Gear swap
Thread Starter
Joined: Dec 2009
Posts: 16
From: California
Gear swap
I am putting a maverick 8 inch with 3.00 gears into my 66 mustang and want to get a lower gear ratio like a 3.50 or a 3:73 and am wondering if it would be cheaper to buy a new third member or just buy the gears and have them changed out. Also if anyone knows where to get cheap 8 inch third members or cheap gears and a swap. Thanks
5th Gear Member
Joined: Dec 2008
Posts: 4,462
From: Texas
I have seen 8 inch third members with better gears and traction lock that were rebuilt on ebay.
If you don't have an OD trans, don't go over 3.50 gears. Personally, I wouldn't go over 3.20 with a non OD setup.
If you don't have an OD trans, don't go over 3.50 gears. Personally, I wouldn't go over 3.20 with a non OD setup.
6th Gear Member
Joined: Dec 2005
Posts: 5,212
From: Hills of California
I agree without an OD unless you're drag racing and never drive it on the freeway anything over 3:50 wont be much fun.
I recommend keeping the 3:00s as the cost required to purchase the new gears and have them installed is not worth the half turn.
Its only worth it if you can install them yourself so the total price is about 160ish for the gears...then its worth it in my book.
at 75 mph its a 500 rpm difference between 3.00s and 3.50s so 3000 vs 3500
-Gun
I recommend keeping the 3:00s as the cost required to purchase the new gears and have them installed is not worth the half turn.
Its only worth it if you can install them yourself so the total price is about 160ish for the gears...then its worth it in my book.
at 75 mph its a 500 rpm difference between 3.00s and 3.50s so 3000 vs 3500
-Gun
Last edited by Gun Jam; Dec 16, 2009 at 01:34 PM.
3rd Gear Member
Joined: Aug 2009
Posts: 723
From: Washington
I am running a lower gear planetary in my transmission and 3.25's in the rear on my turbo car. That way I have the lower first gear to get the turbos to spool faster and get away from a dead stop quicker but still have the ability to get a higher topend speed with the higher rearend gear ratio. Just food for thought.
Thread Starter
Joined: Dec 2009
Posts: 16
From: California
Ya i have an AOD in it as well so with the AOD does anyone have a suggesstion for running gears that will give me a little more off the line than my 3.00. I was thinking of running 3.73 because my stang is gonna be more of a cruiser than daily driver
6th Gear Member
Joined: Dec 2005
Posts: 5,212
From: Hills of California
So forth is .66
thats good news for you.
Depending on how much freeway driving you do you could run 3.80s no problem or 4.11s
3.80 would give you the following 2500 RPM at 75 OR 3100 rpm at 90
The 3.80 would probably give you the very best fuel economy and jump off the line. Fuel economy would either remain unchanged or be slightly better than what you are getting now
4.11s are also a very doable gear now as well 2800 rpm will get you 75 and 3300 rpm will get you 90 mph. The 4.11s would give you a bit more kick off the line slightly noticeable I would think when compared to the 3.80s and I would think fuel milage would now begin to suffer but probably not a very noticeable amount over the 3.80s.
If you place off the line acceleration a higher priority over over fuel mileage get the 4.11s
If you are worried that you might someday take it on long trips or desire better fuel mileage get the 3.80s
I daily drive my mustang with 3.80s I have a .63 OD vs your .66 OD so the results are very similar. I can say Im very happy with the 3.80s and glad I didn't get 3.55s If I had got the 4.11s I think I would have been happy with them as well... SO really your only decision now is 3.80s vs 4.11s don't bother going through the trouble of a gear swap for anything less than 3.80s
One warning: The 3.80s or 4.11s will greatly increase drive shaft RPM this means that if your DS is not perfectly balanced, pinion angle is off a bit, U-joints are worn, Slip bushing in the tail shaft of the trans is worn you are going to be having serious vibration issues. The DS its self will be exceeding half critical speed and approaching critical speed (read grenade speed) If after the gear swap the DS gives you any vibration issues I wouldn't bother messing with it but rather replace it with a 3" aluminum DS from Denny's drive line or from street or track. With 4.11s DS rpm will be 5000 RPM at 90mph vs your current setup of 3600 rpm at 90.
If its running great now with no issues I dont think you'll have any problems with either 3.80s or 4.11s
-Gun
P.S for reference right now you are turning 2000 rpm at 75 (which I consider bogged down) and 2400 rpm at 90
*** all rpm vs speed measurements assume you have a 25" tall tire in the rear.***
thats good news for you.
Depending on how much freeway driving you do you could run 3.80s no problem or 4.11s
3.80 would give you the following 2500 RPM at 75 OR 3100 rpm at 90
The 3.80 would probably give you the very best fuel economy and jump off the line. Fuel economy would either remain unchanged or be slightly better than what you are getting now
4.11s are also a very doable gear now as well 2800 rpm will get you 75 and 3300 rpm will get you 90 mph. The 4.11s would give you a bit more kick off the line slightly noticeable I would think when compared to the 3.80s and I would think fuel milage would now begin to suffer but probably not a very noticeable amount over the 3.80s.
If you place off the line acceleration a higher priority over over fuel mileage get the 4.11s
If you are worried that you might someday take it on long trips or desire better fuel mileage get the 3.80s
I daily drive my mustang with 3.80s I have a .63 OD vs your .66 OD so the results are very similar. I can say Im very happy with the 3.80s and glad I didn't get 3.55s If I had got the 4.11s I think I would have been happy with them as well... SO really your only decision now is 3.80s vs 4.11s don't bother going through the trouble of a gear swap for anything less than 3.80s
One warning: The 3.80s or 4.11s will greatly increase drive shaft RPM this means that if your DS is not perfectly balanced, pinion angle is off a bit, U-joints are worn, Slip bushing in the tail shaft of the trans is worn you are going to be having serious vibration issues. The DS its self will be exceeding half critical speed and approaching critical speed (read grenade speed) If after the gear swap the DS gives you any vibration issues I wouldn't bother messing with it but rather replace it with a 3" aluminum DS from Denny's drive line or from street or track. With 4.11s DS rpm will be 5000 RPM at 90mph vs your current setup of 3600 rpm at 90.
If its running great now with no issues I dont think you'll have any problems with either 3.80s or 4.11s
-Gun
P.S for reference right now you are turning 2000 rpm at 75 (which I consider bogged down) and 2400 rpm at 90
*** all rpm vs speed measurements assume you have a 25" tall tire in the rear.***
Last edited by Gun Jam; Dec 17, 2009 at 01:07 PM.
1st Gear Member
Joined: May 2006
Posts: 137
I just bought a center with LSD and 3.00 gears but want to change it to 3,55 to give my car a little more punch. I have a tricked up C4. I think that would be the peak I could change my gears to. Curious if anyone has done the same and what the results where