[Z06] 3.90's Installed...
Thread Starter
Racer
Joined: Aug 2007
Posts: 444
Likes: 6
From: Richmond Texas
3.90's Installed...
Busted the differential and trans. output shaft after going to the track a few week back and while it was being repaired I decided to upgrade to 3.90's, gforce trans.output shaft and 300M left halfshaft. My car has a larger cam so I figured it would help alot with the low end "lag" alot of BIG cam cars have.
I put about 350 miles on the for a break in, although I'm not sure a diff needs it? From a 1st gear roll it gets into its powerband ALOT faster, 2nd gear is VERY strong, gotta be ready to hit 3rd quick. 4th redlines (6800rpm) at 125mph, so they are perfect for going across the traps at peak power for a cam or H/C car, I ran 11.60's before and I am thinking it will do 11.20-11.30 with these gears and the cold temps.
Ill update with ET's once I hit the track again (might be a while lol) but for anybody wondering 3.90's are PERFECT for a less than 450rwhp C5 Z06, if I had a standard T56 I would do 4.10's for sure. BTW my car is DAILY driven 60 miles, it is revving just over 2,100rpm @70mph.
I put about 350 miles on the for a break in, although I'm not sure a diff needs it? From a 1st gear roll it gets into its powerband ALOT faster, 2nd gear is VERY strong, gotta be ready to hit 3rd quick. 4th redlines (6800rpm) at 125mph, so they are perfect for going across the traps at peak power for a cam or H/C car, I ran 11.60's before and I am thinking it will do 11.20-11.30 with these gears and the cold temps.
Ill update with ET's once I hit the track again (might be a while lol) but for anybody wondering 3.90's are PERFECT for a less than 450rwhp C5 Z06, if I had a standard T56 I would do 4.10's for sure. BTW my car is DAILY driven 60 miles, it is revving just over 2,100rpm @70mph.
Drifting
Joined: Apr 2005
Posts: 1,620
Likes: 3
From: Vancouver WA
[QUOTE=sprayed1998;1572266025]Busted the differential and trans. output shaft after going to the track a few week back and while it was being repaired I decided to upgrade to 3.90's, gforce trans.output shaft and 300M left halfshaft. My car has a larger cam so I figured it would help alot with the low end "lag" alot of BIG cam cars have.
I am considering doing this to my track car. what brand of gears did you get and your source? Any whine with the new ones while driving?
I am considering doing this to my track car. what brand of gears did you get and your source? Any whine with the new ones while driving?
Instructor
Joined: May 2009
Posts: 230
Likes: 0
From: Clarkston MI
I was planning to go with a 3.90 over the winter based on some of the gear/speed calculations I've done.
4th gear is topping out at 125 though? What size tires are you running.
According to the calculator I was using the on the M12 the 3.90 should get you to 135.5 with a 295/35/18 tire. Just trying to figure out the difference, 10mph is a big one and I won't be able to run that gear if that's the case.
This is the website i was using to help decide the gear to use..
http://xse.com/leres/bin/gearratio?t...le=35&wheel=18
Keep us posted on the ET results!
4th gear is topping out at 125 though? What size tires are you running.
According to the calculator I was using the on the M12 the 3.90 should get you to 135.5 with a 295/35/18 tire. Just trying to figure out the difference, 10mph is a big one and I won't be able to run that gear if that's the case.
This is the website i was using to help decide the gear to use..
http://xse.com/leres/bin/gearratio?t...le=35&wheel=18
Keep us posted on the ET results!
Burning Brakes
Joined: Nov 2009
Posts: 773
Likes: 1
From: Okinawa
as far as gear brands...the only aftermarket gears for the c5 vette are Motives....my first set were silent...i broke them when i busted my trans output shaft..my replacement gears were noisy due to defective set of gears...got them replaced and now this set is silent again...have probably 3000 miles on my new set
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Thread Starter
Racer
Joined: Aug 2007
Posts: 444
Likes: 6
From: Richmond Texas
I may have to go back out and check my speeds @ various RPM's. But I am sure I cannot hit 135mph in 4th gear. BTW my car seems to have corrected itself as far as the speedo is concerned, I changed the settings to 3.90 in HPTuners and it threw my speedo WAAAY off. Put it back to 3.42 and it is spot on (according to the signs that display speed, hehe) The gears are motive brand and unless installed correct they WILL whine, whining is caused 100% by not being properly setup.
Le Mans Master
Joined: Dec 2007
Posts: 8,375
Likes: 97
From: Somewhere in the Mid 9's TX
I like GForce, but I just had EG do a complete 3.90 built rear end from RPM last week because of the discount on the complete rear end installed for November. I snapped mine too at HRP 4 weeks ago.
http://www.youtube.com/watch?v=ElYUTdQswqA
Love the new gears, can't wait to get back out to the track.
http://www.youtube.com/watch?v=ElYUTdQswqA
Love the new gears, can't wait to get back out to the track.
Last edited by winters97gt; Dec 1, 2009 at 02:13 AM.
