Front driveshaft vibration

[blast]

I have a vibration in my 1985 chevy k10 4x4 caused by the front driveshaft at speeds from 10-20 mph.  Any faster and it goes away, or so it seems.

I've confirmed it's the front driveshaft, removed it, and drove around in 4 loc (np203).  No vibration at all.  Lot's of snort too  , I definitely need the 2wd conversion real soon. but anyways......

There's some play in my driveshaft slip yoke here:



Here's the driveshaft in place, is it too much of an angle for this?



The suspension has a little lift, but the transfer case is dropped almost an inch too.  Here's the front block under the springs:



I took the driveshaft off my 76 and it was pretty much the same length and there are twice as many splines in the 76 driveshaft, and it had minimal play.   Here's the driveshaft from the 76:



Here's the splines on the 76.  It has about twice as many as the current driveshaft.

I would have taken pictures of the splines on the other driveshaft, but I took these all after I put the original back on.



I changed the u-joint on the 76 driveshaft, and put it on the truck.  Very very very bad vibration at all speeds.  I went about 100 feet and went back to the driveway it was so bad. 

So, I took the good u-joint (same u-joint for both shafts) off the 76 driveshaft and used it on the original shaft and put it back on the truck.  The vibration from 10-20 mph is still there.  I am sure it's the slop in the slip-yolk.

So, I guess my question is, is there a better or lengthened driveshaft that I should be using?  The splines don't stick out on either one when in place.

Is that angle to the axle too much?  Do I need to correct that?   

And, why didn't the driveshaft from the 76 work?

Oh, and while I'm at it, is it bad to run a np203 with the front driveshaft removed?  The vibration from 10-20 isn't bad, but it's enough to have concerns about something else breaking because of the vibration.  Would it be better for me to just remove the front driveshaft and drive it in 4-loc until I find a new one?

[77 step]

Wow!  I think the first thing to do is to get rid of those lift blocks in the front.  Lift blocks in the front is a no-no.  It is unsafe.

The driveline angle does look pretty steep, but I think you are right.  The slop in the splines is probably causing your vibration.

Possible fixes for the driveline angle are to lower the transfer case, or to rotate your rear axle to reduce the angle.  Lift kit companies sell tapered shims with their kits to do this, or you can actually rotate the axle by drilling out the plug welds, and rotating the tubes (pretty involved)

Another possible fix would be to get a custom driveshaft made with cv joints.

Good luck!

[blast]

Wow!  I think the first thing to do is to get rid of those lift blocks in the front.  Lift blocks in the front is a no-no.  It is unsafe.

The driveline angle does look pretty steep, but I think you are right.  The slop in the splines is probably causing your vibration.

Possible fixes for the driveline angle are to lower the transfer case, or to rotate your rear axle to reduce the angle.  Lift kit companies sell tapered shims with their kits to do this, or you can actually rotate the axle by drilling out the plug welds, and rotating the tubes (pretty involved)

Another possible fix would be to get a custom driveshaft made with cv joints.

Good luck!

Blocks are that bad, eh?  I didn't know that.  How involved would that be to just pop the front blocks out?  Does any of the steering need adjustment after that?

How about blocks in the back, how bad is this, you can see one of the rear blocks on the left, I think it was 5", should I be taking these out too?:





And how important is it that the front driveshaft is perpindicular to the axle ?  It appears to me to be over a couple degrees off perpindicular, but I think the transfer case can be moved a little towards the driver's side to line that back up.   Right?  Is that important, maybe the real source of the vibration and why the driveshaft splines are sloppy now?



Here's the crossmember, it looks like it may be pushed towards the driver's side as far as the slots allow, but maybe not, I didn't remove the bolt to check.





Sorry for all the questions, I'm new to some of this 4x4 stuff.  The front and rear axles were swapped out before I got this truck, and I'm just trying to clean up the mess they left me, and looking for any advice on how to do it right.

[77 step]

You can take the blocks out, but you will either have to buy a kit to lift it properly, or lower the rear also.  Blocks are acceptable, but not really the preferred method of lifting the rear.  The trouble with using them in the front is pinion angle (which you are now experiencing), and more importantly, they cause stress on the u-bolts.  They can get spit out during a panic stop, causing loss of all steering and braking control.


