HELP - Popping noise on hills after a transfer case rebuild

http://www.explorerforum.com/forums/showthread.php?p=2317980#post2317980

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 POP - as if something is snapping back into place).

Sometimes, the noise occurs when you are in the throttle the entire time on a hill (ie, no lifting off the throttle then back into it. It doesn't seem to matter what gear the transmission is in. I have never heard the noise while driving downhill or on flat terrain.

The Transmission Shop (Stegall's) completely rebuilt the transfer case again (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). They checked the transmission, changed the filter, adjusted it and flushed it. No problems were noted.

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...

Alignment was done just before transfer case broke to begin with and suspension check sat at that time...

Lower balls joints were replaced about 30,000 miles ago...

Thinking about pulling front driveshaft again and driving it myself to see if noise still occurs (I know the vehicle better than the shop and know how to make it "do" the noise...).

Any thoughts?

if they ruled out the transfer case, then it leaves the transmission and the U joints, is it just when on hills and only when in 4wd? because i know u joints will make a clacking noise shortly before they shear and your drive shaft drops out... i would see if there is any play in them.

loose motor or tranny mount? i had a similar problem when i replace the rear diff in my bmw. was fine under normal driving but when i gave it some juice i got a pop. ended up being a difff mount bolt that was tight but not tight enough.

Thanks.

The pop/snap occurs in "Auto" not 4 high or low (I realize that this year and many other year's of Explorers are essentially AWD).

The pop is random in nature - sort of. Small or shallow grade hills are not enough to get the pop, that is, unless the hill is very long. Steep hills will usually get a pop, but not always. A hill that gets a pop one day will not get a pop the next....

It just seems odd that the transfer case goes, is repaired, and new noise/pop begins.

The pop is not inconsequential. I mean that you can definitely feel it occur in the drivetrain.

Thanks again for the help. With triplet toddlers, money is still tight.

they did replace the shift motor right......?

Yes, they replaced the shift motor.

it almost sounds like it's slamming into 4wd, but that doesn't make sense especially since they tore it apart twice... does the trans down shift, around the point when you hear the noise? could be like moneyguy said, and be a tranny mount as it kicks into 4wd the trans could be slamming against the mount under the added load... this makes sense in my head, because if it doesn't do it in 4wd which rules out 4wd as the culprit. so maybe it's when the clutches grab in the tcase and put power to the front drive shaft.


sorry i'm not being more helpful.

Justin


EDIT: I have the brown wire mod done, and i have a lit switch, and normally it's dimly lit, and when it engages 4wd it gets really bright, and like you said, on hills the light gets brighter depending on if the case engages. so this could be a partial cause to the pop.

Also Describe the pop, is it quick, metal to metal, hollow? solid?

No it doesn't really sound like metal to metal contact, but I could be wrong.

Usually, the tranny has kicked out of OD and into 2 or D...but I thought it occurred in OD the other day - a lot quieter than while in 2 or D, which is why I'm not sure if it truly happened or not.

Do you think that dropping the front driveshaft will tell me anything? Or is that a waste of time? What about driving up some hills (in the rain) in 4 High?

Do you think that continuing to drive it about 10 miles per day is bad - usually one pop each way to work.....wife needs other vehicle for triplets and work.

pulling the front drive shaft wouldn't necessarily be a waste of time, but if it's what i'm thinking, then it won't have an effect on anything because the case will still engage. i would crawl underneath and look at the trans mount, it might be hidden by a skid plate, and i would try and shake it around after the trucks cool, and inspect the mount to make sure, i would also check the motor mounts, you can do this the red neck way of starting the truck and opening the hood then popping the throttle under the hood, if the motor moves a lot, you have a bad motor mount. if it doesn't you don't. um... like i stated earlier, i would check the drive shafts for play as they could be going.

there are a lot of peices in the drive train that could clunk, so the more you look at the less it can be....

and i'm not sure if driving on it is bad. If it's just a mount... it's not terrible..... however you should get it fixed. if it's a Ujoint, well... your drive shaft could fall off and that's not all that great.

Justin

maybe the front CV joints? one could be getting weak.

Been wondering about the CV joints myself. I'll check some things and repost.

Thanks for everything. I greatly appreciate your help and insights.

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. However, the darn thing still makes the noise.

