Bugout4x4

In the mean time my parts all came in. I have been delayed with a new water line from the well but hopefully I can get my engine back together and running sometime next week.

sambroom

Update: I've got 600 miles on it since finishing up. Commuting, long shakedown drive, a fall canyons drive, and one trail. I just did the last oil and filter change to make sure any contamination is flushed. Oil came out looking new. Cut open the filter, and there wasn't any visible debris. Still running great! When can I relax and trust I put it together right? lol

There are three sounds I am hearing:

1. I'm pretty sure one is coming from the flexplate; a light ticking sound that is only present at idle, and can only be heard from underneath the jeep at idle. You can't hear it from in the cab, and if you raise the RPM just the slightest bit, the sound disappears. I decided it was the flexplate because that is where the sound is coming from, and I can see a very slight wobble to it that is in sync with the sound. I inspected it for cracks and there are none. I'm planning to just run it. If it gets worse I'll just put in a new flexplate... If it breaks... I have free towing as part of my insurance.

2. There is a whirring sound heard from in the cab that sounds like it is coming from the front end. It only occurs while decelerating, or when I go over a bump. It almost sounds like rubbing of some sort, as the pitch lowers as I slow down more and more. doesn't matter if the jeep is in drive or neutral, 4-wheel or 2. It happens when coasting or braking. The sound obviously has to do with movement of the jeep. I've checked my wheel-wells, hubs, drivelines, u-joints, serviced my diffs, and checked the front drive shaft. Those are all good, so I'm thinking I may just fix the issue with the radio until it gets worse.

3. At 80 mph or over, there is a low-pitched hum that sounds to me like its driveline related. Not the tires. Maybe a bearing that is just starting to go out? I had a similar noise on a truck a while back that turned out to be a bad u-joint on the driveline But I already changed those out when I first pulled the tranny....

Any ideas on what else I should check on these noises?

Bugout4x4

1. Dave and I talked about that flexplate issue. Something is amiss with that. Could it have got bent when handling the motor that came out? Or when you did the trans? I asked him if it is possible to bolt these up backwards and he explained it is not likely for a couple reasons.

2. Do you know for sure the the wheels are bolted up good and tight? A slightly loose wheel will make this type of sound. Another source would be alignment, if it is out of alignment the tires can produce a noise like this. Actually an under-inflated or over-inflated tire can do it too.

3. This hum could be from normal ring and pinion wear. I have this in mine and even after being serviced it still hums. I need to reset mine again but I am hoping to do this when I pull it apart to install a lunch box pretty soon.

Good to hear it is a runner!

sambroom

1. I'm betting its just bent a small bit. Could have happened dropping the motor in, or maybe when the flexplate was hitting the mud guard when I had the thrust bearing issue. You really can't install the flexplate wrong because the bolt holes are spaced a certain way, so it only fits one way, but to be sure, I marked it before I took it off. The washer is on the right side, so it goes crank flange, flexplate, washer, bolts. The flex plate has a slotted ring on the rear side for the speed sensor, so no way to get it backwards. I seated then torqued the bolts in a 6point star pattern like you would with a wheel.

2. I installed the wheels with the impact then checked with the torque wrench. Used a star pattern. This jeep had some major suspension/alignment issues when I first got it. Before I got after the motor, I replaced the tie rods and ends, shocks, steering damper, upper/lower control arms and tires in the front. In the back I replaced upper and lower control arms and shocks. After all the suspension work, I took it in to get aligned. Ball joints on the hubs look good. I checked tire pressure. I have some newer tires with off-road tread in the front, I think i'm going to go ahead and switch them to the back, though the sound doesn't sound like tire noise at all. It sounds like it is coming from behind the dash, at about knee-level more than anything. Also, I realized this morning that when I put it into 4WD, the sound is still there, but it changes a little, So I'm wondering if it has to do with the front diff or front driveline?

3. Could be ring and pinion wear. I hoped that after I changed the diff oil, the sound would go away. The old fluid in the diffs was pretty bad. Not low, just dark. The sound stuck around after the fluid change.

dave1123

I don't believe you ever mentioned what t/case you have. With a 4wd, it's important to have the same size and type of tires on all 4 wheels. With the NP249 constant 4wd, it's extremely important to even have the same wear on all 4. You DID mention the noise was the same in both 2wd and 4wd, so I'm assuming you have the NP242.

