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Advice/discussion needed: DTTs. re-gear also?


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So I'm making this the year I sh!t and get off the pot with this. I'm installing DTTs front and ...

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Old 01-07-2018, 10:44 PM   #1 (permalink)
 
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Default Advice/discussion needed: DTTs. re-gear also?

So I'm making this the year I sh!t and get off the pot with this. I'm installing DTTs front and rear. What I need to decide is, do I re-gear or not. Being it's a v6 stick drive train I have the 3.55 gears from the factory. The biggest issue is, I have to decide whether to go with 3.73s or 4.10s, since they use the same DTT part number, and the 3.55's do not. I'm worried about effecting the fuel economy (which has a long term rating of 18.278mpg over 2,580 days and 41,630.40 miles... I did say long term ) but i'm also envious of people getting 20s and better consistently.

I'm currently running MOABs with 245/70R16's as listed in my sig, and i've considered next go-around going with 235/75.
Full 4X Guard armor is planned and the backbone plus winch is getting integrated into the front.

As most of you know I plow and I tow a car trailer occasionally, so factor that all into the equation.

So given all that is and all that is planned, what say the intelligentsia about what would make the most sense in terms of gears.
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Old 01-08-2018, 04:46 AM   #2 (permalink)
 
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Originally Posted by sota View Post
So I'm making this the year I sh!t and get off the pot with this. I'm installing DTTs front and rear. What I need to decide is, do I re-gear or not. Being it's a v6 stick drive train I have the 3.55 gears from the factory. The biggest issue is, I have to decide whether to go with 3.73s or 4.10s, since they use the same DTT part number, and the 3.55's do not. I'm worried about effecting the fuel economy (which has a long term rating of 18.278mpg over 2,580 days and 41,630.40 miles... I did say long term ) but i'm also envious of people getting 20s and better consistently.

I'm currently running MOABs with 245/70R16's as listed in my sig, and i've considered next go-around going with 235/75.
Full 4X Guard armor is planned and the backbone plus winch is getting integrated into the front.

As most of you know I plow and I tow a car trailer occasionally, so factor that all into the equation.
I'd want at least the 245/75R16E for towing... so that's more gear needed right off the bat. So go 3.73+. Cheap/used 3.73s gears (or diffs) are usually easy to find. Even if you go to 4.10 later, the DTT still works.

I put a No-spin (lunchbox) in so I didn't have to worry about future ratio decisions. Haven't towed other that moving a few things around the yard. No plowing either.
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Old 01-08-2018, 10:13 AM   #3 (permalink)
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If only running 29-29.5 inch tire, 3.73s should help you
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Old 01-08-2018, 10:25 AM   #4 (permalink)
 
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I'm thinking 3:73s too, that's the same improvement that an auto gets from 3:73 to 4:10, which is perfect for that size and 4:56 is probably a little short for optimal highway cruising, as 4:10 would be for a stick.

Reading between the lines: I don't want you to get 4:10s bc I probably need them more.
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Old 01-08-2018, 12:48 PM   #5 (permalink)
 
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Originally Posted by tommudd View Post
If only running 29-29.5 inch tire, 3.73s should help you
Yea I don't see me getting crazy with tall tires or anything nutty like that. I treat it like a pack mule, so other than towing and plowing and hauling heavy things, it's I guess closer to a "mall crawler" than anything else. I'm hoping to eventually do some off-roading, but it won't be anything too bizarre or extreme.


Code:
R&P	Gear	rpm @ mph:		@ rpm:	3000
3.55	Ratio	65		shift drops to	speed
1	4.46	-			-	17
2	2.61	-			1756	28
3	1.72	4522			1977	43
4	1.25	3287			2180	59
5	1.00	2629			2400	74
6	0.84	2209			2520	88
Code:
R&P	Gear	rpm @ mph:		@ rpm:	3000
3.73	Ratio	65		shift drops to	speed
1	4.46	-			-	16
2	2.61	-			1756	27
3	1.72	4752			1977	41
4	1.25	3453			2180	56
5	1.00	2763			2400	71
6	0.84	2321			2520	84
Code:
R&P	Gear	rpm @ mph:		@ rpm:	3000
4.10	Ratio	65		shift drops to	speed
1	4.46	-			-	14
2	2.61	-			1756	25
3	1.72	5223			1977	37
4	1.25	3796			2180	51
5	1.00	3037			2400	64
6	0.84	2551			2520	76
So there's the hard numbers for things. I'd lose the ability to cruise comfortably at 90mph, but then I don't do that that often.

Tommudd: so you're thinking I should error on the side of caution and go for 3.73's instead of all out for 4.10's?

Funny fact: she's pretty damn stable at 100mph. I mean you still feel that she's a big girl, but it still handled fine at that speed.
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2007 Jeep Liberty Sport 4x4 3.7L 6spd
  • MOABs with Goodyear Wrangler All-Terrain Adventure With Kevlar 245/70R16
  • JBA UCA 4.5
  • OME 790/948/90009/N32
  • Western Suburbanite 7'4" plow
  • DetoursUSA Backbone
  • HF 12k# winch
WTB: project liberty near N.NJ. stick shift, 4x4, working motor optional, CHEAP

Last edited by sota; 01-08-2018 at 12:49 PM. Reason: I suck
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Old 01-08-2018, 01:22 PM   #6 (permalink)
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My 04 with over 4 inches of lift was stable as well at 100 on the wide open roads
but...
If you would be going to 245-75-16s/265-70-16s I would do 4.10s
but with the sizes you mention stick to 3.73s IMO
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MUDD'S MOTORSPORTS
WE DO IFS LIFT INSTALLS
04 Kilimanjaro Edition
4.5 INCH JBA LIFT/ 32s/4.10s/ etc
03 OVERLAND EDITION, Timberline Green Pearlcoat, JBA 2.5 inch Total Control Lift, Kilby gas tank skid, Skid Row, 4XGuard mixture, MOABs, 265-70-16s, 4.10s, Mudds bumper
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Old 01-08-2018, 02:11 PM   #7 (permalink)
 
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Thanks. After going through this, my un-experienced self is saying "3.73 passes the 'smell' test better than 4.10 does right now." I appreciate your confirmation bias.
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  • MOABs with Goodyear Wrangler All-Terrain Adventure With Kevlar 245/70R16
  • JBA UCA 4.5
  • OME 790/948/90009/N32
  • Western Suburbanite 7'4" plow
  • DetoursUSA Backbone
  • HF 12k# winch
WTB: project liberty near N.NJ. stick shift, 4x4, working motor optional, CHEAP
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Old 01-11-2018, 08:01 PM   #8 (permalink)
 
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Having the 3.73 with the 5 speed I wish I had 4.10s. Wouldn't dare go up a tire size past 240/70/16.
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Old 01-11-2018, 11:19 PM   #9 (permalink)
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If you want a fun liberty, and don't care about mpg then go 4.10 but if you are worried about mpg then go lower maybe even stay stock. If you want 3.73 then I could sell you for cheap my old front differential.
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Old 01-12-2018, 03:38 PM   #10 (permalink)
 
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Originally Posted by CzarKJ View Post
Having the 3.73 with the 5 speed I wish I had 4.10s. Wouldn't dare go up a tire size past 240/70/16.
Can't even really compare the 5 and 6 speed. A 5-4 downshift on the 5spd is like a 6-4 shift on the 6.

A gear change that makes 1st gear redundant seems a waste.
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