What do you have to do to suspension going from small block to big block?

[440charger68]

  I currently have a standard 68 dodge charger 318, 8 3/4 rear, no posi, drum breaks all the way around, no power breaks or power steering.  I have a 440 i want to put in soon with 4 speed, What kind of stuff do i have to change out in order for the motor to work properly? I heard that you have to change out the cross member, is that true? And for the four speed do i need a different drive shaft?

[Ghoste]

Cross member can stay.  Driveshaft will likely have to go.  Torsion bars can stay but you will likely be happier with big block ones in there.  Ditto on the rear springs once you start trying to apply that 440 torque to the pavement.  You will have more work with getting the clutch stuff in there than you will with the actual 318 to 440 swap.

[Chatt69chgr]

Drive shaft is definitely different length.  I think the t-bars were .92 inch on the big block.  Seems like they were .89 inch on the small block.  The rear springs need to be changed.  The cross-member is different for auto and manual and uses a different rubber mount.  Exhaust system is all different.  I believe the starting relay is different for auto and manual.  Radiator is different.  You will need a clutch pedal, z-bar, and linkage.  You will have to add the pivot ball to the frame opposite the bell housing pivot.  It welds on.  Transmission tunnel will have to be added.  Shifter, shifter boot, and chrome boot plate.  Reverse light on dash (I think), Will have to remove the piece on the steering column below the steering wheel if automatic was there and replace with floor auto or manual transmission piece (hard to find too), motor mounts, and you will want to at a minimum convert the front over to discs---------preferably 11.75 inch--------10 inch drum can stay on back,  power booster up to you but you can't buy the required Bendix dual diaphram as it's return and repair at Cardone and everywhere else and Pirate Jacks hasn't seen fit for whatever reason to get one made.  They have been playing around on this for two years so that kind of makes me think they don't really give a rats a__.  There are lots of ways to go on the disc brake conversion now.  Just need to check them out and decide what is best for you.  Also, I think you may have 14 inch wheels.  You will want to go to minimum of 15 inch wheels I would think.  I think the steels were 15X7 from factory.  Or styled steel wheels or aftermarket wheels.  Forgot to mention that you will want to go through the 440 and rebuild it probably as well as the 4 speed.  Not sure what the 440 came out of but exhaust manifolds may be an issue (unless you use headers).  That ought to take care of your loose change for a couple of months anyway.  Good luck.

[Nacho-RT74]

definitelly you'll have everything ready to R/T clone with everything you need to get

BTW, crossmember diff is just since 73

[Troy]

Realistically, you don't have to change the suspension at all but most of it is likely worn out any way so you might as well replace it with the heavy duty stuff. Torsion bars are bigger as mentioned and so are the rear leaf springs. R/Ts had larger 11" drum brakes instead of the smaller (10"?) ones used on small block cars. I'd recommend a disc setup in the front instead of either of the drum options unless you are dead set on having a "correct" clone. The 68 transmission cross member (the bolt-in piece) is different between auto and 4-speed cars. Of course, that isn't a suspension part. The k-frame for the engine is the same but the motor mounts are different.

Troy

[440charger68]

Will my old rear end even stand a chance against my 440? Its a 8 3/4 non posi, and the motor puts out about 425hp.  I would just like to drive while i make money to but a great rear end. Its kind of difficult to restore a car when your only 17 years old.

[Ghoste]

Do you already have a built up 440 and four speed to go in there?

[440charger68]

I have the 440 built up already, completely finished and ready to go, besides water pump. Im working on getting the four speed right now, it 2,000 for the complete setup, and i should have it by February. 

[Ghoste]

The 8.75 could hold up for a long time.  Depends on traction and how hard you start to beat it.  If you're bucks up right now, the length of time the 8.75 lasts behind the 440 really is all up to you and having been 17 once, all I can do is wish you luck.