Weird Vibrations after Clutch Swap

[720Calvin]

Hi Guys, long time lurker first time poster.

 

I have a 1986 Nissan 720 4x4 King Cab 5 speed manual that I purchased about 6 months ago with 115k miles. After buying it, I noticed there was a weird vibration when the car with in 4th or 5th speed and only at 3,000rpm for some reason. The clutch started slipping last week, so I took it to a local mechanic I'd never been to, but had good reviews. I mentioned to him the vibration issue, and he recommended replacing the U joints, which was something I had been planning on doing anyway, so he swapped 4 of the 6 U joints on the drive shaft.

 

I received the car back yesterday and when driving on the freeway, the vibration is now way more pronounced from 2,000 rpm and up in 3rd, 4th, and 5th gears. At 1st and 2nd gears, it doesn't vibrate at any rpm. Any ideas on what could be wrong?

[]2eDeYe]

Welcome. How are the tires?

[720Calvin]

The tires are fairly old, but still in ok condition, the previous owner barely drove it. They do have some cupping, but if that is the reason for the vibrations, why is there so much more vibrating now after changing the clutch and U joints? They're still the same tires from before...

[]2eDeYe]

Just curious, tires are usually the first thing I go to with vibrations as it is easy to rule out. 

 

Not sure if the 720 4x4 has a carrier bearing? 

 

4 of 6 u-joints.. Was that just the rear shaft? 

[Stoffregen Motorsports]

Is the truck lifted? Maybe the rear pinion angle is off.

 

Worn slip yoke bushing in the trans tailhousing is another potential cause for vibration.

 

Have someone drive behind you and look at the wheels/tires to see if they wobble or hop. Could be bent wheels or tires trying to come apart. Flat spots in the tires is common for a vehicle that has been sitting a while. If the tires have been sitting without air, they could be internally damaged.

[datzenmike]

Tire cupping???? This is the most likely cause of the vibration. Front or back, almost always from out of balance or bent rim. Possibly a wheel weight just fell off. Front could also be a worn suspension part like a shock absorber.

 

Not as likely is a balance weight on the driveshaft has fallen off.

 

The reason it doesn't happen in the lower gears is because the driveshaft and wheels are not spinning fast enough.

[Thomas Perkins]

Yes,I had to replace my yoke.I had a remanufactured transmission put in 12/2017 ,and new u-joints and it vibrated. I took it back to the transmission guy and he said the yoke was bad.He luckily found me a brand new one for 135 bucks and that fixed it.I still have the old one,it has worn groves in it.This was back in 12/15/2017.When this happens most people think it is the u-joint.This is the old one.It would vibrate on the highway,and not go very fast.What Ronald did was lift it up and ran it in the air to see it vibrate.He also showed me the new one next to the old one before he installed it.I never throw anything away.

Edited July 27, 2022 by Thomas Perkins

[720Calvin]

4 hours ago, ]2eDeYe said:

Just curious, tires are usually the first thing I go to with vibrations as it is easy to rule out. 

 

Not sure if the 720 4x4 has a carrier bearing? 

 

4 of 6 u-joints.. Was that just the rear shaft? 

I don't believe it has a carrier bearing.

 

Yes, just the rear shaft.

[datzenmike]

The transfer case is in lieu of a carrier bearing. 2wd will have them.

 

If one tire cupped swap the spare on in it's place see what happens.

[720Calvin]

1 hour ago, datzenmike said:

Tire cupping???? This is the most likely cause of the vibration. Front or back, almost always from out of balance or bent rim. Possibly a wheel weight just fell off. Front could also be a worn suspension part like a shock absorber.

 

Not as likely is a balance weight on the driveshaft has fallen off.

 

The reason it doesn't happen in the lower gears is because the driveshaft and wheels are not spinning fast enough.

 

The thing I'm not understanding about it though, is why is the vibration so much more pronounced now after the clutch and U joints were changed? The amount of vibration its getting since the service was done is pretty dramatic from how it was before the service. The tires are the same exact ones from before the service was done, so if it did have something to do with the tires, then I would think the vibration after the service was done should be the same as before the service was done.

[720Calvin]

@Thomas Perkins Thanks for the heads up on the yoke, I'm really suspecting it has something to do with the driveshaft, maybe a bad yoke, or maybe a weight was knocked loose when they took out the driveshaft to change the U joints.

 

@datzenmike I'll try swapping out the cupped tire with the spare, hopefully that's the issue.

 

I'm just really hoping it doesn't have anything to do with how they installed the new clutch and flywheel. I took a chance on this guy, and probably fixing a poorly balanced flywheel would be just as expensive as the original price to change out the clutch. I do want to put it run it on jack stands to see if I can find where its vibrating from.

 

[datzenmike]

15 minutes ago, 720Calvin said:

 

The thing I'm not understanding about it though, is why is the vibration so much more pronounced now after the clutch and U joints were changed? The amount of vibration its getting since the service was done is pretty dramatic from how it was before the service. The tires are the same exact ones from before the service was done, so if it did have something to do with the tires, then I would think the vibration after the service was done should be the same as before the service was done.

 

Who knows? Everything human is subjective. Again tires being cupped is an obvious fault. If only one tire, swap the spare on. Costs nothing and you have to eliminate things one at a time.

 

I would guess that if the U joints were replaced the mechanic would have noticed any damage to the U joint yoke.

