Replaced Rear End, Still having noise

[Meliodas]

So i just spent about $350 to have a positraction differential sent to me after my mechanic said my old rear end was going out. Paid him $220 to install it. Still getting a noise only on acceleration , and it doesnt always happen. It sounds like a desk dragging on the ground. I was thinking could possibly be the wheel bearings, but he said they were fine. Or the cv axle which he also said was fine. Someone who deals with birds in Ohio asked if my driveshaft was making contact with my gas tanks heat shield . Admittedly , I have no tools myself and no jack. I want to bend the heat shield out of the way if possible and see if the noise still occurs. You can hear the engine noise change, and then its followed by this noise, if I let off the gas it'll go away. If I accelerate harder it will go away. Usually happens while im maintaining a certain speed .

 

[theterminator93]

First... methinks it's time to find a new mechanic.

Second... of the numerous ideas and suggestions shared by others in your earlier thread, which ones have you tried/ruled out already?

If the converter or converter clutch circuit in trans is at fault, you won't hear the sound with the converter unlocked in 2nd or 1st gear. Did you try the suggestions posted by @MadMikeyL in your other thread to test the converter?

 

[racecougar]

I'd take a good look at the diff mounts, too.

 

[White Lincoln]

My first thought is the drive shaft / drive shaft u-joints. I sure heard mine going out on the Town Car when they went bad. But I would follow theterminator93's suggestions and see if you can narrow down the noise. Did you replace the rear end links?

 

[KevinVarnes]

Do you hear a clunk when you shift into reverse? I really wish I could hear/feel what you are talking about since it could be so many different things and it is hard to decipher sounds from a verbal description.

 

[Meliodas]

Thanks all, basically the noise is not occurring in second gear at all, only in drive. Like a whirring, grindy type of noise. And there’s no loud clunk in reverse but a slight one yes. There is a noise and you can feel it go in reverse. I have not yet tried to hit brakes slightly while noise is occurring . I have replaced u-joints already

 

[XR7-4.6]

By Drive do you mean all four gears or just the cruising gears after it’s automatically shifted to them(3rd and overdrive)?

 

[Meliodas]

By Drive do you mean all four gears or just the cruising gears after it’s automatically shifted to them(3rd and overdrive)?

I believe it occurs just driving down the street at low speeds, but also sometimes at 50-60mph . Usually I’ll just either ease up, or press further down on the gas and it will stop once it’s shifted gears. If I have the vehicle in drive and go down the street or around town, it’ll occur. 2nd gear never occurs. I can actually get to 60mph in second because of the new diff being larger than my original ratio, but I’m hitting like 3.5k rpms.

 

[KevinVarnes]

See, now that sounds a lot like really bad spark knock. It is really hard to discern from your descriptions and gosh I would hope that your mechanic would be able to tell the difference between a bad rear diff and some of the other possibilities.

So the new rear end has taller (numerically lower gears) than your old one? I'm guessing the 3.8 probably came with 3.27 gears originally. Do you know what the ratio of the new rear end is? If they are different then your speedometer will be off.

 

[Grog6]

get the rear wheels off the ground, on good stands, and block the front wheels. See if you hear the noise. If you do, turn it off.Shift to neutral.
Get under the non-running car, and spin the driveshaft. It's not easy, but you should be able to do it. It may take a bit of effort to get the wheels moving, but not so much once it's moving. Listen carefully for the noise. If you can't move the ds, try one wheel at a time. feel for gravel in bearings type feeling. Something is wrong if you can't spin stuff without noise.
Having just run the transmission, you should be able to spin it without noise in neutral.
If you can't move the ds, but the wheels feel ok, remove the ds bolts at the diff flange. slide the diff forward a bit, drop the diff down, and slide the ds back a bit Now, see if the ds spins easily in the trans in neutral, without noise. If it does, support the loose ds at the rear, so it's straight, and won't wobble. Run the car, gently, in first, and see if you hear the noise.
I'm betting it's a driveshaft problem, but I'm biased.

 

[Meliodas]

See, now that sounds a lot like really bad spark knock. It is really hard to discern from your descriptions and gosh I would hope that your mechanic would be able to tell the difference between a bad rear diff and some of the other possibilities.

So the new rear end has taller (numerically lower gears) than your old one? I'm guessing the 3.8 probably came with 3.27 gears originally. Do you know what the ratio of the new rear end is? If they are different then your speedometer will be off.

I believe my car had 3.55 and now it’s 3.27, but has an 8inch ring gear now. Used to be 7.something. And yeah me too, he just heard the noise and guessed. Never really evaluated it which sucks. Good guy but costed me too much money. A speedometer app is showing an accurate gauge though .

 

[Meliodas]

get the rear wheels off the ground, on good stands, and block the front wheels. See if you hear the noise. If you do, turn it off.Shift to neutral.
Get under the non-running car, and spin the driveshaft. It's not easy, but you should be able to do it. It may take a bit of effort to get the wheels moving, but not so much once it's moving. Listen carefully for the noise. If you can't move the ds, try one wheel at a time. feel for gravel in bearings type feeling. Something is wrong if you can't spin stuff without noise.
Having just run the transmission, you should be able to spin it without noise in neutral.
If you can't move the ds, but the wheels feel ok, remove the ds bolts at the diff flange. slide the diff forward a bit, drop the diff down, and slide the ds back a bit Now, see if the ds spins easily in the trans in neutral, without noise. If it does, support the loose ds at the rear, so it's straight, and won't wobble. Run the car, gently, in first, and see if you hear the noise.
I'm betting it's a driveshaft problem, but I'm biased.

I’ve got a guy down the road who’ll let me use his lift for that. I’ll try it asap. My issue is just how much money I’ve put in her so far. I know the car is worth it but I’m young and need to keep working lol. I purchased it for only $1100, replaced upper lower tie rod ends in front on both sides. Upper lower control arms both sides. Both stabilizer links. Calipers, rotors. Brake pads, brake lines. Two new struts in front, spark plugs and wires. Even bought half of the required amount of merc v trans fluid. Never got around to getting the rest. Been driving on this noise for quite awhile and I’m concerned I’m gonna damage something important. Really good condition for its age and only has 110,000 approx( speedometer is out) lmfao. But total around $3400 . Wish I would’ve become a mechanic . Gonna buy some tools eventually and do everything myself. Thanks all for the replies I’m gonna ring the guy with a lift and see what I can figure out with him.