Diff gear questions....

[wedgemon]

I have a 73 K5 Blazer with a 350/350 combo. Not a trailering or camper special. Just a basic K5.

What diff gears likely came with it??

Also, can you tell if a diff has a limited slip or trac loc of some kind without opening the cover?? It's my understanding that posi's all alow some slip until demand is met - which means with the back end in the air, the diff will spin the tires opposite directions with or without a posi - Right?

I'm gonna pull the covers anyhow, but Im looking for advice for an upcoming junkyard run. Who would want to remove all those junk covers just to investigate??

Thanks for your help!

- Dave

[redz 1970 K5]

Your blazer probably has 3.42s or 3.73s. Those are probably the most common ratios. I would say 3.73s for a base 4x4. Look below, if you look at your RPO codes in your glovebox and compare it to the axle ratios below, you will know what you have.

Here's the axle ratio RPOs:

GT4 - 3.73 Rear Axle Gear Ratio

GT5 - 4.10 Rear Axle Gear Ratio

HC2 - 2.76 Rear Axle Gear Ratio

HC4 - 4.56 Rear Axle Gear Ratio

HC8 - 3.21 Rear Axle Gear Ratio

HE3 - 3.07 Rear Axle Gear Ratio

HO4 - 4.11 Rear Axle Gear Ratio

As far as testing for limited slip , that is a good question. I think you are right- if it's a limited slip, and you just turn the wheels manually, it will feel like an open diff.

My only recommendation would be to look at the trucks RPO codes in the glovebox (if they are still there), and look for the locking rear diff RPO code. You are going to be looking for:

G80 - Locking Rear Differential

[redz 1970 K5]

Hey, BTW PM me and let me know what you want for those pullstrap covers + ride. I can paypal or send you a MO. Just let me know. Thanks!

[wedgemon]

redz - Thanks for the RPO codes. That'll help. Problem is, thing's 34 years old. No SPID sheet anywhere. I'm guessing 3.42 or 3.73 too. Time will tell.

ALSO!! PM'd you about the end caps.

- Dave

[Zoomad75]

I'd bet you got 3.08's with a TH350/203 combo. Thats what most of those had. Use a jack and lift one side of the rear axle so the tire is off the ground (you want the other on the ground or have somebody hold it). Mark a spot on the pinion yoke and on the tire (that is lifted). Turn the tire two full revolutions while counting how many times the pinion turns. You have to turn it the tire twice due to the spider gears. IF the pinion turns just over 3 times you got a 3.08. At almost 3 and a half times you got 3.42's. 3 and 3/4 turns is 3.73's, just over 4 is 4.10's and so on.

If you don't hold one tire the spiders just turn by themselves and the carrier won't turn the pinion gear. The other wheel just spins the opposite direction.

Easy to do.

[wedgemon]

Thanks Zoomad!! That may save some greasy fingers.

- Dave