swapping the whole rear end out of 1985 silverado short bed

[hosscatt]

i know this question has been asked but i missed it. comp been down for awhile. i want to change gear in my truck. i have 350 (300hp) turbo 400  gears now are 273 open rearend. looking to later put 700r4 in truck. tires size is 235/70/r15. my question is what  rearend from later model truck will fit my truck with the least of problems, direct fit. the gear i am thinking of running is 342 or 373.  the local savage yard here in az sell the comp drum to drum rear end for under 50 buck you pull your self  disc brake extra 50 bucks. if rearend is not posi thinking of using powertrax posi any thought on that posi unit?  the truck half ton and 1o bolt rearend

[SUX2BU99]

You will like the upgrade of deeper gears!  Good thing is that alot of 700R4-equipped trucks in the mid 80's seem to have come with 3.42 10-bolts so finding one shouldn't be too hard. What you could also do is look for a 4x4 1/2-ton as they are more inclinded to have 3.73 gears and then all you need to do is swap axles since you have 5-bolt axles now and 4x4 axles are 6-bolt. Changing axles is easy.

I would hate to have to pull a rear end at a bone yard without the luxury of my own concrete floor, jackstands and air tools at my own pace and leisure but in AZ it may be much easier not having to deal with rusted-on bolts. Bone yards around here want $99 at the u-pull so under $50 is great!

[Hertzdaddy]

If you can't find a posi axle you may as well just buy the gears and posi unit seperately and drop it into your housing. Used gears can be found for under $50 and you'll be opening the housing anyway to put the posi in. But for sure, if you can find a posi axle with the right gears the full swap would be the way to go. Just make sure you can get the brake lines off in one piece first. That goes for your axle as well as the swap axle.

[ohio hab]

I have an 1984 C-10, with an built 355 Small Block. Changed axles to 30 spline and went with in my opinion the only good posi unit out there which is an Eaton POSI unit. There are alot of G.M LOCKER POSI units out there, and these are weak in my opinion. On the internet they are often represented as Posi units but they are not. I would put in a new gear, and put in an EATON POSI unit if I were you. You usually have to buy the POSI brand new, they are impossible to find used, and if you do find one they are misrepresented. My truck has a 3.73gear with an upgraded 700R4.

[SUX2BU99]

In my opinion, I wouldn't buy used gears. It's a crap shoot whether or not they will get reinstalled to match the wear pattern that they have been worn-in with and then you end up with destroyed gears in short order. Been there, done that just last summer.

[frito-bandito]

In my opinion, I wouldn't buy used gears. It's a crap shoot whether or not they will get reinstalled to match the wear pattern that they have been worn-in with and then you end up with destroyed gears in short order. Been there, done that just last summer.

I agree, if I didn't swap whole rearends, i'd only use new gears, way too big of a gamble with used gears.

[hosscatt]

thanks everyone for the advice  will prob get new gears and posi unit  i know eaton best  expensive may have to wait couple months. am going to savage yard on half off day to look for complete rear end. so  ican rebuild on work bench and then take my other one out and swap. Another question any one know what years of truck will swap out with the least problem hope later  year will work 99 or so.                                    thanks again larry hosscatt

[frito-bandito]

If I'm not mistaken, anything 73-87 should swap out without much difficulty

[Captkaos]

Least amount of problems would be 82-87 Pickups with 10bolts and 88-91 Suburbans. (2WD if yours is a 2WD)
73-81's will work, but you have to have a hybrid U-joint.