Re-gear vs supercharger vs engine swap for lack of power

Lunch Patterson

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2005 here with a 4.0, 42rle, and 31" hybrid tires. Plans to go to to 33" some day. I'm new to Jeeps, and a shade tree mechanic at best. This is more to learn than anything. I've seen a lot of threads about all of these, but none that really address the pros and cons vs each other.

This post is mostly seeing if my logic is sound on my options. I'd like to make a fully loaded jeep actually able to go up a hill without downshifting to the point it is a 4500 rpm, and still slowing down. I went on a wheeling/camping trip in the Ozarks. Granted said hill was pretty steep, but still on a highway. Going 70 fully loaded and with a roof rack as well. I understand the Jeep is a brick on wheels, but starting to mill over options to get some more power out of it. I also assume there isn't a fix to getting 12 mpg fully loaded and going 70 in windy/hilly terrain.

Re-gear seems to be everyone's "cheap" go to for "getting power back". I totally agree the way theses are geared is horrible. I've also seen people say they get a 1-2 mpg increase after a re-gear. My argument for this situation is I was already at 3k rpm on said hill. While I do plan on re-gearing I don't assume it will fix an actual "lack of power". The engine was not bogged and shifted down to 2nd putting it at around 4500 and it was still losing speed. Perhaps my logic is flawed that 3k rpm in 3rd should have more acceleration than if it were 3k in 4th. If looking at just a "power" perspective. I don't doubt it will drive much better with a re-gear though I don't see it magically fixing this problem.

A super charger seems like the next cheapest/complicated thing on the list. I've seen some posts from Chris about the Magnum Powers super charger and I may message him. This seems like an actual fix to the "lack of power". Basically doubling WHP seems like a dream come true. It also appears to be something I could just bolt on myself, then have tuned. This is what I'm currently leaning to the most. It keeps the engine the same, and seems like a simi-simple bolt on process.

An engine swap seems by far the hardest and most expensive on this list. Though it would also possibly fix the horrid gas mileage. I'd prefer not to have a diesel though, and those seem like the best options for swapping. I really like the 4.0's Ease of working on, simplicity, and reliability. I also feel like a whole engine swap is going to add a lot of "grimlins" at some point to chase down.

Let me know if my logic is flawed on any of these. I'm sure everyone's experience is different as well, and everyone likes their Jeep to drive a different way. I've seen a guy on here that argues 3.73 is a good gearing for bigger tires. I'm only at 31" and I can already tell that isn't true. At least for me personally and how I want to have my Jeep to drive, and feel. That is a wonderful thing about them as a platform. You can make it into anything you want. Thanks ahead of time for all the info that hopefully comes out of this comparison.

TLDR of my though processes

Regear
Pros- "Cheap", better power band, possibly 1-2 mpg increase.
Cons- Not an actual fix to not having enough power

Super Charger
Pros- Actually addresses lack of power, relatively "easy" install, able to be upgraded for more power if wanted.
Cons- Loss of 1-2 mpg, perhaps engine heat, it costs as much as my Jeep did.

Engine Swap
Pros- Fixes power, fixes gas mileage
Cons- Expensive, complicated, I assume will have lots of grimlins to chase down, I don't want a diesel.
 
Re-gear doesn't give you more power, it just gives you a more usable power band. A re-gear should be done regardless of any engine swaps / modifications.

There is no good supercharger kit for the TJ so I will not recommend them. I've run the Boosted Tech unit (garbage) and had a Magnum Powers setup briefly (hint, it's NOT a kit and takes a ton of work to get it working right).

An engine swap is your best bet, but you're going to need upwards of 20k if you want to do it RIGHT in my opinion.

I say re-gear it and learn to live with it. If you want something with more power, get a JK or a JL. Otherwise I would accept the TJ for what it is. Getting more power out of it is going to be more expensive than buying a newer JK or JL.
 
Re-gear doesn't give you more power, it just gives you a more usable power band. A re-gear should be done regardless of any engine swaps / modifications.

There is no good supercharger kit for the TJ so I will not recommend them. I've run the Boosted Tech unit (garbage) and had a Magnum Powers setup briefly (hint, it's NOT a kit and takes a ton of work to get it working right).

An engine swap is your best bet, but you're going to need upwards of 20k if you want to do it RIGHT in my opinion.

I say re-gear it and learn to live with it. If you want something with more power, get a JK or a JL. Otherwise I would accept the TJ for what it is. Getting more power out of it is going to be more expensive than buying a newer JK or JL.
Thanks for the update! You seemed really happy with the Magnum in the older posts. I was about to add a 4th option of just drive 60 up steep hills and enjoy the ride, haha. That might be what it turns into re-gear and slow down. My plan was to just do 5.13 right now. I looked at rpms on grim jeeper. I have 31's but that's still well under 3k at 75, even setting it to 30" assuming It isn't a perfect 31". Those some day upgraded to 33's.
 
