Loud Ratcheting Sound Underneath

[RammaR]

My '96 4x4 XLT just started making a loud ratcheting type sound yesterday when I was slowing down from around 70 to take an exit ramp. No lights, or gauges came on or were out of range, and nothing felt funny other than just hearing this aweful sound. Then it did it 2 more times last night, it seems like it always happens when I'm decelerating, but don't have to be hitting the brakes - it can be just coasting. As soon as I give it gas, the noise seems to go away. Its sorta a ratching sound that seems to be coming from maybe the front / middle underneath the truck. My wife said it sounds to her like an 18-wheeler when it slows down hard (with the air brakes releasing pressure I think).

I checked for any engine codes last night and there are zero. I had the transmission rebuilt about 30k miles ago, and really hope its not it going again this soon. A few searches turned up maybe the transfer case, but its been doing it in 2-wheel drive mode every time, I hardly ever run in 4x4 auto. But did so briefly last night to check for any strange grinding noises with it enganged and didn't hear anything different. But that was at slow speeds in a parking lot so I can't say if it would have done the ratcheting sound or not. Any help would be great!

Thanks

 

[rookieshooter]

Just a thought, check out universal joints. I'm sure a search will give you plenty ways on checking them out.

 

[ExplorerDMB]

This was in the useful threads section: Driveshaft and U-joint Problems

It can still be your transfer case even though it's not in 4wd. Do you hear the sound on turns as well? What kind of rear end do you have? Limited Slip?

-Drew

 

[RammaR]

Its at just over 153,000 miles now and its an open differential -- I believe 3.55 gears. As far as going around corners, maybe but the exit ramp was a very slow curve. Its definately on slowing down, 2 of the 3 times have been going somewhat up hill. No strange vibrations or warnings, just a loud whoooshing / ratcheting type nose until I hit the gas again. At first I thought it was the breaks somehow but hitting / releasing them seems to make no difference at all. It doesn't sound like its from the back end either although possibly the front driveshaft area, I'll read up on that thread -- thanks for the quick feedback, keep it coming.

 

[Doug]

Check your u-joints but it sounds like your t-case is going.

 

[RammaR]

k, will check the u-joints. would bad u-joints damage the transfer case, should I replace them anyway? Another thread said that Jasper had a good replacement T-case, any other suggestions?

 

[wingot]

my car makes loud noises when i dont disengage the auto hubs after getting out of 4wd... but i dont think thats your problem.

 

[RammaR]

Ok, another update and a few questions.

Step 1: Before putting it up on jackstands I tried to rotate the front and rear drive shafts (in park). The front driveshaft rotated slow but smooth without any real slop or play in it. As expected the rear drive shaft didn't rotate at all.

Step 2: I lifted it on jackstands and put it in neutral. Now I can manually turn the rear driveshaft, however there is a fair amount of play in it. Meaning I can start to rotate it before the rear tires will start to turn, and if I turn it back the other direction there is a bit of a clunk. It doesn't feel the same in rotating it as the front shaft. Although I don't have enough experience with this to say if its 'excessive play' as mentioned in the haynes manual. How much is normal? But other then a clunking when quickly starting / stoping the spin or changing direction there isn't really any grinding or squealing noises.

Step 3: The other thing I noticed while turning the rear drive shaft is that it turns the front as expected, but if I turn the front shaft it barely moves the rear shaft. I'm in 2-wd mode, so i'm not sure if this is normal or not. I had the front drive shaft replaced about 3 or 4 years (~50k miles) ago, which might explain its better connection.

Step 4: When I was under the truck I noticed a lot of fluid that has dripped down over and around the from passenger side suspension. At first I thought it was a possbily grease from the CV joint boot, but it looks intact. I followed it up to the highest leak point and it looks like its coming from a tube that runs back down to the front differential. Here is a picture of it:

Could there be something wrong with the front dif that's causing both the ratcheting sound and the leak? I changed fluid in both the front and read dif's back at 100k miles and in the transfer case. But haven't really touched them since. Hope this helps us get closer to a solution.

I can take pictures of the u-joints, t-case, or dif's you they would help anyone. Thanks again!

 

[CDW6212R]

My 99 vent tube is on the driver's side. I have heard of excess fluid being pushed out of the vent. You should recheck the front diff. level. The fluid should be just below the opening in the side fill hole, not up to it, or draining out. The spec is like 1/4" below the hole.

Are the differential seals clean and dry? Have you been in any water that could have gotten in the diff? Good luck,

 

[RammaR]

Dif seals look good, only leak is from that tube. I checked the fluid level in the front and it seems ok, maybe a little high if anything. I must have overfilled it back when I did the change as that overflow leak has been there for quite some time.

