Drive shaft vibration after 14 bolt SF swap with ujoint adapter.

[Mav2u]

So I did my 14 bolt sf swap a little while ago in a different thread.

I used a 14 bolt to 10 bolt ujoint adapter to join the drive shaft to the new pinion.

I also used a 6 degree shim from http://diy4x.com/ to bring the pinion angle up. The ujoint was almost touching itself to the pinion side on rotation.

The vibration only occurs at low speed like from 0-30 mph. Once I get up to 40mph or so it disappears pretty much. Also if I'm driving at say 15 mph an feeling the vibration and I let off the gas at let the truck coast the vibration disappears. So it seems to be worse when I'm putting tension on the ujoint by giving the truck gas ( putting tension on the driveline ).

So is this a cause of the ujoint? Or is it also related to the new different angles on the ujoints at the transfer case an at the axle pinion? But why would it disappear once I got up to say 40 mph or faster?

I could upload pics of the angles if that would help?.

 

[Hogback Fabrication]

It's driveline angles

 

[jwobbs]

It sure sounds like your angles are off a bit. I had the same problem when I swapped in my sf 9.5. It was out of an 89 pickup so the perches had to be moved and the shop that did it didn't get the angles right. Took it out and put in a full floater and problem went away. I was confused because I only got the vibes going less than 25, got down there with an angle finder and sure enough it was off.

 

[jeff in co]

I'd say lets see some pics.

I'm still working on the funding of mine but I have learned a few things. I changed out my u-joints less than a year ago and just recently got a new transmission. I've had some vibration so they suggested sending the driveshaft out to verify my u-joints were going bad again.

After the driveshaft company reviewed everything, they basically said that my yokes were worn out and allowing the new u-joints to have a little "extra" movement.....thus killing the u-joints prematurely. They suggested a new driveshaft, new joints and then balance it. They emphasized even if my driveshaft was good, balancing it would do a world of good too. Price for everything....about $175. I am working on this now.

So, it could be your u-joints or driveshaft but I also think your angles may be off a bit, too.

I did ask how long u-joints should last and he said:

At 3 degrees, 5000 revolutions = 100,000 miles
At 5 degrees, 3500 revolutions = 70,000 Miles

 

[Mav2u]

I'll upload some pictures in a little while.

Here are the angles.

Transfer case down angle is 9 degrees.

Driveshaft angle is 19 degrees

Axle pinion is 17 degrees


I have new ujoints on both sides of the driveshaft.

I haven't balanced the driveshaft yet though.

 

[jeff in co]

Do you have normal u-joints or one CV one? If they are normal then the t-case and the pinion angles need to be parallel (but not at zero degrees from level). So your t-case is at 9 degrees, and the angle between the the t-case and driveline is a net 10 degrees.

If your pinion is at 17 degrees, your net is 2 degrees (assuming it is pointing more upward). I think you need to point your pinion yoke down another 8 degrees to get it parallel with the t-case.

Make sense?

 

[Mav2u]

Here are the images.

Note that my driveway has a 2-3 degree up angle. So you'll need to consider that with each angle.

 

[Mav2u]

Here you can see the axle pinion. I shimmed it with a 6 degree shim to bring it up. It was rubbing at the top between the driveshaft and the axle pinion before I shimmed it. You litteraly could barely slip a piece of paper between the two points before.

 

[Blue85]

I can't see the pics, but the T-case output and pinion need to be parallel. It sounds like you have 10 degrees in the upper joint right now. Bringing the pinion down to 9 will bring both angles up to like 11. It might be close enough just by getting rid of the shim. 11 degrees is enough angle to cause a little bit of vibe, but it will be way smoother than the mismatched angles you have now. I ran for a few years with 13 degrees in the joints. It was noticeable, but not terrible. It shouldn't be binding at 11 degrees.

Or you could shim another degree or 2 up and then swap to a C/V style shaft. But I would try matching the angles first to see if it's smooth enough for you.

 

[jeff in co]

I guess the only thing I don't understand is the binding with the pinon pointed back down?? It makes sense to remove the 6 degree shim to get it to a much closer, parallel layout......but shouldn't the driveshaft and pinion be OK with some minimal angles??

Is there an issue with the conversion joint and making that connection too close to create the area where the the two rub??

I'm concerned now because I am just about to do the same thing.

With a t-case drop, my angles are more like 7 degrees in each direction with my 10 bolt axle.

