Which Gears?
Thread Starter
Joined: Jun 2006
Posts: 2
From:
Which Gears?
So i have a 99 Ford Mustang 3.8L, automatic 4R70W Tranny and i want to replace the stock 3.27 rear end gears. Im not sure if i want to go with the 3.73, 4.10, or ive heard of a 3.90. I run about 2,000 Rpm at 65 MPH now. I want more bottom end speed but i dont want to sacrifice gas mileage too much and i just dont know which gears to choose or what all i will need to buy. I know ill need the gears of course the posi trac assembly and new bearings etc. I dont know what else ill need or what brands to buy. Someone please help me, im stuck between a rock and a hard place! Thanks 99 PONY
6th Gear Member
Joined: May 2005
Posts: 7,445
From:
RE: Which Gears?
ORIGINAL: 99 PONY
So i have a 99 Ford Mustang 3.8L, automatic 4R70W Tranny and i want to replace the stock 3.27 rear end gears. Im not sure if i want to go with the 3.73, 4.10, or ive heard of a 3.90. I run about 2,000 Rpm at 65 MPH now. I want more bottom end speed but i dont want to sacrifice gas mileage too much and i just dont know which gears to choose or what all i will need to buy. I know ill need the gears of course the posi trac assembly and new bearings etc. I dont know what else ill need or what brands to buy. Someone please help me, im stuck between a rock and a hard place! Thanks 99 PONY
So i have a 99 Ford Mustang 3.8L, automatic 4R70W Tranny and i want to replace the stock 3.27 rear end gears. Im not sure if i want to go with the 3.73, 4.10, or ive heard of a 3.90. I run about 2,000 Rpm at 65 MPH now. I want more bottom end speed but i dont want to sacrifice gas mileage too much and i just dont know which gears to choose or what all i will need to buy. I know ill need the gears of course the posi trac assembly and new bearings etc. I dont know what else ill need or what brands to buy. Someone please help me, im stuck between a rock and a hard place! Thanks 99 PONY
Seriously, I had the 4.10's, and before someone comes in with the typical myths, it DID NOT hurt the top speed, I drove all over the Pacific Northwest, and got 24 MPG, it did NOT cause my engine to run at 7000 RPM's at 60 mph..matter of fact, it ran at aboot 3000RPM at 75. The one thing it did do, was the permagrin factor.
The Godfather
Joined: Sep 2005
Posts: 15,480
From: Temple, Texas
RE: Which Gears?
Yea, on 99-04 I say go with 4.10s, because 3.73s, while noticible, won't be as much as a help as 4.10s. Now yes, you will burn more gas, but the average seems to be about 1 more mpg over 3.73 which hits your stock mpg by about 1 mpg. You'll need a tuner to reset the speedometer, I'm selling mine for $275, and you'll need the bearing kit for the install, and some good ole royal purple rear end oil.
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