8 3/4 transplant into my 66

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blackdart66

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Hey all,

I am a couple weeks away from really worrying about this, but I hung an A body 8 3/4 under my 66 Dart. My car was a factory V8 car but I have to be honest, I tore the original rear end out of it right away and I have no idea what it was. I did check and my original driveshafts U joint fit perfectly into the the pinion yoke on the 8 3/4. I am also staying with a 904 so I am sure that is all the same. My question is, Will I need a different length driveshaft ??
Thanks all !


​

dart progess 007.jpg


dart rear on ground.jpg
 
yes, i believe its about 2 inches shorter (exact measurements will have to be taken)
you will need the 8 3/4 shock plates and larger u-bolts as well
 
I also did this swap on my 66 Dart,I used a d.shaft from a 73 swinger 318/904 car.I changed out the rear u-joint for the .489 center.Length of driveshaft was a bolt in!
 
Way back in 1972, I had a '64 Valiant (original car was a 273, 3-speed stick with a ball-and-trunnion driveshaft) and a 7.25" rear.

From a local junk yard, I purchased a 1971 340/4-speed/8.75" rear end and driveshaft, all out of a rolled '71 Demon. As I said, everything came out of that car. My car had a 106" wheelbase; the Demon's wheelbase was 108".

Once I had the engine and transmission bolted to the mounts, and the rear-end bolted to the springs, I decided to fit the driveshaft into place to see how much too long it was. The wheelbase of the car it came out of was 2" longer than the car it was now in.

Surprise!!!! It fit perfectly! I was sure it would bottom out in the tailshaft case before the rear U-Joint lined up, but that didn't happen; it has a little over an inch of free forward travel in the tailshaft with the rear wheels on the ground.

I used it "AS IS" and it never gave any problems, but this has remained a mystery to me for thirty-seven years.. It should NOT have fit without cutting. I thought I was losing my mind....

I wonder, to this day, how that was possible, but I really didn't have the money to have the driveshaft cut, so I didn't ask questions.... I just was thankful it worked.

How this relates to your situation, I'm not sure, but it might be possible for you to use a stock 340 A Body driveshaft and avoid cutting one up.

Be sure to measure twice before trying that, though... I might have been just lucky, I dunno...:happy6:

Good luck!
 
Well, that is interesting...........but it makes me wonder cause the 108 frame connectors fit my car perfect.

That black car is sweet by the way.
 
blackdart66 said:
Hey all,​


I am a couple weeks away from really worrying about this, but I hung an A body 8 3/4 under my 66 Dart. My car was a factory V8 car but I have to be honest, I tore the original rear end out of it right away and I have no idea what it was. I did check and my original driveshafts U joint fit perfectly into the the pinion yoke on the 8 3/4. I am also staying with a 904 so I am sure that is all the same. My question is, Will I need a different length driveshaft ??
Thanks all

blackdart66, your dart might have already had a sbp 8 3/4 w/ a 741 gear
case. Anyway, here are measurements for 3 rears, 7 1/4: 10.09 centerline
of axle shaft to centerline of rear u-joint, 8 1/4 is 11.69 and 8 3/4 is 12.35.
If you knew the orig. rear you just subtract and thats how much you shorten
your d-shaft. I just did this in my 65 Valiant.​
Click to expand...
 
Cool thanks for the info.......I am sure it wasn't an 8 3/4. It had bolts holding the rear cover on......... I am not up to speed on the differences between the 7 1/4 and 8 1/4......The 8 3/4 I have now is all installed and converted to the LBP axles.
 
Only experience I have is from switching the 7 1/4" rear to an 8 3/4" in my 64. Had to shorten the driveshaft 2 1/4", which is pretty much right on with Orv Grote posted.
 
If you're asking me, I don't know. At the time I was still using the B & T. I THINK they say you should push the yoke all the way into the trans, then pull it out 1" & measure to the rear for the length.
 
Bill Dedman said:
Way back in 1972, I had a '64 Valiant (original car was a 273, 3-speed stick with a ball-and-trunnion driveshaft) and a 7.25" rear.

From a local junk yard, I purchased a 1971 340/4-speed/8.75" rear end and driveshaft, all out of a rolled '71 Demon. As I said, everything came out of that car. My car had a 106" wheelbase; the Demon's wheelbase was 108".

Once I had the engine and transmission bolted to the mounts, and the rear-end bolted to the springs, I decided to fit the driveshaft into place to see how much too long it was. The wheelbase of the car it came out of was 2" longer than the car it was now in.

Surprise!!!! It fit perfectly! I was sure it would bottom out in the tailshaft case before the rear U-Joint lined up, but that didn't happen; it has a little over an inch of free forward travel in the tailshaft with the rear wheels on the ground.

I used it "AS IS" and it never gave any problems, but this has remained a mystery to me for thirty-seven years.. It should NOT have fit without cutting. I thought I was losing my mind....

I wonder, to this day, how that was possible, but I really didn't have the money to have the driveshaft cut, so I didn't ask questions.... I just was thankful it worked.

How this relates to your situation, I'm not sure, but it might be possible for you to use a stock 340 A Body driveshaft and avoid cutting one up.

Be sure to measure twice before trying that, though... I might have been just lucky, I dunno...:happy6:

Good luck!
Click to expand...

I did the same thing with my '66 Cuda. I picked up a '68 Dart GT that had a trashed body, but solid running gear. It had a 727 instead of a 4spd, but the same deal applies.

