Do you need a different length driveshaft?

yes

I would do the change and see if you can have your driveshaft shoten locally I'm almost sure that the 8 3/4 pinion yoke sticks out further, its longer, than the 8 1/4 does Let us know what you do BTW, you may have a 7 1/4 instead of the 8 1/4

Dimensions.

find the correct donor shaft for your rear axle & if you have one cut mockup so you can get an exact/correct C to C number (I like 5/8-3/4" end play) loaded/level. Wouldn't hurt to check the end play of a donor shaft during installation also

According to the chart it's about 5.8" too long.

The factory yoke to seal clearance is WAY too generous in every application I've seen. There is often more than 1.5" of clearance and 3/4" is plenty for a leaf sprung car.

I'd recommend installing the old driveshaft and checking yoke to seal clearance before you cut anything. If there is 3/4" or more, it will be fine. As long as it doesn't bottom out, the more spline engagement, the better.

You mean 5/8" right?

If there is no dust boot on the transmission you could probably get away with the shaft you now have.

Fixed...


Edited for getting TREED!!!!!!!

I thought the 8-1/4 didn't come out till late 70 early 71. Don't remember ever seeing a Charger-Coronet with anything but an 8-3/4 in 69. I changed out quite a few carrier bearings after that time from defects in the 8-1/4. In fact I can't remember seeing any in the 71-72 Charger just the 4-door Coronets. 1973 up, a-b-c base models 8-1/4, e-body 8-3/4. Could be wrong been awhile.

It is definitely an 8¼" rearend.



Unfortunately, a lot of 318 '69 Chargers came with a 904 transmission and an 8¼" rearend like mine did, rather than a 727 and 8¾". The changeover seems to have happened at some point during the 1969 model year. I asked about this a couple of years ago on another forum:

http://www.dodgecharger.com/forum/index.php?topic=104494.0



Thanks for the chart. I assumed there would be some difference in length; I just didn't know if it would be enough to matter.

I had several 318 69 chargers with the 8 1/4 axle.

The 8 1/4" rear was a new addition for some 1969 model year cars.

"Unfortunately, a lot of 318 '69 Chargers came with a 904 transmission and an 8¼" rearend like mine did, rather than a 727 and 8¾". The changeover seems to have happened at some point during the 1969 model year. I asked about this a couple of years ago on another forum:"


Well that's what I like about this forum, never too old to learn something new. What a bummer by the way, couldn't see Dodge doing that to a great car just to save a few bucks.

That's right:

If you save $5 on 100,000 cars it's a half-million. Every car manufacturer does the math.

R.

They didn't sell 100,000 Chargers total but I know where you're coming from, dad worked at Fisher Body-Buick division in the 50s and said they would look for a haft cent to save.. In retrospect I don't think you could get the 904 with anything but the base rears. Upgrade the rear and this got the 727 I guess. Got two Dusters, one is 3 on the tree 6 cyl-7-1/4, other is synchronized 3 speed 6 cyl-8-3/4 so I'm thinking packages. Question for the group, where there any 318-904 mated to the 8-3/4 or just the 318-727 from 66-68 in the big cars- b&c bodys?

In the thread I linked to earlier, someone posted:



I don't know if he intended to type 8¾ instead of 8¼ or not.

I sold a 68 Coronet 440 h/t a couple years ago that was 318-904-8 3/4...

My '70 Swinger also has 318, 904 & 8 3/4".

My '70 Coronet came with 318, 904 & 8 1/4".

Thanks guys, just don't hear much about the standard engine-trans-rears