Trying to track down a vibration

[MrGoodpliers]

My '72 suburban has a pesky vibration that I'm hoping you all can help me locate. It feels like it is in the driveline or rear (all of the frontend stuff is new and it's been aligned). I also just switched back to rally wheels and noticed no difference, so I don't think the tires are out of balance. Engine and trans have about 17k on rebuild. When under power, it cycles-- starts, builds, climaxes then stops every few seconds. When coasting it is constant. My guess is the driveshaft or the rearend. Any ideas?

[Eichorst69]

Does it have a two piece drive shaft? If so, then it sounds like the back half of the shaft is not clocked in the correct position.
Or maybe the center carrier bearing.

Rob

[MrGoodpliers]

Ahhh, yes I didn't think of the support bearing. I was thinking about u-joints or the shaft being out of balance. There's a good driveline shop in town, I'll get them to check it out. If it's not the driveshaft, I'm guessing rearend axle bearings? Anyone know of a good website that with instructions on how to replace them? I've never been inside a rearend (trucks or otherwise......) and have always been a little intimidated by them.

[greasy68]

Check the U-joints. I had a hlluva time tracking down a similar vibration due to a u-joint. I bought new wheels and tires because I was sure it was an out of balance something. It turned out to be the u-joint. They are pretty cheap compared to a rear end or drive shaft. It is pretty cheap to get them replaced and at least eliminate them as a source of your vibration. I think the if it was the rear end axle bearings it would be making a ton of noise and it would be more constant but evey failure seems to be a little different.

[cdowns]

take the driveshaft to a driveshaft shop have new ujoints and carrier bearing installed and a balance done

[tjvending]

I have the same thing but mine gets load around 30-50mph, sounds like a high pitch, let off of the gas and it goes away, back on the gas its starts again, no noise if under 30. What do you think? TJ

[dznucks]

i am just going to throw this out there......but check your exhaust system.
i had a similar problem and it ended up being a broken exhaust hanger. i would get this cyclic vibration that can and went at certain speeds.
might not be your problem but thats been my experience.

[boogie67]

Might not be the same thing but I had an Impala with a vibration.It turned out to be the rearend was low on grease.Greased it up vibration went away.

[Eichorst69]

Double check the drive shaft clock position (alignment) when you have the the center carrier bearing looked at.
If the shaft is out of alignment, the vibration would be from both the U joint yokes not operating with the right geometry, and you would have lost the shaft mass balancing which was done originally.
Orientation of U joint yokes should look like this.
[]-o]--------[]---[o-----------------o]-[]

1 2 3 4 5 6 7 8

1 is the front flange, 2 is U joint, 3 is front half shaft, 4 is centre bearing and spline, 5is U joint, 6 is rear half shaft, 7 is U joint, 8 is rear flange.

Make sure it's this way, but if it still vibrates, take it off, and reverse the shaft 180 degrees on the spline so it still looks the same as above.
Those are the only two positions where the orientation looks the same.

Rob

[Eichorst69]

This one makes more sense!!!

[]-o]--------[]---[o-----------------o]-[]

1--2--- 3--- 4---5------- 6---------7--8

1 is the front flange, 2 is U joint, 3 is front half shaft, 4 is centre bearing and spline, 5is U joint, 6 is rear half shaft, 7 is U joint, 8 is rear flange.

Rob

[chris71]

just for kicks i would crawl under the truck and grab the pinion yoke on the rear end and see if you can shake it side to side at all, there should be no play at all, but if it is an original rear with no rebuild the pionion bearing could be outta wack. i have seen a 57 chevy rear do this. you could literally move the pinion yoke side to side a fraction of an inch. check to make sure the nut on the pinion isnt coming off too. just throwing some more ideas out there. the axel bearings are easy to replace, you need a puller though:

1. jack up truck and put on stands
2. remove wheels, drums, and diff cover
3. take out the bolt that holds in the shaft in the center of your carrier, slid the shaft out
4. have a person push in the axel on each side while you pull out the C clips that hold each axel in.
5. slid axels out.
6.remove axel seal with seal removing tool or screwdriver
7. use puller to pull out old bearing
8. use bearing/race installation tool to install bearing and seal
9. slide in axels and install C clips
10. reinstall shaft and bolt from the carrier.
11. install cover and fill with lube
12. put wheels back on.

its easy, all you need is a tool or two, it would be good to find some illustrations though if you are a first timer. good luck.

[tjvending]

How hard is it to replace the rear pinion? Any pictures available? TJ

[chris71]

Originally Posted by tjvending

How hard is it to replace the rear pinion? Any pictures available? TJ

not something i would do, replacing the pinion means taking out the carrier, some serious work, i think you need to replace the pinion and ring gear as a set. i would take the rear to a shop that can do it. dont get me wrong you can do it with the right tools, it is just complicated, you have to get the spacing just right, i mean down to the thousandth of an inch or so. if the pinion bearing was out of whack you wouldnt need to buy new ring/pinion, but would still require complete disassembly as i remember. sorry no pics. rockville, hell, i work in rockville

[tjvending]

Chris71,

Any place around Rockville that you know about?

[MrGoodpliers]

I pulled the driveshaft last night, but before I did I gave the shaft a good wiggle around the support bearing. Lots of play, so that looks to be the problem... I'll let ya'll know on reinstallation.

[MrGoodpliers]

OK, got it back in after new support bearing, 1 u-joint and balancing. It is much better. The cycling vibration at speed is gone, but I now notice a little shimmy in 1st and 2nd gear. Trans mount maybe???