K5 rearend advice

[Tiger5]

After talking to the boys at Off Road Design, I am thinking of doing a 14 bolt 6 lug swap. So i understand I need a 1988 thru 1989 6 bolt rear end. 9.5 ring gear with 33 spline axle rear end. Any advice? I need a 4.11 gear and some sort of posi or limited slip. I have 4 weeks until my custom front springs arrive. So I have time.

 

[Bent77]

I think the date range is wider, but not certain exactly

My 6 lug SF came out of a 1990. I have an ARB in it, and was able to find the 4.10 factory gear

 

[obijuank5]

It's a great swap. Alot of the brake hardware swaps over. It comes with a 1350 pinion yoke so you'll need to address that as well as spring perches and shock mounts. The front studs won't match the rear now so male sure you either get lugs to fit your new studs or change the front studs out to match.

 

[Bent77]

Mine actually had a 1310 drive

 

[imiceman44]

After talking to the boys at Off Road Design, I am thinking of doing a 14 bolt 6 lug swap. So i understand I need a 1988 thru 1989 6 bolt rear end. 9.5 ring gear with 33 spline axle rear end. Any advice? I need a 4.11 gear and some sort of posi or limited slip. I have 4 weeks until my custom front springs arrive. So I have time.

I have a factory gov loc with 4.10 gears if you don't find this ratio.
I will take $100 shipped for it.

 

[dyeager535]

I don't *believe* there are really any surprises with the 14SF. If it's 6 lug, check the width...if it's the width you are looking for, and right ratio, you are GTG.

Your driveshaft length will shorten by approximately one inch with this swap (compared to a 10 bolt), so make sure you factor that in as you are looking at it all.

Gov-lock is all you will find for a factory traction aid in this vintage 14SF. IMO, and in this axle, the gov-lock is fantastic, but that will depend on your usage. If you need a true locker, it's not. BTW, you cannot test a gov-lock like you can posi, but in the past I found wrecking yards didn't know this...taking the cover off before purchasing any used axle is always a good idea, you will learn just about everything you need to know once the cover comes off. Gear ratio, gov-lock or not, condition of the gears, rust, etc.

Any form of limited slip (posi) in a truck is generally not a great idea unless it's purely street, where limited slip might hold up. The way posi works isn't well suited for trucks that see offroad. A Truetrac is also an option, again depending on what you want to do. There is still no substitute for a true locker.

 

[jeff in co]

If you can do it all in a wrecking yard, that would be best. I found a 14SF under the square body 3/4 ton suburban (8 lug). Then roamed around the yard to find a later model truck with a 6 lug, 14SF axle. I think you can look for 88-95 or so era pickups. There are two widths of the 14SF in that era. Need to find the wider of the two.

then take the axleshafts out, take the backing plates and all brake hardware from the 6 lug one.

Then pull the backing plate and axleshafts out of the 3/4 ton suburban and install the 6 lug stuff. The 6 lug axleshafts are about 1/2" longer so in the end, you'll need to add a spacer plate to move the drum backing plate in the correct position (custom made). But otherwise, you end up with a 6 bolt, 14SF that will bolt up directly because the spring pads and shock mounts are ready to go.

After doing all that, I walked out of yard spending $100 for a "modified" 14SF, 6 lug. You might get lucky and find one with 4.10 gears too.

If you do, grab the front axle (4.10 gears), swap over your older spindle, axleshafts and brake hardware.....that will convert 8 lug to 6 lug.

 

[dyeager535]

Oh, also forgot that the lug studs won't match up with anything earlier, definitely not the 7/16" in the front. 14MM for the 6 lug axles, which doesn't work well with OEM wheels due to the diameter and lug nut taper. If aftermarket wheels this may not be a concern.

 

[jeff in co]

^^^ yea, mine are mis-matched. The rears are larger than the front lugs. Tire shop always gets confused when they rotate and balance. But my stock Rally's do fit the larger lug.

 

[dyeager535]

But my stock Rally's do fit the larger lug.

They/mine fit, but the issue was with the lug nuts. That may be a lug nut design difference, but my lug nuts didn't fit the holes in the wheels well. They ended up pinching the wheel like a bolt, instead of tapering into the hole. They held, but it screwed up the wheels.

That is the main reason I went with the 1/2" studs front and rear.

 

[jeff in co]

Good to know. I would like to ultimately get them all the same size.

 

[imiceman44]

They/mine fit, but the issue was with the lug nuts. That may be a lug nut design difference, but my lug nuts didn't fit the holes in the wheels well. They ended up pinching the wheel like a bolt, instead of tapering into the hole. They held, but it screwed up the wheels.

That is the main reason I went with the 1/2" studs front and rear.

I had a blazer that had the 1/2" studs all around d44/12bolt.
I loved it and never worried about braking studs.

 

[Tiger5]

Alright boys n girls, I have an axle coming. It will arrive Monday. 1992 Z71 rear axle. 3.73. Will know more then. Will need to know about adapting. Thanks to all.

