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Rear end swap advice

bhemi

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I have a 1974 Satellite Sebring Plus. It has a an 8 1/4 open in it now. 400 engine and a Torqueflite. This weekend I picked up an 8 3/4 housing from a '71 Charger with a 489 case, it has 2.73 gear and is an open. It came apart but with the factory axles.

I want a limited slip like a Truetrac as the goal is to do a stroker kit on the 400 eventually. Say 500 hp max and street driven. Advice on gears and LSD would be appreciated. I am assuming the housing is a straight swap. New axles? Which bearings?
 
I hope that you got the U bolts and the brackets. They are different than the 73-74 models.
Chances are the 8 3/4"gears are 2.76. Ma Mopar didn't have the 2.73 ratio, Chevrolet did. A factory Power Lock is a great differential. Maybe contact Dr Diff. He is a great source for axle and brake kits.
 
I haven't had any experience with the Truetrac style LSD but another solid option which I have several 8 3/4's setup this way is to get the 68 and older Power-lok style diffential, you can make it fairly agressive or not. Or another option is a new one from Dr Diff and if you have any questions he can steer you in the right direction with whatever you would need.
https://www.doctordiff.com/8-3-4-clutch-type-sure-grip-powr-lok.html
 
What type and amount of driving will the car be used for? 3.23:1 or 3.55:1 are reasonable compromise ratios. Get rid of the rubber spring mounts.
Mike
 
What type and amount of driving will the car be used for? 3.23:1 or 3.55:1 are reasonable compromise ratios. Get rid of the rubber spring mounts.
Mike
Just fun street driving. It won't ever be a daily driver. I like to road trip and don't want too high a gear. I am also thinking about a newer transmission with an overdrive 4th gear.
 
I hope that you got the U bolts and the brackets. They are different than the 73-74 models.
Chances are the 8 3/4"gears are 2.76. Ma Mopar didn't have the 2.73 ratio, Chevrolet did. A factory Power Lock is a great differential. Maybe contact Dr Diff. He is a great source for axle and brake kits.
I got neither. U bolts should be easy are the brackets reproduced?
 
I got neither. U bolts should be easy are the brackets reproduced?
Yeah but you'd be better off getting used ones. The new are at least $60 each if they are still being made.
 
I agree with the advice to call the doctor.
Make a list of everything you have, what your goals are, and give him a ring.
He will fill in the blanks.
 
I hope that you got the U bolts and the brackets. They are different than the 73-74 models.
If you get the shock mount plates from a 71/72, are the they and the springs interchangeable with 73/74?

bhemi, sorry, don't mean to hijack your thread.
 
If you get the shock mount plates from a 71/72, are the they and the springs interchangeable with 73/74?

bhemi, sorry, don't mean to hijack your thread.
No worries it's all good info
 
From what I remember, the attachment points are the same. The difference is in the rubber isolation changes they implemented in 1973.
They had a much larger front bushing in the leaf spring and the U-Bolts and brackets are designed for the large rubber pads they used to isolate road noises.
 
From what I remember, the attachment points are the same. The difference is in the rubber isolation changes they implemented in 1973.
They had a much larger front bushing in the leaf spring and the U-Bolts and brackets are designed for the large rubber pads they used to isolate road noises.
I recall that too now that you said it. Just didn't know if the springs would have to be 71/72 or could you keep the 73/74 springs and use the 71/72 plates and u-bolts to eliminate the rubber isolators.
 
That I do not know. The later setup had a big hole in the center of the leaf spring bracket but I suspect that the leaf springs themselves still just had the standard 3/8" pin/bolt through the center. If so, you could keep the springs but the soggy rubber bushings at each end could be a problem if you are putting a lot of power to the ground....Flex, wheel hop, etc.
 
Stupid question. Are the spring and mounts for the 8 1/4 completely different?
 
They are the same. The 8 1/4, 8 3/4, car 9 1/4 and the Dana 60 for cars all use the same 3" axle tubes, same size U bolts but the length may vary depending on the thickness of the spring pack.
 
Well it's going to take me a bit to get it sorted out. I will post pics as we get into it. Expect more questions.
 
If you are planning on an overdrive transmission why not go with some deeper gears like 3.91 and have the best of both worlds? You'll have good acceleration plus good cruising with the OD trans.....
 
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