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maine dak
Dodge Dakota
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1/03/2004
15:11:17
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 Subject: bigger tires and gearing
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i've got a 99 dak 4x4 with 235/75/15 tires on it. i'd like to go up to the 31's that came on most other daks, but i'm worried about rearend gearing. it has a factory 3.92 ring and pinon in it now and driving around town now it seems way under greared. turning only 1500 rpm around 40mph. sure i could turn off the overdrive but theres a reason that its there. just wondering what my options are.
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vern
Dodge Dakota
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1/03/2004
17:29:42
| RE: bigger tires and gearing
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go with the bigger tires
and shut the o/d off,o/d around town is basicly
killing mileage,working the trans more than it needs to be[heat build-up]
o/d is alright on the highway 50mph and up
anything under 45mph the trans is shifting from o/d to drive and back again,every time you slow and speed up,stop and go,stop and go.........etc
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DrDakota
Dodge Dakota
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1/03/2004
20:58:44
| RE: bigger tires and gearing
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I have a '01 AWD CC w/ Stock gearing (3.55), and went from a stock 31" tire to a 33" tire (along with 3" body lift, 2" blocks in the rear and about 2" torsion bar lift to get them to fit comfortably).
I have only noticed a small loss in power and it shifts just fine. I just got back from a 2000 mile road trip from SouCal to Northern Utah and back without any problems.
My gas mileage went down just a tad, about 6%. My odometer is low by by approx 6% (and of course my speedo is up about 6%).
Overdrive was not a problem, but I can see if I was driving more steep winding road I may turn it off.
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wildAKmoose
Dodge Dakota
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1/04/2004
00:00:55
| RE: bigger tires and gearing
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With the 3:92,s in there it should be great with the oversize tire. 1500 rpm at 40 to me should be a good thing for mileage, I always thought I like better mileage.
Vern, question? I just thought this was a plain old 4 speed auto, and OD is just the highest gear which is 4th, and the button simply an over ride. Am I wrong, or is there a difference between 3speed/OD and a 4 speed auto. Mine is in OD even in town, cause I figure why not get into 4th when you can, like on the 45MPH boulevards. Seems that if it were getting a noticebly warm tranny, then you'd have a problem inside, especially when there's no load in the bed.
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DrDakota
Dodge Dakota
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1/04/2004
01:06:42
| RE: bigger tires and gearing
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Our OverDrives are a little bit more complex than that, atleast the new 45RFE and 545RFE are (did I get those numbers right?). They have two second gears, 4th is a locked-out torque converter and the 545 has two overdrives. The second overdrive is 'programmed' by the computer...the only difference between the 45 and the 545 is the program. I think thats how the dealer mechanic explained it. Our trannys are quite the engineering marvel.
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maine dak
Dodge Dakota
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1/05/2004
13:38:09
| RE: bigger tires and gearing
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thanks for the advise guys. think i'll go with the big tires, shutting the o/d off sounds like a good idea, it does seem to be shifting alot around town. i'm pretty sure you got it right with the tranny #'s. the 3.9's come with the 42re, 5.2 44re, 5.9 46re and now with the 4.7 it does come with the #'s you gave.
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vern
Dodge Dakota
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1/06/2004
09:02:18
| RE: bigger tires and gearing
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Message:
its a little more difficult to explain the in,s and out,s of the shift.
but o/d is for the highway...why do you think mopar put the on/off switch in your truck.
its not a option they thought that would look good there.
its so you can stop the up and down shifting in town and towing/stopping needless shifting and heat in the trans/keeping the motor in its power
band and it will help gas mileage if you use it properly.
hope this help clear it some.
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