Rearend Change
Thread Starter
Teching In
Joined: Nov 2009
Posts: 21
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Rearend Change I'm running a 9" Ford rearend behine an LS1 and 4l60E. I'm changing from a 3:70 ratio to a 3:43. I have Dakota Digital gauges so I can set the speedo but will I need to have the computer retuned? Thanks for any help, Neil
Staging Lane
Joined: Jan 2009
Posts: 59
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From: Bella Vista, AR
Shift Points You may not be satisfied with your shift points verses throttle position unless you did not change them when you put in the lower gears in the first place. The PCM has tables that tell the transmission what speed to shift from each gear to the next. Most LS1 FBody cars with automatics came with 3:23 gears and if your shift points were revised when the 3.73 gears were installed you will find you car shifting very quickly (lower speeds than optimal). If only the Dakota was using to revise the speedo when installing the lower gear set, then your settings will be closer to correct when you go to the 3:43 (which was stock for FBody with manual transmission). If you are wanting performance you should stick with the 3:73 gear set, and if you are looking for gas mileage you should go back to the 3:23 gear set this engine and transmission combination GM decided upon.
I know you can use the PCM to tune shift points if your setup allows that. There are settings in the PCM that look like they are for speedometer setting, but that's not what they are for, if you try to use them that way it screws things up.
