Rear end vibration shuttering? - Chevy Nova Forum
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Old 18th-May-2017, 10:39 PM   #1
tracker64
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Rear end vibration shuttering?

I picked up my 1974 Nova tonight! Very happy, and fun to drive.
It has the 250/6 banger. I guess a 250 tranny? 3 speed.
I was told it has a posi rear, but I can't verify that as of yet.

When pulling out on a hill, it has a shuttering/vibration in the rear. Pretty rough on a hill, until you get moving.
When turning a sharp bend at a slow speed, same thing like a shutter/vibration in the rear.
Pulling out easy you can feel it, but barely!!

Once your rolling, its smooth, no howling, very smooth.

I don't know if it is in the diff, just guessing? Any advice guys?? Thanks you!
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Old 18th-May-2017, 11:19 PM   #2
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Easy way to check for a posi- jack up both rear wheels and with the car in neutral have a buddy hold one wheel while you rotate the other wheel. It should make the other one rotate in the same direction if it is a posi, if it is an open differential the other side will do nothing.
Worn posi's can chatter, especially if there is no / incorrect friction additive in the differential. Usually you will only experience it on corners, when the wheels are rotating differentially. Try changing your rear end lube and use the correct additive.
Might be worth checking your u joints ask well.
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Last edited by bptactical; 18th-May-2017 at 11:28 PM.
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Old 18th-May-2017, 11:41 PM   #3
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Arrow

I would start with the differential, assuming your have a 10 or 12 bolt diff... Make sure the big nut is tight on your pinion yoke, then jack the diff up and put the trans in neutral grab a hold of the drive shaft and check for play (backlash). Then once you've done all that pop the diff cover off (hold your nose - it could be quite nasty) and check your 4 bolts that hold the end caps on either side of the carrier; they should be torqued to about 60-75 ft-lbs. While you're in there check the ring and pinion gears for missing/chipped teeth. If everything checks out your limited slip clutches are going out OR you might be able to get away with draining all the fluid adding some 85-140 gear oil and a limited slip additive (add the additive first on the refilling stage). I've topped mine then realized I forgot the additive. Let us know what you find.
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Old 19th-May-2017, 12:24 AM   #4
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Thanks guys!!! I'll be under it tomorrow. I was curious about the u joints. But it does seem like a diff issue. But I will check the u joints for sure.

I was wondering what weight. So 85/140?

Does the local chain stores sale the proper additive for my car?

If it is posi. I heard of modifiers and additives unless their the same thing. I dont know what kind to get.

I hope if thats it. I can put fluid in and the additive and smooth selling.
Very nice once you pull out. Just the pulling out part it gets cranky or tight bend at a slow speed.
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Old 19th-May-2017, 08:06 AM   #5
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Good info previously posted. What I found in my rear end was worn clutches and broken shims. Mine reacted and felt similar to yours. Good luck.
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Old 19th-May-2017, 09:08 AM   #6
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Straight, conventional 90wt gear lube is what you want to run. Most of the 85/140 I have seen is synthetic which, while good lube is a waste for a higher mile diff and if it has a minor leak, will become a major leak with synthetic.
Go to a GM dealer and ask for "LSA" a.k.a. "Limited Slip Additive".
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Old 19th-May-2017, 09:51 AM   #7
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Great info guys. I hope mines not busted up inside. Yikes!! Sounds like a big expense to start out with.
I have some 80w/90 on hand.
There's a Chevy dealer right near me. I didn't know if advance or Napa had the additive.
I'll be on it today and see if anything is evident before I pull the cover.
Although I plan on changing that fluid anyhow.
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Old 19th-May-2017, 10:27 AM   #8
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Is there any way of telling if it's a factory posi or not?
My Eaton said no to synthetic in there!
I think we used Lucas diff stuff in my sons GN rear.
I didn't put anything in my eaton the last time I had the cover off.
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Old 19th-May-2017, 11:20 AM   #9
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This car is all factory. Nothing has ever been altered. If its posi its factory. Im going in the garage shortly here to check the ujoints and stuff like that first.
Then I'll pull the rear cover. I hope the diff stuff is all okay inside. I imagine that could be expensive. Kinda nervous right now.
Although beside a tight turn or pulling put on hills its very smooth.
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Old 19th-May-2017, 01:30 PM   #10
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Gonna guess the plates are smoked or the S spring has collapsed on the posi if it is a factory unit. If they are don't fret too bad just yet, the S spring is available and there is a member here, "JBimmolate" who is a whiz on these differentials and has been very helpful.

Now figuring out how a 6 popper can smoke the plates is another thing....
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Old 19th-May-2017, 01:32 PM   #11
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Quote:
Originally Posted by Sycho01 View Post
Good info previously posted. What I found in my rear end was worn clutches and broken shims. Mine reacted and felt similar to yours. Good luck.
Crap...I didn't get in the garage yet or even look at my car.
I told my buddy about what your issue was. He said I might be into about 1000 dollars to fix mine if thats the issue?? WOW!!
Honestly I have no idea what rear end is in this 74 6 banger set up.,

Last edited by tracker64; 19th-May-2017 at 01:38 PM.
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Old 19th-May-2017, 01:40 PM   #12
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Originally Posted by bptactical View Post
Gonna guess the plates are smoked or the S spring has collapsed on the posi if it is a factory unit. If they are don't fret too bad just yet, the S spring is available and there is a member here, "JBimmolate" who is a whiz on these differentials and has been very helpful.

Now figuring out how a 6 popper can smoke the plates is another thing....
Yeah theres only 100hp, maybe 70hp at the rear wheels? Unless he ran it low on fluid and filling it back up will help, which I don't have that kind of luck....ugh...
If its a posi, only going by what the owner told me.
I'll open the rear up today later on. I don't know what I'm looking at though, unless its obvious that somethings broke.

Last edited by tracker64; 19th-May-2017 at 01:58 PM.
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Old 19th-May-2017, 02:47 PM   #13
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I didn't pull my rear cover yet. I'll try to post a photo on my photo bucket when I get down the house. My left rear leafspring the rubber bushing is almost completely missing. Like it's tore up and blown out. I don't know if that could cause that issue or not maybe you guys would know?
My rear end though does have two little ears on the bottoms like one on each side I don't know what rear end that means. It's not the perfectly rounded bottom.
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Old 19th-May-2017, 03:13 PM   #14
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Darn right the bushing(or lack thereof) could cause a shudder.

https://www.jalopyjournal.com/forum/...ar-end.694334/
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Old 19th-May-2017, 04:10 PM   #15
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Originally Posted by bptactical View Post
Darn right the bushing(or lack thereof) could cause a shudder.

https://www.jalopyjournal.com/forum/...ar-end.694334/
I so hope this could be the issue!!

Here's some photos of the drivers rear bushing.

Also, I did remove the one bolt and clean the rear tag up. Its a posi.

And it must be a 8.5 rear? If I am right according to the link you put up.

Dunno if thats good or not?

I will change my fluid and add modifier regardless since people often ignore it.

Here's some photos. I know photos can't make a noise or anything. But hopefully this could be causing the issue?

Let me know if you can see the photos...My dang photo bucket will not work with me on copying the links to the photos.

http://s1074.photobucket.com/user/bm...?sort=3&page=1



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