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Discussion Starter #1
I was wondering. I have need of a better set of gears in the 76 I have and I also have a 72 Elky sitting right now that has a 12 bolt and something better than a 2.73:1 gear set. So I am courious if the rear end off the 72 would fit, un-molested, in the 76?

I can measure it but that will be some days away and I figured if someone already knew then I could be ahead of the game when I can get around to working on them.

If they'll swap then I'll take the 72's rear put it on the 76 have better rear end. I am planning on Tubbing the 72 so I probably will not even use this rear end otherwise but you never know.
 

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Pete: I've looked at this question for a couple of days to see if anyone else had a comment, but none so far. The short answer is NO. I don't know about suspension or driveshaft issues, but it is too narrow.
 

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Taking a 72 to put in a 76 would be considered going the wrong way by most. I had a 77 malibu & liked it. The 72 rearend is a 1 1/2, 2 in norrower but I am not sure of the control arm location.
 

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Discussion Starter #4
I was just looking for a quick fix for my tall gears in the 76, since I have three Elkys. I rebuilt the 80's rear end with 4.10:1 gears, PowerTrax and that will be behind a 700R4. That was the better part of a grand for all that. I was not really wanting to spend money if I could have used the 12 bolt from the 72 I have.

I wanted to see how much better my ETs would go with something better than the 2.73:1 gears I have on my 76 now. Sometime in its future I'll stick in an Overdrive 700R4 or a 200R4 that is built for it in it. Then I'll be ready for a 4.10 in it too. But without that overdrive a 3.73:1 is about as much as I would go because I drive my 76 a lot on and off the highway and I don't care to be driving around @ 3200 RPM and up.

The 72's Rear End will eventually be chopped down by about 4 to 6" to accommodate tubbing the rear on it. I am not stuck on keeping that rear end just yet but I am not ready to give it up either. I might need a Dana or something more substantial than the 12 bolt. If I do I have a use for the 12 it will no doubt be in the 80. Its 10 Bolt 7.5" will no doubt demolish its self within a year of its completion. Too many ponies in front.

The "Corporate", that is what Richmond gear calls it, 8.5" in the 76 is a pretty strong rear end considering it is only about .25" smaller than the 12 bolt. So I will probably keep that rear end but it will eventually be upgraded to the Power Trax and new Ring & Pinion.

Like I said I was looking for a "Quick swap". I guess that's now out of the question.
 

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ElkyPete said:
I might need a Dana
A Dana? What do you plan on running? If you need something that strong, I suggest a Ford 9". It's much easier to find parts for it, and in turn will cost you a lot less. Plus the carrier is quite easy to replace compared to the Dana, 12 bolt, or 10 bolt. With a 9" Ford, you could have 3:23 gears Monday thru Friday, and change out the carrier on Friday to 4:10 or 4:56 gears for a lil weekend fun at the track. Dana rearends are expensive! I bet you could build yourself a Ford 9" for about the price you could sell that 72' 12 bolt for. I am building a 9" for my 84...piece by piece...my budget is $1250...half of what Currie sells theirs for. I know what your thinking "A Ford rear in a Chevy...NEVER!" :mad: Sometimes you just gotta go wit da flo bro! :lol:

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Dang, You got alot of ekly stuff going on. :)
 

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Discussion Starter #7
[quote="theelcaminofactory] A Dana? What do you plan on running? If you need something that strong, I suggest a Ford 9". [/quote]

In the 72, over 1100 ponies in a BBC, Pro Street is what I am planning. Ford 9s and Chevy 12s are pretty close to the same as far as strength. Dana, I realize is a Truck chunk but with what I'll be putting it through the little extra power it absorbs will be negligible.

76 is a driver, the 80 SS is show N' Go and the 72 will be all track. I kind of hate to put her in a shape that will limit the places I can drive it but I want to do one "Top of the line" Pro Street machine with these projects and I've determined that the 72 is the best candidate out of what I have to do it with and it will look super.

