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Unread 07-05-2012, 11:35 PM   #1
FujativeOCR
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CVT Gear Ratio/Final Drive Ration question...

ATTN: GRAMPS....maybe you have some insight to this...of course everyones knowledge is welcome.

But Gramps...I finally did some homework on the CVT2/CVT2L gear ratio/final drive ratios you've mentioned on here before, and finally made some sense of it all. As you've pointed out....both tranny's have the same gear ratio range as each other....2.349:1 to .394:1. But the difference in the Off Road Patriot is the Final Drive Ratio (transaxle?) of 8.135:1 on the Off Road version, vs. 6.12:1 on the normal 4x4. So this then, does explain why my Patriot runs at 3200 RPM at 75 mph, when everybody elses would run at about 2400 rpm at the same speed.

(side note: Jeep should not advertise the CVT2L as a different transmission with a separate lockable low ratio, when all it actually does is lock the same CVT into it's lowest range...2.349:1 x 8.135:1 = 19.11:1...it's very deceiving, because it changes ALL available gear ratios, not just the low one).

Anyway the point of this all...a question... Is it possible to change the final drive gears to match the normal 4x4 ratio of 6.12:1....on a Off Road Patriot? I don't have much of a 4x4 truck background and not sure what this would entail, but it seems like real truck guys do this all the time on Wranglers/Full Size pickups or whatever. It seems that if all the software and shift lever controls are computerized or internal to the transmission, then what effect, if any, would new final drive gears have?

I'm thinking along the lines of how off roaders install Dana 44/60 axles or whatever, which I think changes the ratio with it? So could one do a similar swap on a Patriot? :crosses fingers:

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Unread 07-08-2012, 12:50 PM   #2
FujativeOCR
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I found a 3 year old thread on another forum talking about this. Apparently the difference in FD1 and FD2 is only the rack and pinion gears in the differential. Nobody in the thread ever said if they got around to swapping them though. Im goingbto visit a 4wd shop and the dealer this week and see if its possible.
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Unread 07-09-2012, 10:19 AM   #3
Gramps
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These would be some of the challenges faced doing a conversion.

Freedom Drive II Off-Road Group includes these things plus some bolt on items:

Electronics that are not changeable:
4-Wheel Drive Off-Road Mode, Brake Lock Differential, Hill Descent Control & Hill Start Assist are all electronically controlled by the PCM as programmed by your VIN (the 4WD characteristics are not an option that can be chosen like tire size.)

Yes the rack & pinions are different as are the half shafts, plus the modules for the Brake Lock, the Hill Descent & Hill start assist.

Just changing the mechanicals of the Final Drive ratios in both the front and rear may adversely affect the control of the PCM and braking systems. The MK's are computer and a coupling disc connects the front and rear; unlike the transfer case style that are mechanically controlled and connected by a gear box. Nobody has ventured to do this because of the programming by VIN. It would be a rather expensive project to have fail.
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Unread 07-09-2012, 10:29 AM   #4
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I'm sad now.
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Unread 07-09-2012, 10:43 AM   #5
Gramps
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There are ppl looking specifically for the FD II package. You may be able to turn it over and get what you really want. Sorry it's not a 'good' news day.
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Unread 07-09-2012, 01:14 PM   #6
FujativeOCR
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Isn't the normal FD1 4x4 an inch shorter as well? I like the ground clearance and 140 amp alt on mine.
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Unread 07-10-2012, 10:01 AM   #7
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I did all of my measuring and calculations from the '07 - '09 before they changed a few tire sizes and at that time the FD I was only half an inch shorter than the FD II. Everything was compared to the base FWD Sport model. I covered this before http://www.jeepforum.com/forum/f98/5...1/#post4091410

I have a more detailed explanation of this somewhere.....
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