 

[Mav2u]

I can't see the pics, but the T-case output and pinion need to be parallel. It sounds like you have 10 degrees in the upper joint right now. Bringing the pinion down to 9 will bring both angles up to like 11. It might be close enough just by getting rid of the shim. 11 degrees is enough angle to cause a little bit of vibe, but it will be way smoother than the mismatched angles you have now. I ran for a few years with 13 degrees in the joints. It was noticeable, but not terrible. It shouldn't be binding at 11 degrees.

Or you could shim another degree or 2 up and then swap to a C/V style shaft. But I would try matching the angles first to see if it's smooth enough for you.

I put the shim in because the vibration before was bad an the fact that the pinion an driveshaft were making contact at the top of the joint.

 

[Blue85]

OK, I went to your site and saw the pictures. The strap was hitting yoke on the driveshaft? It just doesn't look like there should be a problem putting 6-7 more degrees in that joint. But if it IS hitting, that will definatlely be a big vibe, quick wear and possible breakage.

Are you sure you have the right U-joint in there? Is there visible wear from where it was hitting? You could grind just a bit at the interference points, but that should be for clearance at droop, not ride height. Your angles look decent, I've seen setups running with more angle and no interference, so something doesn't add up.

 

[Mav2u]

OK, I went to your site and saw the pictures. The strap was hitting yoke on the driveshaft? It just doesn't look like there should be a problem putting 6-7 more degrees in that joint. But if it IS hitting, that will definatlely be a big vibe, quick wear and possible breakage.

Are you sure you have the right U-joint in there? Is there visible wear from where it was hitting? You could grind just a bit at the interference points, but that should be for clearance at droop, not ride height. Your angles look decent, I've seen setups running with more angle and no interference, so something doesn't add up.

Yes, before I shimmed it it was rubbing just barely at the screw heads on the axle pinion. Taking the shim out out would drop it back down to the rubbing points again an I will get the vibration back at all speeds!

 

[Hogback Fabrication]

Do you have a transfer case drop?

For a single jointed shaft, the angles are off for sure. The pinion is pointed up too much.

However, for a CV shaft (which is what you need to fix your vibrations), it's practically dead on.

 

[jeff in co]

Do you have a transfer case drop?

For a single jointed shaft, the angles are off for sure. The pinion is pointed up too much.

However, for a CV shaft (which is what you need to fix your vibrations), it's practically dead on.

Chris - If he was going to go the CV shaft route, is it OK/Acceptable to have that large shim in there?

Mav, do you have a rear lift block and then a shim? You might just go to a driveline shop and ask how much it would be to get a CV shaft driveline installed. That would definitely help your situation.

As noted above, maybe a t-case drop is in order. I have one and like I said, my angles are closer to 7 degrees....

 

[Mav2u]

Chris - If he was going to go the CV shaft route, is it OK/Acceptable to have that large shim in there?

Mav, do you have a rear lift block and then a shim? You might just go to a driveline shop and ask how much it would be to get a CV shaft driveline installed. That would definitely help your situation.

As noted above, maybe a t-case drop is in order. I have one and like I said, my angles are closer to 7 degrees....

Do they make a slip yoke cv shaft?? I have the 241 np transfer.

What would it take to make my two angles in the right zone?? Give me both versions. The transfer case drop, the drive shaft drop!

 

[jeff in co]

Not everyone's choice but I got this pic from 496truck's set-up.

If you price it, let me know what it costs.

 

[Mav2u]

I took the truck out for a drive again an the vibration seems to be a little bit less. I might try a driveshaft balance first to see if that corrects an vibrations.

 

[496truck]

Awesome, Jeff. You beat me to it, I was gonna show him the same pics. The answer to the slip yoke CV end is "Yes" cause I have one. I think that shaft cost me just over $300 which was a new shaft, new CV slip yoke, new rear joint, and rebuilt CV all balanced up.

Balancing your shaft most likely isn't going to help cause it wasn't vibrating before the swap, right? Your angles are off, plain and simple. Try the t-case drop for a cheap and easy solution. You want the angles within 1.5* of each other with the pinion biased downward because of axle rotation under load. As an example... if your t-case is 7* down you want the pinion 6* up.

 

[Mav2u]

Guess my mistake on welding the spring perches off by 3-5 degrees has come to bite me back in the ass!!!

Guess I'll either need a transfer case drop to help get me back into the zone or the cv joint option!!!

Lesson learned on welding new spring perches on the axle!!