Chevy & GMC Vans

OK, so I have the original t-case in and the front driveshaft out.

I have another question for your gurus of Astro:

Can I drive with the front drive assembly (front diff) out? This could save me an extra trip to the pick-a-part.

(Also: I have the service manual and it says to put all the bolts back in the exact same placement as they were taken out, so I shall do so)

So, apparently there are two gear ratios for front drive assemblies, and I have no obvious way of knowing which one I have. I do not have the parts sticker and the axle tube is not stamped.

3.43 and 3.72 (at least). If you don't have the code sticker, you can either split your old front diff case and look at the ratio stamped on the ring gear, or you can very carefully count the number of driveshaft rotations it takes to turn the rear wheel one rotation. It would be interesting to look inside the front diff to see what went wrong.

With one rear tire stationary, it took under 3 1/2 turns to make the tire rotate twice, so I'm guessing it has to be 3.42

Sigh, this part appears to be rare. There was one AWD van in their yard I think, but I don't know what years are compatible. I think they changed the front assembly in '97?

This is starting to look grim

3.42's are, I believe, the most common ratios run in the vans, I'm not sure about the S10 and Blazer, but I bet they're pretty common in those too. The front ends were all the same design from sometime in the early 90's until the end of production in '05. The difference in the earlier models is that they have very large flanges where the halfshaft would bolt up to the diff. This is very obvious when you see one.

Also, if you want to be sure yours is 3.42, you could pull the rear cover off the rear end and look on the ring gear (it's probably due for an oil change anyway). Also, somewhere on this site are the codes for the various ratios, that will make your hunt easier.

Yea, well, there aren't any codes to look up.

If they have a Blazer w/3.42 can I use it?

I meant using the code for the donor, it could save time in the salvage yard.

In any case; yes. S10 pickups and blazers use the same front diff as the Astros. You will want to put your passenger side axle and tube on the new diff as the S10/Blazer has a axle disconnect. I have an S10 front diff in my van.

Also, are you sure it's the front end and not a CV joint? Though unlikely, a blown CV joint could also allow the driveshaft to spin freely.

here are the codes for the diff ratios, good luck!

GT4 Rear Axle: 3.73 Ratio
GT5 Rear Axle: 4:10 Ratio
GU5 Rear Axle: 3.23 Ratio
GU6 Rear Axle: 3.42 Ratio

Why can't I use the blazer tube and just set it to lock (not disconnect)?

As for the CV joint, the front driveshaft mount spins freely like a top.

Man, I just want to fix this so I can go rock climbing [-o<

ball wrote:Why can't I use the blazer tube and just set it to lock (not disconnect)?

Not a problem, you could do that.

ball wrote:Man, I just want to fix this so I can go rock climbing [-o<

Might be backcountry skiing by the time you're done Where you climbing?

I was climbing on the east side of the sierras in June, but then the van started having issues and headed to Oregon (land of no climbing).

I'll call the place tomorrow and see what they have. Fingers crossed!