Compatible 12-bolt Rear Diff's

[Captkaos]

Is that with you dropping the truck off?  or you dropping the diff off?  I think a buddy of mine that used to do it charged $200 minus parts with it OUT of the vehicle. 

[SUX2BU99]

That's with it in the truck  ie. driving it to their shop and they do it on the hoist.

Any ideas on what to look for in this combo u-joint? I looked on Jegs and they just give diameter dimensions.  I think I saw somewhere there are basically 3 commonly used yoke dimensions that most manufacturers used on their rear ends.

[SUX2BU99]

Went out today and looked at the "10 bolt" I found at a local place for $150. Was pleasantly suprised to find out that it was actually a 12 bolt, and lo and behold, we open it up and it's a posi! Fluid looked good and no visible metal shavings that I could see. Counting the teeth would have been difficult just because of where and how the diff was sitting but the guy found the numbers stamped on the ring gear and on it was "10:34" amongst others. I'm really hoping that means 34 pinion and 10 ring teeth....

Anyway, I did buy it. I really should count it just to be sure but now I have it home (well, in the back of my truck) I can look it over really close. I feel I got a good deal since it's a 12 bolt posi and as far as I know, the ratio I was wanting. It's covered in light surface rust from sitting outside but I plan a thorough clean up, cover it in Chassis Saver and put some new brake lines on it most likely.

Things are freakin' heavy though. It's going to be fun getting it back out of the truck and then installing it.

[choptop]

That sound about right. I have an in=law that works for a drivetrain company that quoted me the same price, but normally it costs around $1100-$1200. But that's with new gears, bearings seals the whole nine yards.

[SUX2BU99]

To me, that's just alot of money for not a whole lot of gain. I did some net searching and found that GM did offer a 3.40 ratio, RPO HE4. So I'm pretty happy thus far that I found exactly what I wanted, for the price I wanted. Dude even said too bad for him he quoted me on the price already, now that he found out it was a posi, he would have quoted me more. Score for me!

Hopefully the brakes won't cause me any grief. I only plan on putting new hard lines on it and repainting the housing and drums.

[SUX2BU99]

88 will be a ten bolt, if its 4x4 it will be 6 lug if its 1/2 ton. No other option.
10 bolts are a direct bolt in. the u joint is wider and the caps are bigger diameter. It still bolts right in with no modifications. You have to replace the u joint with a combo joint. 10 bolt size one way, 12 bolt size the other. Bolt in!
 Anything from a pickup, suburban, blazer will be a direct fit. Vans do not fit.
 As far as using a 4x4 10 or 12 bolt 4x4 / 6 lug, all you have to do is swap your axles, baking plates, brakes, & drums over to make it 5 lug.

I know this is an old thread but the question is similar since I might just be hunting around again for another donor diff. So if I wanted to take a 4x4 12 bolt and make it fit my 2wd I need to swap the axles and I'd swap over all the brake stuff anyway since it was all new as of July last year. Why though do the backing plates have to be transferred? Isn't that the same as the axle flange? I can't recall what held that on. Was it 4 bolts?