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Discussion Starter #1
Hey new to the site, first post. I've looked over the site for a couple of days and found some good info but now looking for some specifics about my project. I'm working on following items (327, 700r4)and I plan to install them in the next couple of weekends.
I'm now looking for upgrading my 8.2 10 bolt. Today I found a 1970 impala being parted out, it has a 12 bolt rear. The yard wants $400 for the diff drum to drum including the control arms? Is this a direct fit swap? What should I be looking for, not sure about gears or posi. I have already dropped the PG tranny and drive shaft so I figure I should tackle all of the drivetrain now. Any advice would be appreciated.
 

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The rear will fit but you'll have to use your 66 top arms. The lower arms are all the same. You may want to box the arms in if your going to run some horse power. Numbers on the passenger axle tube will decode to what gear is in it and weather its a posi or not.
 

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And I guess that I am not familiar with CA pricing, but $400 for a diff that is probably a 2:73 open seems like an awfully high price. I literally scrapped one a couple of years ago because I couldn't get any interest at $100. It had no arms or backing plates, but still..........
 

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Welcome to the Team JR!

I agree with Larry's assessment. The numbers are stamped on the front of the passenger side tube about in the middle. You may have to wire brush the tube to be able to read them. Just take a clear in focus picture and we can decode the letters and numbers you find there.


And I guess that I am not familiar with CA pricing, but $400 for a diff that is probably a 2:73 open seems like an awfully high price. I literally scrapped one a couple of years ago because I couldn't get any interest at $100. It had no arms or backing plates, but still..........

In Tampa FL a 12 bolt rear end sells from $400 to $750 for an open rear. Just a bare housing will go for $175 to $250 depending upon whether it is a coil spring car or with the more desirable leaf spring brackets welded on the tubes. I personally usually pay no more than $500 for a complete rear end. By the time I rebuild it with all new bearings, a new Eaton 31 spline Moser modified PosiTraction with Moser axles, and a new set of gears I am pushing the price of a brand new Moser rear end that is 40% stronger than the factory 12 bolt.

Brakes don't make any difference in the price of the housing as every one either bolts on the full size 11 by 2 inch drums (replacing the smaller 9 inch drums) or goes to a third or fourth generation Camaro PBR disc brake set up for their car.

Big Dave
 

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400.00 For a open 12 bolt is cheap around here. A posi will run close to a grand.
 

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Discussion Starter #6
The rear will fit but you'll have to use your 66 top arms. The lower arms are all the same. You may want to box the arms in if your going to run some horse power. Numbers on the passenger axle tube will decode to what gear is in it and weather its a posi or not.
Do I use the lower control arms on my 66 or do I need to use the ones off the donor car?
 

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Wow. And I 'coulda used that money! I had to do something with it, but the scrap value probably wasn't $20.
 

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700R4 uses the same 27 output spline as your PowerGlide or TH350. Unfortunately that out put shaft is about 2-5/8th inch further back than you would find with a TH350. This requires you to shorten your stock drive shaft (measure twice cut once).

As to your universal joints all cars use the same 1310 size universal joint (up until they went metric when GM installed a 3R universal in place of the 1310). According to Denny's FAQ in reference to the question as to when to upgrade from the stock 1310 to a 1350 they said this:

When is it necessary to upgrade to 1350 series?
It is always a good choice to upgrade to the 1350 series components whenever your application is used for racing or with high horsepower and street use. Stock driveshafts were designed to handle a modest amount of horsepower. If your application has more than 400 horsepower then its time to consider a new shaft.​
As to more parts to buy: I would buy a 12 bolt rebuild kit from Randy's Ring and Pinion that will give you all new Timken bearings and seals.

http://www.ringpinion.com/

Denny's Drive Shaft can source you a new drive shaft if you do not have a drive shaft shop in your home town.

http://www.dennysdriveshaft.com/c19_chevrolet.html

As to your control arms I do not think you need aftermarket replacement tubular control arms:

http://www.ebay.com/itm/65-66-Impala-Rear-Upper-Trailing-Arm-Control-Arms-/200379532751

As far as that goes even these aftermarket versions are deficient as you would like to have an adjustable upper arm to compensate for lowering the car. I think that you would be best served by boxing in your stock stamped steel control arms and replace the stock rubber bushings with plastic bushings.

Shocks and replacement springs should take care of everything except rebuilding or replacing your rear brakes. I recommend rebuilding what you have now replacing all of the small parts

http://www.rockauto.com/catalog/moreinfo.php?pk=308520&cc=1322222

and replacing the wheel cylinders along with new shoes and drums only if needed.

http://www.rockauto.com/catalog/x,carcode,1322222,pgname,Brake%252FWheel%2BHub,a,www.google.com%2BSearch%2Bfor%2B1966%2BCHEVROLET%2BIMPALA%2B7.0L%2B427cid%2BV8

Big Dave
 

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65-70 Impala lower arms are the same.
 

