Rear diff question (not a conversion!)

[terrible]

Ok so I've asked this of many other forums but never this one. Here's your chance to impress me

My car had 135k on it when I bought it (92 5spd gsx). It was all stock with a shitty engine rebuild (felpro and the like). I was very impressed when I bought it but it had a clunking noise in the rear that wasn't a cv joint or the driveshaft. Well a year later I finally took the diff out and found some teeth missing. Turns out the ring had a few teeth missing and so did the pinion. I ended up buying a used rear section from a junkyard and installing it. It works great and I've never had any problems with it. However, it seems to be getting louder, almost like gear whine. I went on a trip a few months ago (700 round trip miles) and when I got home just driving around town, the diff seems even louder. Almost like it's "wearing out" really quick. There isn't any clicking or banging just a whine. It isn't a real loud whine but kind of a low bearing noise whine.

I've never met or spoke with anyone that has worn out or broken a four bolt diff. Can a driveshaft being out of balance cause a rear end bearing to go bad? I've priced these things and the only way to get them is through the factory (big bucks). I've really thought about taking out the driveshafts and having them rebalanced since I installed new universal joints.

What do you guys think I've got going on here? Also my car has no sound deadning left and I was hoping to ride in some one elses car and have it sound exactly the same as mine. I have no clue where to even start here. Unless I barrow some one elses diff and see what that does.

Here's a pic of my factory rear diff.

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[pneumo]

Never met anyone who broke a 4 bolt? You haven't talked with Azrael!

Check the gear ratio of the rear diff, cars with auto trannies had a different rear diff gear ratio than manual tranny cars. You can find the gear ratio printed on a sticker on the diff cover, manual diffs are 3.5x. auto diffs are 3.3x

Also check the gear ratio of the transfer case. There are some JDM T cases out there with different gear ratios that will mess up your car quick.

for more details on gear ratios, see www.VFAQ.com/mods/Trannies.html

Like you said, having the driveshaft balanced is a good idea,too.

 

[terrible]

I know enough to know about gear ratios. It's been on the car for over three years now, if it was off in gear ratio it wouldn't have lasted a day

Who's Azrael? Has he broken them with ignorance or just had them do something similar to mine?

 

[pneumo]

Azrael is a member on this forum who had endless rear end problems. Make that 4 bolt rear end.

So if it's not the gear ratios, that narrows it down. I wish this was one of those problems where I could say exactly what it was, but you have to do some detective work. Check the alignment of the driveshaft, rear diff mounts, rear suspension mounting points, and check the rubber mounting points for looseness. Check the driveshaft for dents from road debris. Disconect the driveshaft from the rear diff and check the pinion for freeplay and roughness.

It's also possible the bearing whine is a wheelbearing going bad, or a carrier bearing, or a U-joint, or..?

 

[Lordpaxin]

a automatic rearned in a 5speed tranny, will over time, destroy the center differential.

 

[EROK81]

So your old ring and pinion wore out/broke and you took the broken differential out of the rear end. Then got a junkyard one and installed it in your old housing?

Is that right or am I just reading it wrong?

Most of the time you can't just "throw" a new diff in an old rear end with out resetting up the ring and pinion. The problem you are having is probably bearing noise from them wearing prematurly because of not setting up the gears/preload correctly.

Unless you did reset everything up, then nevermind the above statement.

 

[terrible]

Nope, bought the whole chunk from the boneyard. Came out of a 92 5spd with 83k on the clock.

 

[terrible]

I can't refuse but my wallet sure can

Honestly it isn't that bad but I'm afraid one day bopping down I77 @ 120+ it's going to A: let go and I'm walking B: lock up and I'm in the hospital C: do nothing and give me an aneurysm from thinking about it for too long.

What I'd love to do is pick up the drive shafts and rear end out of your can and bolt them in mine one at a time taking a drive each time until the sound goes away.

 

[unsivil_audio]

Sorry to bring this post back from the dead, but what would happen if you did run an LSD auto rear end on a Manual tranny? (the viscous coupler has been welded up; dont know if thats really relevant info or not)

 

[terrible]

If you do that and weld the center dif I'm not sure what would break 1st. The problem is the gear ratios of the two rear-ends you are talking about differ buy a few hundreths of a turn (not sure of the ratio).

 

[pneumo]

...if it (the rear diff) was off in gear ratio it wouldn't have lasted a day

There's your answer^