drive shaft shortening

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thanson_mopar

thanson_mopar

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ok guys the car is a 74 duster, slant six three speed, converting to 360 four speed, 7.25 rear right now. the drive shaft needs to be shortened for this rear correct? anybody know how much it need to be shortened?
 
Will a shop be doing this for you? If so measure from the back edge on the tail shaft (behind the lip of the seal) to the flat part on the rear pinion yoke where the u-joint straps bolt on. I had mine done and this is how they wanted me to measure. Of course, you need to do this when these items are installed in the car. The shaft only took one day to make at my shop. Keith.
 
66340SEDAN said:
Will a shop be doing this for you? If so measure from the back edge on the tail shaft (behind the lip of the seal) to the flat part on the rear pinion yoke where the u-joint straps bolt on. I had mine done and this is how they wanted me to measure. Of course, you need to do this when these items are installed in the car. The shaft only took one day to make at my shop. Keith.
Click to expand...

thanks, yes a shop will be doing the shortening for me. You just answered my next question on how to measure the drive shaft. So it is easier to measure once the new combo is in?
 
Had mine done last summer and the shop I used said to shove the slip yolk all the way in on tail of the tranny and measure from center where the u joint goes to center of u joint on the rear end, then subtract 1 inch to get total over all length. If you are going to the bother of changing the engine you might want to get rid of the 7 1/4 to an 8 3/4. If you do much cowboying with the newer installed 360 it will probably break the 7 1/4. If this does happen and you decide later to fit a 8 3/4 you will need to shorten (rebalance) the drive shaft all over again.
Just a thought.
 
340 swinger said:
Had mine done last summer and the shop I used said to shove the slip yolk all the way in on tail of the tranny and measure from center where the u joint goes to center of u joint on the rear end, then subtract 1 inch to get total over all length. If you are going to the bother of changing the engine you might want to get rid of the 7 1/4 to an 8 3/4. If you do much cowboying with the newer installed 360 it will probably break the 7 1/4. If this does happen and you decide later to fit a 8 3/4 you will need to shorten (rebalance) the drive shaft all over again.
Just a thought.
Click to expand...

lol, i knew someone would say somthing about the 7.25. The truth is that i AM going to put a 8.75 suregrip rear with 3.91 gears. But It will not be done being built for several months for money reasons. High school prom is coming up in 2 months and my engine trans combo will be in the duster, just need to get the car drivable. I am going to be really easy on it while breaking in the new motor anyway so im not worried about breaking the little rear while its in. I hate to have to shorten the driveshaft twice but theres not a chance in hell that the dusters not making it to prom soo....anyway thanks for the measurment ill write this stuff down for when the time comes to adress the driveshaft.
 
If you are not changing the rear end yet the 3 speed driveline will work with the 4 speed. But, you most likely have to change the trans yoke. Most 833's have a 727 style yoke.


Chuck
 
An A-body 833 is the same length as the 3 speed (and 904) so if you just change the yoke to a 833 yoke then you can use your stock driveline. I have always had an 833 yoke on hand but have heard of people using 727 yokes being they are the same spline.

If you are going to use a B/E body 833 in your car then you will need to shorten your driveline because the B/E 833 is the same length as the 727 (which is 4" longer than your 3 speed).


Chuck
 
340mopar said:
An A-body 833 is the same length as the 3 speed (and 904) so if you just change the yoke to a 833 yoke then you can use your stock driveline. I have always had an 833 yoke on hand but have heard of people using 727 yokes being they are the same spline.

If you are going to use a B/E body 833 in your car then you will need to shorten your driveline because the B/E 833 is the same length as the 727 (which is 4" longer than your 3 speed).


Chuck
Click to expand...

I guess i didnt know that the a body four speed was the same length as the three speed (i thought it as the same length as the 727), is it the same length as the 904 automatic then too?
 
Nobody mentioned the different sizes of U joints. Isn't it possible he might need an adapter U joint to connect the 833 yoke to the /6 driveshaft?
 
You can get the 727/A833 size yoke with either the small or large u-joint. But in either case you should be installing new u-joints anyway.
 
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