Bigger tires, but not re-gearing?

[KPOD]

So once I get my lift installed, I'm looking at running some 37s. Whether or not they are 12.5, or 13.5" wide yet I have not decided. One thing that has come up in talking with the lift guy, is possibly re-gearing.

My hoe came with the 3.42s, which with stock tires (31" 265/70R16) at 65MPH turns at almost 1700RPM in OD. Now, if I keep the same gear ratio, and stick on 37s, I'm running 1400RPMs (according to this site http://www.csgnetwork.com/multirpmcalc.html). Other than slow acceleration and loss of torque, is there any other downsides to not re-gearing? A mechanic friend of mine said that since the ECU is programmed to lock the torque converter at a higher RPM, my transmission will burn out since I'm never cruising at the intended RPMs (without re-gearing). Is this true, and is there any way to re-program it so the torque converter locks at a lower RPM?

What other cons are there? I'm assuming I'll have no towing capability at all anymore? What about idling at a stop light, and taking off. Acceleration is gonna be absolutely terrible compared to 31"? Any chance of idling or bogging out due to such low RPMs?

The pros I see are, the engine runs at way less RPMs when cruising.

 

[Fishin757]

my friend did the same thing and he just had to buy a new axle because his diff blew up.. not sure if its related but im sure re gearing would cost less than a new axle if it is related

 

[strokinpower]

It's hell on the whole drive train.

 

[KPOD]

To get both front and rear axles re-geared (and re-built in the process) I'm looking at $2k (includes labor and parts). That's why I'm asking.

 

[_Dylan_]

it's going to be a total dog. I'd be surprised if it even went into overdrive at 65.

It's an easy way to kill the transmission.

 

[KPOD]

it's going to be a total dog. I'd be surprised if it even went into overdrive at 65.

It's an easy way to kill the transmission.

Bleh, that's why I was wondering if it was possible to re-program the ECU to have any effect on the transmission.

 

[SunlitComet]

sun's point of view, if you do not regear to match the oe rpm +1-300 more. just park it as a lawn ornament or kiss your drivetrain goodbye in less then six months.

 

[DirtyBlackHoe]

Not regearing and running 37s on 3.42 gears is going to be hell on the trucks drivetrain (just as stated above). It puts a lot more stress on the transmission.

 

[KPOD]

Well then, if I'm gonna end up re-gearing, might as well look at swapping out the 10 bolt for a 14 bolt, as I sure as heck don't want to replace the 10 bolt after a year of running the 37s on there.

 

[_Dylan_]

I've seen broken 10 bolt axles shafts with 33s on a mud truck. I would never run 37s with a 10b.