Mileage *increase* with gear swap!!!

[Riles]

Hey guys, I just wanted to let everybody who is considering getting 3.73's know that your mileage does not suffer!

I just drove home from notre dame (indiana) to new jersey, and I didnt have to fill up 4 times like usual (one when i left, and three stops along the way, usually making it home with 3/4's tank)

I actually got 23 MPG! I cruised at 80 the whole time, which puts the RPM's around 3000.

I was surprised too.

I used to see like 19 MPG, but it actually went up!

I did use seafoam in my engine prior to leaving (like a week before) and I dont know if this helped at all.

[mjparme]

What did you have before the 3.73's? I have 3.08 gears and I get 30 mpg on the Interstate. This is with SLP CAI, Whisper Lid, and K & N. Prior to those mods I got 28 mpg. I have a 1999 3.8L.

I am considering getting 3.42 gears. Please don't tell me my mileage is going to drop that drastically? I expect some drop but hopefully not more than 1-2 mpg. I use my car as a daily driver, otherwise I wouldn't care.

[Bliggida]

No, it will never drop "Drastically" The reason why is that every 4th generation F-body came with an overdrive gear (or two!)

Because you have an overdrive gear you can run any gear you want. Even with 4.11's you won't see much loss (compared to the power gain) by running them.

If you go up two gear sizes you should see a performance gain. So 3.08 to 3.42 would be a nice gain. But being that there were 3.42 optioned Y87 cars - and their mileage isn't any different than what yours is - neither will yours be. It will be negligable - the mileage per gallon loss.

Stop worrying, start installing.

By the way, for all that don't know. Installing 4.11's on an M6 car, means you are still going to be cruising 70 MPH BELOW 2000 RPM!!!

[ May 11, 2003: Message edited by: Bliggida ]</p>

[dstrbd1]

i've got 4.10's and can run 26mpg on the highway, 21 in city/rush hour traffic.

[Tri-Flo 99]

ok heres my take on it (went from 3.08 to 3.42 PROGRAMMED0
in town, better bc overdrive hits at 40 or so now instead of 45 or 48 (maybe +1.5 mpg)
hiway- well its turning exactly 10% more, i can get 29 or so at 75 now, vs 32 before

well worth it for the huge perf. increase- total cost (gears, lsd, computer, install)- just 400

[Camarorulz]

I don't really keep track of it that much, but my city gas mileage is ~18-21 mpg, and I drive quickly (not hard, just a little quick) and this is the mileage I got with 3.08s. BTW, 23 mpg is not impressive at all on the highway for a 3.8. Maybe your numbers are off?

[ May 11, 2003: Message edited by: Camarorulz ]</p>

[Justin Kirkham]

Wow you guys have bad mileage. I see 24 city, 32 highway... [img]tongue.gif[/img]

-Justin

[02PewterBird]

<blockquote>quote:</font><hr>Originally posted by Bliggida:
If you go up two gear sizes you should see a performance gain. So 3.08 to 3.42 would be a nice gain. But being that there were 3.42 optioned Y87 cars - and their mileage isn't any different than what yours is - neither will yours be. It will be negligable - the mileage per gallon loss.
<hr></blockquote>

It's probably a small difference, but they might be using the rating for one gear option as the rating for the other. We have an 02 Trailblazer with 3.42 gears, and 3.73s and 4.10s were optional. Chevy uses the EPA ratings for the 3.42s for every Trailblazer, even if they have 4.10s. You might see an improvement still. It's been a while since I've looked, but people were saying that they were getting better mileage with 3.73s than with 3.42s. The gears were no cost options at the time, but we just took what the dealer had.

[PewterBird]

Now I have been to a few different places around the united states, and the term "city" is kinda loose, considering that some places are just a little more conjested than other. I have 3.42s and I drive "city" and I get about 19.5 mpg. But my definintion of city here is where I drive stop and go for 10 miles everday for never getting above 40 mph for about 15 minutes each way, then I take a shorttrip on the freeway for 5 miles at about 65, then back to another low mphstop and go drive for anothe 5 -10 minutes. Isn't LA fun.
And for contrast. If I lived in Rapid City, SD, it just doesn't compare as "city" driving.

The whole point is, to take in the idea of what "city" you are driving in, when it comes to milage.

02PewterBird, you don't go to CSULB, do you? cause there is a new pewter bird there, so now I am not the only one anymore at school, Hey its a long shot, what the ehh?

[ May 12, 2003: Message edited by: PewterBird ]</p>

[Riles]

Lol, I know that I have bad mileage- I wasnt trying to brag about good mileage, I wrote this post to let people who are afraid of bad mpg with gears know that it's not to true at all.

[mjparme]

<blockquote>quote:</font><hr> well worth it for the huge perf. increase- total cost (gears, lsd, computer, install)- just 400<hr></blockquote>

Where did you get the gears and lsd? And where did you get your computer reprogrammed? I think I found the gears and lsd at slponline.com but haven't figured out if those are the only parts I need. The Zexel Torsen I found at SLP costs only $99 but is doesn't specifically say it is a limited slip.

[Tri-Flo 99]

gears from ebay (80 from a y87 20k car)
computer off a board member (80, 2000 pcm so i cna use HPP3)
LSD- (slp 100)
install - local camaro club buddy (125)
misc stuff (crush shims, gaskets...30)

[Riles]

I think I drive way to hard- it seems like everybody gets around 20 mpg in the city.

I usually only get about 12 mpg in the city. I have to fill up alot and I dont drive very far. But my god, I love flooring it!

[Bliggida]

I get 25+ in the city. But yes, if I decide to GT3 the car around traffic. I'll get about 10 MPG.

[MegaHertz]

I'm just curious if you got the computer reprogrammed after, if not your milage readings are off.

Your odo will read more miles than you actully went i believe.