Whine during coast

I hope that you are all well.

I own a 1998 Explorer with about 170,000 miles on it. Recently my Explorer began a high speed whine. The noise occurs when above 40 mph and your foot is removed from the accelerator.

I'm a little short on cash...is it possible to just pull the front driveshaft and keep driving the vehicle? I reside in the Southeast and have no real need for 4WD.

Thanks,
Divepro

Thread extracted from the 4405 Rebuild Diary.

I dont think the transfer case or 4wd is the problem on your vehicle, but rather the pinion gear at the rear axle (it's loose). This is pretty common for high mileage vehicles and we see this in second generation Explorers that have at least around 100k or so miles (yours has 170k so thats expected).

One way you can check this is to unbolt the rear driveshaft from the rear axle (uses a 12-point 12mm socket) and push the flange at the front of the rear axle up and down. If you get any "play", then the pinion nut is loose and chances are, you need to replace the pinion bearings.

Thanks. I paid the local Ford dealer a diagnostic fee, and they believed that its the transfer case. I think that they placed a bunch of accels or microphones on various drivetrain components and made their best guess.

As I said, the noise occurs when I let off the accelerator while at or above about 40 mph. When below about 40 mph, I don't hear the noise, which doesn't mean that it is not occurring though. If I need to decelerate while above 40 mph, but use two feet (one on the brake and the other on the gas to maintain the accelerator slightly depressed), I don't hear the noise.

Thanks again for any help.

One other important detail - the noise seems to be coming from the transmission area. However, that may not mean anything, as vibrations and sounds have many transfer paths...

Well if the culprit is indeed the transfer case and you have the v6 4.0L engine, then yes you can pull the front driveshaft and drive on w/o any problems. However, if you have the v8 5.0L engine, then yes you can pull the front driveshaft but the vehicle will "creep" slowly if the vehicle is parked on an incline.

Thanks again, and yes, it is a 4.0L V6 SOHC. I guess that I have some work for this weekend. I'll let you know what I find.

divepro99 said:

Thanks. I paid the local Ford dealer a diagnostic fee, and they believed that its the transfer case. I think that they placed a bunch of accels or microphones on various drivetrain components and made their best guess.

As I said, the noise occurs when I let off the accelerator while at or above about 40 mph. When below about 40 mph, I don't hear the noise, which doesn't mean that it is not occurring though. If I need to decelerate while above 40 mph, but use two feet (one on the brake and the other on the gas to maintain the accelerator slightly depressed), I don't hear the noise.

Thanks again for any help.

Click to expand...

That would be the classic symptom of the shift rail bore/shift fork issue in the transfer case. By keeping the drivetrain loaded in the forward direction, it keeps the gears in position. Decelerating (also known as over-running) forces the gears apart, and the low range gear set rubs something it shouldn't due to the shift fork's inability to hold the gears in place due to either wear on the fork or wear on the shift rail bores. (Holy run-on sentance, Batman!!)

The short version is that you need to either rebuild your case, or swap one out with less miles.

And to answer the next question, any Borg-Warner 44-05 from 98-01 will work for you. a '97 *might* but will likely cost more and have an extra sensor you don't need. Omega Machine re-machines the shift rail bores in the case halves, but they're not cheap.

Did I miss anything?

Thanks. I was thinking of just pulling the front driveshaft to see if it ran OK without it. If so, I intend to keep the driveshaft out and turn it back over to my wife - it is hers after all. Any thoughts?

Pulling the front drive shaft isn't going to help at all.

You need to do what Joe said- rebuild this case or get a different one.

OK. I don't have the money to replace everything, nor do I have the time (with toddler triplets). Is it the rearend, is the transfer case, or is it something else? What quick and painless checks and/or tests can I do to eliminate possible problems. I really appreciate the help - just running on a few hours of sleep each day.... Thanks again.

Its the transfer case. Find a field, try 4 low and see if the noise doesn't happen in low.

KPT said:

Its the transfer case. Find a field, try 4 low and see if the noise doesn't happen in low.

Click to expand...

What will that tell me?

Took it to a reputable mechanic (supposedly) and he thinks that it is a transmission problem since it didn't make the noise in 2nd gear for him....however, I tried driving home in 2nd gear and it made the same noise while lifting off of the gas above 40 mph (within 1 mile of his garage). So much for his credibility...

What is a fair price for a rebuilt transfer case, that is, with machined/corrected bore holes?

What is a fair price to remove the old transfer case and install the rebuilt transfer case?

Any other checks that I can do...been a couple of weeks but still not a lot of money in the bank to fix her....

It may not/shouldn't make the grinding noise in low as the hi/low collar is in a different position. This piece is what is grinding against your shift fork if that indeed is the issue.

It was around $300 in parts when I rebuilt my t-case. I used a rear case half I got free off another forum member though.

The sleeved case halves are high dollar, I think omega machine is the only place that does that.

Just got it back from Stegall's Transmission Shop in Greenville, SC... They did a great job and answered tons of questions about it and my other 4WD. The problem was a bad shift motor which damaged the range hub. Both case halves looked great so was not my problem... but it turns out that alot of transmission shops in the upstate of SC will fix that problem, so Omega is not the only game in town.

$616 for everything and she's back on the road and runs great.

