Thread: A dumb question about Diffs.

Not a dumb question.
"Open" or unlocked diffs will turn the opposites backward.Limited slip and locking diffs turn the opposites the same way.
Andrew

An open differential is a device that allows the two output shafts to turn at different speeds but the two shaft speeds still average out to the input shaft speed divided by the diff ratio. So if the input shaft is held stationary the average speed of two output shafts will also be zero. That means that one can happily turn forwards while the other turns exactly the same speed backwards.

Now if the input shaft isn't locked, ie it is going through a transfer case centre diff and there is a bit of friction in there, turning one wheel will make all the others move. Add up all their speeds and it'll still be zero as the trans isn't turning.

This short film is still one of the best illustrations of how a differential works, of course there are many others you can look at:

[ame]https://www.youtube.com/watch?v=K4JhruinbWc[/ame]

He really pronounces the h in wheels, doesn't he.

I'm thinking, cool whip....

Originally Posted by jonesfam

I thought with an open diff the other wheel wouldn't spin?

Only if the other wheel was on the ground or otherwise locked. (This is how traction control works - applies brakes to the wheel which is off the ground - so drive goes to the one on the ground).

I was the same jonesfam. No matter how much people explained it it didn't make sense! Now i understand it and it looks way more complicated then it is!

The video above is one of the best at explaining how it works. Once you've got your head around it try the manual transmission
[ame]https://youtu.be/RQWejyx0gi8[/ame]

He explains it so well you'll be mechanically minded in no time :thumbup:

Cheers

Dan

Thanks so much for the replies.
I will be re-building diffs in no time............I don't think!
I will have to watch the videos when I get home, no speakers on the work computers.
I think Diffs & Gearboxes are just incredible pieces of engineering but I have trouble fathoming how they work, how they tolerate the stresses they are put through etc.
It amazes me that people came up with all this stuff years ago.
Jonesfam

I almost understood most of it. Thanks for posting that. Not having taken anything much apart its always a bit of a mystery to me what does what - so that film was good to see.
cheers,
D

As a teenager I tried explaining a diff's operation to a mate but he didn't understand the concept until I showed him a diff centre.