What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

The Shop Truck

1971 Chevy C20 with a custom flat bed.
Overview Gallery Discussion
I pulled the shaft this morning and swapped in a brand new Spicer non cross drilled u-joint. It was a definite improvement, but the vibration is still there and gets progressively worse. I let off at 90 this time, but it was getting pretty bad still.

I sent an e-mail to Gearstar, I measured play on the output yoke, .012" fully inserted and about .023" pulled out about 1.5" which is about where it sits at ride height. That seems a bit excessive to me, I thought the roller bearing output would be tighter than the bronze bushing, but apparently not.
 
I talked to GearStar and the driveshaft shop. I'm going to get a new 4" aluminum shaft made, I also have the 3.73:1 gears on the way, but if the driveshaft fixes it for now I will wait to install those. Both of them thought I could use a bit more spline engagement and an aluminum shaft.
 
Which shop are you using? I went with AZ driveshaft and they didn't want to do a steel shaft for a c10 short bed. I asked them then why, when did the factory did it? Then got the story well its close to where we call it but we will do it.
 
I went to AZ Driveshaft. I generally use Phoenix Rack and Axle for my offroad stuff since AZ Driveshaft is more expensive and won't do the crazy 1/4" thick DOM shafts I wanted. AZ Driveshaft does a lot of drag race and hot rod driveshafts (as well as Shannon Campbell's U4 shafts) and that's what I need. The current one piece steel one is 66" on center of the u-joints, the new one should be about 3/4" longer and aluminum.
 
I want to say mine was 62 inches long so it doesn't surprise me they won't mess with it and you don't either.
 
Babaganoosh said:
I want to say mine was 62 inches long so it doesn't surprise me they won't mess with it and you don't either.
Click to expand...
The one in the Silverado is even longer, but I don't remember off the top of my head how long. I have issues with driveline vibration sometimes in that, but it isn't too bad.
 
I have vibration with the 2 piece shaft in the crew cab. About 48 to 53mph. I read somewhere they don't recommend the intermediate shaft be shorter than 18" which is the length of mine. I've wondered if I made it 3 or 4" longer if it would help.
 
The thing I don't understand is that an aluminum shaft doesn't really change the "critical speed" by much, but somehow they just don't vibrate as bad I guess.

If I could drive through the vibration, I would be OK, but since it just kept getting worse I think the driveshaft would self destruct in a 1/4 mile pass.
 
r3dd0g said:
The thing I don't understand is that an aluminum shaft doesn't really change the "critical speed" by much, but somehow they just don't vibrate as bad I guess.

If I could drive through the vibration, I would be OK, but since it just kept getting worse I think the driveshaft would self destruct in a 1/4 mile pass.
Click to expand...
Aluminum doesn't change the speed, it's just less rotational mass so speed doesn't affect it as much, it's like unsprung weight on off road vehicles, you want the least amount for a smoother ride
 
Are aluminum ones usually larger OD as well? Supposed to help with rigidity, right?
And is the diameter of the aluminum one going to get more cozy with your exhaust? Although it won't care as much as carbon fiber, correct?
 
6872xtc said:
Are aluminum ones usually larger OD as well? Supposed to help with rigidity, right?
And is the diameter of the aluminum one going to get more cozy with your exhaust? Although it won't care as much as carbon fiber, correct?
Click to expand...
He did say 4" aluminum driveshaft
 
6872xtc said:
Yes, I just didn't remember the OD of the current one. And clearance dimensions.
Click to expand...
I don't know of any steel driveshafts on pickup trucks that are 4", unless they are aluminum.
My van has an aluminum 6" diameter 8' long driveshaft
 
Iceman is correct, it is a 4" .120 wall aluminum shaft. The old shaft was a 3.5" .086 wall mild steel shaft, nothing special.
The area where it's close to the exhaust is right behind the transmission, so while it will get closer, it doesn't move much there so it shouldn't be an issue. The issue is where it goes through the modified crossmember:
IMG_20240601_123529002_HDR.jpg

I already heated up the bottom plate I welded on that goes under the shaft in that picture and beat it into submission. I feel like I moved it 1/2" so I should be fine. The other issue is the bolt that sticks out from the air tank mount right above the shaft, I actually had a witness mark on my old shaft from where the tip of the bolt hit the shaft when the bags were dumped. I ground the tip of that bolt off since this picture was taken and that fixed the issue before, but obviously I need another 1/4" of clearance so that bolt/nut may have to go away completely.
My current bump stops have settled out a bit and the truck will no longer roll when the rear bags are dumped, I ordered a set that's 1/2" taller to fix that and hopefully give me a bit more space here. There's also a 3/16" spacer I had to put under the trans mount when I put the 4L85E in that I'll take out.
Basically, it's going to be close and I need to get the shaft before I know what all I have to move/modify.
 
r3dd0g said:
I picked up the driveshaft this morning!
IMG_20250319_091204219.jpg


Unfortunately some idiot told them it had a 1350 u-joint at the rear axle when it actually has a 1410 :whistle:... I'm hoping they get it fixed for me later today, but it may not be until tomorrow.
Click to expand...
Don't fire the guy who messed up the U joint spec! :haha:

He means well!
 
I thought they were a little slow but also thought maybe they have a back log. Either way I wasn’t in a rush but of course I wanted it now.
 
I dropped it off this morning, not getting it done the same day doesn't make them slow. They got the initial build done in one day.
 
You must log in or register to reply here.

Latest Posts

Top Bottom