If you decide to lower it, your existing shocks will most likely be too long, and bottom out under compression.  Your brake lines will likely be too long.  You will need new u-bolts and should probably have an alignment.

The closer you can get a driveshaft to straight in all directions, the better.  This includes side to side and up and down.  Obviously there needs to be an angle in the up and down direction, but the lesser the angle, the happier they are.

[Blazin]

Ditto on the blocks up front. That truck shouldn't even be on the road with them in it. Good way to get someone hurt or killed.
I would take it off the road until they are out, then see if you still have a vibration. If you do it could be the play in the shaft, a bad u joint, it might be bent!
As far as side to side it doesn't matter. The shafts on all of these trucks are not strait to the frame, they run toward the right side a little bit.
if i remember correctly a 203 will not move without the front shaft in place, unless it has allready had the part time conversion done to it. I may be wrong, its been a long time since I have owned a 203.

[blast]

K, thanks guys.

I'll take out the front blocks.  They are only two inches, and it appears that the front is about two inches higher than the rear anyways.  If that doesn't help the pinion angle, I'll put some shims up front to aim the pinion at the transfer case.

I'll probably leave the rear blocks in for now, that should leave the truck level, and eventually pop them out when I get a legitamate lift kit on this truck.

The NP203 will move the truck with the front driveshaft removed, but you have to put the transfer case in 4-loc.  I'm just not sure if this will hurt the np203 over time or not. 

[VileZambonie]

If the transfer case is locked and the front shaft is removed it won't hurt the t-case. Running on dry pavement all the time in 4 lock with the driveshaft in will.

[1976Scottsdale]

How is the double joint at the back of the shaft?  Mine was doing the same thing when I first got it and the joints were bad at the back, I had a bigger, thicker shaft in the garage so I just swapped it out.  Blocks in the front have laready been covered quite well enough so I am not gonna beat you up over them.  The rear blocks are alright for most people, springs are better, the blocks just have a problem with causing axle wrap, but in a normal application they will be fine. The front blocks are easily removed, jack up the frame until the fron axle is hanging and lower it slowly after removing your u bolts.  Then just take the blocks out and use shorter bolts when you bolt it up, watch your shocks and lines to esure that they are not binding.  Other than that you should be fine.

[blast]

The double joints were good on both the front drive shafts that I tried.  The driveshaft from the 76 seems to be a bit stiffer, like it had less miles on it.  But that shaft had really bad vibration when I tried it.  I thought for sure that if I put the good driveshaft from the 76 in, that I would be vibration free.  But the good driveshaft with less slip yoke wear caused the truck to vibrate more.  So it's gotta be my pinion angle.   I'll be taking the blocks out as soon as I get the u-bolts.  Then hopefully the good driveshaft will work, the current one is shot, but the play in it actually reduces my vibration right now, hehe, kind of acts like another u-joint. 

[blast]

I just took the blocks out today.  Much better.  Thanks guys!

No vibration at all now with the original sloppy yolk driveshaft.  I haven't tried the good driveshaft yet, but will soon.

Steering seems fine.  Drives straight and doesn't pull at 60.

There is still about a 2-4 degree angle between the axle pinion and the driveshaft.  I think 2-4 degree axle shims would remove that totally.

Which brings me to caster, if I do put the 2-4 degree shims under the springs, do I need to start worrying about caster?  The axle is a gm corporate 10bolt.

[77 step]

I just took the blocks out today.  Much better.  Thanks guys!

No vibration at all now with the original sloppy yolk driveshaft.  I haven't tried the good driveshaft yet, but will soon.

Steering seems fine.  Drives straight and doesn't pull at 60.

There is still about a 2-4 degree angle between the axle pinion and the driveshaft.  I think 2-4 degree axle shims would remove that totally.

Which brings me to caster, if I do put the 2-4 degree shims under the springs, do I need to start worrying about caster?  The axle is a gm corporate 10bolt.

Good Job!

If it steers well now, and there is no vibration, I wouldn't put the shims in.  They are not necessary.  To answer your question, I wouldn't guess it would affect your caster too awful much.  Either way you go, I would keep an eye on tire wear for a while to make sure they wear evenly.

[VileZambonie]

Caster won't cause tire wear. As long as it's withing a degree left to right you'll be fine. If it's more than 1° it will pull towards the side more negative. Also if it's too positive it can caue wheel shimmy like if you push a shopping cart too fast.