Blown diff?

Jessegroves · Postby **Jessegroves** » Sat Jul 30, 2016 3:57 pm

I believe to have just blown the 4.3 open diff in my na6. It made the same sound as my friends's did when theirs blew. Only difference is mine seems to drive fine. Is this normal? Or when Diffs blow do they usually completely stop working? Could there be another problem..

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The American · Postby **The American** » Sat Jul 30, 2016 4:17 pm

What's making you think it's blown (other than what ever noise it made)?

speed · Postby **speed** » Mon Aug 01, 2016 9:08 am

Yes there "could" be another problem. Best get under there and check it out.
Like the American said, what makes you think it's blown?

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Jessegroves · Postby **Jessegroves** » Mon Aug 01, 2016 8:32 pm

Because of the similarities between the noise of another car, also, when I jack the car up, each wheel spins freely by itself but doesn't rotate the other at all, and when I rotate the tailshaft, each wheel turns in the same direction. Is any of this normal?

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OMY005 · Postby **OMY005** » Mon Aug 01, 2016 9:16 pm

Jessegroves wrote: Is any of this normal?

Not for an open diff. Broken sun gears or cracked carrier not letting them mesh properly.

Andrew.

StillIC · Postby **StillIC** » Tue Aug 02, 2016 8:54 am

Jessegroves wrote: Is any of this normal?
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Apart from the noise, it is all normal for an open diff. I suggest buying a technical Lego kit that includes a differential so you can get a good understanding of how an open diff works.

Your diff isn't blown, but it sounds like you have a problem.

hks_kansei · Postby **hks_kansei** » Tue Aug 02, 2016 1:40 pm

Put the car in gear before rotating a wheel to see if the other side spins opposite.

If it's in neutral you'll sometimes just get one wheel turning and the tailshaft.
Putting it in gear stops the tailshaft turning.

Normal operating for an open diff is:
Turn tailshaft - both wheels rotate same direction.
Lock tailshaft and turn wheel - other wheel rotates opposite direction.

As for different condition, without opening it up the simplest check is to drain the oil and inspect it for fragments.
It's normal to have some sediment, but it should all be very very tiny particles, like talc.
If there's bigger nuggets it's a sign of possible chipped teeth or wear.

Usually diff whine is a worn crown and pinion.

It could also be he gearbox thrust bearings worn and making a whine.

hks_kansei · Postby **hks_kansei** » Tue Aug 02, 2016 1:41 pm

Or wheel bearings.

Rolley · Postby **Rolley** » Tue Aug 02, 2016 7:03 pm

Here's a very good/simply explained tutorial from the 1930's on the basics of how an open diff works.

https://www.carthrottle.com/post/vF6OI4/

Jessegroves · Postby **Jessegroves** » Tue Aug 02, 2016 11:37 pm

Thanks for the help guys, although I already knew how a diff worked prior, I appreciate the replys on how to diagnose weather there was a problem or not, cheers

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