need help with upgrading my 8 1/4 rear end.!

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Tduff01

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Thanks in advance for any help. This will be my first rear end work I have done and I need help upgrading my 8 1/4 rear end. 1972 Duster was a slant six and now putting in a 340. I know every loves the 8 3/4 rears but my 8 1 /4 is already in the car and I've heard and seen a lot of people running the 8 1/4. It's only going to by street cruising and car shows and having some fun. Probably no drags. I just don't know where or what to get the stuff to upgrade this rear end. Anything will help from where to get the stuff and what all to get and gear ratio? I'm pretty new to choosing gears and all that. Thank you so much for any help or links for place to get stuff from.
 
Well, the gear ratio should compliment the cam, converter and suite the driving needs and style of the intended purpose of the car and its driver.

Knowing what camshaft you have is a start and the intended purpose would be a great help in suggesting a gear ratio.
More driver than strip is a good description. It just leaves a little in the table for a decent suggestion.

On the rear itself, a brand new center section in a sure grip is the best start.
Following it up with stronger axles is your call. Stock axles will take 400hp all day long, all night long & into the morning.

I do believe in the past I have seen rear covers with a bolt set up that contacts the rear ends cap bolts to help stop flexing within. I think this is an extreme measure to go with and is a sign of maybe that person should have upgraded the rear end instead.

Summit racing, Jegs, Manciniracing.
 
Thank you. I will know cam info next week when we start the rebuild and order parts.
Driving is just going to be cruising around enjoying the car. Driving to car shows and cruise ins. Of course having some fun smoking some tires and getting on it every now and then. But will not be at drag strip any that I am planing for awhile. As for converter do you have any suggestion with a mild 340 build to 400 hp. And a B&M or TCI auto 727 trans.
 
In have a 8 1/4 in mine with a 440 and no problems it is the little rear that can. I have plenty of parts/gears for them if needed also. Here is a thread that will cover your questions.
The 8 1/4 thread
 
In have a 8 1/4 in mine with a 440 and no problems it is the little rear that can. I have plenty of parts/gears for them if needed also. Here is a thread that will cover your questions.
The 8 1/4 thread
Thank you. I will look at that thread. Good to know you have parts too. I may be needed some before my build is done lol.
 
Pay attention to the carrier if it had 2.45 gears and higher you are limited. It is covered in the thread pretty well.
 
Thank you. I will look at that thread. Good to know you have parts too. I may be needed some before my build is done lol.

The 8 1/4 is a good rear.... So is a GM 10 bolt but they don't get the publicity that the more known name rears get.... I would have to go sub 11's before making a change to a different rear and even then it all depends on how you got to the stripe....

If you are not intenting on sub 1.50 60ft. times on a regular basic by all means use the rear. You already have the BBP axles. And they are super easy to setup.

Good luck,
JW
 
Converter recommendations come with a known cam, and engine perameters as well as car weight and gear ratio and intended use.

I myself went here for a custom built converter which is no more expensive than one from the bigger companies with the same power ha doing capabilities.

Mine was ordered with the future in mind with anti ballooning plate, billet covers etc....
The fellas that built it stated;
"It's good until 650 HP, no problem!"

Here is there web site which also contains an order for that you can veiw. It is similar to other places that do this kind of work. The more you can fill in the better off and easier it is to get what you need. They are also racers themselves, so, if you lack some info, it's really not a huge problem. You just have to know where your going & where you want to end up with how your doing it.

ProTorque High Performance Drag Racing Torque Converters

My transmission was done by this guy here on Long Island. He is and has been very well known for decades around here for ace work. Freedy Brown "fbperformance"
high performance, 4r70w, transmission, AOD, racing, Freddy Brown
The Mopar page; Mopar Transmissions
 
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