Also another gentlemen, MikeHart, is having the same problem with one interesting commonality ---- "....has been doing this for about 3 weeks just after I put a different t case in it after a year of driving it without the shaft in."

http://www.explorerforum.com/forums/showthread.php?p=2335680&posted=1#post2335680

Any thoughts? At this point, I see no reason to keep the front driveshaft out, so I plan to reinstall it tomorrow, unless someone can think of a reason to keep it out and test something else...

same issue

I have a 98 explorer awd as well. I had the transmission replaced over a year ago (with a 70k rebuilt tranny) and just recently (in the last 2 months) I began to have the same issue you are describing. Sort of a pop or slight shudder when lightly accellerating uphill, however it goes away when you let off the gas or accelerate more heavily. It shudders/pops between once and twice a second for as long as you keep the acceleration constant through 15-30 mph.

I'm wondering if it's the transfer case, I plan on checking and changing the fluid to start out with and hope it's not my tranny!

Never have figured it out...

Honestly, I quit looking for the problem. Don't get me wrong the noise is still there. The tranny shop that rebuilt the transfer case did a good job with several rebuilds at no cost to me. They also check the tranny, changed its filter and fluids...

The front drivshaft is still out.

The noise has become more frequent, that is, it occurs on shallower hills than previously. Let me know if you figure it out. I would love to know what the problem is or was... wife wants to get rid of it...but I don't want a payment nor do I wanna spend that kind of money for a frigg'in mini-van!!!

Anybody have any luck with this problem? My problem is described exactly as the OP posted, except for not having changed out the tcase. The front seal on the rear diff had to be replaced recently and the noise started happening before it was repaired. Everything else is the same, slow hills I will hear a pop.

Poppin noise is chain

My 99 xlt 5.0 had same problem. All the experts steered me to CV's, etc, but ultimately discovered the transfer case has gears driven by a chain. Chain was stretched enough to "pop" under load, slipping a gear cog. Also, I bought a used transfer case and installed, which fixed the problem.
Hope this helps.

Still having problems....

Rhobo said:

My 99 xlt 5.0 had same problem. All the experts steered me to CV's, etc, but ultimately discovered the transfer case has gears driven by a chain. Chain was stretched enough to "pop" under load, slipping a gear cog. Also, I bought a used transfer case and installed, which fixed the problem.
Hope this helps.

Click to expand...

Mine is a 4.0 L 4WD and I believe that the 5.0 is AWD. I have not tried running it in 4WD to see if that is the problem. I don't know if my transfer case is "under load" when in 2WD.

My problem has steadily gotten worse, that is, the popping noise now occurs when climbing hills, when driving on the flat (steady speed or accelerating), or even downhill if I get into the accelerator hard. The noise does not seem to occur at low speed unless climbing a hill (under-load ?). This happens with or without the front driveshaft installed.

My mechanic used a set of chassis phones and believes that the noise is coming from the transfer case. So the tranny shop pulled it out again and feels it is something else. They said the case looks great inside and cannot find any problems ... I think that they replaced the chain last summer, as well as most of the other “guts”. CVs, mounts and exhaust appear to be fine.

Wife refuses to drive it because of the noise. Any thoughts? The thing is good shape otherwise, so I hate to just junk it, but we are nearing that point as I don't trust it much more than my wife. Being stranded with toddler triplets would no be a good day. The tranny shop has been great – no charges beyond the initial $600+, and they want another crack at it when I am back in town… I'm working in a different city during the week now, which is not helping my problem.

Thanks.

Can I...

Can I have the tranny shop just gut the transfer case, such that it a 2WD (eg, remove the chain)? And see if it still makes the noise? Trying to think out of the box here. I live down South, so I don't need 4WD.

Thanks.

Do you or your mechanic buddies have access to the shop diagrams for your transfer case? My mech friend and I were at odds until he pulled his out (the manual) and we realized how the chain could cause the noise - when slipping.

This sounds wrong - but, it is possible that they didn't replace your drive chain in the transfer case - and that the replacement one they tried had the same problem.

Sorry to seem so obtuse, but there are only so many possibles; one being that humans are involved.

But, can I just have the tranny shop pull the chain out and run without it?

I don't have access to any diagrams, nor have I seen one of these things opened up, so I don't really understand how the chain slips and results in a noise.

Thanks for the help.