Driveshaft question

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Woodsman341

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1975 Dart Sport, currently has a 904 with an 8.75 Sure Grip. I have a local 727 I would like to buy to rebuild and eventually replace the 904 with. I know the driveshaft will be different, but is there a standard length for this combination, or do I have to wait until the transmission is in and measure the distance?

Thanks in advance.
 
Woodsman341 said:
1975 Dart Sport, currently has a 904 with an 8.75 Sure Grip. I have a local 727 I would like to buy to rebuild and eventually replace the 904 with. I know the driveshaft will be different, but is there a standard length for this combination, or do I have to wait until the transmission is in and measure the distance?

Thanks in advance.
Click to expand...

IMG_5432.jpeg
 
Error just slightly on the short side so you do not break
the tail shaft on transmission going over bumps or rough
terrain.
 
TrailBeast said:
I know it sucks to wait, but it is always best to measure once the trans is in.
Click to expand...

You're right...it sucks to wait. :) plus I have the chance to get a rebuilt 727 and pick from a small selection of driveshafts from a fellow Mopar man who is moving soon. I guess I can measure what's in it now for the shaft, do the math on the trans difference and pick one that's closest. Worst case scenario is that I have to get it modified which is the situation I have now anyway. :)
 
GTX JOHN said:
Error just slightly on the short side so you do not break
the tail shaft on transmission going over bumps or rough
terrain.
Click to expand...

Well I'm thinking about it, will the transmission mount crossmember that I already have for the 904 work for the 727?
 
You existing trans mount should work fine although I
do not have much experience with spool mounts.
You will gain durability with the 727 but no performance
gain whatsoever, the 904 takes less HP to operated and cheap
2.75 planetary gears are available for it which help low to moderate
HP combos.ull

You will need to acquire a different converter, hopefully a 10 3/4 unit if
you are interested in performance.
 
Your transmission crossmember and mount will work right back, same bolts and all. One thing you need to check on the proposed 727, is to see if it has the mount on the bottom of the tailshaft housing for shift linkage for console floor shift cars. If your car is a column shift, no need to even worry about it. The difference in tailshaft housings on small block 727's depends on whether it was a truck/van trans or a car trans. Car housings will have the little mounts cast into the bottom and truck housings will. Snap ring access plates are on the side of truck tailhousings and on the bottom of car housings.
 
Inertia said:
Always wondered why those tailshaft housings broke .
Click to expand...

Usually when the housing breaks it’s because of an out of balance driveshaft.
Too long and they jam the trans internals together causing end play clearances to go away and smashing parts together.
 
TrailBeast said:
Usually when the housing breaks it’s because of an out of balance driveshaft.
Too long and they jam the trans internals together causing end play clearances to go away and smashing parts together.
Click to expand...

Lol, this was 1/4 mile, B-body Dart, with a 426 hemi grafted in.
I knew he solved the issue, didn't hear the cause .
Prob 2nd gear shift.
Thanks.
 
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