Hello,
There don’t seem to be any recent posts on this topic and my local repair shops are unable to offer any solution so I’m hoping someone here can help. I have a 2003 Ford Ranger (Edge), 4.0 V6 with manual transmission—104,000 miles. Here's the problem: In 4-wheel drive, when descending a grade (and only when descending a grade), the drive train clunks. Many times it’s quite alarming. And, for an instant or so (on occasions), it almost feels like the engine’s rpm’s pickup. One shop I went to said it was the Transfer Case Motor—“100% sure—can’t be anything else” and gave me a price of over $400 to replace it. I declined. I reasoned, If it was the motor malfunctioning, why was it only doing so under these specific conditions? Why wouldn’t it malfunction randomly at other times--like going uphill? But I did replace the motor, at a much more reasonable price. Unfortunately, It did not solve the problem. The drivetrain still clunks in 4-wheel drive when descending a grade. I live in a remote area of the Colorado Rockies and use the truck frequently to climb the mountain roads in my area and the grade down is about 7 miles, so it’s a major issue. Does anybody have any ideas? Thank you.

Richard

 

Are using 4WD on dry pavement ?

 

Thanks for your question and interest in my problem. The short answer is no, I rarely use the 4-wheel drive feature on dry pavement. I live in a somewhat remote area of the southwest Rocky Mountains of Colorado. The primary 4-wheel drive use of the vehicle is to get me from an elevation of 9,000 feet (where I live) to an elevation of 10,500 feet for hiking and back-country skiing, wood-gathering, etc. It's about 7 mile stretch of well-maintained dirt/gravel mountain road except in the winter when it is snow-packed most of the time. On either the dry dirt or snow-packed road, (it makes no difference) the behavior is the same---in 4-wheel drive during descent (an only during descent) which I'm in all the time while descending on the snow-packed conditions, the drive train clunks. You can hear it very clearly and feel the vibration thunk through the floor and sometimes it feels like the engine even surges a little as (I don't know), but maybe as the torque on the drivetrain is momentarily released (pure speculation on my part). So that's how it behaves. Thanks. I'd love to get this problem solved.

 

More info: Today there was a skiff of new snow on the hill. It could just be my imagination, but I thought maybe the slick conditions on the road had made the “clunks” more frequent. And then I tried an experiment: I’ve always been in 4-wheel low coming down the hill, not wanting to use 2nd gear because it necessitates riding the break too much. But today I did shift into second and there were no clunks until I allowed the vehicle to speed up enough such that (and I hope I am explaining this correctly) there was more torque placed on the drivetrain. You could almost sense it was going to happen. Then, sure enough, there was a clunk. I slowed down (still in 2nd) and no clunks again. And so I tried the experiment one more time and allowed the vehicle to speed up again, as soon as second gear began to resist the added speed, there was a clunk. But the road was slick so I shifted back down and the clunking then returned to it’s usual random, frequent, intervals. It was a good ski though.

 

Has a shop actually looked at it, or have you just talked to them?

I'd be checking transmission mount, U-Joints, Rear spring mounts (both ends)

 

Are your tires on the front and back the same size? It sounds like the drive line is loading up until the back tires slip to relieve the load. Of course, if someone replaced one of the diffs. it could be a problem with different diff. ratios. Not sure why you need 4 wheel drive going down hill, but it should work. I have found that steering in snow in 4wd is more approximate than in 2wd.

 

The first thing I thought centered on the clutch.
Perhaps you're causing your clutch to slip.
21 years of use may have polished the flywheel and friction plate.
Any oil leakage into the bell housing would complicate the dynamic.
I don't know if a neglected PCV system (the valve and "L" hose run begins at the back of the left valve cover) could drip enough to encroach the bell housing.

I doubt that the axle ratios differ. That would be glaring whenever in 4WD. Try it on a straight run of dry road; you'll know.

 

I appreciate your input. I will add your suggestions to the list of things I will have the repair shop check into next week (hopefully). I did just recently change the PCV valve.

 

Nelbur, Thanks for taking the time to reply. Yes, tires are the same size. I don't know about the diffs. I bought the truck 10 years ago and have put only 30,000 miles on, it hasn't happened on my watch. As for 4-wheel drive going downhill--very steep, snow packed mountain road with "don't look" drop offs. And I've noticed my wife does not reach for the door handle quite as often when I'm in four wheel drive.

 

How to duplicate the sound of a clunk in your drive train: Before taking my truck to what would be a new (third) repair shop, I wanted to see if I could find a way to duplicate the clunking sound in my drivetrain on a flat, dry paved road because there is no place in the area where repair shops are located (60 miles away in the "valley") where they could test drive it while descending a hill. So I drove out on the county highway near my house, put the truck into 4-wheel drive high, shifted into low gear and took off. I got going up to about 4,000 rpm's, putting a lot of torque on the drivetrain. it was time to shift into 2nd, but instead of shifting into 2nd I quickly took my foot off the gas. One second, two seconds and "Whap! There it was. I passed this information on to the technician at the new repair shop before returning back home with my wife in her car. The next day, the technician called and said he too was able to duplicate the sound using the same method. He checked the oil in the transfer case and found it to be black with metal filings. He even went so far as to send me an email with a picture of the oil. He said he could try changing the oil (doesn't know if it would work), or he could put in an expensive new transfer case or look for a used transfer case. He will email me options with prices. Nice. Good service. Anyway, the problem is on its way to being solved (I hope). But it ain't gonna be cheap.

 

Changing the TC fluid as a first repair is the thing to do. It's the simplest and cheapest thing to do.
I believe Ford back-specced all their transfer cases to an LV fluid. They take <1 qt. of fluid.
I used Valvoline Maxlife Dex-Marc LV in mine. The drained fluid was 14 years old and quite dark.
And while I had no such clunk, my truck shifted through its ranges more crisply and "precisely-sounding".

 

Thanks. I think I will give that I try.

 

Problem solved. As I mentioned earlier, I found that by putting the vehicle in 4-wheel drive high and then taking off in first gear, racing the engine to about 4,000 rpm's and then quickly taking my foot off of the gas, I could duplicate the clunking sound my drivetrain was making. This was important, because two previous repair shops I had taken the truck to were unable to duplicate the sound. The (new) mechanic who worked on my truck used this procedure and he too was also able to duplicate the sound. He checked the transfer case fluid and found it to be black with metal filings (even showed it to me) . He recommended a remanufactured transfer case which I agreed to. And yes, that solved the problem. An expensive proposition to be sure, but I'm grateful to have it fixed and sometimes ya just gotta do whatcha gotta do.

 

How much was the new transfer case? ...if it's not too personal a question.

 

Remanufactured from Napa--$1,724 just for the part, plus a few hundred for labor. That was a yikes(!) moment. But the problem was, I only use the truck to drive up into the mountains to hike or ski or maybe go in to town to get the mail. And it only has a hundred and four thousand miles. So how could I justify buying a "good" used truck for about 15 to 20 grand to accomplish those ends? And how could I trade it in or sell it, knowing it had a terminal disease? And on top of that I'm an old hippie guy and the last time I checked, I ain't immortal. So I figured, what the fig, fix it and drive it. Took it up into the mountains yesterday on snow-packed roads. Runs great!