how can i find out what the gear ration in my 2005 libby crd?

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05 CRD Limited, SEGR Kit, EHM, Selectrack Alpine DVD, 6000k HID headlights, Aux Lift Pump, 2.5" straight pipe, Diablo Extreme Puck, Euro converter
02 SLT Cummins H.O. 6spd manual with southbend 3850dd, fass 150hd, ddp 150hp injectors, arp studs, adrenaline stacked w smarty, traction bars, 6 inch stacks, level kit, bhaf

3.73,only ratio offered for the CRD with auto trans.

perfect thanks!

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05 CRD Limited, SEGR Kit, EHM, Selectrack Alpine DVD, 6000k HID headlights, Aux Lift Pump, 2.5" straight pipe, Diablo Extreme Puck, Euro converter
02 SLT Cummins H.O. 6spd manual with southbend 3850dd, fass 150hd, ddp 150hp injectors, arp studs, adrenaline stacked w smarty, traction bars, 6 inch stacks, level kit, bhaf

Will 3.55 fit in the liberty. It would lower the rpm's and hopefully increase mileage.

The rear would be an doable swap, but the front will require some work to get a pinion that will fit the front housing. I think it is shorter requiring the shaft to be annealed or tempering to "half hard" with out softening the pinion gear, re-maching the length, splines, and such to match up, rehardening and tempering the machined area. You will have a gem, but unless you have the heat treating equipment a lathe, milling machine with DRO, index head, spline cutters, and lots of time, you will go broke. If you work for a CNC machine shop that has the heat treating equipment, you could mod 3.54 pinions to fit the front and sell them. Sir Sam or TJKJ2002 might know what would work for your donor gears to redo.
You could find a bolt on overdrive, but you would be doing a lot of drive shaft rework and redoing mounts, cross members, etc. I did that on a '73 Chevy I had a Perkins Turbo Diesel in years ago and traded off on my CRD.
If you have to drive a lot of rural back roads one option is using an '03 RAM 1500 5.7L /545RFE TCM and follow the training procedure. viewtopic.php?f=5&t=70718

It drops the RPMs a lot for better fuel economy and a lot cheaper than swapping out gears.
I have the machine tools, but with my road warrior job and lots of Hunny Do at home, doing the 3.73 to 3.55 swap is not an option in my lifetime.

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2006 Pearl Green CRD
Magnaflow 2 1/2" Cat Back
KJ Extra Leg Room Brackets, Carter Lift Pump, V6 Airbox, ORM
Fuel cooler, Oil Separator, Progard 7
Gauges EGT Boost Trans Temp Oil Pres, Michelin LXT AT2 245 70 R16
7,000# Draw Tight hitch, PML EX Deep Trans Pan
Centrifuge, SunCoast, Transgo, RAM TCM, InMotion Stage 2
Wife's 99 TDI VW Beetle

I have a pre-F37 TCM. My shifts are fairly low. I'm looking for highway mileage and the Ram TCM won't help. Fifth gear is still fifth gear no matter what you do.

Didn't the six speed manual tranny gas engine KJs come with 3.55 gears? If so everything would swap right over.

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05CRD: GDE Hot ECU & TCM tunes, Provent, Cat filter, Facet lift pump, TransGo kit, Florida TC, Samcos, stainless brake lines, HDS thermostat, Renegade light bar,
Bilstein adjustables, Al's Gen 4.5 Arms, 235/85-16 Duratracs, DTT rear, Elocker front, EVIC+TPMS, Turbo timer, McNally pillar gauges, Weeks Stage II kit.

Yes. New 3.55 gears are available from Jeep.

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