Rotary Drag Racing The place to post your racing stories and info

Transmission gear ratios.

Thread Tools
 
Search this Thread
 
Old 04-16-06, 04:47 PM
  #1  
7s before paint!!!

Thread Starter
iTrader: (2)
 
13B-RX3's Avatar
 
Join Date: Aug 2003
Location: Philly/Texas
Posts: 3,814
Likes: 0
Received 0 Likes on 0 Posts
Transmission gear ratios.

When i went through my Doug Nash 4+1 i documented my gear ratios. After talking with one of my PR friends he told me my ratios needed to be changed. The transmission ratios that are in it right now are 1st-2.40 2nd-2.22 3rd-2.07 4th-1.33 5th-1.00. What he recommended is 1st-3.05 2nd-2.07 3rd-1.65 4th-1.33 5th-1.00. I am running a 28" tire with a 4.89 gear. Does this sound right before i order $800 worth of gears or will it not make a lot of difference? Thanks for any input.

Allen
Old 04-17-06, 10:20 PM
  #2  
7s before paint!!!

Thread Starter
iTrader: (2)
 
13B-RX3's Avatar
 
Join Date: Aug 2003
Location: Philly/Texas
Posts: 3,814
Likes: 0
Received 0 Likes on 0 Posts
Any advise guys?
Old 04-17-06, 10:34 PM
  #3  
Newb

 
Swolbynos's Avatar
 
Join Date: Jun 2003
Location: Yukon, OK
Posts: 928
Received 0 Likes on 0 Posts
i dont think too many people change their gearing because it is so expensive
Old 04-17-06, 10:55 PM
  #4  
7s before paint!!!

Thread Starter
iTrader: (2)
 
13B-RX3's Avatar
 
Join Date: Aug 2003
Location: Philly/Texas
Posts: 3,814
Likes: 0
Received 0 Likes on 0 Posts
Yeah, i guess this is kinda a weird question that very few would have an opinion on. The stock ratios on a 3rd gen have a lot taller first gear with a large jump between first and second. 1st-3.48 2nd-2.015. I think that large a jump would be undesirable for a full drag car. Does first need to be that low to get a good launch/60ft in a light car? Or would the 2.40 actually help spool the turbo by lugging the motor a little?

Allen
Old 04-23-06, 11:45 PM
  #5  
Full Member

 
Michael_Rudy's Avatar
 
Join Date: Jan 2005
Location: Kelowna, B.C. ,Canada
Posts: 218
Likes: 0
Received 0 Likes on 0 Posts
I would leave the gears you have in, less gap means less rpm loss and keeps you in the power band better
Old 04-24-06, 04:29 AM
  #6  
7s before paint!!!

Thread Starter
iTrader: (2)
 
13B-RX3's Avatar
 
Join Date: Aug 2003
Location: Philly/Texas
Posts: 3,814
Likes: 0
Received 0 Likes on 0 Posts
Thanks for the advise. I am really worried about getting the car off the line. It is a light car but i am worried about the 2.40 first with my 11 lb chromolly flywheel and my Tilton 7.25 clutch. I'm think it would really hurt my 60' times. I am also concerned that the other gear setup will hurt my ET. I don't have enough experience with rotaries to know witch way to go.

Thanks Again
Allen
Old 04-24-06, 01:36 PM
  #7  
Full Member

 
Michael_Rudy's Avatar
 
Join Date: Jan 2005
Location: Kelowna, B.C. ,Canada
Posts: 218
Likes: 0
Received 0 Likes on 0 Posts
I think it would be best so sacrifice a little on the 60ft, for the gain you will get with the closer gears. Excpecially with that monster turbo. Also, there are guys running power glides, C4's, and TH350's with rotarys, they do get the torque multiplication, which helps since there first gear is similar to yours, but you will be able to launch at a much higher rpm, so i think it will be a fair trade off.
Old 04-24-06, 08:49 PM
  #8  
7s before paint!!!

Thread Starter
iTrader: (2)
 
13B-RX3's Avatar
 
Join Date: Aug 2003
Location: Philly/Texas
Posts: 3,814
Likes: 0
Received 0 Likes on 0 Posts
Found a site that does transmission comparisons. With the gear set that is in it now it will go over 60 MPH in first gear. Is it just me or is that way too high?

http://www.fatboyraceworks.com/gears...raph&Compare=1
Old 04-25-06, 12:21 AM
  #9  
Full Member

 
Michael_Rudy's Avatar
 
Join Date: Jan 2005
Location: Kelowna, B.C. ,Canada
Posts: 218
Likes: 0
Received 0 Likes on 0 Posts
Hmm..... i bet they would run similar 1/4 times, just with differnt 60ft's and trap speeds.
Old 04-26-06, 03:12 PM
  #10  
Senior Member

 
rotaryengineering's Avatar
 
Join Date: Feb 2003
Location: SoCal
Posts: 331
Received 0 Likes on 0 Posts
Run what you have in the Trans now

I would recommend running what you have in the Trans now. Once you get to the track and start playing with tuning and boost you'll be surprised at what turning up the boost will do.
Old 04-30-06, 08:12 PM
  #11  
7s before paint!!!

Thread Starter
iTrader: (2)
 
13B-RX3's Avatar
 
Join Date: Aug 2003
Location: Philly/Texas
Posts: 3,814
Likes: 0
Received 0 Likes on 0 Posts
Well i finally decided i am going to swap the gears. I started thinking about it and in the first 3 gears there is only a speed difference of 9.62 MPH. I figure even if it didn't bog off the line there was no way i could shift it that fast.



Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Linda_Lovelace
General Rotary Tech Support
0
09-18-15 10:04 PM



Quick Reply: Transmission gear ratios.



All times are GMT -5. The time now is 02:01 AM.