4WD not working after a strange series of problems

[Whiplash]

I have a 97 XLT 5-Speed Automatic with 188,000 miles. Right now the 4WD is not engaging. I'm going to give a little history with some detail to explain how this happened.

6 months ago, I had a sudden problem happen as I was driving downhill. It was a high pitch grinding noise. Took it to a couple shops and everyone was telling me I needed a transmission. Went to a 3rd place which was a transmission shop for another opinion and the guy there gave me the correct diagnosis of a transfer case problem. He was able to resolve the problem, though it took two visits. After he gave it back to me the first time, it wasn't making the grinding noise as often, but it still did it sometimes. After some more time with it, he fixed it fully. He told me it just needed more work on "the bearings." Whatever that means, I took his word because it was fixed.

Off and on for the last 6 months, I was having speedometer/cruise control issues. I saw it once right after he did the work where the needle swayed back and forth. Then I didn't see it until the cold weather came. One month ago it started getting very bad. 2 weeks ago I was scheduled to go back to the transmission shop to have the speed sensor replaced. He had earned my business because of the correct diagnosis of my previous transfer case issue.

However, the weekend before that I noticed another problem which I told him about at my appointment. When accelerating in overdrive, there was a jumpiness. It was not smooth, almost felt like I was driving over a small bump every second. This was occuring while it was entirely in overdrive, and was easiest to reproduce while accelerating from 50 to 65 mph or so, but could happen at any speed as long as it was in overdrive.

Here's where it starts to get fishy: I left the truck with him and he claimed to have observed the problem. He said it was "slipping" real bad in overdrive. He told me to rebuild the transmission now, before any more damage was done. I trusted his opinion and had him go ahead with the rebuild. It made sense given the amount of miles on the truck. After I got it back, I noticed some shuddering when making tight turns. I figured it might be a power steering issue, since I was already scheduled to have that worked on by my regular mechanic and in fact that's where I was driving it right after I got it from the transmission specialist. I had the power steering fluid refilled two weeks prior, along with new shocks and brakes, but there was a leak and I knew I would be going back for a new pump and everything.

Once I got it back from there, it became apparent that the shuddering was not a power steering issue. After some driving around and taking some sharp corners, I concluded that it was stuck in 4WD. That means that after the transmission rebuild, they left it stuck in 4WD. I took it to his shop and left it for him. The next day he looked at it and claimed my tires were under inflated, at 13 psi and that was the cause of the problem. That didn't sound right at all considering I had been up and down the NJ turnpike both days the weekend prior. The tires shouldn't lose that much air just sitting in his lot. But, I got it back and the shuddering had stopped.

A few days later I get an error code on my dash. the 4WD and 4WD LOW lights were blinking 6 times every 2 minutes. I also had time to put it on the highway and determined that my overdrive problem was still there! That's right, the problem that caused him to rebuild the transmission was there exactly as before! There is also a rubbing or grinding sound heard when slowing down especially when turning. I don't know what that is. Gave it back to him and he supposedly replaced another sensor and made the error code go away. Note also that the battery had been disconnected. Not sure if he always does this for every job or did it just to clear the code. He fixed the overdrive problem, said it was to do with the transmission fluid pressure. I don't know, whatever he did fixed that one. But he had no answer on the third problem, the rubbing sound.

So, I wanted to verify his work. I have been testing the 4WD system and have determined that only 2WD is working. When I switch to 4WD high, nothing seems to change. I can take turns with the wheel cut all the way and get no shuddering. I can drive up and down the block supposedly in 4WD low. I can step on the gas while in dirt and watch the back tires spin faster than the front. Yet, the lights on the dash indicated that it is switching into 4WD. 4WD Auto does not engage when I make the back tires slip, either.

That's where I am today. I don't know what he could have done. I am not mechanically inclined, but I have tried to do my research here. I do know that I am getting a very bad feeling from a guy who had always been nice and seemed trustworthy. I know that I gave him a 4WD truck with a bad speed sensor and overdrive problem, and got back a 2WD truck with a weird rubbing sound at low speeds. Could the sound have to do with the 4WD system? Furthermore, could the overdrive jumpiness have been the 4WD trying to engage? I could be off with those two questions, but I'm just trying to follow some logical explanation. I'm thinking I'll take it to my regular mechanic and get his opinion on what's going on.

Do you guys have any advice?

 

[Whiplash]

Second Question

Update: I've had it on a lift both at my regular mechanic and the transmission shop. While it is engaged in 4WD High and idling, I am able to grab a front tire and hold it still while the other spins. Usually the back left tire will not even spin or it will move very slowly.

I have always been under the impression that 4WD High and Low were locked so that all the wheels were forced to spin at the same rate. That's what I have always observed in the past. That's what I think I was feeling earlier when it felt locked in 4WD. Obviously, it's not for taking turns on pavement. The transmission guy is saying that it could only be one wheel on each axle spinning and still be working right.

