Rear end clunk

[MusclecarJohn]

Hey everyone, I just started noticing a sort of clunk from the rear diff in my 92( 2:59s w/ posi of course), I hadn't changed the rear diff oil or anything so I don't really know if it may be low or low on additive or not, the clunky sound happens when I back up with the front wheels turned sharply? mostly when it's warm from driving and it only clunks one time then stops, my concern is maybe it's the spider gear? I had a 91 z28 that had this noise but that was much worse, and it turned out it was the spider, just wanted to ask before I checked my fsm etc. btw, my 92 has 76,000 miles Thanks guys

 

[92BlackVette]

Change the fluid. I let mine go too long, now mine clunks everytime I back up and turn sharply. I changed the fluid, additive twice, but either the clutches/spider gears have issues now. Use the additive otherwise you are wasting your time. It doesn't really matter anyways to me concerning my clunking sound because I am going to put 3.73, w/ a master rebuild kit so it works out in my case. I have 150,000 miles on my 92/ZF6. OEM Opti too, haha

Its cheap to change the fluid so do that first and worry about the bug gears later...

 

[MusclecarJohn]

Thanks 92BlackVette, sounds like good preventative advice to me, I will change it and surely add the additive BTW, how much will you have to fork over for the swap?
I would like to someday get 3:07s in my 92, but just want to keep her in top shape anyway Thanks

 

[vetteoz]

Can you determine if is from the center or the wheels?
The outer axles commonly get a rust build up on the splines between the hub and axles giving a clunk sound

 

[MusclecarJohn]

vetteoz, I can't really tell if it's from wheels or center but I will drive it again tomorrow and try to determine exactly where noise is coming from, thanks for your reply

 

[surfer93]

It could also be the rear hub going out, jack the rearend up and grab the wheel at the 3 and 9 o'clock position and push in and out, if you have more than an 2 inches total travel, then your hub is on its way out.
Do this test at th 12 and 6 o'clock to check u-joints.

Good luck!

 

[92BlackVette]

Thats a good test too, I have my wheels off all the time in the rear, I did that test when I had my shocks of two weeks ago....same issue....

w/ a Dana 36, my guy that I use only lists 2.59, 3.54, 3.73 for your rear end. There maybe more guys who read this that can source other ratios. All of them regardless from are like $711.54 WOW! Spider gears are $704.58, Master rebuild kit $169.70.

GM / GMC / Chevrolet Corvette Dana Spicer D36-ICA Rear Differentials - Cases & Spider Gears,Installation Kits,Positractions,Rings & Pinions,Shims & Seals,

Just FYI. Ring and Pin. for a Dana 44 is like $265.63. To get you converted the drive shaft changes, plus you still have to find a D44, so costs will quickly add up to convert. I plan on putting in a new spider, master rebuild, and 3.73 for my new 396 going into it.

The sound will eventually get louder if your fluid change doesn't do the trick, mine clunks really louds now, Its been doing it for like 50K miles, started off quiet, got louder over time. I changed all u-joints, fluid, checked all parts for wear, nothing....so there you go

 

[vetteoz]

w/ a Dana 36, my guy that I use only lists 2.59, 3.54, 3.73 for your rear end. There maybe more guys who read this that can source other ratios. All of them regardless from are like $711.54 WOW!

Cheaper here
C6 Parts : C5 and C4 Used Corvette Body Parts : Corvette Suspension : Front Bumper : Vette Parts : Corvette Repair and Salvage

3.07 was a factory D36 ratio and available in the aftermarket.
If only going to 3.07 cheaper to look for a take out head or complete diff and get it freshened up instead of buying / installing new gearset.
Master install kit + posi clutches ($60 ) + labour cheaper than than new gears alone
D36 complete with suspension go for $500

 

[vetteoz]

Or
3.07 Head and batwing $350

C4 CORVETTE DANA 36 DIFFERENTIAL ASSEMBLY 307 RATIO VGC:eBay Motors (item 170381565179 end time Oct-10-09 06:35:27 PDT)

 

[MusclecarJohn]

Thanks guys for all of the info, I will change the diff oil and additive first off then see how it helps, I will keep you guys up on everything...John

 

[MusclecarJohn]

Just an update you guys, seems like what vetteoz said was right, I'm pretty sure it's not a clunk from the diff but rather a kind of pop from the hub area on right rear wheel, surely rust build up. I will change the diff oil and additive out anyway but can you guys tell me how we clean / prevent the rust that builds on the wheel hubs and axles etc? these areas seem so prone to rusting from all the washes etc. :eyerole