[Stoffregen Motorsports]

 

18 hours ago, datzenmike said:

I would guess that if the U joints were replaced the mechanic would have noticed any damage to the U joint yoke.

I wouldn't assume that. 

[Thomas Perkins]

My u-joints were replaced twice by 2 different places and no one noticed the bad yoke,guess it's not a common thing to go bad..When my transmission went bad in 2017,it was making a noise.I could not figure where it was coming from.Took it to a few places and they couldn't either.Even took it to a muffler place and they said it may be from Transmission.Then I took it to a transmission shop and it was pouring down rain,we drove it around but the noise from the rain made it impossible to pin point where the noise was coming from.So I left it with him.It was vibrating and not going fast on the highway.When he installed new transmission and new u-joint.I drove it home.The noise was gone but the vibration and not going fast was still happening.I took back and he found out the yoke was bad and said he will look for one and found one and it fixed the problem.But he did mention to me when he first gave it to me that it was still vibrating.If you look at the yoke,it just has lightly grooves in it and not something real noticeable and who would think that would cause the problem and how many yokes have mechanics dealt with,just nothing commom.How many 720 owners have had this problem.Do the pictures of my yoke stand out.If I seen it for the first time,I wouldn't think it is bad and who examines every little thing.But this is my experience I had back then.You can rub your finger across the yoke and not feel the grooves.He noticed the grooves in it when he took transmission out and said something about I may need another one after driving it.It took him a good while to find me another transmission.Shops don't want to go inside transmissions,they will find you a remanufactured one and that is what he did.Jasper also sells them.My engine is Jasper,but it would of cost me 200 more for a Jasper transmission.My wife has a Jasper transmission in her 2004 Lincoln ls.Here is my yoke receipt.He got it from a shop in town.They had one left.I keep all my receipts. He quoted me a price of 135 for it like it was high and like he would keep looking.I said get it and put it on.

Edited July 28, 2022 by Thomas Perkins

[NC85ST]

I wouldn’t count out the clutch. Did they replace or surface the flywheel. I made the mistake of not doing that on my Frontier and ended up doing the job again. I don’t know if it was the flywheel or the clutch, but I replaced it all and now I don’t have a problem.

[datzenmike]

Flywheel surface needing a resurface would affect engagement but once driving it would have to be badly out of balance to cause more vibration.

 

How many tires are cupped?

[MikeRL411]

On 7/27/2022 at 9:03 AM, 720Calvin said:

The tires are fairly old, but still in ok condition, the previous owner barely drove it. They do have some cupping, but if that is the reason for the vibrations, why is there so much more vibrating now after changing the clutch and U joints? They're still the same tires from before...

 

If you do not pay attention it is easy to install the drive shaft 180 degrees out of balance.  That's why you mark the shaft and tail positions before you remove the U-joint.  Put the vehicle up on a rack and look at the driveshaft when rotating.  If it visually vibrates you have your answer.

[MikeRL411]

1 minute ago, MikeRL411 said:

 

If you do not pay attention it is easy to install the drive shaft 180 degrees out of balance.  That's why you mark the shaft and tail positions before you remove the U-joint.  Put the vehicle up on a rack and look at the driveshaft when rotating.  If it visually vibrates you have your answer.

 

Old trick. Put 2 worm clamps on the vibrating drive shaft and slowly spread then apart until the vibration is balanced out.  Old farts trick.

[Stoffregen Motorsports]

16 hours ago, MikeRL411 said:

 

If you do not pay attention it is easy to install the drive shaft 180 degrees out of balance.  That's why you mark the shaft and tail positions before you remove the U-joint.  Put the vehicle up on a rack and look at the driveshaft when rotating.  If it visually vibrates you have your answer.

For a two piece shaft, yes. I understand that the 4x4s have a single shaft in the rear. Can't get 180 out on a single.

[datzenmike]

The 4x4 has a splined slip shaft. Don't know if it was apart but perhaps the spline was put in out of phase?

 

 

 

[Stoffregen Motorsports]

Oh, that. Yeah, could be possible, but they don't come apart very easily, so I doubt the mechanic took the two halves apart.

[MikeRL411]

23 hours ago, Stoffregen Motorsports said:

For a two piece shaft, yes. I understand that the 4x4s have a single shaft in the rear. Can't get 180 out on a single.

 

I can. The U joint has 4 lugs.  I will bolt up 180 degrees out easily. Just pull the drive shaft or rotate the engine.

[datzenmike]

Only the flanges, one or both, would be 180 out.

 

More likely the balancing weight fell off or if taken apart the slip shaft spline if off a few teeth. It may not be possible to fit the spline other than correctly, I don't know, but you could visually look at how the U joints are lined up.

 

Still haven't addressed the tire cupping. Find what's causing that. Suspension, bent rim, wheel weight fallen off.

[Stoffregen Motorsports]

Driveshafts and tires make different vibrations. Wheels and bent axles too. A driveshaft that's out of balance (or with worn joints) will make a fluttering drone not in rhythm with the RPMs, and may go away with throttle input. Bad tires will feel like you're riding on a washboard road. Bent axle shaft or wheels will feel like you have a loose wheel, depending on how bad it is.

 

A driveshaft that's out of phase will feel like the whole truck is coming apart. It can actually be quite dangerous. Not only to the driver, but can tear up transmission internals.