# 66/67 Rearend



## Shadetree Racing (Apr 15, 2015)

hello all,
i am looking for some advice on the value of a rearend i am looking to sell, i bought this rearend in 1989 but never put it on my car, the information on the unit is listed below.
i do not have an idea of what it is worth in current condition:

late 66/ early 67 8.2 BOP posi- YH on drivers tube, 3:55 gearing.
date code=G146
8783393
55.5" backing plate to backing plate
28 spline axle
1971 ring & Pinion gear, 7/16 bolts with 11/16 head- 1.25 pinion nut.

the bolts were spot welded, not sure why see picture.
i know the highest value is to someone who would want the correct unit for their car, i just dont know what a cone style unit interest is anymore.

any input is appreciated


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## PontiacJim (Dec 29, 2012)

Shadetree Racing said:


> hello all,
> i am looking for some advice on the value of a rearend i am looking to sell, i bought this rearend in 1989 but never put it on my car, the information on the unit is listed below.
> i do not have an idea of what it is worth in current condition:
> 
> ...



Never easy to put a price on it. May be of interest for an original 10-bolt, but most serious engine/car builds will go with something that can handle bigger HP, like a 12-bolt or 9". Although for a '66-'67, it can be used in other years if originality is not an issue. 

The 3.55's are a good gear, but it may not be a good gear for 70 MPH highway driving, so would be a great gear for local cruising.

Posi is a plus as long as it works and does not need a rebuild.

The welded nuts are what would cause me to pass on it. Why are they welded? Is the bolt hole stripped? Were the bolts coming loose? and why? But someone else may just run it and take a chance.

You could bring it to a shop that rebuilds rear ends and have then try to disassemble it and inspect it to make sure no issues, and then re-assemble it so you know it is a good unit - which may help sell the rear end at a higher price.

So as with all things, go high at first and see if you get any bites or interest. I might start with $500 and drop down from there. Personally, because I am cheap, I think $250 range a more fair price and something that someone might take a chance on.

Just my opinion. :thumbsup:


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## michaelfind (Dec 14, 2018)

I have been running a similar rear end for many years and have honestly been very rough on it. Many, many hard accelerations through the years. I actually have three of these rear ends. Only one is the 3.55 with the posi unit. Is there any way to rebuild these so that they are somewhat comparable in strength and durability to a 12 bolt rear end? Although mine is not original for my 65 GTO, I like that it has a stock type appearance and would like to keep that appearance if possible. I actually have the original 65 rear end, but it is not even a positrac. I've considered rebuilding it to regain that extra inch or so of clearance at each fender well, but I think even the shorter axles are harder to locate these days. Rebuilding it might be an expensive adventure in frustration.

Suggestions? or has this already been tried through the years and proved to be a waste of time and money.

Thanks
Michael


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## michaelfind (Dec 14, 2018)

One more thing. Now that I look at your pictures more closely, you do not have the coil spring center holder, just the flat mount spot. I believe that makes it a 66 rear end at the latest. They needed the "hold down clamp" to keep the spring in place. For originality purposes, that may make it more valuable to someone.:smile3:


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## PontiacJim (Dec 29, 2012)

michaelfind said:


> I have been running a similar rear end for many years and have honestly been very rough on it. Many, many hard accelerations through the years. I actually have three of these rear ends. Only one is the 3.55 with the posi unit. Is there any way to rebuild these so that they are somewhat comparable in strength and durability to a 12 bolt rear end? Although mine is not original for my 65 GTO, I like that it has a stock type appearance and would like to keep that appearance if possible. I actually have the original 65 rear end, but it is not even a positrac. I've considered rebuilding it to regain that extra inch or so of clearance at each fender well, but I think even the shorter axles are harder to locate these days. Rebuilding it might be an expensive adventure in frustration.
> 
> Suggestions? or has this already been tried through the years and proved to be a waste of time and money.
> 
> ...



Nope, you won't be able to build it to match a 12-bolt. I've hammered on them pretty hard as well and not blown one up. The issues arise when you have the posi and you go with wider/stickier tires that grab. If you have "skinnies" or even the single legger, you are better off because the tires will break loose rather than bite and put all the torque through the rear-end.

The 8.5 10-bolt can be built to handle as much as a 12-bolt. These are 1971 and 1972 A-body cars. They are found under many other years, but you would want an A-body rear. I read that Pontiac still used the 8.2 in '71-'72. Several drag racers I know use the 8.5, one under a BB Nova.

