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Whining noise when accel and decel but not in neutral, HELP!

23K views 30 replies 7 participants last post by  KingTJ 
#1 ·
Ive had my 2000 TJ 4.0 auto 141,000 miles for a couple of months. Recently ive started to notice a whining noise that i originally thought to be road noise from the 32x11.50's coming from underneath the jeep. While driving im unable to really tell where the sound is coming from. I first noticed the noise when letting of the gas and decelerating (coasting) in gear. The noise sticks around until i get down around 15 mph and virtual disappears. Also when im hearing the whine i can feel "drag" somewhat holding my jeep back and not allowing it to free role as much as i think it should. But, when i take it out of gear and put it in neutral as im moving the drag and whine both go away. recently ive noticed that the sound is also apparent when accelerating through gears, gets higher with rpms, and starts over after shifting. The noise seems to somewhat go away soon after shifting into third gear. From what ive read, wheel bearings, u joints, drive shafts, pinion bearings, differnetials, and unit bearings seem to be the main culprits of this simillar problem. Im a newb to the jeep world and literally have no idea where to start numbering things out. All input, opinions, and ideas would be much appreciated. Thanks in advanced,

Jake
 
#2 ·
Update: After more inspection and reading up on the forum, I'm convinced that the whinning noise i hear through 1st and 2nd at low RPM's is just the gears in the tranny winding up(they have a name i just cant recall what people have been refering to them as.) Feeling somewhat better about that and thinking it may be niormall considering all my fluids are up and in great condition, ive still got a whinning/grinding sound while comming off throttle. I've somewhat out ruled the possibiity of the noise coming from wheel bushings or unit bearings. Correct me if wrong but i feel this way because if the noise was being caused by either, i would still be able to hear the noise after shifting into neutral and rolling? does this go for the rear diffential as well? Please, anyone with any input please respond im driving myself crazy over this.
 
#3 ·
KingTJ said:
Update: After more inspection and reading up on the forum, I'm convinced that the whinning noise i hear through 1st and 2nd at low RPM's is just the gears in the tranny winding up(they have a name i just cant recall what people have been refering to them as.) Feeling somewhat better about that and thinking it may be niormall considering all my fluids are up and in great condition, ive still got a whinning/grinding sound while comming off throttle. I've somewhat out ruled the possibiity of the noise coming from wheel bushings or unit bearings. Correct me if wrong but i feel this way because if the noise was being caused by either, i would still be able to hear the noise after shifting into neutral and rolling? does this go for the rear diffential as well? Please, anyone with any input please respond im driving myself crazy over this.
I think I am having the same issue you have. I have really bad grinding when decelerating after taking my foot off the gas. Grinding goes away when clutch is engaged so not the throw out bearing. I have an 01 Wrangler Sahara with the NV3550. I am pretty sure it's the tranny as the noise seems to come from underneath the shifter. I plan on having the rear diff fluid changed out tomorrow and have the ring and pinion checked then. Did you find out what your issue was?
 
#4 ·
The other day I changed the front and rear differential fluids and inspected the ring and pinion. All looked good with no metal shavings or anything of that nature. I hoped that the grinding would subside after the fluid change, but it hasn't. Took it in to have it looked at and the guys at the shop are convinced its the ring and pinion going back but I told them everything looked good after inspected. I guess my next plan of attack will be to change the ring and pinion unless something cheaper would make sense to change before hand.
 
#5 ·
Yeah, I have heard everything from ring and pinion to pinion angle and even throw out bearing. Mine literally does everything yours is doing. On decel its nothing but grind and its like the tranny or rear diff is slowing the jeep down by itself like something is trying to lock. Gonna do the rear diff today and will see what that does. Dunno where to go from there. Maybe someone will chime in by then.
 
#6 ·
The only other thing I haven't looked into yet that I still may consider are bad u joints on the driveshafts. They say they can make the same type of noise under load and that would be why I hear it when accelerating and hear it for a little bit while slowing down until the load isn't high enough to put pressure on them. I'd like to think its not my rear diff after inspecting and changing the fluid with all things looking good. Only way to know Forsure if its ring and pinion is to replace it.. Not really looking to do that just yet. Let me know how things go after changing your diff fluid and checking things out.
 
