JBrady

I posted this in the SC forum but cannot link to it yet due to tech diff on the new board. Anyway, I want to change gearing from the stock 3.27s to 3.76. Will this cause any driveability or ECU issues on a 96 model? Where/how to get speed properly re-calibrated?

Mean Gene

JB - Not sure about the SC but the GS speedometer reads off the tranny. I changed to the 3.76 LSD from RMM & haven't had any problems with the speedometer or ABS system. Haven't hit the rev limiter yet but have heard that some guys experienced that. Mo's new tranny ECU ( when released ) will solve that problem by allowing quicker shifts & custom programming for any other mods U've made.

JBrady

Mean Gene, If the car calculates MPH by counting RPMs at the tranny then changing the rear gear or tire diameter will absolutely change the speedo reading. If the cars measure axle RPM then the gear change would not affect it but a tire diameter change would. Are you sure your speedo is correct?

Mean Gene

JB - My humble apologies to ya! The GS has front & rear speed sensors at the WHEELS - DUH!! Once again I yield to your superior engineering knowledge! BTW - I had my speed checked by running side by side with a State Trooper buddies' cruiser & also his radar so I knew the speedo was right - just I was wrong in this post. Also didn't get a chance to drag thru the quarter this weekend as it rained but will attempt it again ASAP. Man, I remember the days for adding gear reducers whenever I changed the gears in my Camaro. This is a WHOLE lot better & accurate!

LexusRules

front and rear? then why when you do a burnout does it tell you how fast your wheels are spinning?

JBrady

MG, no appologies required. Just don't jump my *** when (not if) I fubar.

So apparently Toyota uses the ABS sensors to guage vehicle speed. Maybe just the rears? I hope that my 96 LS400 has the same config. Of course larger or smaller diameter tires would still be a problem.

Mean Gene

Sasha - Best guess is that the speedo registers off the rear sensors & your wheels are turning doing a burnout ( get that TC, man!! ). The front sensors are probably, as JB says, readings for the ABS. I'm guessing here but it makes sense. Also, the sensors send feedback to the VSC so all the wheels should be monitored, right? Where's LexTech when U need him!!?

LexusRules

forgot about VSC, its always off! haha no its not just kidding, but when i get the car it will be! eww thats the worst feeling having your foot to the floor and hearing tick tick tick then have no power!