2 Piece Driveshaft Question for my 3800

[lmdangerous]

I am putting a 250 late mo0del six and a 2004r trans in my 1951 JS pickup. My drive shaft is 2 peice with a swing bearing . I dont think a one peice will work ( will be to long to balance etc) . Will I need to lower the swing bearing mount to line up with the new 2004r trans - as the out put shaft on the 200 4r is going to be a couple of inches below that of the old SM 420 4 speed , or will the small angle be of any real concern. I have seen some Aux. trans drive shafts that were at all kinds of angles and the only part of the drive shaft that will be moving up or down will be the second part that is behind the swing bearing. I really dont want to reinvent the wheel , and the 2 peice drive shafts work well enough in big trucks so I dont figure Ill ever hurt it.
thanks LMD

[_Ogre]

i'd stay with the 2 piece drive shaft, it wouldn't handle any torque with a 1 piece shaft
realistically your 200r4 should be the same height as the sm420
automatics have a little more bell housing than a stick,
you will need to modify the floor pan a bit

it's not a good pic of what i'm talking about but the mod to my 58 floor pan is minor
maybe a 8x12'' triangle

[formergreen]

I am using the same tranny in a 51 3/4 ton, split drive shaft. I am interested in this thread to see what is the best rought aswell.

[OrrieG]

If the angle is not extreme (3-4 degrees is good, 7 is usually the maximum without a CV joint) it should be ok. Lowering it should not be a big deal. A long time ago, when it was 2wd, I put a granny 4 speed in mine that came with a two piece drive line. It was the right length, I just used a piece or channel for the center bearing mount and paid attention to the angles. Drove it from 78 to 85 that way as a daily driver and camping fishing hunting rig.

[lmdangerous]

I am actually going to us the tubular crossmembers that I got from classic .I am going to lower it a small amount , and modify the trans cross member so I dont have to change my floor pans at all. I have already considered using a lowered swing bearing mount if I have to - wont be that big of a deal, I just want some input from those that have been here done this.I also dont want to run the risk of a drive shaft that is to long and no way to balance it. please speak your mind guys, you guys helped me put disc on a 3800 and retain the stock axles so i figure why go anywhere else.
thanks LMD.

[mr48chev]

I'd want to keep the front half of the drive shaft level or angled slightly down as it goes back but not angled up so that it increases the angle that the middle U joint works at. I don't see any issue with lowering the center support except that it makes for a bit more work for you. The idea is to have the smoothest angles for the drive shaft Ujoints to work at or make sure you carry extra Ujoints.

[Trucknut57]

I used to have a two piece drive shaft in my 57'. I lowered the carrier bearing mount 1 1/2" from where it attached to the frame. This helped to reduce the rear shaft angle and actually reduced the vibrations.
The only problem I ever had, was that the stock type carrier bearings kept folding over. If I got onto it to hard it would break the bearing housing and then the driveshaft would just flop around.