Thanks for all the help and recommendations. I truly appreciate it....on to the next project.

btw omega prices (as of May 2009) were:

Rear case half $175
Front case half $95
Modified shift fork $50

What is the max difference that I can run between front and rear tire tread depth? Recall the explorer is 4WD, so at what point will I negatively impact the newly rebuilt transfer case? In other words, can I replace only the rear tires and run with a 4 or 5/32 inch difference between the front and rear tread depths (same brand and original size 255 70R16 -stock size)...

Thanks again.

Still having issues...a new popping noise

Well, after the transfer case was rebuilt, the Explorer began to make a popping type of noise when climbing a hill (under load). The noise has not occurred except for climbing a hill. The majority of the time, the noise occurs when you lift off the gas then get back into the gas hard … like climbing a hill with a curve. Sometimes, the noise occurs when you are in the throttle the entire time on a hill. I have never heard the noise while driving downhill or on flat terrain.

The Transmission Shop (Stegall's) completely rebuilt the transfer case (replaced all of the guts at no charge to me), but the noise still occurs. Then they replaced the transfer case with another rebuilt transfer case to rule it out the transfer case as the problem (again at no charge to me).

The rear diff was checked satisfactory with no issues, the front drive shaft was pulled and the mechanic thought that the front diff was the problem…well, $450 later, the popping noise is still occurring…

Any thoughts?

Thanks again for any insight that you can provide me with.

OK, I've got your original thread now. Did you check the CVs, motor mounts, trans mounts and exhaust bolts. Between the two threads Im not clear. Does the noise occur on over-run (letting off the gas) or under load or when switching between gas on/off. If so, which? Pushing down on gas or letting off of gas. Is it one single clunk and then its quiet or does the noise repeat.

Easiest "hillbilly" way I know to check CV's, with auto trans, is to sit in Park. Bring idle up to 1200 rpm or so. Put other foot Firmly on break. Now while holding break with one foot and gas with other, shift from park to reverse. The idle will drop some as reverse engages. Don't change anything. Now shift to Drive and sit there for a few seconds. Then back to Reverse. Repeat this a couple times. This places the entire drivetrain under load intermitently and in two different directions. Any slop will usually show-up.

If you hear the noise, you've just ruled out the Differentials/suspension and pointed to one of the 4 things I mentioned before (CV, trans mount, engine mount or exhaust braket). This will build heat in the trans. So don't do it all day. Just a few times while listening for the sound. Then let the trans cool down.

If you do try this, keep your foot down on the brake hard. Make sure nothing is in front or behind you. We don't want any accidents. Also, don't get the idle up above 1200 too far. Can you say "Unintended acceleration".

Here's the whole story...

http://www.explorerforum.com/forums/showthread.php?p=2336078#post2336078

I own a 1998 Explorer with about 170,000 miles on it. My problems began with a high speed whine. The noise occurred when above 40 mph and your foot was removed from the accelerator.

Stegall's Transmission Shop in Greenville, SC rebuilt the transfer case. They did a great job and answered tons of questions about it and my other 4WD. The problem was a bad shift motor which damaged the range hub.

Well, after the transfer case was rebuilt, the Explorer began to make a popping type of noise when climbing a hill (under load) - 30+ mph. The noise has not occurred except for climbing a hill. The majority of the time, the noise occurs when you lift off the gas then get back into the gas hard … like climbing a hill with a curve (in the throttle, out for a sharp curve, and back into the throttle and a loud POP - as if something is snapping back into place when the load is reapplied by getting into the throttle hard).

Sometimes, the noise occurs when you are in the throttle the entire time on a hill (e.g.,never lifting off of the throttle for a curve). I have never heard the noise while driving downhill or on flat terrain. Also, the noise is a single event/clunk and quiet/silence. The noise does not occur two or more times in quick succession. However, it has made the noise twice on one hill (noise - silence - noise but not in quick succession).

The Transmission Shop (Stegall's) completely rebuilt the transfer case (replaced all of the guts at no charge to me), but the noise still occurs. Then they replaced the transfer case with another rebuilt transfer case to rule it out the transfer case as the problem (again at no charge to me).

The rear diff was checked satisfactory with no issues, the front drive shaft was pulled and the mechanic thought that the front diff was the problem…well, $450 later, the popping noise is still occurring…

The explorer seems to steer just fine and is not a suspension issue - I think. However, I did put new shocks on it this past summer (after the transfer case rebuild)...but I don't remember if the shocks were installed before or after the popping noise began...

I pulled the front driveshaft, checked a lot of bolting tight (one skid plate bolt was loose), sprayed WD-40 on the ends of the torsion bars. I didn't check the exhaust and have not had an opportunity to "hillbilly" check the CVs. However, the darn thing still makes the noise. Any thoughts?

One other piece of info...I did notice that the right front upper ball joint boot is torn in several places ... I jacked up the lower control arm to remove any load and did not feel any movement; however, it will need to be replaced. All other ball joints and their boots are OK....

Thanks Joe for the help. I greatly appreciate it.

Give "hillbilly" check (see above post) when you can. Also, I take it the noise persisted with the front driveshaft out. If so, you have completly ruled out the TC. I had a dull clunk a long time ago that only happened when I drove over several small bumps, like broken pavement. I had just installed new shocks too but it turned out to be a bad lower ball joint. They didn't look bad but when I replaced them it went away. Try the check and get back to us.