After playing with the drive shafts some more while in neutral, I really don't hear any grinding or squeeks while turning it. So I'm leaning away from the U joints being the root cause. Pointing more and more as the transfer case from what I've found in searches. Anyone have any experience in replacing one?

 

[RammaR]

Ok, I'm convinced its the transfer case and am going to attempt to rebuild it as a learning project. I found a shop that will repair the front and rear case housings to correct the worn holes. Does anyone have a list of parts that should be replaced during the rebuild? A preffered brand or source? I'm sure the 'fork' needs ot be replaced but bearings, seals? etc... trying to make sure I have everything upfront so its not a 2-week project.

Thanks!

 

[GJarrett]

If it's a ratcheting sound that occurs when you let off the gas, it is a part in your transfer case called a "range slider". You need to replace that part and probably the fork and/or inserts that go along with it. If you don't get it fixed it will eventually wear enough to not engage. Mine just started it at 161,000 miles. I saw the part and the wear. Over time, the ends of the teeth wear down on the ends and the tcase gear slips on it. It will do it whether you are using 4wd or not.

Call Stephens Transmission in Chesnee, SC to get the parts. (864)461-4583. This ought to fix your problem if you also fix the worn holes in the case.

 

[RammaR]

Thanks,
I think i'm looking at doing the:
shifting fork
shifting fork cam
range gear
range slider

although the range gear/slider might be the same thing?

 

[BuffaloXplorer]

I'm not sure if we're talking about the same leaky tube, but while i was detailing my engine, i looked down at the vacuum "bubble" behind the passenger headlight and saw that this tube was leaking and making a mess of things below. Here's a shot from above - it does seem to be attached to the same tube as seen in your pic.

Also, how bad would it be if the tranny fluid is (extremely) overfilled? I just checked the fluid level and it appears to be almost 1 1/2" over the xxxxxx mark.

 

[RammaR]

Buffalo,

That looks like it could be the same hose. If it is then it runs down to the front differential, not the transmission. Unfortunately, I'm not sure what would happen if the trans fluid was extremly overfilled - but the level is temperature sensative so that could be part of the reason its high.

 

[BuffaloXplorer]

Nope, the fluid level is always high - cold or hot. To be honest, it's likely been that way since last April ('04) when i had the tranny & tc rebuilt, as i haven't added fluid to it since. I do check it regularly, but i've always assumed the dipstick caught more fluid from the sides of the tube while being pulled out...now i'm pretty certain that it's just that full.

As far as the leaky hose goes, i did recently notice that the CV beneath the diff is always wet with fluid, but i just ignored it. I wonder if it's wet from the hose or wet from a diff leak. I should probably look into that before i take the 6-hour drive up to the Adirondacks.

 

[ANMAN]

I get the same nasty noise in my 98 AWD, from time to time, when I get up to highway speed. It's a very loud rattle accelerating, decelerating, turning. I can put it in neutral and rev the engine no noise, put it in gear it's back so it wasn't engine or another thought, heat plate, but they were all secure. My first instinct was that it was a destroyed U joint lost a cap or something, but both rubber boots up front are fine, I can spin them in neutral and there's no nastyness. Wheel bearings are fine.

Then I noticed my front drive shaft was a little loose, took it off, noticed the CV joint rubber boot was gone, and the grease inside was contaminated with dirt, took it to the parts store..still not sure if it could be the culprit to make THAT much noise. The store didn't have it, neither of their warehouses did, never heard of the thing going bad, soooo... it was $200+ so I filled it with grease and put it back on and pray that it's not my transfer case.

So now i am down to..
25% I found the problem and band-aided it
45% It still could be a front axle shaft U Joint
25% Transfer case
5% ??, front axle?

 

[RammaR]

Parts are all here, so planning on rebuilding the t-case this weekend. But now I am having another problem in the front differential that i'm not sure is related. The leak from the front differential overflow tube was really bad when I got home tonight -- a large stinky puddle on the garage floor after a few hours. As pictured above the front passenger side is covered in grease but when I checked the fluid level a few days ago it was just below the fill hole. Does it make any sort of sense that a problem in the t-case might be affecting the front diff fluid level somehow? Or am I about to have to rebuild it as well?

Thanks.

 

[project92]

have you check the valve in the front diff they have to Breath that tube may be clogged....

 

[RammaR]

I didn't know that there was a valve to check. Are you referring to the while plastic end peice on the vent tube -- like a check valve maybe? or something in the differential itself?