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Discussion Starter #1 (Edited)
I Have A 1982 Coupe De Ville With The Buick Built 4.1l V-6... The Original Trans Is Junk And I Have Another Th-200 With The Multi-case Design Ready To Go Into It?
My Problem Lies In I Do Not Want To Put It All Back Together With The V-6 I Want More Get Up And Go....
I Have A 350 Chevy That I Can Have Rebuilt In A Few Weeks But Want To Hear From People Who Have Done It Already Or Tried It Already I Don't Have The Time Or The Money For Surprizes.
The Way I Figure I Have Minimal Electronics On Car Now, A Four Barrel And Wanna Keep It All That Way. I Know About The Exhaust, And New Motor Mounts. By The Way Will A Set Of Mounts Out Of Say A 1990 Fleetwood With A 5.7l Be The Ticket?
Or I Have My Eyes On A 1981 Coupe De Ville With The Wunderful V-8-6-4? Is That A Better Bet?
Also Have A Lead On A 1978 With A 425?
Are Either Of Those Better Bets Considering A Beefy Trans Would Probably Come With Either?
Any Input Will Be Greatly Appreciated.
 

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I have a 1982 Sedan Deville here which was swapped to a 425 and later a 500 that will be used by my son next year when he begins terrorizing the streets. Better not but anyway... Any swap will have jokers in the deck. You really need a whole donor car to do any of the swaps mentioned. If you use the Chevy then you will need to come up with something to control transmission lockup. You will need pretty much a whole new exhaust system. If you use an older Cadillac then the 2004R trans will need to be seriously beefed up and you will have to fabricate and/or buy a transmission shift cable setup to hook to the carbonator. If you got a whole 1977/8/9 donor car then you could swap the engine, transmission, exhaust and real axle. I've done it this way several times. A lot of people used to like the Oldsmobile engines too. It really depends on what you can dig up for the Frankenstein.
 

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Discussion Starter #3
Why rear Axle? I wanted to keep the v-6 gears there are 3.23:1 most others caddys had 2.56:1 that just hurts no matter what you are running for a motor!
 

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OK. Well the 77/8/9 have 2.28:1 gears for economy. Your original gears from the V6 will make that car fly......right to the gas station. They work great with the overdrive though. I forget anymore if your original rear axle used the saddle u-joint connection or the flange. That needs to be figured into the equation.
 

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Discussion Starter #5
I guess my questions is how long will a TH200 and the stock rear last behind a SBC 350 with a very mild cam, and bored .030, because I have the motor it is already apart and ready for the machine shop and I can get it done, and back in the car around $750. And was this the one that required a rigging for the trans to shift or was that one of the caddy BB?
 

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All the detent cable brackets and stuff for the trans should be easy to find for a small block Chevy. Just remember that you need a carbonator that has the extra tang thingie for the trans detent cable. The 2004R was used in Grand Nationals so it can be made to take some soup. That part rests with your trans guy. I had one done years ago with an updated pump and some bearings where bushings originally went. Also a hardened sun shell. Big problem with building to Grand Natonal spec is you can never find the correct torque converter. Mine was behind a 500 and it never shifted correctly under full power. You will still need a lockup controller or build your own from a relay and a vacuum switch out of a mid 80's S Blazer with lockup.
 

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Discussion Starter #7
Ok another Question on the Rear ends? Is the 1977-79 sedan devilles running the same rear end as my 81 coupe? Specifically if I buy a 1978 parts car so to speak will the driveshaft from the sedan work in the u joint cups on my rear in the car? Also if not will changing the input yoke on the rear help any, or will they even interchange? How about the yoke and spline counts on the tranny? Any help would be greatly appreciated!!!
 

