whining in overdrive

[slowmoe]

I have a 99 grand cherokee. 4.0 with select trak. Since 5K mi, whenever it engages in overdrive, especially underload, it sounds like there is some type of clutch that engages and a consistent faint whine continues. This happens at 55-65mph all the time. The car now has 115k mi on it. So far, via the Lemon Law, it has had the rear axel rebuilt 2x, the transmission replaced and the transfer case replaced all in efforts to resolve this problem. However, the incessant noise continues. Your thoughts are appreciated.

[slowmoe]

Are ya out there "thread killer"

[satan]

Hmmm...

'99 Grand w/ auto tranny behind a 4.0 ...

You get a whine just after (or immediately?) the thing shifts into 4th at 55-65mph, which is exacerbated with power requirements ???

(hmmm...) Hard to tell without listening to the whine --

It's not uncommon for noises to "appear" once you're in overdrive (the one's that are there all the time, but only show whine the engine is slowed reducing it's cover noise). Let's assume that that’s probably NOT it for the moment.

The nature (pitch, tone, location and all that) of the whine is totally relevant - can you determine/describe "where" the noise is coming from?

Is the whine sound like a dremel/dentist's drill, or ???

Is there a sort of "air leak" quality to the whine, like a sizzle or a hiss ?

Does this whine vary in pitch with road speed?

Can you FEEL anything when this happens?

Next time this happens get to a point driving where you can safely repeat the noise - (On / OFF) know that this is consistent and repeatable...

...Then, right in the middle of where it's making the whine - lighly apply your parking brake (this should add additional power requirements, which should make the noise louder if I'm understanding things). What actually happens?

...Again, right in the middle of where it's making the whine - barely touch your brake pedal (not looking to cause drag here, just enough pedal to turn on the brake lamps) - what happens to the whine?

...Again, right in the middle of where it's making the whine - pop it into 3rd, what's it do?

...Again, right in the middle of where it's making the whine - pop it into Neutral, what's it do?



--------- Right now, given the data that you're presenting I can't even venture a guess -- the "worse under load" tends to push the issue into the working drivetrain (engine, tranny, t-case, rear driveshaft, and rear axle)... but not exclusively - have you tried pulling your front driveshaft and seeing if the noise repeats (to conclusively eliminate the front-end as the noise source)? -

At that kinda speed (shaft RPM probably near 2.8Krpm) - everything whines.

I also didn't see anything that talks about the supporting systems for the probable components (all 3 engine mounts, exhaust hangers, UCA/LCA bushings, etc)- since everything is already making noise - there's always a chance that something is rubbing on something else (motor mounts are notorious for this - and the things that lay next to a torquing engine, like auto-tranny cooling lines!)-- after 115K you'd kinda expected that you'd find something like that!

I didn't hear anything about u-joints -- are they OEM (WHY???!!)? If you change em (or just for fun) pull the driveshaft and rotate it in the rear diff-yoke 180* then reinstall it... I've also seen driveshafts "sing" (it's a higher pitch than you'd think); the shaft will find a resonant frequency -- for "testing" this can usually be attenuated by adding uniform heavy tape wrapping 1/3 of the shaft length in from each end (I like to use qty=2 cheap ace bandages wrapped really tightly and secured with sports tape...) - the resonant frequency should change if that's what you're hearing. (the fix is a new drive shaft - Tom Woods' won't oscillate or find someone to fill yours with foam or plastic grocery bags...)

This is all speculation on my part, but may provide some additional things to look into -- without hearing the whine, and getting an good idea of where it's coming from... it's kind of a turkey shoot (could even be a front wheel bearing!)

any help?

Ever thought about replacing the bushings on the t-case shift linkage?

[RipRip]

You wanted him you got him. Nice reply satan.

[slowmoe]

I never thought I would say this but, Satan, thanks for the help.

Seriously, thank you for the thoughful and educated repley. That kind off information was exactley what I was hoping to find.

The whine does sound more like a drill than a hiss of sizzle.

The whine does vary in pitch with road spead and load. Under load at low speads in overdrive it is a deep grawl. At high speads it is a high pitched whine.

It happens exactley as the trans shifts into overdrive. You can actually hear something like a clutch engaging.

It is repeatable. If I am driving up a hill at 55-65 and lift my foot off the accelerator, the whine stops. As soon as I reapply the gas, I hear the same clutch-like sound and the whine begin again.

If I shift into 3rd there is no sound. Although, I think there my be a faint whine. However, as the rpms off all involved is so high, it is tough to hear.

If you put your right ear over the climate control vents in the center dash you would hear the sound loadly and clearly.

There is no pronounced vibration from any other part of the car. Although, possibly some in the steering wheel and accelerator pedal.

You mentioned the drivetrain as a possible culprit. I started hearing the sound at about 5k miles. It was very faint then. The dealership thought that I was crazy. At 33K another mechanic told me that I better replace the trans before it drops out of the car. This is what initiated the lagal action against Daimler Chrysler.

