Setting up driveshaft...

So I finally got the car up in the air to hopefully properly determine what I need to do to set my driveshaft up correctly... this is in a '55 coupe with R1, 4-speed, and rear end from a later car. The driveshaft is from a '61 Hawk 4-speed and is 3-1/2" in diameter. I am using (for now at least) the correct factory mounts everywhere and have the thin spacers between the bellhousing and the rear mount. I am using a crossmember from a later car; I did not drill the holes for the 4-speed mount, I used a crossmember that already had them in it from the factory.

It appears that the engine/transmission are not only offset to the pass. side but that the whole assembly is angled slightly so that the tailshaft of the transmission points slightly to the pass. side. This makes sense as the pinion is also slightly offset to the pass. side, but it looks like due to this there is a potential for interference between the driveshaft and the floor near the inside of the pass. side footwell. It also appears that it's off center enough that even if I had a custom 3" driveshaft made that it still might be an issue. One guy I spoke to that makes driveshafts said that with the length of this shaft he would not recommend going any smaller than 3". (The automatic driveshaft was 2-3/4" and I didn't have these problems, but the FOM tailshaft is also a lot longer.) Should I drill new holes in the crossmember and straighten out the engine? That looks a little iffy...

Also it looks like I need to get a good angle gauge; I think the pinion angle is off... I do have some vibration going down the road. I attempted to put the car up on stands and level and it looks like there's a pretty severe angle at the pinion, I'm not sure if I still unloaded the rear suspension some when I put it up on the stands or if I really do need to rotate it up. I guess I will have to set it back down on the ground and measure ride height and try again. I went through this previously with the automatic and eventually just gave up and tried some angle shims (they worked) but this time since I think it's going to be the final combination I ought to "do it right" to make sure I don't have too much angle on my U-joints. Any advice from anyone who's gone through this whole process before would be appreciated...

thanks,

nate

Reply to
N8N
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Only cure I know is to graft a driveshaft tunnel from one of the later models designed for a single piece unit...

JT

Reply to
Grumpy AuContraire

Nate, Rule of thumb for u-joints.. Whatever angle you put into the driveshaft up front, you should take off out back.. So... Horizontal: If you have a 1 degree c*ck in the engine to the right, then there should be a -1 degree c*ck in the driveshaft at the pinion. Vertical: Same deal, except now you introduce suspension travel and pinion rotation. If (at ride height) the trans end is down 2 degree's, then the pinion should be up 2 degree's... But a lot of people put the pinion just a tad down from that, as it tends to rotate up on accelleration. Jeff

Reply to
Jeff Rice

I have a one piece in my 54, and had a one piece in my earlier 54 with the Chevy engine and 4 speed. The earlier car would rub sometimes when the suspension bottomed but that was never a problem. I had traction bars to reduce the windup of the rear end under acceleration.

Reply to
Alex Magdaleno

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