Need fitment info on 12 bolt rear end from newer trucks

[Raceaprilia]

I have 1987 with 273 geared 10 bolt rear. With planned ls swap I am looking for 342 or 373 posi gear 12 bolt at local wrecker.

There is couple of trucks/suburbans there from 1973 up to 1992 that have GU6 G80 or GT4 G80 5 lug rear ends for $200-250. None of those two setups are placed in square body.

Up to what year will rear end fit directly on 1987 truck? I am not able to get any exact info searching around here. I am sure somebody asked already but I just don't find any answers. Any input will be great. Thanks

[mrolds88]

On 1/2 ton to 1/2 ton 73-87/91 will swap. However there is a caveat. From 73 to 80 ish uses one style of parking brake cable setup and the later uses another. I am pretty sure (and if I'm wrong I will get corrected) you should easily swap your brakes onto any 10 or 12 bolt you find. Now There are differences between the 1/2 ton 2wd and 4wd rears. Most notably the axles (6 lug vs 5 lug) As for the housings I cannot say one way or the other. But there are so many around to choose from. There are also 2 versions of the 10 bolt. One has 28 spline axles, they were from late 70s to 87 or 88 then they went to the 30 spline units. Only place you'll find them is under a Burb or Blazer. Confused yet?

[bdiamond]

The gov-loc posi units are considered "timebombs". They are the ones with gears and levers rather than clutches or cones.

[aggie91]

With some simple mods the 10 bolt in your truck can withstand the LS swap.

I have a 10 bolt with 3:73 gears that I am going to use in my '85 with a LS swap. Only changes I am going to make are to replace all the bearings and seals. Once I have about $300 saved up, I will put in a Spartan Locker diff into the stock carrier.

For you, I would look at Moser, Yukon Gear and Axle or similar companies and replace the Ring & Pinion, the carrier and maybe up grade the axles to 30 spline with the gears you want...

Axles: http://www.moserengineering.com/axle...spline-29.html
Posi Carrier: http://www.yukongear.com/PartsList.a...+Positractions
Gears: http://www.yukongear.com/ProductDeta...px?ProdID=5309

[Raceaprilia]

I am in dilema now. One way I would like to get stock posi rear to just put it in and drive. Checked some blown G80 online just now and that makes me get a stock burb rear with GU6 only that fit straight on my truck with no modification, and just add new locker after if i want one...On the other side I could use 10 bolt that came with truck and put new internals in it. By my understanding from another member here original driveshaft Will fit from stock C10 700R4 in truck to future 4L60E with proper adjustment of engine and trans on mounts. There is another benifit of using stock 10 bolt. Either way it will still cost some money lol. Anyone here that have already did gear and posi install on 10 bolt to share correct part nr to check on prices and then make decisions?

[Raceaprilia]

Originally Posted by aggie91

With some simple mods the 10 bolt in your truck can withstand the LS swap.

I have a 10 bolt with 3:73 gears that I am going to use in my '85 with a LS swap. Only changes I am going to make are to replace all the bearings and seals. Once I have about $300 saved up, I will put in a Spartan Locker diff into the stock carrier.

For you, I would look at Moser, Yukon Gear and Axle or similar companies and replace the Ring & Pinion, the carrier and maybe up grade the axles to 30 spline with the gears you want...

Axles: http://www.moserengineering.com/axle...spline-29.html
Posi Carrier: http://www.yukongear.com/PartsList.a...+Positractions
Gears: http://www.yukongear.com/ProductDeta...px?ProdID=5309

I missed the bottom section where you did put in the link to parts to swap the rear guts. I should probably change all bearings too? it is right around 1K all together then.

[aggie91]

Yes, replace ALL the bearings and seals when doing this.

If you order the axles from Moser, make sure you tell them you want the 30 spline for the stock width rear end. I think the axle length is 31 5/16" long for a stock rearend.

[slotard]

Originally Posted by Raceaprilia

I am in dilema now. One way I would like to get stock posi rear to just put it in and drive. Checked some blown G80 online just now and that makes me get a stock burb rear with GU6 only that fit straight on my truck with no modification, and just add new locker after if i want one...On the other side I could use 10 bolt that came with truck and put new internals in it. By my understanding from another member here original driveshaft Will fit from stock C10 700R4 in truck to future 4L60E with proper adjustment of engine and trans on mounts. There is another benifit of using stock 10 bolt. Either way it will still cost some money lol. Anyone here that have already did gear and posi install on 10 bolt to share correct part nr to check on prices and then make decisions?

700R4 and 4L60 are the same thing, 4L60E is the same basic tranny with electronic controls. The later 4L60E (with removable bellhousing) is an inch and a half shorter than the earlier one or 700R4.