Honestly that's such a small difference that it won't be to noticeable. If you go with the 3.55 you most likely wouldnt need to buy the Hypertech programmer. Since the 3.7 liters came with 3.55 as an option the dealer should be able to program the new gear ratio....
2007 4.7 Liter XK | Front Modified OME HD Lift | Rear 4" Superlift | JBA UCA's | Rusty's Rear Adjustable Track Bar | Rysty’s Adjustable Upper and Lower Rear Control Arms w/Heim Joints | Mickey Thompson Classic III 17x9 Wheels | 315/70R17 Goodyear Duratracs | Airflow Snorkel | Flowmaster 40 Series Muffler | Superchips Flashpaq | Mopar Skids | 4xGuard Belly Guard | American Rebel Rear Diff Cover | Rear Powertrax No-Slip | Front Electronic Locker | Rear Heat/AC Delete
RPMs for 3.55 will increase by 16% over 3.07 gearsOriginally Posted by psycho787
RPMs for 3.73 will increase by 21% over 3.07 gears or about 5% difference between the 3.55s to 3.73s.
06 Red Jeep XK 3.7L V6 QT1, RC 2" with 1/2", 1-1/4" Wheel Spacers, Rubicon Moab Rims, Grabber AT2 LT265/70-17, Rocky Road Supersliders, Fastman Throttle-body, K&N Cold Air Filter, JBA Headers, Front Tow Hooks, 2" receiver front & rear, Wired for winch front & rear, ARB Onboard Air, Trans Temp Gauge, Aux Trans Cooler, Sport Roof Crossbars, Skid Plates, RS5010 Rear Shocks, JKS 2034 Front & 2001 Rear Disconnects
How much do you have invested in the 3.73's, if you don't mind me asking?
2008 3.7L QT-1 dark blue Jeep Commander // 3+" modified OME lift with 3/8" Rocky Road strut spacer // 4" rear SL springs // 265/70/17 Goodyear Duratracs (Load E) // 1.5" spidertraxx spacers // F-150 Monroe Load Levelers // 4xguard matrix, front guard, belly guard, and rock sliders // 130 watt KC Daylighters - 2 // Airflow snorkel // Thrush welded exhaust // Defender Roof Rack with side ladder // Hypertech Max Energy Programmer
More than I should, but I'm also adding a manually controlled ELSD in the front. You can buy rear aftermarket 3.73s, it's the fronts that cost a lot if you want new, only Mopar makes them. Otherwise a used front differential out of a 4.7L with 3.73s will work, but the pinion flanges may be different.
06 Red Jeep XK 3.7L V6 QT1, RC 2" with 1/2", 1-1/4" Wheel Spacers, Rubicon Moab Rims, Grabber AT2 LT265/70-17, Rocky Road Supersliders, Fastman Throttle-body, K&N Cold Air Filter, JBA Headers, Front Tow Hooks, 2" receiver front & rear, Wired for winch front & rear, ARB Onboard Air, Trans Temp Gauge, Aux Trans Cooler, Sport Roof Crossbars, Skid Plates, RS5010 Rear Shocks, JKS 2034 Front & 2001 Rear Disconnects
Jay paid $450 for the front differential from a local junkyard out of a 4.7 Liter WK, approx. $300 for the rear Motive Gear 3.73's and $230 for the Hypertech Speedometer Calibrator. So total cost was $1,000 for the 3.07 to 3.73 swap. Labor was free since we did the install.
2007 4.7 Liter XK | Front Modified OME HD Lift | Rear 4" Superlift | JBA UCA's | Rusty's Rear Adjustable Track Bar | Rysty’s Adjustable Upper and Lower Rear Control Arms w/Heim Joints | Mickey Thompson Classic III 17x9 Wheels | 315/70R17 Goodyear Duratracs | Airflow Snorkel | Flowmaster 40 Series Muffler | Superchips Flashpaq | Mopar Skids | 4xGuard Belly Guard | American Rebel Rear Diff Cover | Rear Powertrax No-Slip | Front Electronic Locker | Rear Heat/AC Delete
If I could pick up those 3.55's for 300 from cmdrjim and get the programmer for like 250, I would end up paying 550. That's not including install, but I am able to get a discount, as a member of my Jeep group is the owner of an off-road shop. I'm just not sure if I want to regear without going with the more powerful 3.73's. Or, I could just hold off and upgrade to the OME lift and an offroad winch bumper
2008 3.7L QT-1 dark blue Jeep Commander // 3+" modified OME lift with 3/8" Rocky Road strut spacer // 4" rear SL springs // 265/70/17 Goodyear Duratracs (Load E) // 1.5" spidertraxx spacers // F-150 Monroe Load Levelers // 4xguard matrix, front guard, belly guard, and rock sliders // 130 watt KC Daylighters - 2 // Airflow snorkel // Thrush welded exhaust // Defender Roof Rack with side ladder // Hypertech Max Energy Programmer
Gears first. Then OME and bumper. Or all three...lol
2007 4.7 Liter XK | Front Modified OME HD Lift | Rear 4" Superlift | JBA UCA's | Rusty's Rear Adjustable Track Bar | Rysty’s Adjustable Upper and Lower Rear Control Arms w/Heim Joints | Mickey Thompson Classic III 17x9 Wheels | 315/70R17 Goodyear Duratracs | Airflow Snorkel | Flowmaster 40 Series Muffler | Superchips Flashpaq | Mopar Skids | 4xGuard Belly Guard | American Rebel Rear Diff Cover | Rear Powertrax No-Slip | Front Electronic Locker | Rear Heat/AC Delete
My other concern is I have an extended Carmax warranty. I'm going to speak with someone at Carmax this afternoon to see how regearing would affect my warranty
2008 3.7L QT-1 dark blue Jeep Commander // 3+" modified OME lift with 3/8" Rocky Road strut spacer // 4" rear SL springs // 265/70/17 Goodyear Duratracs (Load E) // 1.5" spidertraxx spacers // F-150 Monroe Load Levelers // 4xguard matrix, front guard, belly guard, and rock sliders // 130 watt KC Daylighters - 2 // Airflow snorkel // Thrush welded exhaust // Defender Roof Rack with side ladder // Hypertech Max Energy Programmer
It will probably void the warranty.
2007 4.7 Liter XK | Front Modified OME HD Lift | Rear 4" Superlift | JBA UCA's | Rusty's Rear Adjustable Track Bar | Rysty’s Adjustable Upper and Lower Rear Control Arms w/Heim Joints | Mickey Thompson Classic III 17x9 Wheels | 315/70R17 Goodyear Duratracs | Airflow Snorkel | Flowmaster 40 Series Muffler | Superchips Flashpaq | Mopar Skids | 4xGuard Belly Guard | American Rebel Rear Diff Cover | Rear Powertrax No-Slip | Front Electronic Locker | Rear Heat/AC Delete
I think 07JeepXk is correct.
06 Red Jeep XK 3.7L V6 QT1, RC 2" with 1/2", 1-1/4" Wheel Spacers, Rubicon Moab Rims, Grabber AT2 LT265/70-17, Rocky Road Supersliders, Fastman Throttle-body, K&N Cold Air Filter, JBA Headers, Front Tow Hooks, 2" receiver front & rear, Wired for winch front & rear, ARB Onboard Air, Trans Temp Gauge, Aux Trans Cooler, Sport Roof Crossbars, Skid Plates, RS5010 Rear Shocks, JKS 2034 Front & 2001 Rear Disconnects
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