#7 ·
Will do. May even swing by an aamaco Transmission place here locally on wednesday to see if they can trouble shoot it. I am almost positive it is something in my transmission as I can hear and feel the grinding right under the shifter. Almost like the flywheel is grinding against something but hopefully it's something smaller and easier to repair as I wouldn't attempt to touch anything in the tranny as I am very new to this. Anything else I will try. Matter of fact, fixed my vacuum leak this morning after chasing down the leak thanks to this forum. My daughters were so impressed! lol.
 
#10 ·
It is for me. I saw that this member has almost the same problem that I am referring to. I did take it by a shop today and the master mechanic ride with me for a bit and said it sounds like the pinion and carrier bearings are bad in the rear diff. He's going to pull the cover off on Thursday morning to see if that's the case. Will report back once he does this.
 
#12 ·
UFOtestpilot said:
Isn't this issue connected to the other post you made where you said you found a LOT of brass shavings/dust in your transmission fluid?
Not for me. When I bought the jeep the transmission was slipping a bit. I dropped the skid plate and cleaned out all the garbage in the plate and soon realized my input and output shaft seals were leaking. Haven't gotten a chance to change them yet but topped the transmission off with fluid and checked the condition before adding. Nice red color with no burnt smell what so ever. After verifying the transmission was in good shape, I then moved to checking into the differential. After changing the fluid in both, I've gotten no improvement in the sound I hear. I also inspected the ring and pinion and the spider gears and they all looked great. Just confused where to look next and how to tell whether the pinion bearing is the issue without it showing any obvious sign of wear.
 
#13 ·
Bigkidneys said:
It is for me. I saw that this member has almost the same problem that I am referring to. I did take it by a shop today and the master mechanic ride with me for a bit and said it sounds like the pinion and carrier bearings are bad in the rear diff. He's going to pull the cover off on Thursday morning to see if that's the case. Will report back once he does this.
BigKidneys, today I took my rig out in the garage and got both back wheels off the ground. Rotated one wheel back and forth watching the other wheel roll the other way with no out of ordinary sounds. Got under my rig and rotated the drive shaft back and forth. Had a little play when "rotating" which I've heard is normal. What I found next is not normal. The drive shaft had play up and down and left to right without rotation. After a little reading I've assumed that my pinion bearings are both shot and its putting the pinion at a bad angle causing the grinding noise. Had a mechanic look at it as well after discovering and he said the same things. I've found it soon enough that the pinion seals haven't started leaking and hope that after putting apart and changing with a master install kit, the sound and drag will go away. He says that the angle that the pinion is at right now could have a lot to do with the drag. He claims all new bearings should set the pinion back to the right angle and fix my problem. Well see!
 
#14 ·
What size lift do you have? I was reading the same regarding pinion angle and that you don't always need to shim when you only lift the jeep up to 2.5in. Anything more you likely need to shim to keep the pinion angle somewhat normal. That play tends to happen when the pinion angle is too much. I'll have my guy check on Thursday and et you know as well. I did notice today that my grinding is happening now all the time. It's louder on decel but still grinding all the time even with the clutch in.
 
#15 ·
Bigkidneys said:
What size lift do you have? I was reading the same regarding pinion angle and that you don't always need to shim when you only lift the jeep up to 2.5in. Anything more you likely need to shim to keep the pinion angle somewhat normal. That play tends to happen when the pinion angle is too much. I'll have my guy check on Thursday and et you know as well. I did notice today that my grinding is happening now all the time. It's louder on decel but still grinding all the time even with the clutch in.
Well that's the funny thing. The jeeps suspension hasn't been lifted at all. Not yet :) hehe. However, the PO did have a 3 inch body lift installed which will be taken off and replaced with a 1.25 and a 2.5 suspension lift within the next month. So, my pinion angle has nothing to do with a lift as a BL wouldn't effect it. That is what led me and my mechanic to believe my pinion bearings are shot not holding the pinion in the correct position causing the grinding and drag. After replacing the bearings, the pinion "should" align correctly and sound normal again.
 
