2001 Chevy Suburaban 1500 4x4 Vibration 70MPH

[1500j]

2001 Suburaban 3.73 rear end towing package LT. No lift factory everything. Just put new tires on it as well. 212,000 miles.

 

Ive had a 70 MPH somewhat harmonic vibration that has been happening the past two months. Its comes on @ 65 peaks @ 70 and is gone by 74mph.

 

Ive done many things. I have had the rear U Joint replaced twice. Once by me and once after I took it to a driveshaft balance shop.

 

 

HERE IS WHAT IS INTERESTING!

 

If I take the rear driveshaft out plug the transfer case and run the Suburban as a Front Wheel Drive truck in 4x4 the vibration does not occur. It drives smooth as silk when in 4x4 with ONLY THE FRONT WHEELS PULLING the suburban.

 

Any guesses as to what it is???? Its killing me. I cannot figure it out.

 

I just had the driveshaft balanced and they put a new Spicer u joint in while they did it. They said the front one is in very good shape.

 

Thanks, Im new here so if this needs to be posted elsewhere. Let me know

 

 

[Jsdirt]

I would've done the front if you're doing the rear anyway ....

 

That's the only variable left ... unless the shop has a rookie running the balancing equipment .. or the equipment is junk.

 

Usually bad U-joints can be felt at lower speeds as well - around 30-40 mph. Higher speeds are usually wheel balance issues. Nothing is set in stone though, especially these days.

[Doug_Scott]

From my own experience with Chrysler rear wheel drive products from the 70's to the late 80's, a vibration that comes in at about 45mph, but goes away at approx. 55mph, and then return again at speeds over 70mph were almost always due to driveshaft out of phase. Keep in mind that I was seeing these vibrations after rebuilding transmissions. Like most others, never thought that rotating the driveshaft 180 degrees by disconnecting the shaft from rear end, turning it a half turn, and reinstalling it would correct it, but it did.

 

Another common item is checking the u-joint for play only and saying it is good, no play in it. You need to remove the caps and check the trunion (the shiny part of the cross shaft) for any marks or shadows. To do it properly, you need to also remove the caps that are pressed into the driveshaft to check the trunion on each of the cross shaft. You cannot possibly check the u-joint completely without removing it from the drive shaft.

 

Can the shop that is balancing the shaft install the shaft into the same environment the shaft runs in? By that I mean can they duplicate the angles at both ends of the shaft and include the u-joints in the balance? The shaft can be perfectly balanced with u-joints running at zero degree offset, and still vibrate like a pig when the u-joints are angled at 6 degrees each, under load.

 

Removing the shaft and running only one end of 4wd verifies the issue MUST be in the rear driveline system. The only actual parts that can vibrate as you describe, are u-joints, driveshaft, and drive shaft phasing. Standard troubleshooting is to do the free stuff first if there is no obvious problem found.

[02suburbanZ71]

rear end or driveshaft.

[1500j]

Thank you for the quick replies!

 

I did two thing to this Suburban besides change all oils when I got it last October.

 

1. I removed the Smooth Ride rear ninnovat (SP?) shocks and replaced with heavy duty springs and shocks. It did raise the SUV up 1.5 inches ( the old shocks/springs sagged)

2. When I had the driveshaft off I noticed the rear U Joint was rusted nearly tight so I replaced that. (Never Vibrated EVEN WHEN RUSTED)

 

Now I didn't get it up to highways speeds after these changes so I never noticed anything right away. But later on a trip I noticed a harmonic vibration in the 65-74 mph range.

 

I immediately thought driveshaft U joint so I replaced it AGAIN. For 8 bucks it was worth the shot thinking the first one was bad. (First one was a more expensive HD version) I grabbed a cheap one and did it again.

 

The 2nd U joint did not help. So I assumed maybe I did something and the Drive Shaft needed balanced.

 

I took the driveshaft out, ran it in 4x4 and it was smooth as silk so at this point I decided to pay to have driveshaft balanced, they also put a Spicer U joint in while they did it.

It still Vibrates.....

I am not sure how or what equipment they use to balance. They have a good reputation here in Des Moines. Certified Powertrain. Its pretty much all they do.

 

Now today I thought about the running angles and loaded the rear of the Sub up with rock to lower it 1.5-2 inches to see if that helped. The vibration still there.

 

Now this is a ONE piece driveshaft. I assume out of phase does not apply with it. The front slip yoke has a keyway but the it can go into the transfer case in unlimited orientations. Should there be key on the transfer case output shaft to keep the slip yoke from going on wrong? I sorta assume the keyway allows lube to flow in and out of the splines...

 

My thoughts.

 

1. Its still the driveshaft.

2. Somehow its out of phase at the transfer case (this does not make sense to me tho)

3. Rear End. I would assume a pinion bearing or such would make noise under load at all speeds and not be harmonic at just a certain speed..

4. Somehow when "PULLING" the truck with the front tires it tightens something up that is loose on the front end that is vibrating.

5. Transfer case.

 

Any other tests or things you guys can think of for me?

 

Thanks

[Doug_Scott]

The out of phase I commented on was on single shaft. In my experiences, it was simply the u-joint to pinion flange, it only goes on two ways, but one way would vibrate, the other way would not. This may be specific to Chrysler products(maybe they balanced driveline installed on initial assembly, don't know) and could be reproduced every time, on every model from late 70's to end of RWD. I have had many say it won't do that, but also have many examples where it did exactly that. Once I found that, I started marking every shaft I removed, regardless of brand. Took a second with a piece of tire chalk that I always had anyways.

