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st0878

Differential Problem

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I have had a thunking sound comming from the rear end of my 76 Z that is getting progressively worse. I pulled and lubed the 2 half shafts and couldn't locate the cause. I sounds like bad bearing or if you had a tire out of round. I checked the two wheel hubs and they rotate freely and have no play. Today I found that if I put the car in neutral disconnect the half shaft and rotate it while still in the differential that the passenger side of the dif. was producing the sound. It also has about a 1/4 inch of rotational play. I had an extra half shaft so I swapped it out. Same problem! The thunking sound repeats once for each rotation of the tire. It seems to be coming from the differential bearing or is it possible that I've lost a tooth? I tried changing out the differential oil and refilled with 2 qts. :stupid:

How do I determine the problem without dropping the diff? And If it is the bearing can you change it out without dropping the dif, or is that my only option? If someone has had this problem or can link me to an article I would greatly appreciate it. I know very little about working on or troubleshooting differentials and need as much detail as possible. This isn't the differential of my dreams and I was considering going to 3:9 or 4:11 in the future. For now I'd like to just keep it limping along until I find a good price so I don't want to dump too much money into this unit doing a complete overhaul.

Sorry if I rambled on too long. Thanks in advance for your advice!

EZ

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If the noise is coming from the inside of the diff, the only way to repair it is to pull it. You might be able to diagnose the problem by just pulling the rear cover, but you will need to drop the diff to repair it if it is a bearing or gear problem.

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Hey 2ManyZs,

I will be getting into a Z diff. for the first time soon. I don't have problems with the existing diff. in the car, but that it is a 4:63 and we're getting killed down the straights. Well, I found that 1 of the three extra diffs. in my shed has 4:11s in it, and last night I traded an extra Nascar Pop-Secret race ticket for this weekend, in exchange for his help at his shop to put together a 2nd diff. with the 4:11s in it.

So, now the question is I gotta figure out how to get Cindy to pull the diff. out of the car? Looks straight forward, any warnings I should give her? :stupid:

Thanks Craig

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I'd warn her not to do it unless you are there to lend a helping hand.... ROFL

It's pretty straightforward, but that diff is pretty hard to handle for one person if the car isn't high enough. Best to use a floor jack under it, which needs an extra pair of hands to operate while one person steadies the diff, unless you have a set up like this one.

http://www.baddogparts.com/index.htm

Look under Products.

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sto878, when you drained the oil was it full of chipps or did it look like metallic black paint ? Like 2many said to do any repair, the diff must be pulled. However if you are short on funds what you can co for a short time is to remove the back cover and clean out any chips or broken parts and just replace the cover with a new gasket and oil. At least you wont have loose parts flying around in side the diff. This should get you by for a while , untill you can find what you need. I had a roller bearing get inbetween the ring gear and the pinon while I was doing about 70 , this was in a hot rod '32 Ford I had. It felt like I had just been hit in the rear by a truck. Not a good thing.

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Yea, getting the car high enough up on stands, but undo the half-shalfts, drive shalft, front & rear supports, and steady it while she lets it down. She's got the steady hands, she hates the way I let things down- BAM!

While the diffs. are getting worked on, she reminded me that now is probably a good time to put in some new U-Joints. Are there ones not to use for track? some better than other?

Many years ago I talked her through a clutch job on her old 68 Mustang, she'll try anything now. Couple months ago she change plugs, wires, and cap on her 98 Chevy Astro Van, ever try to get to those things?!

You start from inside the passenger seat taking the center console out! :alien:

...sorry didn't mean to mess up the topic of this thread...

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Thanks beandip. I changed the oil before I realized that the diff was the root of the problem. I DID make it a point to check the drain plug for shavings. I actually thought it looked pretty clean. I found an 83 280zx 3:9 on the other side of Florida today ($250) and am debating whether to risk spending $100 on bearings, seals and cover gasket when I'm not sure what the problem is and if you can fix it without any exotic equipment. The fact that there is a CAT frickin 4 HURRICANE hovering around off the coast of Miami ain't makin it easy for me to plan any exploritory differential dropping this weekend! I think I'll wait till Monday to buy it just in case I don't have a car come Sunday.

Still like to find an article or something that details an overhaul.

Thanks again!

EZ

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Rebuilding a diff. is not a easy job to tackle at any time . Personally I wouldent attempt it , and I do almost everything on my cars. When it comes to the trans and rear ends I defer to the pros. Setting the gear lash is ctitical. If you pull the diff your self and take to a shop and have them do it , that would keep the cost down . But if you are wanting the 390 gearing I would just go that route. You will end up spending the same amount in the long run at least, and this way your done . Just do the install. I cant remember , does the '76 have a R-200 allready? If not you will need the mustash , bad spelling, bar and its bolts , not sure about the half shafts, I used mine from my 180 and they worked fine. I wint with a 370 but would prefer the 390s . I dident find one and this one was $100.00 so I bought it. Good luck on both the storm and the Z. Gary

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Thanks Gary, that's what I needed to hear! Sometimes you just need someone to talk you down from a stupid idea! The $250 ........ well I guess it wouldn't the first time I had to drop trowel for the old bit&^%...

Seein how Halloween is coming up I'll already have an old pumpkin for the kids ta boot!

Yes the 76 was the first year that the R200 reared it's ugly head.

Still would be nice if someone did an article on how rebuild the differential if all the tools were available at Harbor Freight that is......

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Post the request on the suspention section . I am shure there is someone that knows differentials inside and out. Phred is an engine gurue, escanlon paint body and electrical ,2manyZ all the above. there are many many more. Just ask.

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Yeh think all of them have contributed to some of my other posts. This site is my first stop for z-car info. I don't know if you read the "What you do you do for a living" thread but I was impressed with the resumes of just about everyone that replied. Thanks for your help.

EZ

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