#16 ·
I would change NV3550 lube to Redline MTL and see if that helps.It is a very noisy transmission and the Redline will help a lot.It only takes 2 quarts and not knowing what you have in there is suspect. If your pinion bearings where out your seal would most likely be leaking gear lube bad.
 
#17 ·
I was having the sound prior to switching it last week to RP but did get some Redline MTL in yesterday so that will go in when I have the rear diff checked on Thursday morn. Figured I'll kill two birds with one stone while up on the lift.
 
#18 ·
ohioviper said:
I would change NV3550 lube to Redline MTL and see if that helps.It is a very noisy transmission and the Redline will help a lot.It only takes 2 quarts and not knowing what you have in there is suspect. If your pinion bearings where out your seal would most likely be leaking gear lube bad.
I guess I should have rephrased what I said. I don't necessarily think both bearings are bad but I do I would go ahead and replace the front and rear while I was in there. You're right in saying that once both bearings go bad your seal will leak pretty profusely but the mechanic and I are both under the impression that atleast one is shot (probably the rear) explaining the up and down and side to side motion of the pinion and the grinding noise but the front one is still holding on not allowing a leak between the differential and the yoke.
 
#20 ·
Not sure if we are talking about the same thing as I am a noob to jeeps and mechanics but I priced a rear diff bearing and seal kit at advance auto parts and it's only $90 and tha's for all the bearing and seals in the rear diff. Will have him check for any play in the rear driveshaft as well while he's there if he doesn't do that already.
 
#19 ·
Didn't mean to say I don't think both are bad then turn right around and say I do lol I think I stopped writing in mid sentence and forgot to delete that part. I don't necessarily think both bearings are bad.
 
#21 ·
Bigkidneys said:
Not sure if we are talking about the same thing as I am a noob to jeeps and mechanics but I priced a rear diff bearing and seal kit at advance auto parts and it's only $90 and tha's for all the bearing and seals in the rear diff. Will have him check for any play in the rear driveshaft as well while he's there if he doesn't do that already.
This is a diagram from my parts manual for my year and model and the Dana 35 which I have. Numbers 4 and 7 are your front a rear pinion bearings. The pinion goes through them in order to allow it to spin freely and also stay in the correct position against the ring on the inside of the differential. Numbers 5 and 6 are a spacer and a shim while number 3 is another seal or race. This whole kit can be purchased and it may be the one you priced already. I'm suspect that atleast one of those bearings are bad on my rig so I will go ahead and purchase the whole kit and replace them all as it would be silly not to while I've already got it all apart.
 

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#22 ·
Yep, looks to be the same thing I am doing. I will know for sure tomorrow. The mech said the ring and pinions rarely need to be replaced but won't know till he opens it up. Counting down the hours. In the meantime I just turn up the stereo! lol.
 
#24 ·
Bigkidneys said:
Yep, looks to be the same thing I am doing. I will know for sure tomorrow. The mech said the ring and pinions rarely need to be replaced but won't know till he opens it up. Counting down the hours. In the meantime I just turn up the stereo! lol.
Haha I hear ya. But your mechanic is prolly right. I opened my diff cover to drain the fluid and inspect and the ring and pinion both looked great with no metal shavings or anything out of the ordinary. With this being said, when its caught early enough, most of the time the pinion hasn't done any damage to ring but if left untreated, you'll see a lot more problems than just the pinion bearings. Like Dextreme said, I think we're on the right track :)
 
#26 ·
Well, had the bearings replaced tonight and he was right, it was the bearings! They were so marred it was ridiculous! When he drained the fluid there was so much "silver glitter" in it from all the metal savings, it looked like David Bowie and Elton John had a party in there... Lol. He also noticed my wheel cylinders were bad and needed a brake job so had that done as well. Now she is as quiet as a mouse and couldn't be happier. Good luck with yours buddy!
 
#27 ·
recently ive noticed that the sound is also apparent when accelerating through gears, gets higher with rpms, and starts over after shifting.

Jake
This statement tells me the cause of your noise is in the transmission and not the diffs. If it were the diffs, it would not change when changing gears. Could be the tranny filter is plugging up and restricting fluid flow. If so, the whining you hear is possibly the pump screaming.
 
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