned out to be 2:76.
Things can happen in nearly 50 years and I also plan on re-gearing my rear end again.

[GR8-68]

No problem, thanks for letting me know

[davischevy]

Originally Posted by flashed

How do I find out the gear ratio ?

If it is a 350 automatic truck, and no special call out on the spid, it's probably a 3.08 open.

Of course guesses are worthless.

[invicta455]

Hate to piggy back on this but it panhead 59 passes may I get inline for the one near Greensboro

[GR8-68]

I have decided I am going to part out the truck, I will give panhead59 first opportunity at purchase. I will take 400.00 for it and picked up at my location. That is hub to hub and I will have it pulled out and ready to load, I now have an electric hoist we can drop it right in your truck or trailer with ease

I will give panhead until Thursday evening then move on to other interested partys

[invicta455]

Fair enough just lmk

[flashed]

Mine is a 3 on the tree ,not sure what original motor was if the one in it is not original ,it is a V8 . Twelve bolt rear with heavy duty springs .I need to go back up there with a floor jack .

[panhead59]

GR8-68- I will pass on your rear if it is not a posi. If it is a posi, I'll take it. No hurry at all. I have one avail. @ $375 locally, but it's not a posi. I was/am mainly looking for a posi. Thanks anyway. I sent PM B-4 reading your post saying it was a 373. Posi or not- that is the ?

[panhead59]

Flashed- POSI? gEARS? tks

[flashed]

Have not had a chance to go back to the bodyshop where my parts truck is at .

[panhead59]

I do not WTB a rear anymore. I am going with a new axle kit from Yukon Gear and Axle. $320 shipped gets me new axles, drums, bearings, seals and studs. Tks to all that replied!!!!!