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PACADDYMAN said:
Ok another Question on the Rear ends? Is the 1977-79 sedan devilles running the same rear end as my 81 coupe? Specifically if I buy a 1978 parts car so to speak will the driveshaft from the sedan work in the u joint cups on my rear in the car? Also if not will changing the input yoke on the rear help any, or will they even interchange? How about the yoke and spline counts on the tranny? Any help would be greatly appreciated!!!
IIRC and it has been 13 years since I did one of these conversions....the 77,8,9 rear axle uses an 8-7/8" ring gear. My Chilton parts book lists the exact same ring gear part numbers as being an 8-3/4" axle when used in other GM lines. It is not the same axle as the '81. The old one weighs about 25 pounds more. Everything is a bolt-in until you get to the pinion flange. If you have a Cadillac built engine then you get the Cadillac flange. AFAIK The Buke V6 drivetrain uses the saddle yoke. I've always wondered if the u-joints will work with the saddle type yoke but always just switched to the round Cadillac flange. Swapping the flange can range from easy to whoops I just screwed up the pinion depth! You have to torque the nut slowly and see if the gears have the same amount of backlash as before removal of the yoke. If they start to get tight before resonable nut torque is reached then you are either in for a new crush sleeve or you might get lucky with a jam nut arrangement. 1980 and up lost the constant velocity u-joints so the new driveshaft will lend itself to less maintenance, lower weight and easier modification. Keep it around. 2004R output splines are different than TH400 but u-joints are similar so those yokes can be swapped. You will find yourself looking for a posi axle soon enough and will not be too happy with the wheelspin you get with those 3.23's. I'm not even talking about hotrodding. The thing will spin tires on damp pavement while trying to take off at a normal rate. If you are really picky and have a good steering column out of the old car, you might consider swapping it into the newer car if it is also getting a 3 speed transmission. The shifter detents built into the column match the forward speeds of the transmission. Speedometer clusters swap also for the correct readout.
 

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Discussion Starter #9
So let me see if I have this straight the best bet is to swap the yoke on the driveshaft and use the one out of the 82 coupe if it swaps over. If not I will have to try and swap the flange off of the 78's rear end and use that driveshaft setup. Right? But the driveshafts setup are relatively close to the same sizes and I won't need to get a driveshaft built or modified?

Man I wish that V-6 would have held out a little longer!!!

And Thank You Ape Man for being so Patient and understanding.
 

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Well I just hope that next time I try out something like building a particle accelerator someone will help ME out a little. The driveshaft will land up being 3/4" too long when you put the 8-7/8" axle into a car with a driveshaft for the 8.5" axle. It might need the rear wheels on the ground in order to get it in place. Been there. Gone many miles with some that would not fit without lowering the car. No problems.
So, yeah. If you want to keep the axle from the newer car and are using a TH400 then swap the front yoke over. Unless I forgot something it will work fine.
 

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Discussion Starter #11
Well The 78 With The 425 Feel Through So I Picked Up The 1981 Coupe With The V-8-6-4!!! I Am Going To Drive It Home Tonight And See How Bad It Rolls Out. I Also Want To Check It Over Underneath Really Good Because This Car Was Used On A Farm For Three Years Not On Road And No Inspections?!?!? If It All Checks Out Ok I Will Probably Just Swap My Wheels And Stereo Over To It And Sell The Other One Off In Parts Or With The Bad Motor. But I Haven't Decided As Of Yet. Any Other Nuances Involved With Switching A 368 V-8-6-4 Fi Into The 1982? Does This One Stil Have A Th400? Should I Run The 8-6-4 Set Up Or Not?
 

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Discussion Starter #12
Just To Put Out The Feelers. 1982 Cadillac Coupe De Ville 4.1 Liter Buick Built V-6 Everything Works Trunk Pull Down, Power Seats, Cloth Interior Rare? I Don't Know, Windows, Door Locks, Power Antenna Straight As An Arrow As Well I Might Add, Bad Stuff Motor Is Knocking Still Drove But Getting Worse Quickly. Trans Is "iffy" I Have Another Waiting To Go Into It. Door Panels Inside A Little Worse Then Normal Wear And Driver's Side I Purchased The Wrong Window Switch So I Cut Out The Hole To Fit It Sideways Works But Not Original. Have Hub Caps Locks For Them And Three Good Center Caps. Original Radio Missing As Well. Great Setup For 425/472/500 Conversion. Asking $300 For Car And Trans. Located In Eastern Pa!
 
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