I know that almost everyone in drag racing is running a ITR or GSR transmission. The higher final drive gears (4.7 and 4.4) are great for engines that dont produce a lot of torque. Kinda like pedaling a bike up a steep hill while using the biggest gear in the back. The bad thing about this is the motor has to turn over more to get the same distance than using a smaller gear in the first place. Since the LS transmission has a 4.266 final drive, tha means the engine wont have to turn over as many times to get the same distance as a GSR or ITR transmission (while keeping the same diameter tire).

To my question>>

If i'm going to be running a stroker motor (95mm crank stroke) which will produce much more low end torque than the stock 89mm stroke, should i get the LS tranny since my peak RPM will be lower (prob around 9000 rpm)?

I'm aiming for a 9 second car that could run the in SFWD class. That means i'll be doing about 150 mph at the end of the track. With the LS tranny, 9000 rpm and 24.5 inch slicks, i'll be doing about 160mph in 4th. That means i wont have to shift to 5th. Isn't that a good thing?

 

i think i would do a gsr tranny and taller slicks?

 

If you're going to have an engine with enough power to propel you into the 9s... larger slicks may be needed. Never driven one, but I'm just thinking it's safe to assume some traction loss.

 

i went 10.0@141 with an ls tranny on 24.5's with my rev limiter in the ballpark of 9k rpm if that helps any

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Used2beAb16 &raquo;</TD></TR><TR><TD CLASS="quote">i think i would do a gsr tranny and taller slicks?</TD></TR></TABLE>

....exactly

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Turbo-charged &raquo;</TD></TR><TR><TD CLASS="quote">i went 10.0@141 with an ls tranny on 24.5's with my rev limiter in the ballpark of 9k rpm if that helps any</TD></TR></TABLE>

What kinda motor did you have pushing that (bore and stroke) and do you wish you went to the GSR in the hindsight?

Here's what i'm thinking. If i use the LS tranny, i'll stay in the powerband longer on each gear because of the longer LS gear ratio's. Here's the speed @ each gear chart at Fatboy Raceworks page. The LS tranny is in GREEN and the GSR is in RED.
http://www.fatboyraceworks.com...are=1

The LS and GSR transmissions are fairly similar, so i dont know why people hate on the LS so much. This chart is the:

Crank Revolutions per One Tire Revolution

Gear LS GSR Difference in Revolutions
1st 13.77 14.21 .44
2nd 8.11 8.36 .25
3rd 5.41 5.98 .57
4th 4.13 4.54 .42

As you can see the GSR transmission lets the engine revolve a little more per tire revolution, thus more torque, thus each gear tops out faster. Is this a good thing or bad thing when a stroked engine already has plenty of torque? I dont know. I'm just rambling. Throw me some informed input. Thanks.

 

if you rev to 9500 you can do 152 in 4th. i would say take it a little higher and run the GSR, LS trannys are crap.

 

GSR would be better, helps you get through the gears quicker than a ls tranny

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Turbo-charged &raquo;</TD></TR><TR><TD CLASS="quote">i went 10.0@141 with an ls tranny on 24.5's with my rev limiter in the ballpark of 9k rpm if that helps any</TD></TR></TABLE>

We have gone 9.66 @ 146.7 on an ls tranny on 24.5's with my rev at 9K as well.

 

i now have a gsr trans in the car..i picked up a couple mph but not really any ET...however i had some other stuff going on with the car so thats not a real fair comparison....

however...when my car was my daily driver i went to the track every weekend...i went 11.50-11.60 each and every pass down the track with a b16 trans. i put an ls trans in the car and went 11.40 with 2 less mph.

i'd go with a gsr trans.....but people make too much of a big deal about the LS trans i think. its not ideal, but people make it seem like its going to take a second off your ET

 

thanks for the replies. I'll really consider using a GSR instead of the LS. I'll just have to think about it for a while.

 

LS trannies have that tall gearing and break easliy under high hp applications.