Drive Shaft opinions & thoughts

[70GMCer]

Over this Winter, I hope to install my 700R4 into my lwb. I had planned on cutting and balancing a spare original 2 piece shaft for the swap. Seeing that the 700r4 is 2 3/8" longer than a 350 short shaft, I was going to cut 3" off the 2 piece shaft that I have read is recommended.

Since I've have been getting all the measurements together, I found in my garage, (hiding) a 1 piece drive shaft that came out of a 84 burb. I put the 2 shafts side by side, (see pic) to see how short the burb was to the uncut original from our trucks.

It looked close enough to work I thought. So, I took measurements too see. This is what I came up with.

I measured the full length of both shafts, including the yokes.

2 piece 77 1/2"
burb 73 3/4"
difference 3 3/4"

The burb is 3/4" shorter than I need to cut off the original. Look at the size of the one piece shaft. I would sure like to use that.

Would 3/4" short be to much to chance using this shaft. There would still be enough of the slip yoke into the 700r4. I know in the past, I have said I agree using the 2 piece in our lwb trucks. But, this big one would be great in my opinion.

Anyone????

[herb101]

Which set of holes are your engine stands bolted too? If they are on the front now, you could get a little engine setback and make up the difference by moving to the back set.

Herb

[70GMCer]

Originally Posted by herb101

Which set of holes are your engine stands bolted too? If they are on the front now, you could get a little engine setback and make up the difference by moving to the back set.

Herb

They are mounted in the front for V8. I thought of that, but my exhaust would also have to be changed and I have the engine all setup the way I want it. I'm using after market tube motor mounts.

[Longhorn Man]

the diameter on that single shaft is rather large. You think it'll go through the crossmember and not hit, and maintain a full range of motion to the rear suspention?

[cdowns]

the fools proof way to measure a driveshaft is with engine and tranny in place and rear end in place with the truck at ride height and weight crawl under with tapemeasure in hand than you get your measurement yoke to yoke. the frigureing type of measureing youre doing usually results in at least 2driveshafts being built

[70GMCer]

Originally Posted by cdowns

the fools proof way to measure a driveshaft is with engine and tranny in place and rear end in place with the truck at ride height and weight crawl under with tapemeasure in hand than you get your measurement yoke to yoke. the frigureing type of measureing youre doing usually results in at least 2driveshafts being built

I'm just going buy what I have read at countless sites and what people have told me that have did this same thing. 3" cut for the swap. I will be doing the measure twice and cut once thing when I am ready. Just getting opinions on this 1 piece for now.

[70GMCer]

Originally Posted by Longhorn Man

the diameter on that single shaft is rather large. You think it'll go through the crossmember and not hit, and maintain a full range of motion to the rear suspention?

That's one thing I didn't look at. I'll have too check on the opening. If it does fit, do you think that this would be a good size 1 piece for what I want to do?

[Longhorn Man]

well, I agree on measuring the truck, and going by that measurement. No drive shaft shop would cut anything if you told them this. They'd say go get me truck measurements.

[Brad]

Originally Posted by Longhorn Man

the diameter on that single shaft is rather large. You think it'll go through the crossmember and not hit, and maintain a full range of motion to the rear suspention?

It'll fit no problem.
Go for the 1-piece!!!!

[70GMCer]

But, do you think 3/4" too short will be ok?

[Phaedrus]

If the difference in transmission lengths is 2 3/8" why would you cut 3" out of the drive shaft? That plus your 3/4" difference would mean your slip yoke would be riding 1 1/8" further out than it is now, which doesn't leave much in the transmission on the short powerglide/th350/700r4 style slip yokes. If when you get the transmission actually in the truck and measure the length and your one piece shaft is too short, one option might be a longer slip yoke. We use one that is about 2" longer on some rockcrawler and extreme articulation apps.

[Brad]

Originally Posted by 70GMCer

But, do you think 3/4" too short will be ok?

Ideally, you want about 3/4" of the actual slip part of the yoke sticking out. You can go up to about 1 1/2" but only run it that way temporarily. I had to do that for about a month and I was fine. It just puts more pressure on the U-joints and seal and increases wear.
Any more than that and you're asking for serious trouble.