Troubleshooting vibration

[commradd]

So i started a thread like this in the transmission section a couple days ago, but it should probably be here since it is likely not the transmission. I just bought a 1991 extended cab 2WD ranger with the 4.0L and an automatic. I have a vibration that seems to be noticeable at lower speeds, but becomes very distinct about 50 MPH. About 65 MPH is where it seems to peek. About every second or 2 it groans for about a second or 2. In other words, the vibration seems to come and go with about a second interval at 65 MPH. Since it doesn't seem to be every tire rotation, i'm guessing the tires are probably fine. I replaced the carrier bearing because the rubber around it was becoming cracked and moved a lot. The vibration was dampened a bit by doing this, but it is still there. I checked the oil in the rear diff and it looked new with no metal flakes. When I had the driveline off I checked each u-joint and they all felts tight. So here is my questions for proceeding:

1) Even though a u-joint feels tight, is it possible it could be bad enough to cause a vibration?

2) After driving it, would a bad u-joint become hot?

3) By blocking the rear axle and running it up to 65 MPH, will touching a stick to the driveshaft in different placed help narrow down the vibration to a specific u-joint or unbalance (not exactly safe i know, but this would be carefully done)?

4) Does the rear wheel bearings use grease, or does it share the diff oil?

5) Could it be the transmission or torque converter?

I've read a ton of threads here related to this very same issue. The resolution to most of them never got posted. Some of them ended up being different things. I'm stuck at work all day so I have plenty of time plan my evening of troubleshooting in cold weather Sorry for all the questions, but the more I know the easier this will be. Thanks!

 

[martin]

U joints fail not only by becoming loose they can also become solid due to rust etc. If one has failed in this manner it can certainly cause a vibration. you would have to remove the driveshaft and move the joints to see if they have any tight spots.

usually not.

running a vehicle up to speed while it's lifted off the ground is very dangerous and I doubt it will help as the suspension will be sitting in a not normal attitude and the drivetrain will not be loaded.

rear wheel bearings are lubricated by the diff oil.

I doubt it's the trans or converter.

Check your pinion bearing is not loose.

 

[commradd]

When I had the drive line out, I moved all the u-joints around and they felt smooth and tight, but maybe under pressure a dry u-joint will vibrate. Also, I wiggled the pinion before I put the drive line back on, and it seemed normal. About average backlash and it didn't slide in or out. I guess I should drop the drive line again and put a wrench on the pinion nut. I hate to start replacing things like u-joints when they appear fine, but if I don't it will drive me crazy wondering.

 

[ati190]

It's very possible he has a bad u-joint. When he replaced the center support bearing, the vibration lessened. I'd suspect a bad front u-joint. They are cheap, and easy to replace. I'd start there. Is the vibration noticeable in the cab, under the drivers seat mostly? Or does the entire truck vibrate?

 

[GoodOld85BlueBalls]

Does your drive shaft have a carrier bearing on it? Also did you check out the slip joint on your driveshaft when you had it out?

 

[retep88]

I have a 91 and it likes to vibrate at 65 mph as well, it's just the nature of the beast. It likes to vibrate at that speed. Assuming that your U-joints are good here is what I would do/check

1) Try to pin point the sound of the groan. Figure out where it's coming from and that will narrow down what is causing it

2) check the shocks. They might be totally shot and need to be replaced

3) check the balance of the wheels. They might be out of balance and that will cause vibration.

4) Check all the suspension attachment points. See if any of them are rusted up, or frozen.

I don't know how much more to tell you with out hearing or feeling it myself. I hope this helps with the diagnostic.

 

[adsm08]

Does your drive shaft have a carrier bearing on it? Also did you check out the slip joint on your driveshaft when you had it out?

He said he replaced the carrier and it lessened the vibration.

I don't remember what exactly replacing that involves, but is it possible you got the shaft out of phase putting it back together? That will definitely cause a vibration

 

[Shran]

He said he replaced the carrier and it lessened the vibration.

