Has anybody broke a driveshaft in a imco ext box.I will be putting 1200-1300hp thru it. Im just worried about the extra length shaft being weaker then a short standard shaft.

Ive been running imco scx drives for years with 1300hp to each drive and I've never had a problem with anything breaking above the lower drive.

and thats with extension boxes and the longer driveshafts. as long as you keep the u-joint and coupler well greased you shouldn't have a problem. Its not a common breaking point. Most guys will have drive gear failure long before seeing the driveshaft break.

I think the longer input shaft gives it a lttle "torsional" cushion, Smitty

yes i agree, having a little flex will save parts from breaking, you will have a drive failure long before you have 1 of those shafts break.

Thanks for your guys input.This would be the new style xr joints on a scx drive.

The one part I've never broken is the Imco extension box shaft. Honestly shocked that I haven't yet actually...

Before upgrading to XR shafts, I did break a std u-joint(1.077cup) IMCO shaft right in the middle where the old shafts tapered to a pretty small diameter.

The new XR shafts are a lot beefier, with no taper. As mentioned, probably not a weak link.

With that said, when I broke my port helmet in Oct(picts on pg4 of the broken transom plate thread), I did however bend the XR shaft. I mounted an old gimbal bearing in a vice and spun the shaft in it, and the splined end has at least 1/2" of run out.

LE

I was told at one time to make sure there are no nicks in the shaft, causing a weak point. But I have not heard of any failures. I just installed the new one for the SCX and it is a beefy unit.. I wouldnt worry about it.

We broke one in the Svl with 550 HP. It had over 10,000 miles on it and was 4 years old. It broke about 4-5 inches north of the U joint.
Steve