3 speed auto transmissions
 

Do any three speed automatic transmissions only use one planetary set to get the three forward gears plus reverse? I know it's possible, just don't know if it was ever in production.

Also, is there a good website that shows exploded views of various automatic transmissions?

Thank you,

Chris

Re: 3 speed auto transmissions
 

www.wittrans.com has some pretty good exploded views for a lot of different trans makes.

Ryan Walther
Stock 315

Re: 3 speed auto transmissions
 

Thank you.

Re: 3 speed auto transmissions
 

Chris, I don't recall ever working on a 3 speed automatic with only one planetary set. And I worked on most every domestic 3 speed built since around 1955.

Re: 3 speed auto transmissions
 

If nobody has produced a three speed automatic with one planetary set yet, there must be a fundamental reason why. It is possible though.

Just haven't figured out yet what it is...

Re: 3 speed auto transmissions
 

Possible how?

Re: 3 speed auto transmissions
 

I've been thinking about this all day and then it hit me , Renault had what was called a ravignaux planetary assembaly that had compound planet gears ..used on a type 4139 trans
I'm looking for one of my old AMC school books,[ they were way better than the Frenchie's manuals ] for a blow up of it. if I remember correctly it had 2 sun gears , 1 annulus gear and compound planet gears.
I'll have to dig thru the stuff I had hoped I'd never have to use again!



Found a description and an excellent engineering web site.

http://www.mathworks.com/help/toolbo...avigneaux.html

Re: 3 speed auto transmissions
 

You have to connect two pieces together, say the sun gear and the ring gear. If they are connected by a clutch and the input is the sun, the ring gear would have to spin at the same speed.

This is an odd way of doing this, but I think it would work.

Re: 3 speed auto transmissions
 

The issue is gear ratio spread with a single, simple planetary set.

Using VERY ROUGH calculations with a 70 tooth sun and 100 tooth ring gives the following:

Low gear= 2.43:1
Second gear = 1.0:1
High Gear = 0.59:1

These are pretty unrealistic gear ratios for a small block chevy as a three speed. But it was a good thought experiment.

Re: 3 speed auto transmissions
 

Looking at the obvious mechanical disadvantage of a planetary overdrive of that configuration, I feel strength would be a major issue. What's on paper doesn't always hold up on the track.