3 speed auto transmissions

Chris Hill · 02-03-2011, 11:00 PM

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

reera · 02-04-2011, 08:59 AM

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

Ryan Walther
Stock 315

Chris Hill · 02-04-2011, 01:05 PM

Thank you.

Alan Roehrich · 02-04-2011, 01:22 PM

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.

Chris Hill · 02-04-2011, 03:05 PM

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...

Jim Cimarolli · 02-04-2011, 04:18 PM

Possible how?

Tom Goldman · 02-04-2011, 05:01 PM

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

Chris Hill · 02-04-2011, 09:22 PM

Quote:

Originally Posted by Jim Cimarolli

Possible how?

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.

Chris Hill · 02-04-2011, 10:43 PM

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.

Greg Reimer 7376 · 02-05-2011, 12:24 PM

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.

02-03-2011, 11:00 PM	#1
Chris Hill Senior Member Join Date: Jan 2002 Posts: 655 Likes: 8 Liked 244 Times in 26 Posts	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 __________________ Chris Hill https://ihmusedparts.com

02-04-2011, 08:59 AM	#2
reera Junior Member Join Date: Jul 2007 Posts: 50 Likes: 3 Liked 31 Times in 6 Posts	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 Last edited by reera; 02-04-2011 at 09:02 AM.

02-04-2011, 01:05 PM	#3
Chris Hill Senior Member Join Date: Jan 2002 Posts: 655 Likes: 8 Liked 244 Times in 26 Posts	Re: 3 speed auto transmissions Thank you. __________________ Chris Hill https://ihmusedparts.com

02-04-2011, 01:22 PM	#4
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,115 Likes: 1,572 Liked 1,829 Times in 414 Posts	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. __________________ Alan Roehrich 212A G/S

02-04-2011, 03:05 PM	#5
Chris Hill Senior Member Join Date: Jan 2002 Posts: 655 Likes: 8 Liked 244 Times in 26 Posts	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... __________________ Chris Hill https://ihmusedparts.com

02-04-2011, 04:18 PM	#6
Jim Cimarolli Senior Member Join Date: Mar 2002 Location: Sulphur Springs Texas Posts: 743 Likes: 146 Liked 166 Times in 46 Posts	Re: 3 speed auto transmissions Possible how?

02-04-2011, 05:01 PM	#7
Tom Goldman VIP Member Join Date: Jan 2003 Location: Allentown,PA Posts: 2,476 Likes: 889 Liked 882 Times in 236 Posts	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 Attached Thumbnails __________________ Tom Goldman 1500 SG , 1506 STK Last edited by Tom Goldman; 02-04-2011 at 05:17 PM.

02-04-2011, 10:43 PM	#9
Chris Hill Senior Member Join Date: Jan 2002 Posts: 655 Likes: 8 Liked 244 Times in 26 Posts	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. __________________ Chris Hill https://ihmusedparts.com

02-05-2011, 12:24 PM	#10
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,136 Likes: 172 Liked 705 Times in 219 Posts	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.