3.76 LSD vs. Gas Mileage
congrats!
Originally Posted by bitkahuna
No, I don't think so. Your car is at higher rpms all the time while moving with the 3.76 gearing and that will consume more gas.
But you paid a bundle (I assume) for the LSD and install - worrying about a few $ on gas doesn't seem rational.
But you paid a bundle (I assume) for the LSD and install - worrying about a few $ on gas doesn't seem rational.
I'll go out on a limb and say that I disagree with this.
GSTEG, I DO think you'll see a small improvement in mileage but I can only go by theory, not fact. (I can do that in a month or so when I put in my 3.76 and compare my around town driving)
Of course, you'll have to try to *not enjoy* the extra oomph of the gearing or else your comparison will be fudged.
The reason I disagree with the quote above is simply because you have to factor in an engine's volumetric efficiency. An engine will be more efficient at 2300 or 2500rpm than it will at 1800rpm or 1500rpm. Each engine is different of course.
I can say that I've repeatedly proven this to myself in my GS400 by getting better gas mileage at 80mph than I do at 70mph. Again and again.
It'll cure that laggy feeling though, so, I think you should definitely get it if you haven't already!
Stay away from the torque converter though, I think you're really kill your around town mileage if you do the torque converter! ( I know I did!)
BA
I have 2 tank fulls under my belt with the new 3.76 LSD and my mileage has gone down just about .5 - 1 mpg. I would say I have been driving pretty much the same way I was before.
Pole Position
Joined: Jun 2007
Posts: 243
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From: GA
Just had the 3.76 LSD installed. My GS400 has gone from 2600rpm @80mph with the stock 3.26 gears to 3000rpm @80mph, just as others have reported. Lexus should have equipped the GS400 with the 3.76 from the factory and deepened the 5th gear just a bit. I wish there was a way to slightly reduce the 5th gear to get the highway RPMs down a little. The improved response really makes a difference. I used to manually hold gears in traffic to keep the rpms up, but that isn't needed anymore.
Yeah, that gearing is great! I feel you with the final drive; wish it was a little MPG friendly as well. It was a PITA for me for a while because I got the PI TC installed at the same time as the 3.76 LSD. The upgraded TC changed the shift points so that, combined with the different gearing totally made my car shift weird at first (first week or so) and I was buggin' out...thought my tranny was going to take a ***** but the ECU just needed time to re-learn. Now the car is great minus the higher RPM's. What diff fluid are you using? I am using Royal Purple Max Gear 75w90. Also, if you bought your diff new it is recommended to change the diff fluid again after the first 1000 miles.
Pole Position
Joined: Jun 2007
Posts: 243
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From: GA
Yeah, the ECU was unhappy on the ride home from the shop (idle was really low), so I disconnected the battery for a couple of hours and that seemed to allow it to start learning the new shift points. Went with Valvoline synthetic 75w90. I'll remember to change it at 1k. Maybe one of our industrious CL parts gurus can fab a deeper OD for the 5 speed auto tranny, or maybe going with the 2006 GS430 tranny would work. Not sure how the ratios compare with the GS400 5 speed auto.
To be honest I wouldn't go throught the trouble of trying to fit an '06 GS tranny in there. Even if it were possible it would cost a lot of $$$...and for that type of dough you should/could drop in the 6-speed from the Supra TT. That conversion would be a b i t c h but the performance results would be hands down by far greater than just installing the '06 GS tranny. Everyone ALWAYS remarks that a 6MT in a GS4XX would be a MONSTER! There are a couple of members working on this project as we speak!
Driver
Joined: Feb 2007
Posts: 181
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From: TX
Hey guys.. so I just came from the track yesterday, I ran my 01 430 about 6 times I averaged about 15.2 @ 94mph... So now i'm definitely thinking about getting a rear end up grade... I've been reading alot of posts from the past and I've come to the conclusion that i'm gonna try to get a 3.92 setup... does anyone know what I need to do to get this setup on my car?? What do I need and where can I get it??? Please help!!!