Help with rear end

[Dreadl0ck]

Since I bought the car 3 years ago I've noticed that the rear tires always are locked. Great for burnouts but not so great when going around corners or trying to back the car up (inner wheel when turning skips since it's always locked)

Never opened a rear end before so I Don't know if I could find what's wrong with it but as I see it I have 3 options

1) Drive the car to a shop that can have a look at it ($$$$)
2) Since the differential probably is 50 years old - it might be a good time to replace it - but should I then get new rear axels as well? For this option I need some shopping advice ($$$$ but I get new parts that will last longer)
3) Open the housing and try to look what's wrong (???)

Another concern I have is the 4.10 gearing which is terrible to drive at highway speeds with - so I'm thinking about getting some cruising firendly 3.23 Whats your take on that?

 

[1967coronet440]

Give dr diff a call

http://www.doctordiff.com/

 

[miller]

Another concern I have is the 4.10 gearing which is terrible to drive at highway speeds with - so I'm thinking about getting some cruising firendly 3.23 Whats your take on that?

Of course, the gears you have, is completely your choice. Keep 'em, or change. Is this a 8 3/4"?
Unless there's something worn in the rear, might be worth pulling the member, and looking, since it would have to be at least loosened...to change the gear lube, and make sure you include the additive needed, since it sounds like a posi.
Could be all it needs. But, hard to say without looking.

 

[moparnation74]

Give dr diff a call

http://www.doctordiff.com/

This is who you need to speak too....

 

[747mopar]

I'd have a look first that way when you do make the call you know what your asking for. I'm thinking of 3 possibilities, someone welded the spiders on an open diff, it has a spool in it or it's just locked up. If it's welded or a spool you'll likely be better off replacing the whole pig (If it's an 8.75) but if locked up it might just need rebuilt.

Knowing what rear axle you have would be very helpful, does it have a cover on the back or does it slide out the front. Having an 8.75 changes everything as far as how to proceed. Non 8.75, pull the cover and look.... Very quick and easy. 8.75 pull both axles then the center section.... a bit more work.

 

[Dreadl0ck]

8.75 yes - going to check casting today since it affects available gear ratios.

If I crack it open - what to look for? Any good sources of information on this other than spending countless nights on this forum trying to read up?

 

[miller]

First, suppose you already understand, that carrier is heavy! So, be prepared.
Look for the obvious, worn parts, metal in the drained lube. Of course, should have some, but not excessive.
As mentioned, you have to pull the axles first, at least enough to clear the carrier gears.

Should be gear numbers, stamped on the outer edge of the ring gear, telling the ratio. Center of it, will be the open gears (no posi), or the posi unit. Plenty of references around, showing what each looks like.

 

[Ron H]

What is the car...year, type of rear or housing you might see from exterior? 742 (2) on outside? Post-64? Does it have adjuster plate? Are you hearing noises like a plate wobble or and bearing noise? Can you set a gauge to check axle play/tolerance? Some things to identify before having to rip it out. I encountered a nightmare having my sure grip redone by two outfits that didn't know whey they were doing that went from one end of adj to the other trashing brand new ring and pinion set. Finally a smart buddy took it in to his machine shop where he had time to rebuild it as he was retiring with some play time in the shop before his last day. Lucky timing for me on this. He carefully followed the instructions in my factory manual to a "t" and came up with successful rebuild...as for ratio I went from a 3:23 to 3:55's and if I had to do over I'd have stayed with 3:23 for cruising as burn-outs ain't my thing anymore.

 

[Dreadl0ck]

Sorry for not putting the most important things in my first post.

It's a 1969 roadrunner, originally a 383 car and with both wheels in the air, I can't move them with transmission engaged, but in N both wheels spin the same way when I move one of them.

Cruising is fun but it should still be able to light them up occasionally - 3.55?

If I had more $$$ I'd go with an overdrive but... so many things I want to buy. Suspension, blower... gosh...