The NP242 is unique in it's design because it has 2 different 4wd drive ranges as well as 4lo. There is a differential in the t/case that allows differences in shaft speeds between the front shaft and rear shaft for cornering and changing traction on surfaces. Here's a rundown on how it works;

1- 2wd, only the rear shaft is driving

2- 4wd part time, both the front and rear are driving, but the 2 shafts are locked together and drive at the same speed with no allowance for changing speed for cornering or tire size. This range should only be used on loose surfaces like mud, sand, or snow.

3- 4wd full time, both shafts are driving, but are allowed changes in shaft speed thru a differential inside the t/case.

4- neutral. This disconnects the t/case from the transmission for towing or for meshing the gears to 4wd low range.

5- 4lo, this acts the same as 4wd part time in that both shafts are locked together but have a lower gear ratio for increasing torque.

Any difference in tire size front to rear has to be made up by the differential in the t/case. Any difference in tire size, L or R, has to be made up by the differential in that axle. Any time an axle differential changes the tire speed, that drive shaft speed changes as well.

I hope I didn't drown you in info, the whole point being to show you why tire size is important. A 1/4" wear on a tire changes it's diameter and it's turns-per-mile enough to affect drive shaft speed. A given consequence of driving a 4wd vehicle is buying tires 4 at a time.

BTW, the shutterwheel on the flexplate is for the crank sensor. When a window in the shutter passes under the sensor, it tells the PCM to fire a spark plug. IDK how that happens because only 3 cylinders fire each revolution and there are 6 windows. It's possible there is a crack where the ring gear is welded to it. You should be able to see this by shining a light on one side and checking the opposite side for light leaking thru.

sambroom

I understand. The new tires are the same size, but are a different brand and have less wear. So likely they are a bit bigger if the threshold is around 1/4 inch. I don't have the awd tcase. So if I keep it in 2wd or 4high should I be ok until I can afford a new full set?

Here is video of the number 2 noise. Note I am pointing the camera directly at where the noise sounds like it's coming from. The sound is quite clear on the video. It also seems to me to have something to do with weight on the front, like when the nose goes down a bit.

sambroom

For noise 1, this video shows the flexplate wobble quite well. The noise sounds horrible in this video. It's not so bad sounding in person.

Bugout4x4

Something important to share about this. No two brands are truly the same size, there can be up to an inch or more difference between one brand and another even though they are supposed to be the same size. They cheat... there is no industry standard like nuts and bolts. There should be... but there is not. They get away with using legal terminology that allows them to stray from true actual physical dimensions.

They are all "Designated as" certain tire sizes and not based on the true dimensions. So they cheat by building them just different enough in true dimensions that it does indeed force 4X4 owners to buy all four of the same brand and model like this. It is deceptive business practice and really does need to be addressed and an industry "dimensions" standard should be put in place.

Bugout4x4

It sucks, but this is the reality of it. DOT needs to Implement an industry standard concerning true dimensions. It can even be a safety issue.

dave1123

The thing that makes tire wear and overall dimension so critical is circumference. A 1/4" difference in diameter relates to 5" in circumference figured at about 30" diameter. This doesn't seem much, but it effects turns-per-mile and drive shaft speed. Inflation pressure can even change the rolling radius of a tire. Adding all this up, considering variances in tire manufacture, makes about the only variable you can control is buying 4 the same and keeping them inflated properly.

Bugout4x4

Yep... Turning your spiders and tearing stuff up the whole time.

sambroom

Is this true in 2wd as well, or only in 4wd?

Bugout4x4

Fronts are independent on a 2x so they can turn at different speeds with no problem, but it can change how the alignment is configured between left and right and wear the tires funny. The rear would be the same as with the rear on a 4X4, different sizes will make the spiders work more and wear faster because they are always trying to compensate for the difference in circumference and rolling speed as Dave says.

Now that would be on a rear wheel drive 2x, it would be the opposite on a front wheel drive. Front wheel drives are very critical about tire size in the front. This is why a doughnut spare should always go on the rear of a front wheel drive vehicle, even if you have to put the spare on the rear first and move the rear to the front to replace a front flat. Not doing this can and has destroyed transaxles in only about 50 miles.

dave1123

I can attest to that! I put a donut spare on the rear of my Camaro one rainy night and ruined my Posi-traction clutches in just 30 miles! Plus, my speedometer wasn't reading right.

Bugout4x4

I get this a lot... "Well it will get me home and I will buy a new tire there."

How far is home from here?

"Only 300 miles"

OK... Well good luck... and it won't be the only thing you will be replacing when you get there. lol