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Old 02-18-2015, 02:25 PM   #1
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3.55 to 3.90

Is there that much of a difference going from 3.55 to 3.90 gears? I have a 5 speed and want more than 3.73


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Old 02-18-2015, 02:28 PM   #2
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Why not go 4.10?

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Old 02-18-2015, 02:32 PM   #3
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Is there that much of a difference going from 3.55 to 3.90 gears? I have a 5 speed and want more than 3.73


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My Mach had 3.73's in it when I bought it. I had my rearend rebuilt in 2013 on warranty and went with 3.55's. I could tell a difference between the two. Not much, but noticeable. It seemed like about 250-275RPM difference on the highway, give or take. To be honest, 3.90's are what I would want to go with if I was wanting to swap gears. Too bad Ford Racing doesn't make 3.90's. I think 3.90's would be perfect for the way our 5 speed gear ratios are.
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Old 02-18-2015, 03:55 PM   #4
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I do a lot of highway driving and 4.10s would be too much. I was thinking just getting a kit and buying the 3.90's separately


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Old 02-19-2015, 11:11 AM   #5
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What year car because the 02-04 cars had a deeper overdrive and a 4.10 in those is like a 3.73 in 01-down.

I would not recommend 3.90s anyway, stick with FORD gears not aftermarket.
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Old 02-19-2015, 11:27 AM   #6
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Motive is the most common 3.90 and they whine like a fire truck


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Old 02-19-2015, 11:28 AM   #7
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In my 01 with the shallower overdrive I still get 17mpg on the highway, that's at 2850 rpm and lots of accelerating and decelerating.


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Old 02-19-2015, 02:07 PM   #8
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The bad thing about it with 4.10's on the highway at ~2,800+ RPM's is if you have an off road exhaust, it starts getting really load. That makes for a long drive when you got that much loud for lots of miles.
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Old 02-19-2015, 02:22 PM   #9
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After my off road midpipe it drones less :p probably due to my new mufflers though

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Old 02-19-2015, 02:36 PM   #10
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The bad thing about it with 4.10's on the highway at ~2,800+ RPM's is if you have an off road exhaust, it starts getting really load. That makes for a long drive when you got that much loud for lots of miles.
Its not too bad. At 2800 rpm with my Offroad H and flowmaster 44s i can actually barely hear it, the drone spot is around 2400-2500 so its quieter in the cabin at 2800rpm.
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Old 02-19-2015, 02:41 PM   #11
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Its not too bad. At 2800 rpm with my Offroad H and flowmaster 44s i can actually barely hear it, the drone spot is around 2400-2500 so its quieter in the cabin at 2800rpm.
That's cool, sounds like it goes a little past that real loud point.
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Old 02-19-2015, 02:48 PM   #12
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That's cool, sounds like it goes a little past that real loud point.
Yea, outside is a different story. Its definitely louder outside at 2800rpm, but the drone inside is less.
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Old 02-20-2015, 08:42 AM   #13
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In my 01 with the shallower overdrive I still get 17mpg on the highway, that's at 2850 rpm and lots of accelerating and decelerating.
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lol and california is trying so hard to control emmissions and gas consumption.
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Old 02-20-2015, 09:05 AM   #14
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4.10s in a .68 overdrive (anything not 02-04) is going to be doing about 2500 rpm with the stock 25.7" tire diameter. The 02-04 cars (or if you swap in an 02-04 trans like I did in my 98) will run about 2300 with 4.10s and stock tire size.

Now... the big issue with the .62 overdrive in a 5 speed is that the fall off from 1.00 to .62 is HUGE and I found that I was always either lugging 5th or running a little too high for just cruising in 4th. IMO, this is why they went back to a .68 overdrive in 2005 and also because 27" tires will bring the RPM down. The .62 overdrive in a close ratio T-56 is great because you have a .80 5th gear in between 4th and final OD so you don't have to choose between lugging OD and revving 4th.
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Old 02-20-2015, 09:43 AM   #15
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Only the Mach 1's had the .62 5th gear in the TR3650 tranny's. The mid year 01 - 04's had .67 5th gear.

I would LOVE to swap to a T56. Aside from the first two gears, I hate the gear ratios that the TR3650 has. With the stock 3.55's I'm always running a higher RPM than I'd like to, or lugging like a mofo. It's just not great for driving. It's great on the drag strip tho!


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Old 02-20-2015, 10:08 AM   #16
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Only the Mach 1's had the .62 5th gear in the TR3650 tranny's. The mid year 01 - 04's had .67 5th gear.

I would LOVE to swap to a T56. Aside from the first two gears, I hate the gear ratios that the TR3650 has. With the stock 3.55's I'm always running a higher RPM than I'd like to, or lugging like a mofo. It's just not great for driving. It's great on the drag strip tho!


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Wrong, all 02-04 3650s had the .62 overdrive gear. This is backed up by lots of documentation available all over the internets and also personal experience getting a rebuilt GT 3650 that had the .62 in it and putting it in my 98.

There is no .67 gear either. If you read that somewhere it is a typo.
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Old 02-20-2015, 10:14 AM   #17
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3.55 to 3.90

Quote:
Originally Posted by scottydsntknow View Post
Wrong, all 02-04 3650s had the .62 overdrive gear. This is backed up by lots of documentation available all over the internets and also personal experience getting a rebuilt GT 3650 that had the .62 in it and putting it in my 98.

There is no .67 gear either. If you read that somewhere it is a typo.

You are wrong my friend. This info has been in numerous places and is not a typo. Check the Mach 1 registry.

The .62 ratio was used on the Mach's because they had 3.55 gears to keep the MPG's within the rest of the group.


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Old 02-20-2015, 10:22 AM   #18
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Straight from the service manual...

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Old 02-20-2015, 10:38 AM   #19
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I need to dig up my treme TSBs when I get home, mine say .68 and a few iv'e seen say .675 but arguing about .01 is kind of pointless. The .62 overdrive from 02-04 is very well documented though and like I said, personal life experience with those with my own car and my buddy's 04GT that had it as well.
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Old 02-20-2015, 10:49 AM   #20
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.01 isn't worth it to argue over.


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