12 bolt from a chevy pickup?

**Eric1987** · 10-17-2008, 08:32 PM

My dad has a 1972 Chevy pickup that has a 12 bolt rear end. Curious as if it would fit my car. That would be a good upgrade right?

**c5z28** · 10-17-2008, 09:20 PM

His truck has leaf springs kind of different isn't it? Also you should get something newer, i'm sure someone else will chime in.

**Eric1987** · 10-17-2008, 09:22 PM

My dad keeps really good maintenance on all of his vehicles hes ever owned. Im sure its in good shape.

**c5z28** · 10-17-2008, 09:30 PM

Even if that is the case your probably going to have to fab it up some to make it fit, more importantly someone who knows if that truck rearend will swap into a late model f-body needs to speak up.

**Eric1987** · 10-17-2008, 09:32 PM

But if it did fit it would save a couple grand?

**Jays00ss** · 10-18-2008, 06:17 AM

Trying to fab up a 9" or 12 bolt in these new gen f-bodies takes more $ and time than it is worth. First off, a 12 bolt from a early 70's chevy pickup is way to wide. you would have to shorten it. Then trying to fab a torque arm mount to work properly is very difficult to do. You would have to cut all the old mounts off and weld all new mounts on. (old chevy trucks had leaf springs, the new f-body has coils)

By the time you are done, You'll have a rear that looks like Frankenstein, spend damn near as much to fabricate, rebuild, find parts, and spend a lot of time trying to get everything set up properly that it is and always has been enevatably cheaper just to buy a new rear from one of the aftermarket folks.

It can be done and has been done in the past, however you need to be one damn good fabricator and have all the tooling at your disposal, including something to re spline your axles, welding new brackets, as well as fabing a new torque arm mount that can handle the abuse.

Good luck to you because you'll need a lot of it.

If you want to play, you are going to have to pay one way or the other with these new gen F-bodies.

**Firebirdjones** · 10-18-2008, 06:32 AM

Jay is correct in his thinking. I've fabbed a few 9 inchers for people.
I do it cheaper than the drop in housings you buy from a supplier,,,much cheaper. But you have to be resourcefull and find a good useable housing in the boneyard. You can buy the torque arm mounts from Currie that are made specifically for the 9 inch center section and bolt right on. Once the rearend is narrowed and your mounting brackets welded on it will look like a factory install. Just takes elbow grease and some knowhow.

Doing a 12 bolt is an entirely different ballgame. There are no torque arm mounts to my knowledge that are made for this housing, and I wouldn't recommend brasing one on there,,,although I have seen this done,,,it's not pretty. Your only real bet for a 12 bolt if you want to keep it chevy would be to purchase a premade housing from Currie, Strange, Moser,,,,that has the torque arm mount cast into the housing.

To go a little further,,,,the truck 12 bolts aren't great for performance applications. They are a slightly different design than the 12 bolt passenger car rearends and therefore not as strong.
The pinion diameter is much smaller in the truck 12 bolt. 1.4xx I believe where the passenger car 12 bolt is 1.625.
Truck 12 bolts still have 30 spline axles and such,,,and the carriers are decent,,,,but that tiny pinion will give you fits with any real HP and there is nothing you can do with it,,,,it's just the casting that dictates the size.
Really not worth the effort for a truck 12bolt.
If you are looking to save some money a 9 inch is much cheaper and easier to fabricate. If you don't have the tools or know anyone that does,,,,then a drop in unit is your best bet. Hope that helps.

**Jays00ss** · 10-18-2008, 06:41 AM

Originally Posted by Firebirdjones

Jay is correct in his thinking. I've fabbed a few 9 inchers for people.
I do it cheaper than the drop in housings you buy from a supplier,,,much cheaper. But you have to be resourcefull and find a good useable housing in the boneyard. You can buy the torque arm mounts from Currie that are made specifically for the 9 inch center section and bolt right on. Once the rearend is narrowed and your mounting brackets welded on it will look like a factory install. Just takes elbow grease and some knowhow.

Doing a 12 bolt is an entirely different ballgame. There are no torque arm mounts to my knowledge that are made for this housing, and I wouldn't recommend brasing one on there,,,although I have seen this done,,,it's not pretty. Your only real bet for a 12 bolt if you want to keep it chevy would be to purchase a premade housing from Currie, Strange, Moser,,,,that has the torque arm mount cast into the housing.