 

[JoeliusZ28]

If you can do it all in a wrecking yard, that would be best. I found a 14SF under the square body 3/4 ton suburban (8 lug). Then roamed around the yard to find a later model truck with a 6 lug, 14SF axle. I think you can look for 88-95 or so era pickups. There are two widths of the 14SF in that era. Need to find the wider of the two.

then take the axleshafts out, take the backing plates and all brake hardware from the 6 lug one.

Then pull the backing plate and axleshafts out of the 3/4 ton suburban and install the 6 lug stuff. The 6 lug axleshafts are about 1/2" longer so in the end, you'll need to add a spacer plate to move the drum backing plate in the correct position (custom made). But otherwise, you end up with a 6 bolt, 14SF that will bolt up directly because the spring pads and shock mounts are ready to go.

After doing all that, I walked out of yard spending $100 for a "modified" 14SF, 6 lug. You might get lucky and find one with 4.10 gears too.

If you do, grab the front axle (4.10 gears), swap over your older spindle, axleshafts and brake hardware.....that will convert 8 lug to 6 lug.

This is exactly what i want to do on my K10. Sounds easier that modifying perches and i want the wider track width anyway.

 

[jeff in co]

This is exactly what i want to do on my K10. Sounds easier that modifying perches and i want the wider track width anyway.

I was out at my junkyard last week...perfect candidate out there now. 90' 3/4 suburban, 3.73 gears. Both front and rear axles there, 8-lug. $100 each. I almost pulled them but quite the hassle for something I don't really need. Just a shame to see it sitting there....

 

[JoeliusZ28]

Hah, thats how I am at junkyards too. Too bad you aren't closer. 3.73 or 4.10 would be great.

 

[imiceman44]

I was out at my junkyard last week...perfect candidate out there now. 90' 3/4 suburban, 3.73 gears. Both front and rear axles there, 8-lug. $100 each. I almost pulled them but quite the hassle for something I don't really need. Just a shame to see it sitting there....

I used to be like that going everyday I had time kust to see if there's anything interesting or rare and I would get it.
Now I have been trying to sell all of it piece by piece for the past 10 years, I can't see a dent.
I need to havr a fire sale...

 

[frankin5]

With the scarcity of Squares these days, looks like retirement money.

 

[K5Jimmy]

I want to express my appreciation to those who shared their knowledge and experience on this build/swap. I would not have been able to do mine without the wealth of info on this site.

The yoke on donor axles were 1310 on the 91 sub 8 lug and the 97 2500 6 lug. The 1/2" studs are oe for 03-04 Jeep wrangler tj. (Perfect fit dorman 610-475). My driveshaft needs to be shorted 1". All 9.5 internals interchange.

This was a very easy project requiring moderate mechanic skills, patience, utube, common sense. I did this with no lift, I used all my cuss words and no help. Don't be intimidated, if I can do it, anyone can.

Thanks, y'all...

 

[aandpman]

I have done this build/swap and love it. Got most of the data from an old post here on CK5 that is really THE go-to post for this swap.

I got fed up with thrashing 10 bolt rears.

Got a mid 80's burb housing from a friend, which was an 8 lug. Used a pair of rear 6 lug axle shafts and brake setup from an early 2000's Express van with the 14bsf, 6-lug. Those shafts are the right width, as long as you use a pair of spacer plates to offset the backing plates by 0.5 inch (iirc). They are a bit longer than stock 8-lug shafts. One benefit was that it widened my rear track by about an inch on each side, so it more closely matched the front width. I could really tell the difference in stablility on the highway. I swapped out the studs to 1/2-20's, and they fit the stock wheels prefectly well. As for the longer snout on the axle, I got a pair of zero-rate offsets from ORD at the same time I bought new u-bolts (yes you need new u-bolts, since the axle tube is larger diameter than 10bolt). Zero-rates are drilled so you can move the axle forward or back a little. That was enough to negate any problem with the slip yoke bottoming out. As for the axle yoke, the 14sf had a 1350 on it, but I wasn't ready to buy/build a new drive shaft. The 1310 yoke from a 10 bolt will fit the 14sf pinion splines, as long as you swap out the seal protector slinger thingy that's pressed onto the yoke with the one from the 1350. While I was in the wrench-a-part getting the axle shafts, I ran across a nbs pickup that had 3.73's and a gov-lock with really low miles. The gears were really tight and had no slop. I mic'd them, and pulled them. I took my time setting them up in the recipient housing to get the pattern correct, and they haven't whined in the nearly 2 years I've been running them.

I have since upgraded the FRONT setup with Cyclic's 4-piston H3 hummer disc brake upgrade (another highly recommended upgrade!), along with some BFG 275x70-R17 AT-KO2's on Black Rhino Arsenal wheels. Will post some pics of what I can. The pic of the stock rear rallye wheel & stock tire shows where the axle center sits with the zero-rate moving the axle aft a little.