weird vibration at speed 60 plus

[75chev4x4]

Yea I will take a few when I get home maybe I measure wrong. I went off the bearing caps. To get the angles. Its a turbo 400 np203 to a 14 bolt if that helps.

[75chev4x4]

Got a shot of the pinion angle at least, best I could do for right now cause its pouring outside I will get some better ones tomorrow.

[shipma2]

my truck did a similar commotion found out it was the rear end take a soup can and pull the drain plug on the rear axle get a little grease and hold up to the ligh to check for metal shavings. also check both axle tubes for leaks . if not that driveline or transmisson

[75chev4x4]

I just changed the oil in the rear diff and had the cover off about 500 miles ago, but I might drain again and take a look if I can't find anything in the driveline angles causing this, thanks!

[geezer#99]

Thanks for the pic.
Looks like your pinion is pointing up.
Earlier you posted it was 7.5* down.
Anywho a question.
Is it a 2 piece driveshaft?

[75chev4x4]

Morning guys, ok so I was confused from something I was reading that if the axle is lower than the tcase the pinion angle is down but ghat doesn't make much sense so I guess it is pointing up 7.5 degrees. The driveshaft has the two u joint ears on each end and that slip yoke part you see near the pinion so I don't know if they call that a one or two piece? Thanks ill try to get some more pics

[sqzbox]

I had a problem with that once. Turns out the slip yoke tines were twisted (to much abuse off road with the 4:10's. I replaced the slip yoke nd problem solved.

[75chev4x4]

Mine looked pretty straight when I had it apart.

[75chev4x4]

I'm gonna have to wait to remeasure my angles, the made in china junk angle finder I bought at lowes broke. Dropped it from about 6 inches under the truck and shattered and needle fell out, jeez. Gonna have to find a better one then recheck my measurements.

[75chev4x4]

OK I got my new angle finder and rechecked my joints. The front u joint at the t case was 5 degrees, the driveshaft slope is 8.5 degrees, and the rear u joint angle was 7.5 degrees. From what I have read subtracting the driveshaft slope 8.5(bigger number) from each joint gives me the working angles. So with doing that I come out with 3.5 degrees for the front and 1 degree for the back. Did I do this correctly??? So I guess I need to get the 1 degree rear u joint angle pointed up more to match the one at the transfer case? I thought I would ask you guys before I order the shims from summit, thanks guys!

[geezer#99]

You want the angle down of the transfer case (yours is 5*) equal to the upward angle of the pinion. That makes them parallel.
Your pinion is pointed up 7.5*.
Therefore you need to point the pinion down 2.5 degrees more.
THose numbers work if you have a one piece driveshaft.
WE still don't know if your driveshaft is one or two piece. A 2 piece had 2 shafts, 3 u-joints and a steady bearing in the middle.
If it's 2 piece you'd need to measure the u-joint angle at the steady bearing.

[75chev4x4]

Its a one piece no carrier bearing in between just has a slip joint in the driveshaft and onky two u joints. So would the two degree shims be ok just put the thick side at the rear of the leaf pack to get the pinion down? Thanks geezer

[geezer#99]

Reason I thought 2 piece was the slip yoke at the back of the driveshaft.
If you put the shim in with the thick part at the back then the pinion will be even higher.
I think you need the thick part to the front.

[75chev4x4]

Ok I will order that and some new u bolts hopefully this gets it.thank you geezer

[geezer#99]

In your pic I see a couple of new shiny u-bolts on your springs. On either side of your axle u-bolts.
You got load levellers on there?

[75chev4x4]

Yea air lift air bags on the rear. Only run 5 psi with no load.

[geezer#99]

Now I see them!!
Sometimes if you have load levellers clamped on you can adjust the pinion angle by how you tighten the clamps.
Air bags won't do that.

[75chev4x4]

Oh ok

[75chev4x4]

Hey guys bringing my old thread back to see if I can get some help. I took the lift off my truck so its a stock height again. I pulled the rear section that bolts to diff and flipped it 180 degrees on the drive shaft. My cups on the u joints are aligned as they were before I flipped the shaft end but still have a vibration. I can go slightly faster b4 it vibrates than b4 I flipped it but its still there. Probably gets up to 65 mph b4 the vibration starts, vibration then a 2 second pause, I cwn feel it in the steering when it does it. Any ideas why b4 I take it to a driveline shop. Im at stock height no crazy angles and the cups line up on joints so I believe im in phase. The truck never had this problem b4 until I changed all the u joints. I dont have a problem taking it in, but if I can fix it myself I prefer that. Thanks for any suggestions guys.

[Ski-me]

On my 89' Blazer, I had the driveline shop install new u-joints as a preventative maintenance thing (330k+ miles). Everything was fine for awhile unil my tranny went out. During the tranny rebuild, they mentioned that my u-joint was bad and needed replacement (6 months old u joints). A little surprise but wanting to get back on the road, they threw in a new one.

2 months later, tranny repair again and they mentioned, bad u joint. So, we sent the whole driveshaft back into the driveline shop.

What they found out was that the yoke part of the driveshaft had slightly ovaled (elongated) the u-joint connection allowing the round u joint cup to connect with an egg shaped yoke.....not good. There was just an ever so slight looseness in that connection. The only repair was to replace the whole joint on drive shaft.

I elected to just get a brand new driveshaft with all new 1350 u-joints (slightly better than the 1/2 Blazer joints).

It drives much better now.

In a nutshell, your transfer case angle needs to be parallel with your pinion angle. So, if your t-case is at 7 degrees down, your axle pinion needs to be at 7 degrees up. This has a tolerance of about 1-2 degrees max differential. So you t-case could be 7 degrees down and your pinion at 6 degrees up (and still be in tolerance).

Good luck! I'd probably take it to a driveline shop and have it checked out.

I think I paid about $300 for a whole new driveshaft.

[Oldriginal86]

Don't know how the shaft is presently installed in your truck with a lot of talk about flipping this and that but the shaft appears to be install backwards. The slip yoke end should be at the transfercase and solid end should be at the rear.
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[y5mgisi]

I have a vibration above 55 with mine. ITs desperately annoying. For me, it appears to be a faulty drum. In the driveway, i put the rear end on jack stands and brought the truck up to 60mph. Vibration. Unbolted the tires, still vibration. un bolted the axle shafts, so that only the driveline would spin, and the vibration was gone. THen i noticed how wobbly the one drum is. I made several videos of it as i tend to over document my driveway shenanigans.

https://www.youtube.com/watch?v=MTpCtPVOcrk


https://www.youtube.com/watch?v=1Dgeq4pcTP8

[geezer#99]

Looks like bent axle flange!

[y5mgisi]

The axle and hub run true. The drum is the messed up part. Keep in mind this is a full floating axle.

[Ski-me]

Originally Posted by y5mgisi

The axle and hub run true. The drum is the messed up part. Keep in mind this is a full floating axle.

Wow,, that's pretty amazing. I would not of thought that could happen. I thought they were more true than that.......thanks for the video.

Do you think the semi float axles are susceptible too?