To go a little further,,,,the truck 12 bolts aren't great for performance applications. They are a slightly different design than the 12 bolt passenger car rearends and therefore not as strong.
The pinion diameter is much smaller in the truck 12 bolt. 1.4xx I believe where the passenger car 12 bolt is 1.625.
Truck 12 bolts still have 30 spline axles and such,,,and the carriers are decent,,,,but that tiny pinion will give you fits with any real HP and there is nothing you can do with it,,,,it's just the casting that dictates the size.
Really not worth the effort for a truck 12bolt.
If you are looking to save some money a 9 inch is much cheaper and easier to fabricate. If you don't have the tools or know anyone that does,,,,then a drop in unit is your best bet. Hope that helps.

Very well said. Also trying to find a good 9" in a boneyard is getting very difficult to do because everyone is looking for them to put in some sort of project.

**squee** · 10-18-2008, 10:07 AM

Originally Posted by c5z28

His truck has leaf springs kind of different isn't it? Also you should get something newer, i'm sure someone else will chime in.

Originally Posted by Jays00ss

(old chevy trucks had leaf springs, the new f-body has coils)

Hate to nit pick, but they had truck arms. with rear coils. Probably wouldn't make the slightest difference though. I'd just buy a 9" housing off Ebay (they have them for our cars for like $900 with axles and all) and throw a center chunk in it.

**Eric1987** · 10-18-2008, 05:00 PM

Okay I thought it was worth an ask. I figured if I could grab that off I'd save me some money even if I did have to mod it a little. And yeah I was over at my dads today and that thing is wide as hell. He says its a heavy duty 12 bolt. And yeah its coil springs with torque arms. Appreciate all the help. Sorry mechanical Knowledge isnt very great but I'm trying.

**Firebirdjones** · 10-19-2008, 09:04 AM

Originally Posted by squee

Hate to nit pick, but they had truck arms. with rear coils. Probably wouldn't make the slightest difference though. I'd just buy a 9" housing off Ebay (they have them for our cars for like $900 with axles and all) and throw a center chunk in it.

Well lets break that down a little further. You and Jay are both right.

They only had the swing arms from about 1967 up through 1972 with coil springs. Nascar still uses this rearend design in the cup cars.

From 1973 and up everything in the trucks were leaf springs.

To go a little further,,,although both designs were 12 bolt housings with different mounting,,,the 12 bolt disappeared altogether from the trucks after 1979 or so. From there the 8.5 inch 10 bolt took over for the light duty applications.

**squee** · 10-19-2008, 12:20 PM

Originally Posted by Firebirdjones

Well lets break that down a little further. You and Jay are both right.

They only had the swing arms from about 1967 up through 1972 with coil springs. Nascar still uses this rearend design in the cup cars.

From 1973 and up everything in the trucks were leaf springs.

To go a little further,,,although both designs were 12 bolt housings with different mounting,,,the 12 bolt disappeared altogether from the trucks after 1979 or so. From there the 8.5 inch 10 bolt took over for the light duty applications.

Yup, the 67-72s had truck arms, but so did the previous models, just not sure how far back. Also, 67-72s DID, actually come with leafs, but only on the 4wds and maybe the 3/4 or 1 tons, not sure about those.

**Firebirdjones** · 10-21-2008, 04:41 PM

Originally Posted by squee

Yup, the 67-72s had truck arms, but so did the previous models, just not sure how far back. Also, 67-72s DID, actually come with leafs, but only on the 4wds and maybe the 3/4 or 1 tons, not sure about those.

Ya the leafs on the older years were heavy duty applications as you alluded to,,,I just didn't mention those because the heavy duty applications didn't use the 12 bolts anyway,,,,they used the 14 bolt with floating axles.

**squee** · 10-21-2008, 05:39 PM

Originally Posted by Firebirdjones

Ya the leafs on the older years were heavy duty applications as you alluded to,,,I just didn't mention those because the heavy duty applications didn't use the 12 bolts anyway,,,,they used the 14 bolt with floating axles.

Or Dana 60 in some cases I believe. Not 100% on that one, but I've seen it...