I'll probably end up with a 12 in both the 76 and 80 somewhere down the street but for now they are weakest in the rear end, the 80 being the most anemic at this time. I figure that one will go within a year of completing it. I've never trashed a rear end to date so it should be fun. :D Smoked some engines and tore up some transmissions but I've never thrown a drive shaft or trashed out a rear end - yet.
 

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I agree somewhat. If you use 28 spline axles, and a single rib case with small bearings, the 9" is about the same or slightly better than a Chevy 12 bolt rear...but if you use the stronger case with 31 spline axles, and a Detroit Locker posi unit or a spool, I think the 9'' is just as strong as the Dana if not stronger. It's all in the parts you choose to use to assemble it. The Ford 9" is also a truck rear. The Chevy 12 bolt will be scrap metal within a short period of time behind 1100hp, the major drawback being the axle C clip retainers. Check out the links page on my website...click on to "COOL LINKS" and read the articles on 9" Ford rearends. Believe me, I am not a fan of anything with the word "Ford" stamped on it...but I gotta admit their 9" rearend impresses the hell outta me!

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May I jump in here?

If I may add something and give away a little of my age at the same time. Ford nines have been winning shadow (or flashlight....same thing different generation ... hmm ttttalking bout my ggggeneration.. oh sorry :oops: ) drags under bowties for alot of time man. If anyone is familiar with Dallas Tx, old California crossing and Forest lane drags in the late 70's really early eighties then you knew the only way to beat a bowtie in the real world was to be in one with a nine behind it. Flat out the best rear end god didn't make. I do have a real question and Elkypete I hope you can help if you would. What are the cast numbers for a posi rearend? I am getting a parts car and the guy says it has posi I haven't looked at it but would like to know before hand. It does have good glass and power windows so it may be worth it. Thanks
 

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Discussion Starter #10
According to what I have read,,,,, A posi will be identified by the tag (small metal tag) on the rear cover. That changes when the rear cover is removed if they didn't replace the tag also. It basically says it is a Positraction. Also if the truck had an original Posi then the glove box will have instruction on how to use it to get out of bogs.

The quickest way to tell is to raise up one side and turn the tire. If it turns then it is probably not a positraction. My understanding about limited slips are that they are what I call "Open Face" just the same as Non-Posi and have nothing in them except the spider gears. If your on a level plane then "generally" if one starts to slip the other will pick up the slack but it does disengage the slipping side. So most of the time you'll see, if they are operating correctly, a start of one black mark on one side and then it will pick up both tires and you'll see two on pavement. On dirt well, possibly that will happen. On a un-level road surface it will only show one mark.

I have a very limited understanding of how they actually was suppose to work. If the Posi Unit is smoked then it could look the same as with a non-posi.

The Ford 9s are a truck rear end. It takes more energy from the power plant to turn that rear end than it does the GM 12. GM also makes a 14 bolt. It has an 11" ring gear but again its for trucks but can be used in an Elky or other autos.

Any car under 500 horses can run a 12 bolt or in some limited models a GM Corporate 10 Bolt with success. You'll also get better times because of the amount of torque is less to make that rear end turn. The 12 bolts are generally 8.75" ring gear and the Ford uses a 9" ring gear. So we're saying that .25" is all the difference in the world?

Any Rear end that you are planning on putting on the track should have a refresh of the gears and bearings. The newer alloys are far stronger than they use to be. A GM Corporate ten bolt is an 8.5" ring gear and for the lighter model Elkys (5th gens) that is good in them up to a 12 second 1/4 and maybe a little more. The 12 should be used for times to about 10s 1/4 and I'd go with the 14 bolt from the general before I stick a Ford rear end under my truck.

I'll put it this way. In the 4th generation El Caminos with a 12 bolt installed using new ring and Pinion from Richmond and their Powertrax Locker and a 350 THM you'll blow up the transmission before you go through the rear end. The 350 is possibly one of the worst transmissions that GM ever designed. Yes it can be made better but why? A 700R4 or a 400 THM is far better. So instead of worrying about the rear end worry about the transmission.

Just some thoughts.
 
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