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bugbyte
Dodge Dakota
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8/07/2007
03:49:23

Subject: 3.7L axle ratios
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Hey guys! I want a little more oomph off the line with my 3.7L 04 Dakota. Since there arenít any engine mods worth doing out there for this engine Iím thinking about new axle gears. I have the 3.55 I am trying to decide between the 3.90 and the 4.10. What does everyone think? This is for a 2wd with a 4spd auto. I do mostly city driving with it, occasionally take it out on the interstate but I rarely cruise over 65 MPH. Iím not really concerned about gas mileage since it sucks anyway.

Thanks for the input.




dakota49
Dodge Dakota
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8/09/2007
22:58:47

RE: 3.7L axle ratios
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Hey Bugbyte, if all, or most of what you do is drive around town I would go for the 4.10, if you can find them for your truck. With the over drive even at 65 your rpm wouldn't be too high. It COULD even help get better gas mileage around town, easier for the engine to pull the load.
I have an 88 3.9 5 speed 4X4, with 16000 miles since I remaned the engine and I am getting right at 20 MPG, I do both city and highway. There are some guys on here with the newer trucks that are doing a lot better than me as well.
Good Luck!
Dakota49 88 3.9 5 speed 4X4



J and J Auto
GenII
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8/09/2007
23:17:18

RE: 3.7L axle ratios
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Hughesengines.com

They are doing throttle bodies for the 3.7 around
a 15hp gain there

I agree if you drive a lot in town and do the
ocansional free way blast 4.10

Even with the 4.10 in o/d lockup the rpm will only
be around 400 rpm higher

3.55 around 1800 60 mph
3.91 around 2000 60 mph
4.10 around 2200 60 mph

Not a real drastic change if you figure it out the
3.55 with a .69 o/d its around a 2.76 final ratio

Larry
J&J Auto

bugbyte
Dodge Dakota
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8/11/2007
02:32:17

RE: 3.7L axle ratios
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Thanks for the suggestions guys. Looks like Iíll give the 4.10 a try. I worked out a spreadsheet to compute the engine RPMs at different speeds. The 4.10 should be great, unless I decide to tow a heavy load down the freeway and need to turn the overdrive off. Since I have nothing to tow, the 4.10 should be great. About 99% of my driving is around town and under 60 MPH. This fall I am having a local shop put in a limited slip diff, so Iíll get the new axle gears at the same time.

Larry, thanks for the tip on the throttle body. I was going to try one of the old style 4.7l throttle bodies but this sounds better. I am glad someone finally got around to making some performance parts for the 3.7l. I hope to see more, because it seems like the performance tuners have largely ignored the 3.7l. Would you mind linking the page with the 3.7l TB on it? I searched the site and could not find it.

Thanks again for the help guys.




Shoe
GenIII
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8/11/2007
03:10:40

RE: 3.7L axle ratios
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If you want cams, superchargers and what not try out KRCperformance.com. Give them a call, they do great work.

Finally... a V8. '01 Dodge Dakota RC, 4.7, 5-speed, 3.92 LSD. = R/T Killer.
well at least a stock one

Gears
Dodge Dakota
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8/11/2007
20:57:40

RE: 3.7L axle ratios
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Bugbyte,
www.theFastman.com has the TB your looking for.
..........Gears



bugbyte
Dodge Dakota
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8/12/2007
06:39:29

RE: 3.7L axle ratios
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Thanks Gears,

Fastman's TBs for the 3.7 seem to be reasonably priced. I'm going to try the 4.7l TB first since I already have it. It it does not perform I'll send him my 3.7 core for a port and polish



bugbyte
Dodge Dakota
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11/13/2007
00:13:23

RE: 3.7L axle ratios
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I finally had the LSD and 4.10 diff put in and they work great. The 3.7l seems to prefer running at the slightly higher RPMs. I'm still getting the same 15.5 mpg around town. I am getting 20 mpg on the freeway with the 4 speed auto, 4.10 gears doing about 65 to 70 MPH. I recommend the 4.10 for the 3.7l with the 4 speed auto.

By the way, I emailed Hughesengines.com and they no longer make a throttle body for the 3.7l.....looks like the Fastman is the only one



dakota49
Dodge Dakota
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11/13/2007
21:02:20

RE: 3.7L axle ratios
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bugbite, sounds like you are pretty happy with the gears.
I like to good news.
Good Luck
Dakota49
1988 3.9 4X4 5speed



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