I took the engine, trans, axle and driveshaft from the '68 and it was a straight bolt in on the '66. I even swaped the torsion bars which were a little bigger and the springs which had an extra leaf. Figured it would give a stiffer, more stabe ride.

I think the difference in the wheelbase is all in the more forward position of the K-frame and front suspension on the '67 and later cars. It looked to me like they were dimensionally the same from the motor mounts back. Could be a little different I guess, but not enough to be a problem. It's possible the driveshaft maybe sat a hair further in past the rear tranny seal.

I'm not a Mopar expert, but I'm assuming this forward position is why all the headers and other aftermarket goodies that are specific to '67 and later cars wont work on the early A's. I know I wanted to try and mount up the '68 sway bar and there was no way that was happening.
 
'68 Dart, 318/auto/8.75 = drive shaft of 52.27 inches.
'68 B'cuda, 318/auto/8.75=Driveshaft of 49.27 inches.
How will that 52 inch Dart driveshaft work in a 106 inch wheelbase that is 3 MORE inches shorter than the 108 B'cuda? I can see the B&T running 2 inches into the driveshaft length, but I can't see a '68 Dart bolting into a '66 Barracuda. How?
The headers won't work due to the 2 inch narrower engine compartment.
 
myoung said:
I did the same thing with my '66 Cuda. I picked up a '68 Dart GT that had a trashed body, but solid running gear. It had a 727 instead of a 4spd, but the same deal applies.

I took the engine, trans, axle and driveshaft from the '68 and it was a straight bolt in on the '66. I even swaped the torsion bars which were a little bigger and the springs which had an extra leaf. Figured it would give a stiffer, more stabe ride.

I think the difference in the wheelbase is all in the more forward position of the K-frame and front suspension on the '67 and later cars. It looked to me like they were dimensionally the same from the motor mounts back. Could be a little different I guess, but not enough to be a problem. It's possible the driveshaft maybe sat a hair further in past the rear tranny seal.

I'm not a Mopar expert, but I'm assuming this forward position is why all the headers and other aftermarket goodies that are specific to '67 and later cars wont work on the early A's. I know I wanted to try and mount up the '68 sway bar and there was no way that was happening.
Click to expand...
Motor mounts were a bolt in?I had to purchas schumachers v8 64-66 specific for V8.(360)
 
Outsider said:
'68 Dart, 318/auto/8.75 = drive shaft of 52.27 inches.
'68 B'cuda, 318/auto/8.75=Driveshaft of 49.27 inches.
How will that 52 inch Dart driveshaft work in a 106 inch wheelbase that is 3 MORE inches shorter than the 108 B'cuda? I can see the B&T running 2 inches into the driveshaft length, but I can't see a '68 Dart bolting into a '66 Barracuda. How?
The headers won't work due to the 2 inch narrower engine compartment.
Click to expand...


I dunno, you might be right, it was 12 years ago. LOL!

I'll have to crawl under the car and measure it. Maybe I did shorten it, if I did I don't remember. I am pretty absent minded.
 
pettybludart said:
Motor mounts were a bolt in?I had to purchas schumachers v8 64-66 specific for V8.(360)
Click to expand...

I had a 360 in the car already that I modified the original mounts to work with. However, I used to eat up those biscuit style mounts so I fabricated some brackets that let me use the later caged bushing style mounts. Haven't had to look at the mounts since. Which is going to be a pain some day way down the road if I ever had to change them. I can't remember exactly what year and model I got them from. DOH!

Back when I used to actually do stuff with this car, a lot of the kits and adapting parts you can buy today either weren't around, or too under ground for me to know about. I've been doing my own adapting for ever so I don't think twice about modifying existing stuff as opposed to buying some of these overpriced swap parts.
 
blackdart66 said:
Cool thanks for the info.......I am sure it wasn't an 8 3/4. It had bolts holding the rear cover on......... I am not up to speed on the differences between the 7 1/4 and 8 1/4......The 8 3/4 I have now is all installed and converted to the LBP axles.
Click to expand...

The 8 1/4" would not have been original equipment in a '66, so you would have had a 7 1/4" unless somebody had swapped one out. And I'm not sure they even made a SBP 8 1/4".
 
I think it was a 7 1/4.......hoping to get it all this weekend so I can measure
 
Well, I took a look under the 66 tonight and measured the drive shaft.

Mine is approximately 44 7/8" center to center. So I guess I must have shortened it and forgot. I did have an 8 1/4" rear with the original 904 in it for a short time before doing the swap, maybe I used that driveshaft?

The thing I am curious about now is if it's supposed to be about 49 1/4", how is mine about 4 5/8" shorter? Is there different length tailshafts that came on the A body 727's? Maybe it's not an original Dart trans?
 
myoung said:
Well, I took a look under the 66 tonight and measured the drive shaft.

Mine is approximately 44 7/8" center to center. So I guess I must have shortened it and forgot. I did have an 8 1/4" rear with the original 904 in it for a short time before doing the swap, maybe I used that driveshaft?

The thing I am curious about now is if it's supposed to be about 49 1/4", how is mine about 4 5/8" shorter? Is there different length tailshafts that came on the A body 727's? Maybe it's not an original Dart trans?
Click to expand...
That's more like it. Duster 340 with a 727 auto. That is a factory shaft.
 
So measurement wise is the 67 and up 8 3/4 shorter drum to drum, than 63-66 factory axle, if this is so is this made up by using a positive offset wheels? Also on the driveshaft, I have a 64 Valiant, 318 with an OD manual trans, I used a driveshaft from a 77 Volare automatic car and it fit with no modification...........
 
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