Rattling noise at low rpm

Hi, I exactly I have a gmc 2002 envoy and I have exactly this problem and we just change the oil and all transmission sensor and is still doing it so what problem can be thank you

sound like main shaft bearing assuming it is manual( if it comes on all the gears)

if it is automatic it must be your torque converter bearing

Sorry for the late reply but, no, it is not related to a loose heat shield. It is a louder rattling sound more like a loose bearing vibrating inside either the transmission or the clutch assembly. Only between 1600 and 1900 rpm. and it is not present under ou over these rpm. The rattle desappear when I lock the 4X4. Dealer is out of solution!!

it s a long shot, but put the explorer on jack stands start engine, put in neutral GENTLy tap on shift gear on transfer case while someone is pushing handle into high. tap gas to change RPM s while working it. put into drive and do the same but put transfer case into neutral, if goes into neutral stop and put transmission into neutral than put transfer case into high. keep in mind if it works don t take it out, or you will be doing all this again. have had shift cables break have someone shift while you try to change lever position. Might be worth having it checked , transfer case is not a transmission. senser, computer, fuses, solenoid relays are just some easy fixes for this problem..

READ THIS (happy ending so far...):
audi a4 2L turbo quattro, manual transmission with 98,000 KM. Perfect conditions, no oil leaks whatsoever.

Left the car off for two weeks in very cold weather (-10C down to -25C). When I restarted, it started immediately but with heavy rattling noise due to camshaft adjuster not getting enough oil pressure. After 3 minutes of warming up (outside temp.: -12C) at very low rpm (below 2,000rpm), I start moving the car. Still hearing heavy rattle noise. As soon as I pass 2,000 rpm, I get a scary red warning, low oil pressure. Turn off the engine immediately. In 1 minute, I re-start the car and the engine lights check ok, so I drive in first gear super slow (1,200rpm) hearing the same rattling noise. After another minute, finally the noise all the sudden disappears and the car starts running just fine.

Called Audi dealer and they told me that in extreme weather conditions, I should warm the engine for 10-15 minutes if necessary before start moving.
Take away: luckily, I didn't screw up the engine since I was using it at extremely low rpm (easy to do with clutch and manual transmission) until the oil reached full pressure. I am pretty sure now that the problem was leaving the car off for such a long time in freezing weather. All the oil flows back to the bottom, and when I restarted it, the cold oil with high viscosity took a long time to reach all the parts of the engine, specially the camshaft adjusters that are actuated by using oil pressure. Next day, the car started at -9C perfectly without making any noise (as usual). Basically, the longer you leave your audi in cold weather, the longer you might hear the rattling noise until the oil reach full pressure inside the engine. My car took 6 minutes to fix it after couple of weeks in cold weather. This makes sense to me; in fact, in the past I only heard the rattling noise after leaving the car off for a couple of days in the winter.
So far, this has had an happy ending....

You'll probably have to change the clutch plate on the flywheel. You'll have to get a floor jack, but a transmission jack is easier to remove the transmission. To remove the transmission you'll have to remove the tortion bars on both front wheels. Also, you'll have to remove the crossmember aft of the transfer case. You'll also have to remove the front and rear drive shafts. The manual says you should keep the transfer case from leaking oil out the back. but, you can just top it off after you're done. Be careful not to damage the seal seal for the rear drive shaft. Anyway, once you get the transmission and transfer case out (you'll have to remove the shift and transfer case levers), you should have enough space to remove the clutch plate from the flywheel on the engine. You should have an alignment tool to make sure the clutch plate is aligned with the crankshaft so you can put the transmission back on.

you might already know but when shifting into 4wd you can shift into 4hi while driving as long as the tires,(all four) are travelling the same speed. you can't shift into 4wd if you are spinning. 4 low you have to completely stop. When you are in 4 low as you know the power of vehicle is greatly increased due to gear reduction. so if you are seeing slipping symptoms, you might want to change transmission filter. It might not be much help to you but it might prevent problems down the road. also when changing fluid be sure to put mopar transmission fluid for replacement on jeep. like gm calls for dexron. the transfer case on dodge and jeeps also takes transmission fluid. I had to replace a t-case on my friends dakota that was making a grinding noise and it turns out a seal had leaked some fluid out and burnt up some bearings. pretty expensive. they are chain driven. hope I didnt get too carried away, because I am not a transmission expert but I just wanted to share what I did know with you.

I have the same problem with my 94 explorer with a manual transmission, Just replaced the trans a month ago because of gear failure and now It's slipping out of gear when the engine isn't under load aka Coasting, was Told By a Really good Trans Guy that this is a failure in the Linkage in the transfer case am about to tear into mine tho It's way over my technical ability but will repost here after I get it torn apart with potential prices for worn parts for the do it yourselfer, And Has to be the issue I hope because the gears in the transmission are in pristine condition the other reason for suspecting the transfer case is that when my trans is slipping and making that weird Rattle Clatter sound coming from the trans if I put it in 4x4 low it drives great even tho the front wheels aren't pulling since I have the front drive shaft off at the moment,, Well Here goes Nothing Wish me luck on this teardown gonna need it..

For the information given, and assuming forr a 94 it has a bunch of miles, I would bet on a slipping clutch along with a pressure plate that is glazed over. I doubt the transfer case, that's just a chain drive mechanism with nothing much to slip in there. In 2 wheel drive the transfer case drives pretty much straight through and shouldn't add to the problem.

If the clutch has over 80K on it, replace and resurface the pressure plate at the same time.

Does the clutch pedal have about 1/4" of play before it begins to engage? If not adjust the clutch play 1st and see if that helps.

Let me know if you have a further symptoms to share.

Doug

Check the heat shield on the catylitic converter,exhaust manifold. Kev-Mn