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Thanks for the update! You seemed really happy with the Magnum in the older posts. I was about to add a 4th option of just drive 60 up steep hills and enjoy the ride, haha. That might be what it turns into re-gear and slow down. My plan was to just do 5.13 right now. I looked at rpms on grim jeeper. I have 31's but that's still well under 3k at 75, even setting it to 30" assuming It isn't a perfect 31". Those some day upgraded to 33's.
I should go back and update those old posts as I am not happy with the Magnum. It’s far from a lot and will take thousands of dollars on top of what it already costs in order to make it work right. It also has a lot of compromises in my opinion.

My general opinion on gears is that you always want to go deeper because most people end up going to larger tires down the road.
 
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Thanks for the update! You seemed really happy with the Magnum in the older posts. I was about to add a 4th option of just drive 60 up steep hills and enjoy the ride, haha. That might be what it turns into re-gear and slow down. My plan was to just do 5.13 right now. I looked at rpms on grim jeeper. I have 31's but that's still well under 3k at 75, even setting it to 30" assuming It isn't a perfect 31". Those some day upgraded to 33's.

Ding ding ding there's your practical answer. Maybe ditch the roof rack and get a trailer.

If you can afford it an LS swap is king. If not just exercise your patience
 
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Ding ding ding there's your practical answer. Maybe ditch the roof rack and get a trailer.

If you can afford it an LS swap is king. If not just exercise your patience
I mean I'm still pulling extra weight either way right? I also don't want to drag a trailer around trails and stuff. Well, if an LS swap is 20k, then no, lol. Time to just enjoy the journey it sounds like.
 
Are you sure your engine is healthy to begin with? My 99 was annoying before I regeared but I never needed 4500rpm...even sustained 6-7% grades on 9000' mountain passes I only needed about 3500rpm to keep the speed limit (granted, the limit on those types of passes is under 60mph). And even the regear didn't change that... I still needed 3500rpm on that pass, I just found it in a different gear.
 
Are you sure your engine is healthy to begin with? My 99 was annoying before I regeared but I never needed 4500rpm...even sustained 6-7% grades on 9000' mountain passes I only needed about 3500rpm to keep the speed limit (granted, the limit on those types of passes is under 60mph). And even the regear didn't change that... I still needed 3500rpm on that pass, I just found it in a different gear.
Yeah, I'm going to check and see if the Cat is clogged, or something. It is super peppy around town. Will accidently chirp tires, etc. It was VERY loaded. Like full to the brim Jeep, and a loaded roof rack, with 2 people in it, 1/2 mile steep hill, trying to maintain 70+. I think it was just too much for it. It also drives fine unloaded. Just a little annoying with the OD being so low on the highway.
 
Yeah, I'm going to check and see if the Cat is clogged, or something. It is super peppy around town. Will accidently chirp tires, etc. It was VERY loaded. Like full to the brim Jeep, and a loaded roof rack, with 2 people in it, 1/2 mile steep hill, trying to maintain 70+. I think it was just too much for it. It also drives fine unloaded. Just a little annoying with the OD being so low on the highway.
Do the OD switch mod, re-gear, then see where you are. I have a 42rle on 33's with 373 gears and it's not horrible if you turn the OD off. It can hold a gentle hill for a half mile or so in N Idaho along HWY 90. If I regear it, I will go for 513 gears.
 
Power is not a substitute for proper gearing, especially off road. There is some wiggle room when you talk about more power strictly for the street, or when using an autotragic transmission strictly for off road, but it's not a one or the other thing practically speaking.
 
Power is not a substitute for proper gearing, especially off road. There is some wiggle room when you talk about more power strictly for the street, or when using an autotragic transmission strictly for off road, but it's not a one or the other thing practically speaking.
This is true my current LS build will have significantly more power than stock and be running 5.38’s.
 
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My stroker is fine with 4.10's and 33's (which most consider pretty undergeared) on the street. Overgeared even. With my AX15 manual tranny though, I find myself working the clutch way too much just on trails off-road. I would hate it if I was rock crawling. Maybe if it was a 3 speed auto it would be acceptable off-road. I dunno. There are definite grey areas and overlap that you might be able to get into with more power, but one is not a solid substitute for the other except in specific circumstances. No way around proper gearing IMHO.
 
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If a hill slows you down in 2nd gear at 4500 rpm, re-gearing is not going to help. You will be going the same mph and rpm in a different gear. What speed and rpm were you going?
 
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