Okay, So got the new SMF in and Valair. The problem is, now I have a vibration at 55-60 only in 5th gear. It might be there in 4th, but I cannot notice it.

It feels like a bad u-joint but those are good.
So, I was thinking about drive shaft angles and yada yada.

Why I think this is that when I put the trans back in, I let the trans just sit on the cross member, and when I bolted everything back up, the angle supports that bolt to the top of the rail didn't bolt up the same as when I took them out, so it looks like its sitting down lower.
Thus means the trans is sitting lower in the tail shaft area.

I know sometimes when the drive shaft is outa wack it can do some strange things.

So, should I jack the back of the trans up and try and line up things again?

*shrugs*

 

I was reading where coon made a comment on the midship bearing and how you needed to position your truck to work on it so that there is not any alignment issues. Sounds like this is what happened to yours in reverse.

 

Yea, I forgot to say I dont have a 2 piece drive shaft.
Thats for later models with the newer transfercase.

 

Yea, I forgot to say I dont have a 2 piece drive shaft.
Thats for later models with the newer transfercase.

 

William I think it had to do with the weight of the truck on the rear wheels allowing the axle to twist a little. Samething may have happened to yours. Figure which side the off set was on and then position the truck on a incline and then loosen it up and see how the alignment is. Then retourque and test it.

 

Uh..... what are you talking about Rocky?

 

Uhm, Rockey, What are you talking about?

 

I think that the coversation was really around the midship bearing replacement and the shim for a lift. But the thought still may apply to yours.

The thought was that sitting on a incline with the brakes set and then you remove the midship and the rear axle twist a few mils and that small twist leveraged out to the midship bearing throws off you alignment and causes a bind on a reinstall.

So I was just thinking maybe something simular happened to yours. DUNNO

Just a thought.

 

Axle can't go nowhere. =)

But always good to have a thought.

I know the angles of the drive shaft as to the angle of the axle and the power train can cause weird things.

Such as the case with a carrier bearing setup with a 2 piece drive shaft. The angles have to equal out a certain way, that is why you have to drop the bearing down to get rid of the vibrations.

The same is with a single piece driveshaft, but they are generally not as sensitive.

I was thinking the incorrect angle I have on the drive shaft at the output of the transfer case is causing a vibration at that speed due to the angles not matching up any longer.

 

Axle can't go nowhere. =)

But always good to have a thought.

I know the angles of the drive shaft as to the angle of the axle and the power train can cause weird things.

Such as the case with a carrier bearing setup with a 2 piece drive shaft. The angles have to equal out a certain way, that is why you have to drop the bearing down to get rid of the vibrations.

The same is with a single piece driveshaft, but they are generally not as sensitive.

I was thinking the incorrect angle I have on the drive shaft at the output of the transfer case is causing a vibration at that speed due to the angles not matching up any longer.

 

come on now. where is all the goods.

need some suggestions here!

 

Other than the straps on the yolk stretched , did you mark the position of the shafts when you removed them ?...

 

no. Shouldn't make any difference IMO. They don't balance the drive shaft in the truck, they balance it on a machine in the shop.

I never understood why people suggest the indexing of them.
Now, if the DS was out of balance when you took it out, it makes sense, cause the drive line is used to it.

Am I wrong in thinking this way? Please enlighten me on this.

I'm really concerned about the difference in the tail height at the moment, thats the easy thing to check, (doesn't cost anything)

And perhaps the straps could be replaced, they looked original. I wish I had the money for some new U-joints as well, they are non greaseables, I hate those. They can start to deteriorate, and you cannot do anything about it.

 

I agree with the logic that it shouldn't matter On the indexing thing.

, I prefer to not take any chances if things are fine to begin with .

 

Talyn, you are correct. It doesn't matter one bit if it's not indexed the same way. Something else is going on.

As for driveline angles, you can change them a little without harm but from the factory they have the angle split set usually 1/2 to 1 degree. More or less than that and you have problems. In other words if both u joints are running at the same angle then it will vibrate. Make them about 1/2 degree different then they won't. That's why carrier bearings are so important.

Rear axles do move too. Quite a bit. When mine is sitting on the overloads it is very slight but off of them and I get driveline vibration all the time when putting power to it. I know I need a carrier bearing. Those springs really twist though and that changes the angles on the ujoints a lot.

This stuff is a lot easier to explain on a tractor with a big shredder hanging on the hitch. You can see exactly what driveline angles do to it then.