Many ask what are the gains seen from changing rear gears. Well I swapped out my 3.42 ten bolt, 3800 stall, 25.75" tire combo for a 4.10 twelve bolt/spool, 4400 stall, 26.25" tires. Race weight is the same.

60's before 1.59 best........1.62-.64 average
60's after 1.49 best........1.50-.52 average

et with comparable has dropped about .25 and mph is about the same

old best run in great air 11.43 @ 119
new best in decent air 11.29 @ 118.5 waiting on some great air for the new combo.

 

cool, i wonder if the stall or the gears helped more.

 

With all due respect, you made 4 changes at once. IMO the stall and spool had more to do with your 60' than the gears.

 

For what it's worth. Nearly stock 97 SS conv.
With.......3:42's.......3:73's

RT.........1.215_____.191
60'.........2.291_____2.175
330'.......6.313_____5.936
1/8m......9.570_____9.091
MPH.......76.01_____79.28
1000'.....12.342____11.775
1/4m......14.733____14.045
MPH.......90.48_____99.52

Only change was the gears. Same track and same weather.
The best run out of 5 each.

 

A 9mph gain sounds a little odd. That's like adding a 100shot.



Ryan

 

Only 3 changes. The spool don't mean **** when I was dead hooking with the HD Eaton posi in the ten bolt. And the tire change was in the opposite direction.

And the stall change was just to stay even. With the change from 3.42s to 4.10s my 3800 stall would have tightened up a lot. The 4400 just let stay the same. Meaning that the launch rpms with the 3.42/3800 and the 4.10/4400 is almost the same but the car pulls way harder and quicker with the 4.10s.

 

I picked up a tenth and a mph when going from 3.42 to 3.73

 

Those numbers have to represent something other than a change from 3.42's to 3.73's. Everything seems way to different.

Rich

 

I ran 2.0x 60 foots (13.64 1/4) with Bfg Drag radials and the 2.73 stock gears. Then I switched to 3.73's (plus a used torsen diff was put in) M/T Drag radials, Pacesetter longtubes and a updated tune for my headers and gears. Now I run 1.8's consistantly with a best 60 foot of 1.87 and best time is in my sig. Going from 2.73's to 3.73's is a huge jump and it feels great. I pretty much dead hooked with both sets of gears as well.

 

Just a thought - anyone consider wind speed and direction before and after those gear changes?

 

That is one thing that I don't measure?track. I do record temp, baro, and humidity for every run.

 

What are you using Al? I need something to record weather conditions. Lots of different gages out there but which in your opinion is the best bang for the buck?

 

[QUOTE=AL SS590 M6]Only 3 changes. The spool don't mean **** when I was dead hooking with the HD Eaton posi in the ten bolt.

With traction being the same, a spool over a posi is
worth .10 in 1/8 just from the less rotational weight.

Emil:93Z,383,Vortech,NOS,Strange spool,4.11,Moser9"

 

I think this is a perfect example of how real world changes, particularly at the low end of the performance scale, are not always predictable. As I said in my post there were NO changes made to the car other then the gears and 3 year of driving or 20,000m.
I am also not saying that this is in any way normal. One thing that very well may have changed was the track condition. As these runs were made 3 years apart.
My gut feeling is, that at 250rwhp and 3800lbs, this may have been the perfect performance mod. for this car.
During the first set of runs I was unable to spin the tires on the starting line and the third/forth shift was way to close to the finish.
With the gears the spin off the line was controllable and the rpm in forth though the traps was much higher.
I think on engines that have had more mods. and start at higher hp before doing gears well see less dramatic difference.

 

For now just a cheap home wall unit that I put on top of the trailer wheels in the shade.