Who is right?

 

[JDraper]

Unless you have a limited slip rear, then the transmission shop is correct. The axles are not locked in ANY stock explorer. A minority of them came with a limited slip rear, but all the front axles are open, so one wheel will spin while the other doesn't. If you have a limited slip rear, then the clutch pack is probably shot if both rear wheels don't turn (not locked, but with some friction). You can rebuild a LS rear for about $100.

All the 4wd system does in the Explorers is provide power to both axles. It doesn't lock the differentials.

 

[Whiplash]

When it was on the lift at my regular mechanic, slight pressure was applied to the brakes then he gave it gas. The rear wheels were trying to spin, but the front were not. The front drive shaft wasn't even spinning. That seemed to support my observation that the power is biased toward the rear wheels. But, the transmission guy said it's going to do that because the front brakes are applied first therefore the front won't move in that test.

I found this: http://autorepair.about.com/library/faqs/bl776f.htm
Is it possible that I was observing the binding sensation a year ago as an early sign of my transfer case problems in August, then the blinking 4WD didn't show until coincidentally after I got it back from the shop last week? That in fact what I thought I observed as proper 4WD operation with all wheels locked was in fact this high torque output from the clutch? Mind you, it wasn't doing this in 4x4 Auto back then as it did two weeks ago, but it was doing it in 4WD high back then. One problem with this theory is that my truck was built in May 1997 which is a month past the date on the article.

Maybe you and the transmission guy are right, and 4WD is more like 2 axle/2+ wheel drive.

That still doesn't explain the strange sound when going slow especially turning. And if this was the fix that was done, why did the guy claim inflating my tires solved the problem? Something still doesn't make sense.

 

[4x4xbrian.com]

I had a 97 sport that would bind on cornering, it had the "auto" 4x4 the problem was in the transfercase, I don't know exactly what part or why but after alot of searching I decided it was the only thing that could do it, I replaced it and it was fine. mabee another bad tcase???

 

[Whiplash]

I have determined that the transmission shop is correct and my 4WD is working properly. I also suspect that the binding sensation when I got it from them was described in the link I posted previously. I suspect that they also recalibrated the GEM when I took it back and they inflated the tires. I will have to ask them. I think the binding sensation I felt a year ago while in 4WD on snow was probably normal. These two things combined in my head to reinforce my longtime belief that 4 High meant all wheels locked together.

It still doesn't explain the strange rubbing sound when I'm going slow and around corners. I had a theory that maybe the rear hall sensor was going bad and the computer was forcing some more torque onto the front wheels. But that seems wrong because I put it in neutral and heard the same sound.

So, I'm still a bit confused.

 

[Whiplash]

I just spoke to the transmission guy and got on the same page again. I asked him if they might have forgotten to re-calibrate the GEM when the speed sensor was done and instead did it when the tires were inflated. He said that made more sense to him as well, then just tire pressure alone. I feel a lot better about the situation now.

So, I'll consider this issue resolved for now. If I find anything about the rubbing sound, I'll post back just to be complete. Thanks for your help guys.

 

[ArsenicAce]

The condition you explained where your indicator lights would show you were in 2wd or "auto" but it felt like your were still in 4wd is a common problem in 97 explorers. I have the same truck with the same problem. Another hint would be your transmission guys comment about the "bearings needing more work". What happens is the transfer case "case" itself wears where the bearing sits in it. This alows the bearing to moveand hense the shaft with it. It would take alot to explain here but the problem lies in this case wear and the method used for engaging the 4x4 in the auto setting by the computer. Esentially the computer uses an electomagnet to stop one component while everything else continues to turn. The part that is held contains ball bearings riding on ramps. When the magnet applies, the clutch assembly "ramps up" and closes the clutch engaging the 4x4. When the main shaft bearing is able to move due to the wear in the case half, the shaft it is supporting moves also. The clutch assembly with the balls and ramp are on this shaft that is now moving out of alignment. What then happens is the clutch ramps up and stays there.. keeping it in 4x4 all the time. Mechanically it is in 2wd, (meaning it is not locked in like it would be if u selected the 4wd setting, but more acting like the computer were always commanding the auto 4wd on). What your transmission guy may have been doin tweaking this bearing is adding shim stock (very thinly rolled copper strips) in the area that holds this shaft bearing, esentially trying to recenter the shaft in its proper position, compensating for the wear in the case. If the problem is now gone and things seem to be working, then i would guess his last tweak got it recentered. This is a bit of a hack fix, but i have seen it work before. The after market does have some reman case halfs available that address this issue. What they do is over size the bore where this bearing sits then put in a bushing meant to hold the bearing in its proper place. This solves the problem permantly as the bushings are much more durable than the original aluminum. Hope this clears it up some for you.