1994-96 Impala SS rear end - Impala Tech
Transmission & Driveline Transmissions & Differentials

 
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post #1 of 12 (permalink) Old 04-02-2013, 11:46 AM Thread Starter
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1994-96 Impala SS rear end

I want posi for my 67, i have a 350 w/200r4. I am looking to get a 1994-96 Impala SS rear end on recomendations from BigDave from other post. Does the drive shaft have to be shorten for the swap. Anything I need to look out for? Also how much should a rebuild be for adding at least 3.73 to the ss rear.

Thanks
Will
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post #2 of 12 (permalink) Old 04-02-2013, 04:32 PM
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Gears will be about 150. The stock Auburn posi is probably worn out, and is not rebuildable. Replace with the Eaton 400lb unit. 400. You'll need a master install bearing kit. 150. Labour. 300. I don't know the length difference between the 8.2 and the 8.5, but it shouldn't be too hard to find online.

Two doors, four doors, wagons, and ragtops.
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post #3 of 12 (permalink) Old 04-02-2013, 05:25 PM
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Compare the cost of all of the small parts (bearings and seals), big parts Gears and a new carrier), labor, the cost of the core. Add in the effort to install it (your labor to change over the mounts), and then look at the price Currie charges you for an 8.5 rear end (with or without disc brakes will affect final cost) that will bolt in.

Even though the lengths between the two rears are similar (within an inch), and the drive shaft will probably fit as is (even though the 8.5 has a longer pinion shaft that should cause the drive shaft to be a bit shorter), the way the rear end bolts in differs between the two cars. The bracketry has to be installed exactly as it was on the old rear end to make it easy to bolt in and so that it isn't a source of vibration.

Big Dave
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post #4 of 12 (permalink) Old 04-02-2013, 06:19 PM
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Unless your 350 is very strong (and with a 200-4R behind it, it probably isn't), it might make more sense to simply put gears/posi in your existing rear, and add aftermarket rear disc brakes.

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post #5 of 12 (permalink) Old 04-03-2013, 07:59 AM Thread Starter
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Thanks for the input. How much power will the 8.2 handle? I am thinking about a weiand 144 blower on my 300 hp 350 sometime down the road. Speaking of weiand 144, will it fit under stock hood?

Will
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post #6 of 12 (permalink) Old 04-03-2013, 11:33 AM
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I would say your trans will go before your 8.2. It will be tough to fit the blower/carb/cleaner under a stock hood. Might be doable with a domed cowl hood.

Two doors, four doors, wagons, and ragtops.
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post #7 of 12 (permalink) Old 04-03-2013, 01:29 PM
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The 200R4 is stronger than Jay gives it credit. Your stock 8.2 inch Spicer rear end was designed to handle a maximum of 300 horsepower. Because it is based upon the Dana 30 series rear end designed back in the fifties it is built with a 50% safety factor so it should handle up to about 450 horse power before it breaks. Trouble is it isn't horsepower that breaks rear ends but torque. Your axles and the side gears that they slide into are designed to handle a maximum of 4,800 foot pounds of torque which sounds ridiculous until you start doing the math.

You take your first gear ratio and your rear end gear ratio and multiply that times your motor's torque to get the final amount of load or torque applied to the rear axle. Without a posi most of that load falls upon only one axle. Aftermarket axles are 20% to 28% stronger than stock axles; yet fit in the stock axle housings due to the use different steel alloys and heat treating. A posi or limited slip axle spreads the load out over both axles halving the load so that also helps a rear end survive drag racing. I say drag racing because unless the tire is glued to the ground by way of a soft rubber drag slick with chemicals applied to the track that literally glues the tire to the asphalt your street tires will slip first.

Big Dave
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post #8 of 12 (permalink) Old 04-03-2013, 06:03 PM
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Quote:
The 200R4 is stronger than Jay gives it credit. Your stock 8.2 inch Spicer rear end was designed to handle a maximum of 300 horsepower.
Dave, how much max HP was the stock TH200-4R designed for?

Quote:
Aftermarket axles are 20% to 28% stronger than stock axles; yet fit in the stock axle housings due to the use different steel alloys and heat treating.
You can also up the spline count on the axles to increase strength. Just like GM did with the 8.5, going from 28 to 30.

Two doors, four doors, wagons, and ragtops.
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post #9 of 12 (permalink) Old 04-03-2013, 08:22 PM
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The 200R4 was designed for use in the Turbo charged V-6 Buick Grand National that cranked out 245 hp which was 45 more horsepower than the Corvette 350 Cross Fire Injection TBI did back in 1982 when they were first used. It was the most powerful production engine that GM made that year. The 200R4 with modest upgrades (similar to the upgrades used with the 700R4 to make it live with more power than it was designed to handle) allow a 200R4 to handle over 1000 horsepower.

Here are the parts and the cost to use:

http://www.cottonsperformance.com/products.asp?cat=73

Here are turn key ready to install trannies:

http://www.cpttransmission.com/2004R_trans_400hp.htm


To add 30 spline axles requires changing the differential which requires rebuilding the rear end. He was looking to survive on the cheap as I understand it.

Big Dave
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post #10 of 12 (permalink) Old 04-03-2013, 08:32 PM
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There's lots of people out there with "built" 200s that haven't lasted very long behind stout engines. Most serious GN guys have gone to something else. However, for a mild engine, they are a good choice.

If he's adding posi, it's the same price to upgrade the splines if he's going to put new axles in.

Two doors, four doors, wagons, and ragtops.
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post #11 of 12 (permalink) Old 04-03-2013, 08:39 PM
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Quote:
Originally Posted by jayoldschool View Post
There's lots of people out there with "built" 200s that haven't lasted very long behind stout engines. Most serious GN guys have gone to something else. However, for a mild engine, they are a good choice.

If he's adding posi, it's the same price to upgrade the splines if he's going to put new axles in.
He curently has an 8.2 inch rear. There is no 30 spline axle for that rear end. If he were to upgrade to the 8.5 inch rear then yes it can be built with 30 spline axles, though he was talking about a rear end out of an Impala SS car that already has the thirty spline axles in it.

Big Dave
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post #12 of 12 (permalink) Old 04-03-2013, 10:15 PM Thread Starter
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Thanks for the reply's, I am looking to spend around $1,000-1,500 on getting posi and gears (3.73-4.10). My 200-r4 was rebuilt before it was installed. From the reply's I am leaning towards having the 8.2 rebuilt with new axles and all the other goodies.
Would realy like to have the 8.5 but I think the shops in my area are a little skecthy to putting the 94-96 rear in my 67.

Will
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