Hi,

92 Explorer xlt. When we put it in 4wd we get a thunk.. thunk.. thunk... as we drive down the road. Just had it in for new brake calipers today and got them to check front end things out - they couldn't see anything and told me I need to take it to another shop (they gave me a few in town) to be looked at - they mentioned the transfer case and transmission as 2 possible sources.

I know I'm being pretty vague here, but it's a real 'heavy' sort of thunk that makes the explorer jump - you can feel it right through the explorer.

Christmas is coming and I don't want to get robbed of all my money or the kids won't get many presents... (only kidding). So, before I take it anywhere else I was wondering what else it could possibly be....

Thanks
James

 

Kind of need a better description on the conditions. Have you had this truck for a while and is this a new thing? You should know these 4x4's are not made to be engaged on dry pavement. If you turn the wheel as such, it will bind and clunck and not sound too good and may break and axel or U-joint... So can you be more specific?

 

Hi,

We bought the truck about 1.5 years ago, it was doing good until the end of last winter when it started this thunking - we kind of forgot about it (baby and all that), until this week when we got a huge dump of snow, our 1st trip out in it and we soon remembered....

Basically, it only does it in 4x4 going forward (reverse is ok), so going down a straight (snow covered) road doing any speed and it's just going thunk thunk thunk all the time - it makes the whole truck jump maybe about a 5-10 second delay between each thunk...

Hope this helps my 1st description...
Thanks
james

 

If it only does it in 4WD, I'd look at front axleshaft u-joints, driveline u-joints, and hubs. Do you still have auto hubs or have you put in manual hubs?

 

Sounds like maybe a bad u-joint.

 

I had the exact same thing happen to my '94 last December. Took it to a tranny shop and they said I needed a new transfer case. I said no thanks. Took it to the local Ford shop and got the "cannot duplicate" response. I said BS and took the mechanic for a ride. He was right, it didn't do it. For whatever reason, the problem went away and haven't had a problem since. I know this really doesn't help you, but I thought it was worth a response since I had the same problem. I'd be interested to find out if you ever get it solved or if by some stroke of luck, your's goes away too.

 

Just thought I'd write an update....

So we took it into a powertrain shop here in town this morning, got a call from them saying that the problem is the front tires....

They said that because there is a lot more tread on the back tires (1 yr old) compared to the front tires (ready for replacing) that when the explorer is in 4wd for every 1 rotation of the back tire, the front is doing more than one - and this is causing the thunking... Anyone ever heard of this before?

So, thinking I'm about to be scammed into buying tires off them, they proceed tell me they don't do tires and there's no charge for the diagnostic.

They did say that 3 u joints need fixing, but that these are not causing the thunking. Anyways, we will know tomorrow once we get new tires on the front.

 

What! Ok 3 u-joints need to be replaced but they don't make a sound? U-joints are steel. If they go bad, bad enough, they rattle and clunk like no tomorrow!

Tires are rubber and flex all over the place. They can absorbe slight variations in diameter, air pressure.... If the tires are the same size, 235-75x15's, and I'm sure they are all 4 the same size, this is not going to be a cause of a clunck. If the u-joints in the front drive axels are bad, this could most definitley cause a clunck.

Even the 2 main drive shaft u-joints can cause a clunk. Which ones did they say where bad?

 

Well, they did tell me which u joints, but I didn't make a note (I don't know much about what / where u joints are - I just know they sometimes need replacing).

The tires are the same size, he didn't say the tires were the thing making the noise (sorry, wasn't too clear on that) - he said it was inside the transfer case but that it's being caused because the front wheels are doing more than 1 revolution for every revolution of the back wheel. i think his words were that the ratio is different between the front and back.

I guess what I don't understand is what they would tell me this if it's of no benefit to them........

 

My point is that the rubber tires will absorb any rotational anomolies as to not damage any metal mechanical parts. U-joints can go bad all by themselves since the stock ones are not lubable. They are on the 2 drive shafts coming off the t-case and between your front diff and the front spindles. So if these go bad they can clunk or even cause damage to the t-case due to the backlash created. If there is noise coming out of the t-case, your tires did not cause it and new tires will not fix it. Suggest you find another "powertrain shop". One that better understands cause/effect when troubleshooting.

 

I've seen something like this on my BII. When the front tires wore out, I replaced them with a new pair same size. After that, everytime I'd use the 4WD (snow, mud), I would get an occasional "bang". Basically, the slight difference in tire diameter was enough to cause the drivetrain to bind up. In my case, there was about a mile or two between bangs rather than a consistent thunk, but I'm not too surprised that old matched with new tires can cause problems.

 

What size tires are in question? Smaller the worse I can imagine this effect. If it's so critical on say 215 75-15 tires, then fill up the worn out ones and let air out of the good tires to match the roling radius. If the noise goes away, I'll believe it. But by then, if u-joints or T-cases have been damaged, you're kind of out of luck anyway.

 

Well, 4 tire shops later and we are still no closer. No one will just put 2 tires on the explorer - thay check the front (old) and the back (1 yr old) and say the diameter difference of the back compared to a new tire is to great. Not even costco (the place we originally got the back tires from) would do it, and they were very surprised that they only sold us 2 last year - they said we should have been told we had to buy 4. Now we are on a receipt hunt so we can go get them to replace the 2 back ones for free while we pay for the front ones.

 

Where are you? What country? I've never heard of anyone not willing to sell a tire? I did have Sears once tell me they wouldn't put on 31" tires on my truck because stock was 235's and they didn't want the liability. This was when Explorers were blowing out firestone tires and killing people so everyone was paranoid. Winston tires then got the sale and now I run 31's.

It's hard to tell what's wrong with your car or how it may have happened. I would suspect driving in 4WD on pavement well before any tire issues. Even if you had different sized tires but ran 4WD only in mud or on ice, the tire would slip and the running gear would not get damaged.

 

I'm in Canada. I tried a couple of other tire dealers here in town today and they both said the same, I either get - 'Head office has told us to only put 4 tires on 4wd vehicles' or 'xxxxx tire manufacturer has instructed us to only put 4 tires on'. - they will sell me 1, 2 or 3 but they will not put them on....

This is our 2nd winter with the explorer and personally only ran it in 4wd on dry pavement when we tested prior to buying. Last year we didn't really use it over winter that much (new baby) but when we did use it we had the thunking.

We found the costo receipt so we are closer to having 4 new tires on it - then we will know for sure if the thunking stays / goes away or reduces........