To build one up would still cost you. Trying to find an original 12-bolt is not cheap. So aftermarket is the best option and just be done with it, all new and no worries. :thumbsup:


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## michaelfind (Dec 14, 2018)

PontiacJim said:


> Nope, you won't be able to build it to match a 12-bolt. I've hammered on them pretty hard as well and not blown one up. The issues arise when you have the posi and you go with wider/stickier tires that grab. If you have "skinnies" or even the single legger, you are better off because the tires will break loose rather than bite and put all the torque through the rear-end.
> 
> The 8.5 10-bolt can be built to handle as much as a 12-bolt. These are 1971 and 1972 A-body cars. They are found under many other years, but you would want an A-body rear. I read that Pontiac still used the 8.2 in '71-'72. Several drag racers I know use the 8.5, one under a BB Nova.
> 
> To build one up would still cost you. Trying to find an original 12-bolt is not cheap. So aftermarket is the best option and just be done with it, all new and no worries. :thumbsup:


Thank you for the facts. I suspected as much. :frown3: I guess a new aftermarket unit will be my long term plan if I ever destroy this unit I am running. As I was investigating the differential currently under my car, I think I have discovered that I at least have the best of options for the year differential I bought many years ago. I was always told it was out of a 69 judge but had no verification. There is an N on the front of the snout. The casting codes on the center unit are 353 above 9795084. The axle housing has 008XH. From what I read at Wallace racing and in the Pinion Head posts you linked to, this is likely a Nodular iron housing with the 4 pinion set up. If that's correct, then the rear differential may live as long as I do. I do not plan to put slicks under this car. Will just smoke both rear tires most of the way down the track!:grin2:


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## PontiacJim (Dec 29, 2012)

michaelfind said:


> Thank you for the facts. I suspected as much. :frown3: I guess a new aftermarket unit will be my long term plan if I ever destroy this unit I am running. As I was investigating the differential currently under my car, I think I have discovered that I at least have the best of options for the year differential I bought many years ago. I was always told it was out of a 69 judge but had no verification. There is an N on the front of the snout. The casting codes on the center unit are 353 above 9795084. The axle housing has 008XH. From what I read at Wallace racing and in the Pinion Head posts you linked to, this is likely a Nodular iron housing with the 4 pinion set up. If that's correct, then the rear differential may live as long as I do. I do not plan to put slicks under this car. Will just smoke both rear tires most of the way down the track!:grin2:




Perfect. I'd run it till it popped if it were mine because it would be worth more to me to use it myself and take my chances than selling it and then having to replace it with a higher cost rear axle assembly. I would work on plan "B" - getting the homework done should you ever need a beefier rear-end just so you have a rough idea of pricing.

It's almost easier to buy a complete & set-up rear end than to locate something, have it torn down, purchase the "good" parts, then get it all set-up again with new parts going into a used housing. I opted for a Ford 9" set-up for the GM A-body. Bolted right up. Reason I opted for the 9" is that they have been around forever, and are under everything from stock, to hot-rods, to drag cars and are still popular today. Parts are easily available and probably will be long after I am dead. 12-bolts....I don't quite see the longevity in them.

You can also build a different center section with another gear ratio if you want to play around. Once it is set-up, no further playing around with pinion depth or gear meshing as its all done when the center housing holding the gears is set-up. Then all you do is pull axles, and unbolt and bolt back in the other set of gears, and slide in the axles. Gives you the option of highway gears if you went on a long trip, around town gears, and all out drag strip gearing if you were so inclined. :thumbsup:


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## varmit86 (Nov 7, 2009)

michaelfind said:


> I have been running a similar rear end for many years and have honestly been very rough on it. Many, many hard accelerations through the years. I actually have three of these rear ends. Only one is the 3.55 with the posi unit. Is there any way to rebuild these so that they are somewhat comparable in strength and durability to a 12 bolt rear end? Although mine is not original for my 65 GTO, I like that it has a stock type appearance and would like to keep that appearance if possible. I actually have the original 65 rear end, but it is not even a positrac. I've considered rebuilding it to regain that extra inch or so of clearance at each fender well, but I think even the shorter axles are harder to locate these days. Rebuilding it might be an expensive adventure in frustration.
> 
> Suggestions? or has this already been tried through the years and proved to be a waste of time and money.
> 
> ...


I do have a late 65 production date YH out of my 66 it is original and untouched from a low mile GTO that has been in my family since day one. I am looking for someone looking for a period correct untouched rear end so I can get good money out of mine or I will just hold on to it. I know when you need something original it always cost BIG dollars and your happy to find it.
So if it is a super nice part and your patient you can get good money for it and not have to sell it for scrap.

There is someone looking under the wanted section for early 67 rear end


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