Thoughts on power upgrades for 2006 TJ 2.4?

pbeach

pbeach

'06 TJ — Navy veteran
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Joined
Jun 19, 2021
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55
Location
Miami, FL
Hi guys.

To say the TJ 2.4L is underpowered is a severe understatement. In the wind, on the highway, a slug. Just a fact.

I’m the original owner, have taken good care throughout. Been told by several trusted mechanics it's in unusually clean and great shape.

Current specs:

- 91021 miles on a well-maintained 2.4L I4 DOHC 16V SMPI Engine
- Dana M35/194MM Rear Axle - 3.73 Rear Axle Ratio
- 6-Speed Manual NSG370 Transmission

After 15 years of frustrating, underpowered local and highway, pedal-to-the-floor on the hills — with upcoming plans for substantial cross-country highway driving, occasionally towing a light trailer, some off-road — your thoughts on my best, most effective options for more power? (not interested in the turbo/supercharge route)

• Swap out the 2.4L for a 4.0L?
• Stay with the 2.4L and regear?

… ?

Massive thx to everyone in advance. Really means a lot.

~ Peter
 
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Chris said:
Sell it for a 4.0 or do a V8 swap if power is a concern.
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Thx. Not an option I'm afraid, Chris. $$s are there for a motor swap/regear. Just not willing to sell. Thinking many here can agree (?): Selling = Selling my first born kid, what can I say?
 
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pbeach said:
Hi guys.

To say the TJ 2.4L is underpowered is a severe understatement. In the wind, on the highway, a slug. Just a fact.

I’m the original owner, have taken good care throughout. Been told by several trusted mechanics it's in unusually clean and great shape.

Current specs:

- 91021 miles on a well-maintained 2.4L I4 DOHC 16V SMPI Engine
- Dana M35/194MM Rear Axle - 3.73 Rear Axle Ratio

After 15 years of frustrating, underpowered local and highway, pedal-to-the-floor on the hills — with upcoming plans for substantial cross-country highway driving, occasionally towing a light trailer, some off-road — your thoughts on my best, most effective options for more power? (not interested in the turbo/supercharge route)

• Swap out the 2.4L for a 4.0L?
• Stay with the 2.4L and regear?

… ?

Massive thx to everyone in advance. Really means a lot.

~ Peter
Click to expand...
What size tires are you running and what transmission do you have?
 
pbeach said:
33s. Didn't want to go too large - I realize the larger-the-tire reasons. 6-Speed NSG370 Transmission.
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The 33's is why your performance is down. Your 2.4 engine puts out enough power for 33's if the engine rpms are up where they should be. The cure is to regear your axles to a lower ratio which will bring the rpms back up to where they need to be. With your 6-speed I'd regear the axles to 4.88 and you'll be happy again.
 
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Jerry Bransford said:
The 33's is why your performance is down. Your 2.4 engine puts out enough power for 33's if the engine rpms are up where they should be. The cure is to regear your axles to a lower ratio which will bring the rpms back up to where they need to be. With your 6-speed I'd regear the axles to 4.88 and you'll be happy again.
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You've confirmed my thoughts, Jerry - Ideal suggestion, man. Thx.
 
I have a 95 YJ with a 4 banger w/ a 5 speed and it was just ok on 31's but when I went up to 33's the poor little guy just died. I re-geared to 4:88's and what a BIG difference. Now I still own the YJ but I could afford to buy a 05 TJ 6 speed with the 4.0 and running 35's with 4:88's and the 4.0 runs circles around the 4 banger.

Re-gear is your answer, or an engine swap
 
Wouldn’t 31s be cheaper than re-gearing? Not that I’m sure the OP wants to take that route, but it seems simpler and cheaper, no?
 
Plumber1 said:
I have a 95 YJ with a 4 banger w/ a 5 speed and it was just ok on 31's but when I went up to 33's the poor little guy just died. I re-geared to 4:88's and what a BIG difference. Now I still own the YJ but I could afford to buy a 05 TJ 6 speed with the 4.0 and running 35's with 4:88's and the 4.0 runs circles around the 4 banger.

Re-gear is your answer, or an engine swap
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Great stuff, Dude. Thx.
 
pbeach said:
Agree.
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Regearing to a more appropriate axle ratio will give an immediate and dramatic boost in performance. I even started getting roughly 25% better fuel mpg after my last regear since the engine rpms were too low before regearing causing the engine to be on the edge of lugging on the highway.
 
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This isn’t Jeep related but I had an F-150 that I regeared from 3:73’s to 4:30’s and the difference was crazy. Around town the drivability was much improved, it stayed in the powerband instead of lugging around at 1200 rpm at 45 mph
 
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