Identification Help

[cah2873]

My son and I are working on a 1984 Chevrolet K20 for his 1st ride. We are getting close to completion. But I have a few questions about the differentials and gear ratio. Here is what I know. The front axle has 4030378 on it. (Sorry- I forgot to count the bolts). Below is a picture. The rear axle has GM6 and NP6969 on it with 14 bolts. Also, below is a picture. The transfer case has 208 on it. The previous owner installed a five speed manual in it to keep the RPm down at 70 mph. It has the numbers 18306. Can anyone please help me identify some of these items?


Well- after 30 minutes of trying to upload pictures- it says that my pics are too large???? Tried shrinking them but they are still too large.

 

[cah2873]

Also- we jacked up the rear end- spin the one tire- and the other tire started spinning in the other direction. Then it stopped. I kept spinning the tire but the other one never spun again. Anyway- 1 complete revolution of the tire was around 2-1/4 turns on the driveshaft.

 

[HotRodPC]

So you have a peg legger open diff. To get an accurate count, you'll need to put one of the rear wheels down on the ground, then respin the wheel 1 full revolution and count the driveshaft spins.

 

[theblindchicken]

Definitely an open differential. Most came with open diffs anyway.

Can do as hotrod says with counting the revolutions. Marking the tire and driveshaft with a piece of chalk will help in counting full revolutions if you're having difficulty telling where it started/stopped.

Also, can use these lists to check what the factory specs were for those axles:

Squarebody Front Axle Codes
Squarebody Rear Axle Codes

But the stipulation with those codes is having a clean-ish axle and spending the couple of minutes to locate those numbers. Definitely helps to determine if the gears have ever been swapped out which could tell you if they've ever gotten new bearings, gear oil, and whatnot.

Here's a visual comparison of the differential cover of quite a few different axles to help determine what you've got under there:

You must be registered for see images attach

 

[cah2873]

I think the rear is a corporate 9.5 14 bolt. I am still undecided on the front one. Maybe a GM 8.5 10 Bolt??
I am able to upload pics from my computer but not my Iphone. Anyway, here a are a couple of pics.

 

[kickdeez]

Front looks like a 10-bolt. If it has 8-lug hubs (which I am assuming it does), then it would be considered the "corporate 10-bolt" front axle. Rear looks like a 14-bolt semi-float..not the "corporate" 14-bolt. The "corporate" 14-bolt is a full-floating axle.

 

[bucket]

Ya, 10 bolt front and 14 SF rear.