Gears question
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Pro
Joined: May 2006
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From: Maryland Heights MO
Gears question
I have a 2000 coupe. I've done heads/cam, intake and exhaust mods. I have about 400 RWHP on the dyno. I have heard a lot that upgrading my gears to 3:73 or 4:10s will make a huge difference and increase torque. Does anybody have advice on this? Actual dyno results? estimated cost of replacing gears? What does replacing gears affect....do I need another tune?
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From: Manassas Park VA
St. Jude Donor '07-'08,-'13-'14, '16-'17
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Drifting
Joined: Sep 2007
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You will lose the same percentage the old gear ratio is vs the new ratio. For example, if you went from a 3.42 to a 3.90 (12.3% difference from 3.90 to 3.42) you will lose 12.3% of your speed at any given rpm. So first gear will go from 52.31mph to 45.87mph @ 6000prm.
Last edited by RespondsWithGif; Jan 12, 2009 at 02:54 PM.
Pro
Joined: Dec 2007
Posts: 663
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From: Show me lower taxes Missouri
I have a 2000 coupe. I've done heads/cam, intake and exhaust mods. I have about 400 RWHP on the dyno. I have heard a lot that upgrading my gears to 3:73 or 4:10s will make a huge difference and increase torque. Does anybody have advice on this? Actual dyno results? estimated cost of replacing gears? What does replacing gears affect....do I need another tune?
Check my profile out and you will see that we have very similar set-ups. I went with the 3:73's with a 3600 stall converter (from 2:73's). Best mod for the buck out there.
As a matter of fact I work off of 270 and Olive avenue. Maybe if we could get some decent weather I could take you for a ride so you could get a feel for it.
Pro
Joined: Dec 2007
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From: Show me lower taxes Missouri
I stated I went to the 3:73's but if I had M6 I would go with the 3:90's. For me it's not about top end it's how fast I can get there in a shorter amount of time. Even with the 2:73's I never had intentions of going 175 mph.
Le Mans Master
Joined: Aug 2004
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From: West Michigan crew Mich
CI 7-8-9 Veteran
St. Jude Donor '07-'08 & '12
I love my 3.73s Its like getting a new car with a whole lot more power The only downside is rear tire wear
Oh and I have a 3200 stall converter also
The only downside is rear tire wear Oh and I have a 3200 stall converter also
Burning Brakes
Joined: Sep 2008
Posts: 1,151
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From: Mechanicsburg PA
As a DIY project the easiest way to change the gears is to buy a whole new differential and install it. New or rebuilt diffs from vendors are pretty expensive - > $1K. But if you keep your eyes open you can sometimes see used ones for sale. Its very easy to find 3:42 takeouts for sale in the $5-700 range, hard for 3:73 and up, although I have seen a few in the last couple months. I don't know what a shop would charge to install, quite a bit I would think, you have to drop the rear cradle so its more than just a little work.
Melting Slicks
Joined: Mar 2005
Posts: 2,364
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From: Rugby North Dakota
you need to do gears AND a stall converter - go w/ 3.73 gears and a 3200 or 3600 stall converter - I didn't look to see what your mods are, but check my sig for my mods - I'm running 3.73's and a 3200 stall - LOVE EM!!!!!!!!
Race Director
Joined: Mar 2001
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From: Whippany NJ
CI 6-7-8-9 Veteran
St. Jude Donor '08-'09
NCM Sinkhole Donor
I still get 28-30 mpg on highway
Last edited by Ikester; Jan 12, 2009 at 07:46 PM.
Safety Car
Joined: Oct 2000
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From: Monticello MN
Go with the 3.73s. And, as suggested, put a stall in at the same time. Yank SS3200 here and I love it. See my sig for other mods (H/C/Intake, etc., etc). I would sugest you may want to just buy a 3.73 differential. I tried to have mine rebuilt and had whining issues. They tried new gears again, in the same carrier, and, for whatever reason, weren't able to shim it up to proper specs. Ended up buying a new carrier which they were able to shim up. Wasn't fun. I split the cost with my tuner and the rebuilder. He had never had a 3.73 gear installation failure before. 
Ed
Ed