 

You don't say if you changed BOTH u-joints, but you do say you replaced one twice. Does your truck have an indexed slip yoke at the transmission end of the driveshaft? I do not recall ever seeing that. Where are you seeing the keyway? On the output shaft of transfer case? I would imagine if that is where you are seeing it, then they are also using the same output shaft for two piece shaft with a bolt on flange on output shaft.

 

If the shaft has been running in a set range of angles, the u-joints tend to wear that way. If you have not changed the front u-joint, I would replace it.

[1500j]

 

 

You don't say if you changed BOTH u-joints, but you do say you replaced one twice. Does your truck have an indexed slip yoke at the transmission end of the driveshaft?

 

doug_scott,

 

Sorry if I confused anyone. I have only replaced the REAR U Joint on the rear driveshaft. Ive done it twice. The balance shop did it a 3rd time to make sure it was right before it left. (they didn't trust the cheap U joint I had in there)

 

The slip yoke at the front of the rear driveshaft that goes into the transfer case does have a keyway built into it. But the slip yoke can be put on any direction you choose because the transfer case output shaft shows no signs of a key. I think they left the keyway in the slip yoke to aid in getting lubrication in there. (my opinion)

 

I will try rotating the rear U Joint 180 degrees and try it out. Easy to do. I think I tried that once, but honestly cannot remember.

 

I lowered the ride height back to the height it was when I got it by using weight in the back but it still made noise.

 

If I could find a driveshaft from a junk yard I am almost ready to get it, and try it out.

 

Thanks

[02suburbanZ71]

I've got small vibration at 65-70. Please post findings

[1500j]

Quick update.

 

I spent an hour or two looking at various things. I took the front driveshaft out and ran it without the front driveshaft and nothing changed. So that can be ruled out.

 

I then rotated the rear driveshaft @ the pinion side 180 degrees in the yoke. Now this reduced vibration by 50%. GOOD ! I don't know why it did considering its a one piece drive shaft. ?

 

BUT there is still a minor vibration staying @ 70 mph. Its almost not noticeable now, but its there. If I go 65 it not there. If I go 75 its not there. But 70 MPH it still vibrates just a pinch.

 

I will take it up to 80 mph slip into neutral and let it coast. Its quiet right up to 70 mph then it throws a little vibration still then goes away by the time I'm under 67 mph. The window is pretty narrow.

 

Its much better, but it still bothers me it not perfect.

Thanks.

[Jsdirt]

If you think about how fast that thing is spinning at 70 mph, it wouldn't take much - maybe a gram ... or a tenth of one ounce - to cause an imbalance. Even a chunk of mud would, if it could withstand that g-force. There is probably an imbalance in both the pinion and the driveshaft - by rotating them, you brought the imbalance to opposing ends, which will cancel each other out.

 

Sounds like that's something you can probably live with - well done.

[02suburbanZ71]

If your that concerned replace the rear drive shaft with one at your local salvage yard. I know it bugs the piss out of me too, 65-70

[1500j]

Another question? How much support should the tailshaft give the front of the rear driveshaft? When I put my drive shaft into the transfer case it feels like there is extra play in the driveshaft.

Ive heard there is a bushing that supports the slip yoke. Should there be much play? Can the bushing be replaced easily ?

 

Please look at this video and let me know if the movement is too much

 

THanks.

 

 

[Doug_Scott]

What is making the clunking noise while you push on the shaft? There is a bushing in the extension housing (or whatever it is called on a transfer case) and will usually have some play in it. The spinning slip yoke will float at speed. About the only time I have seen an issue with the bushing was not being able to fix a slip yoke seal leak. Was not a big leak, but would leak past the seal when driving, and collect in the dust boot part of the seal. That car got a replacement extension housing simply due to bushing being on back order, and I had an extension housing from a wrecker transmission that I got to get the case for another transmission I was doing. Again, not a GM trans. My experience is on Chrysler auto trans.

 

If the vibration is down 50%, chances are you can actually live with it. Stop driving at 70 mph, and put it to the back of you mind. Right now you are unknowingly making it vibrate every time you drive it on highways. Sort of like that squeak you get in the dash, once you know how to make it squeak, you are no longer able to drive without it squeaking. And no one else can make it squeak.

 

The video still shows the original u-joint in the shaft. Either that or you know a shop that installs the u-joints with the injected plastic type stuff to make the locking rings. Usually when they get replaced, you heat the driveshaft with a torch to get that plastic stuff to expand and ooze out the little injection holes.

[1500j]

What is making the clunking noise while you push on the shaft?

 

The clunking is the yoke moving up and down in the tail shaft. Its clunking in that bushing.

 

The video still shows the original u-joint in the shaft.

 

Correct, as mentioned above, I've only replaced the rear UJoint on the driveshaft. The front one is still factory.

 

Ill probably just live with it unless I learn more about replacing that bushing. I think the bushing is cheap, it just getting it out of there.

 

I don't listen to the radio when I drive. So any vibration or squeak drives me nuts.

 

Nothing better than driving down the road in a smooth car/truck .

 

Thanks,

[Jsdirt]

Just FYI ...when I finished doing our '89 S10 Blazer's u-joints ... for the second time in 4 years ... I was surprised to see the nylon still in the fill holes. Even though both times I heated it fairly hot, the nylon still looked as if it hadn't been touched. Usually I need to get them so hot it all burns out of there, but that wasn't the case with this set. Just something for everyone else to be aware of.