driveshaft length rear diff swap

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72swinger619

72swinger619

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Have a 72 dart swinger went from 7.25 to 8.25 a body rear dont know what to do for driveshaft length difference di i cut it if so how much . Does anyone know of a good place to have this work done in san diego area. Or does anyone have a driveshaft that will fit for sale (cheap)in my area. My place of work is moving and are cutting hours due to the move money is tight.
I need to start driving to work asap. My carpool ride no longer will take me to work. All help is appreciated
 
[Here is a chart with the different lengths of driveshafts & trans/ rear combinations.

I did the same swap & the driveshaft length was about 52 1/2". That was for a 904 trans.
 

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Lonewolf3165 said:
[Here is a chart with the different lengths of driveshafts & trans/ rear combinations.
Click to expand...

What is the source for that table? It does not have (or I don't see) either of my combinations - 66 Barracuda 273/904/7.25 or 73 Duster 340/727/8.25

Are the measurement from the center of the u-joints on each end?
 
Ive heard they get shortened 1 3/4" for rear diff swap 7.25 to 8.25 i guess first things firstvfind a cheap local shop
 
7.25 to 8.25 swap is 1.75 shorter. True and balanced shaft isn't a easy to do it yourself.
 
I had a brain fart earlier. Should have said 1.25 rather than 1.75 sorry
 
After finding a good shop i was properly instructed on how to find my new length which went from 54" center to center to 53 1/8 center to center which is only 7/8 shorter
 
I've got a drawing here somewhere that shows 3 differentials and their dimensions.
I would need to hunt it down to be certain that it showed 171/4 difference between 7.25 and 8.25 . Since it came from the interweb too, I don't know its accurate.
Having said all that.. 3/8 inch either way will get the end seal to a new center of travel on the front yoke. I would rather go to the short side. I sure wouldn't want to bottom the slip yoke and damage something.
I suppose measure twice and cut it once applies.
3/8 one way or the other doesn't matter ? ( that's what she said ). :)
 
Since you're a welder... If you know how to properly seperate/grind the end-piece/yoke from a driveshaft and be able to shorten the remaining shaft nicely with say a pipecutter, you could do all the work yourself. Save for balancing usually.
Make sure to keep the yokes on both ends of the tubing aligned, as they are now.

If you weld cleanly you probably could drive the car as-is without balancing, but having it balanced is advisable.

I've shortened the same driveshaft in my '73 Dart twice myself and still can get the car upto 80mph without serious vibrations.
I first went from a 7-1/4" axle to a 8-3/4" and later on from a 904-transmission to a A518.
 
BigBlockMopar said:
Since you're a welder... If you know how to properly seperate/grind the end-piece/yoke from a driveshaft and be able to shorten the remaining shaft nicely with say a pipecutter, you could do all the work yourself. Save for balancing usually.
Make sure to keep the yokes on both ends of the tubing aligned, as they are now.

If you weld cleanly you probably could drive the car as-is without balancing, but having it balanced is advisable.

I've shortened the same driveshaft in my '73 Dart twice myself and still can get the car upto 80mph without serious vibrations.
I first went from a 7-1/4" axle to a 8-3/4" and later on from a 904-transmission to a A518.
Click to expand...



You can not do it yourself with out truing the shaft.

You don't just cut the weld yoke off and join it to a tube, thats WRONG, and can be deadly at the worst case scenario, but very well could put you in a hospital when that shaft comes thru the floor at 60 mph because of the vibrations it has going on you don't feel, which is weakening it, and you're in a hospital with bills costing more than your car.


But that $70 you saved doing it yourself is gonna be awesome......

.

Please, use these forums right and not for not well thought out ideas.

When you don't know why and how something is done or it's workings YOU don't give bad advice that can kill someone.

Driveshafts can and do cut thru what people believe are impenetrable items, safety loops can and do get cut thru and floors and cages and seats and people.


.
 
Supershafts said:
Call the shop doing the work and have them explain what they want from you for measurements.
Click to expand...

This^^^^^^^^^!

Having it done professionally isn't all that expensive. I have a shop about 12 miles from my house that builds driveshafts, they charged me 90 bucks to shorten, install U joints that I supplied, balanced and painted.

It's perfect!
 
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