I don't remember what exactly replacing that involves, but is it possible you got the shaft out of phase putting it back together? That will definitely cause a vibration

IIRC it is near the slip yoke or on the slip yoke. If the splines on that don't match up exactly where they were before it was taken apart, that will throw the driveline out of balance. I don't have a truck that has a 2-piece driveshaft anymore and I can't go look, so I may be wrong.

If you're sure the u-joints are good, make sure none of the weights have fallen off the driveline. Next step with that may be to take it to a driveline shop and have it balanced.

Shocks, suspension, etc in my experience have never caused a vibration. A tire out of balance or one that threw a belt definitely will, but only at higher speeds. Since the carrier bearing helped, logic points to a driveline problem.

 

[adsm08]

yeah, if i was in your place I'd just take it to get balanced. It is probably your issue, and will save you the headaches. get a quote from a drive line shop to get it done, and then get a quote from your dealership to get it hose clamp balanced. both are equally effective, one is probably going to be a lot cheaper.

 

[GoodOld85BlueBalls]

He said he replaced the carrier and it lessened the vibration.

Yea I missed that

+1 for having a shop ballance it.

 

[commradd]

It vibrated before I replaced the carrier bearing, and replacing the carrier just helped dampen the noise. So it wasn't the carrier. I did mark the drive shaft so i put it back together the way it was, assuming it was balanced in the first place. I have only owned the truck for a few days so anything is possible. There was a very tiny amount of play in the slip joint on the longer part of the drive shaft. So little, that i'm almost certain that it couldn't possibly cause this kind of vibration even at high speeds. I've seen way worse before on other rigs with no vibration. At lunch I started it up while on blocks and let it idle while in gear. I watched the tires and i did notice that both rear tires seemed a bit flat on one side. I don't know how much it would take, or even if a couple flat spots could produce a vibration like this as well as the groan that comes and goes every second or so at 65 MPH, but I suppose I need winter tires anyways. If these tires were cheap, and if the rig sat for a long time, maybe they have a permanent flat spot. If this doesn't do it, next step is probably to take the drive line in for balance and new u-joints. I'll report back... Thanks for all the help!

 

[adsm08]

worst case scenario, any flats from sitting should wear out in 20 miles. if it goes away after the tires, i'd say you prolly threw a belt.

 

[commradd]

Pulled the tires while it was on blocks, still a vibration even without wheels and tires. Tightened the pinion nut about 1/3rd turn also. had a friend run it up to 60 MPH where the vibration peeked and held a stick to the drive line in different spots. No abnormal vibration thru the stick, but maybe I wouldn't actually see/feel it like that. Seems like I would though if it can vibrate the truck that much. Also rotated the drive line 180 degrees where it bolts to the pinion, just for kicks. Rev'd up the motor with tranny in neutral and no vibration, so it's not the torque converter. Then took it for a test drive and and it still vibrates. I found a drive line for $30 on craigslist from a wrecked 2000 ranger extra cab 2wd. It seems like I read somewhere on here that a newer drive line will fit, can anyone confirm that? If so, it would be a cheap way to rule out the drive line.

 

[Shran]

The newer driveline should fit assuming it's the same length. BUT you have to move the carrier bearing crossmember.

Something we haven't looked at yet is motor mounts and tranny mount. Unlikely, IMO, but worth checking.

 

[commradd]

I replaced the u-joints in the drive line. Not bad, only $5.99 per u-joint for the Heavy Duties. I was expecting more. Still that rotating vibration though at high speeds. The new u-joints really helped quiet it down though, and there is less total vibration now. So once I get the actual vibration fixed, this thing should ride like a caddy! Also, when i had the drive line down, I started it up and put it in gear and sped up to 65. No vibration, so I can safely say the tranny is out of the picture. It has to be wheel bearings or diff bearings. My next step is to jack up only one side, and run it to 65 MPH only long enough to listen for vibration. I know spinning the spiders isn't that good for them, but it's probably the easiest way to narrow down the side. If it vibrates on both sides, then it will be the diff. At least in theory. To be continued...