Now only because required by legal action , the dealership replaced the rear axel. It was already replaced once at 26K!! ( peace of junk ). That did not fix it. Next the dealer replaced the the transfer case. That did not stop it. Then they replaced the trans. That stopped the noise just long enough for me to be out of warrenty - 13K when the noise returns.

I never thought the trans needed to be replaced. It always shifted well and never missed a beat. I think that when they replaced the trans they tightened or adjusted something that soon fell out of adjustment again like when the car was new. It took 5K to loosen when new and 13K to loosen when the 2nd trans was put in. Does this sound like a valid thought? When could it be?

I am looking forward to your repley.

[satan]

I thought that I'd posted a reply to this yesterday, but I guess I didn't...

Did you try the test ?:
...Again, right in the middle of where it's making the whine - barely touch your brake pedal (not looking to cause drag here, just enough pedal to turn on the brake lamps) - what happens to the whine?

Do you have any paperwork on the replacement transmission? Specifically, look for data relating to the replacement of the torque converter and/or the torque converter lock-up solenoid.

I don't have the ECU to tranny wiring diagrams for anything that new (or any Grand Cherokees anyway) , but ...

... I'm thinking that his could be in the lock-up of the torque converter: in the converter itself, the solenoid, or what controls it all. I'd need to see the control wiring harness to design a tool/test for you though.



When was your tranny last serviced? (drain and fill or full-on flush?)

Next time you stop after driving with the whine for a while - look at your ATF (do you have any bubbles on the stick or is the fluid foamed/lighter colored at all -- while you're looking, is it pretty clear plum-wine red?)


If it's been a while since your last service, maybe a complete flush would be a good place to start (just to clean everything out and start with 100% fresh fluids again) - barring that, a drain and re-fill with a high quality ATF (Synth or semi-Synth or ? with an additive like Seafoam or Lucas Tranny Fix). Dumping enough fluid out to allow you to fit an entire bottle of Lucas Transmission Fix in there would be a minimum effort.


The Torque Converter should be locking in the top few gears as controlled by the ECU and information fed-back from the tranny itself. My guess is that this is the "clutch" that you mention hearing -- this is all toward the front of the tranny which is also supported by the location where you hear (feel as a vibration in the accellerator pedal) the whine. If the solenoid is bad, if the control circuit and/or wiring is not right, you could be working with partial lock or a condition where something is oscillating. It could also be that the converter is not balancing well (internal damage) and that you can only hear it in overdrive...

Something I didn't think to ask is how all this behaves in 4-lo -- the tranny gears should be the same, but the load may not be enough to generate the noise for ya...

[seRob]

My Father in law had the same problem on his 99. I remember him taking it in a couple times for different things and finally they figured out exactly what it was. I'll have to ask him later on the details.

[slowmoe]

Satan and Rob,

Thanks for the responses. Satan, the records for the trans replacement read:

1- 5012464ac trans package
10 - AFT +3 fluid
1 - spacer
1- tiestrap

Does the trans pkg include the tourque converter, solonoid or wiring you mentioned?

I did perform the test and the noise increased

The trans was replaced 13K miles ago. Previous to the replacement it was serviced at the dealership at 30K intervals as were the front and rear axels. As stated earlier, the rear was replaced 2X the front is now making the same noise that the rear did when it needed to be replaced.

As an aside, this seems like very poor engineering to me. When you follow the recommened fluid changes and use quality products (mobil1 80-90 front and rear), you expect that major parts will last a long time. I have never had to replace an axel in my life. Even on cars with 300K plus on them. In addition most of these miles were highway without towing!! What gives?
I thought Jeeps were suppose to be tough.

Okay, now that I have vented once again...

Stan, the trans was always a beautiful red. No discoloration, no bubbles. How could I further diagnose potential t-converter issues?

Rob, I am looking forward to hearing what happened with your father's.

Thanks again for the help, all.

-slowmoe

[satan]

Hmmm...

I can't tell ya what's in the 5012464ac trans package...
... may be worth a dealer call (though I suspect with qty=10 of ATF that you did at least get the TC drained...)


Have you ever run the serial number on your engine through any system?

This is WAAAY out there, but...

... (if what's left of my brain works) the 4.0s intended for automatic trannies have a bushing installed in the crankshaft to reduce the bore enough to hold the torque converter's center pin (where the manuals use the full crank bore to push in a pilot bearing)... - if you had a manual crank/engine with an auto behind it, maybe the Torque Converter is a little wobbly under a full load?

I dunno if it'd work, but you could drop the inspection plate and pull the TC bolts all out and see if there is latteral play -- (should be none - and probably the seal into the front pump would keep it from wobbling at all...) It'd at least give you a chance to look at the TC bolts and spin the TC 180* and reinstall/torque the bolts to eliminate them and the TC mounting ears as a possible problem...

I'm thinking that if your fluid is happy and all of that that your lock-up is probably happy enough -- Ususally when the lock-up croaks there are heating issues (engine and tranny) which'd show as crappy fluid.

I'd almost be interested in seeing the results of a pressure test and solenoid diagnostig (Aamco or equiv) - but that's getting into the $

[seRob]

sorry I haven't checked back in. I forgot my FIL was out of town and won't be back til next week...
I'll talk to him then.