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Discussion Starter #11
Great site by the way lots of great info…
I went to the yard in hopes of looking at 12 bolt to get a number you guys can help me id. No luck, the car is stacked 3 high. I was able to count the bolts and see new gasket sealer on the cover. I made a deal $365 as long as it turns freely, picking it up Saturday. Having a 327, 700r4, 12 bolt in a 66 impala is 3.73 gears the optimal choice? Also I realized I have a electric speedometer assembly? Can I just find a manual one at a wrecking yard and switch it?
 

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Great site by the way lots of great info…
I went to the yard in hopes of looking at 12 bolt to get a number you guys can help me id. No luck, the car is stacked 3 high. I was able to count the bolts and see new gasket sealer on the cover. I made a deal $365 as long as it turns freely, picking it up Saturday. Having a 327, 700r4, 12 bolt in a 66 impala is 3.73 gears the optimal choice? Also I realized I have a electric speedometer assembly? Can I just find a manual one at a wrecking yard and switch it?
Your gear ratio is determined by weight, gearing and operational RPM of the motor (tire size is lumped in with the gearing). The factory thought a 3.07gear ratio was optimal with a 1:1 transmission. With a 700R4 you have a 0.7:1 final drive ratio at the transmission which is roughly a third fewer revolutions. With a 3.73 and a 700R4 transmission (and 28 inch tall tires which is about average in size) your motor will be turning 2,400 RPM at 70 mph on the interstate. You will also be only spinning the motor at only 1,500 RPM at 45 mph cruise speed. This is ideal for a stock cam and similar to what the factory had in mind for your motor's operating RPM.

If you have a cam that has a power band of 2,500 to 6,400 RPM because you want to hear that rough idle sound you will not be able to drive at less than 70 mph unless you down shifted the car at speeds less than 70 mph. With that cam then you can cruise in third gear (1:1 final drive ratio) with a 4.11 gear as it will be spinning at 2,500 RPM in third at 45 mph.

A radical cam shifts power higher up in the RPM (to make more horsepower). Horsepower is Torque applied over TIME. So the more RPMs or revolutions Per MINUTE the more power you make. So you have to spin the motor higher to get that power. Since every motor has a fixed amount of power it can make you have to rob Peter to pay Paul by shifting the power range above where it is useful on the street. This is what radical cams do, and it is why you get that rough idle rumppitty rump sound. It is the sound of the motor dying at idle because it doesn't have enough power at low RPM to keep the engine running. You don't hear a race car idling at the race track do you? They drive at wide open throttle all the time which isn't how you drive on the street.

As to the mechanical speedometer yes, you can find a pick-up truck in the bone yard that will have a mechanical gear speedometer long after cars switched over to electric speedometers. Or you can buy any of the parts you need for your transmissions from these people on line.

http://www.transmissioncenter.net/s...______va.htm?gclid=COmAyreg2LwCFfBj7Aod92kA2w

You need to tell them your tire size and gear ratio and they will ship you the correct gear set to make your mechanical speedometer accurate. If you find enough trucks with gears and don't mind taking apart transmissions in the yard (to swap one gear for another since the yard won't sell just a gear set disabling a good transmission thereby loosing a sale). Here is an article that describes the effort to calibrate a speedo by trial and error:

http://www.hotrodhotline.com/calibrating-speedometer


Big Dave
 

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Discussion Starter #14
Any pointers on how to measure the driveshaft, before I go get it cut? Can I just have them cut 3" and rebalance, considering the 700 is 3" longer than the powerglide?
 

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Any pointers on how to measure the driveshaft, before I go get it cut? Can I just have them cut 3" and rebalance, considering the 700 is 3" longer than the powerglide?
No you can not do that. Besides last lime I looked it was 2-5/8th inch difference not three so where are you measuring from.

Big Dave
 

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When you get your new transmission installed you can at that time measure the distance with the car sitting level on it's wheels (this is easier on a drive on rack).

If you don't have a drive on rack in your garage you can put the car up on strong jack stands with the suspension compressed by the axles sitting on the jack stands with the car body level. You would them measure the distance with a folding eight foot long wooden carpenter's rule that will not sag under the weight of gravity like a tape measure will to get the most accurate reading.

Big Dave
 

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Discussion Starter #18
Finally picked up the 12 bolt, 2.73 gears non posi. I will order some parts to upgrade it, might get the car driving with the stock 10 bolt for a few weeks until i can invest the time and money.
 
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