Driveshaft questions

[mechanixman]

My 52 1 ton had a 2 piece driveshaft. I just replaced the motor with a SBC and a t-5 transmission. I have just finished getting the motor running, and everything else to complete the the drivetrain. Right now I'm having some trouble with the driveshaft.

I was looking at it with the guy who was going to shorten the driveshaft for me when he noticed the center bearing can move back and forth quite a bit.. He was saying the bearing support shouldn't move that way, because it's the only thing keeping the drive shaft from moving. Now that it will have a slip yoke in the front, and the sliding driveshaft in the rear. I found a bushing on jim carter's but i didn't know if this would fix the problem or not so I went on the stovebolt forum and found some interesting things, but not what I was looking for. they mentioned that above certain speeds, you can get some serious driveshaft wobble.

So my questions are
I plan on driving my truck on the highway more often than not, should i even keep the 2 piece driveshaft?
I like to think that it's a little more protected, being that it'closer to the frame. I imagine the truck driving over brush, and through snow, and other obstacles that could come up and whack the drive shaft other components, and having 40% up high, and the back half come in at a steeper angles, it's less exposed to extra stress. (Basically more ground clearance) Please correct me if I'm wrong.

If I do keep it, what can I do to make sure the support and carrier bearing stay in place?
If I do keep it, What can I do to make sure it doesn't walk?

Thanks

[alaska gasser]

I would go with a 1 piece if you can. What is your overall length from the center of 1 u joint to the center of the other?

I got mine from a guy that thinks it came out of a mid 80's suburban and it is 69.5" center to center.

I had a '98 chev suburban with an aluminum driveshaft and it was quite long also.

[OrrieG]

x2 your oil pan, front crossmember and rear axle are going to be the limiting points, not the drive line. If the center bearing is moving at all you will have problems and it will probably cost as much or more to get it corrected than just getting a one piece drive line. In high school we put a 396 in a 63 Impala and the center universal was the weak link, got real good at replacing them next to the road when they broke.

[mechanixman]

Thanks for the quick response guys.
I measured the from u-joint to u-joint, I need a 75" ±1/16" drive shaft. The guy that's cutting my driveshaft said he can't make anything above 70". Because with any serious rpm, the driveshaft will bow out quite a bit. He mentioned that on newer trucks, GM has been cheating a little bit by making a 1 piece driveshaft 71"-74" by making it 5 inches in diameter and aluminum.

You can kind of see why the bearing was able to move in the first picture. The bearing couldn't move in relation to the bushing, but the bushing could just slide back and forth in the bracket.

But nevertheless, we found a solution. It turns out that where the driveshaft sits in the carrier bearing, the diameter and length are the same as new shafts. He pulled this out, and it looks good! The only thing is it needs about a 1.25" spacing for it to sit in the same place as the original. But that really won't be a problem.

[nvrdone]

Interesting info you are getting from your driveline guy.
I've got a '49 - 3100 with a 327, M21 & 12 bolt with a single piece drive shaft. It had a 2 piece shaft when I got the truck. The shaft is 3" dia out of a Ford pick up that was shortened to fit. Sorry I don't remember what year - it went in about 35 years ago. Anyway, the shaft was cut & balanced by a local drive line specialty shop & has held up really well - no vibrations, blown u joints etc. The truck is lowered and still drives gravel roads, freeways etc and I've never had anything hit the drive shaft.
Bottom line - I'd go with a 1 piece shaft. But that's just my 2 cents

[mechanixman]

Nvrdone, I believe the difference is that i own a 3800, stock frame and all. Which includes it being 20' long bumper to bumper, and a 9' bed. I believe that's where I can't have a 1 piece and you can.
That was just my speculation about stuff coming up and hitting the driveshaft. But I do stand corrected! (thankfully)
But there are drive shaft calculators out there, and based on the dimensions of my shaft, the critical speed of the shaft would be just under 4000 rpm.

[OrrieG]

I missed the 9' bed and longer chassic first response. I would probably stay with the center bearing and get it set up right.

[nvrdone]

Sorry - I also missed the 1 ton / 3800 also.
With the small block & 5 speed, I would be concerned about twisting up the original shaft. ( ask me how I know that one)
Is there a shop in your area that could build a custom shaft with bigger u joints & larger diameter tubes even with a center bearing? I've seen some big shafts under F350 / F550 diesel box vans

[mechanixman]

Originally Posted by OrrieG

I missed the 9' bed and longer chassic first response. I would probably stay with the center bearing and get it set up right.

Hearing that from you Orrie, I'm even more confident in this setup.

Originally Posted by nvrdone

With the small block & 5 speed, I would be concerned about twisting up the original shaft. ( ask me how I know that one)
Is there a shop in your area that could build a custom shaft with bigger u joints & larger diameter tubes even with a center bearing? I've seen some big shafts under F350 / F550 diesel box vans

This guy seems to be one of the only drive line guys in my area, but that's fine, he's very reputable. His dad owned one of these shops and he grew up owning one of the branches of the business. Then a decade or so ago he split off and started his own company.
I think the drive shaft is fairly substantial? As for U-joints, I'm using the stock 1350 U joints that go with the truck. The problem was that the yoke I pulled out of the s10 was a 1310 U joint. He said he could either get a converter U joint, or he could turn down a bigger yoke so it fits the t5. I chose the latter of the two, that way I 1350 joints across the board.

Here's that shop if anyone's in this neck of the woods, and needs some work done.
http://brake-align.com/Brake_Align_Home.php

[mechanixman]

Well it's all said and done.
For about $250, I had the front half of the driveshaft shortened, both halves balanced together (It was balanced as one piece, thus those two yellow lines on each shaft), new carrier bearing, new U-joint, and basically had a new yoke made. And just to top it off, he blasted and painted the smaller shaft. He said he would've done both, but the bigger shaft didn't fit in the sandblaster.

[OrrieG]

That is not a bad price, I paid about $175 in 1985 to have my one piece shortened and balanced with new universal joints. Good attention to detail balancing them together.

[whitedog76]

What's the make on that carrier bearing? I'm putting a SM420 in my 3600 truck, that originally had the 3OT. I'm probably going to have to change driveshafts too.

[skysoldier173rd]

Go with the one piece, quick easy, cheap and it works. I had mine made up from a nice long one from an old chev wagon. Just measured what it needed to be and took it to a truck service company. They balanced, shortened and installed new ujoints and it has been perfect.

[mechanixman]

Originally Posted by whitedog76

What's the make on that carrier bearing? I'm putting a SM420 in my 3600 truck, that originally had the 3OT. I'm probably going to have to change driveshafts too.

Hey, I'm awfully sorry about responding so late. It's been a busy week, and I just never got around to answering this. When I went to pick up the driveshaft, I asked him just in case anyone else was wondering. He said that it was used on a lot of late 70's fords, but the part number is a spicer number. So if you look up this : spicer 211139x in google, you'll find what you're looking for.

[whitedog76]

Thanks for the link, Nick.

I'm definately going to save that number.

Your the first person I've seen that's used a late model carrier bearing.

[mechanixman]

Yeah no problem!
Really? I'm surprised no one else has done it.
Again, all you'll need to do to make it fit is cut off the old dust shroud thing and use the ones that come with the bearing. (the thing highlighted in yellow)