Thinking About Manual Swap on My 3.7 KJ – Need Opinions

[KJlibertyBR]

Hey folks,

I’m from Brazil and I have a 2004 Cherokee KJ (your Liberty), with the 3.7L V6, solid axles, control arms suspension and running on 40” tires.

As you probably know, here in Brazil all KJs came only with automatic transmissions. No manual versions were ever sold here.

I’m currently considering doing a manual transmission swap while keeping the stock 3.7 engine. Another option would be to replace both engine and transmission with a diesel setup – but that’s a bigger project.

So I wanted to ask:

For those of you in the U.S. who have driven or owned a Liberty with the 3.7 + manual combo, is it a noticeable improvement over the automatic?

Is it more responsive, better torque delivery, more usable off-road?

I feel like the automatic gearbox is robbing a lot of power from the 3.7, especially when crawling or climbing.

What would you do in my place?

→ Stick with the 3.7 and install a manual trans?

→ Or skip straight to a diesel swap?


Photos of my build are already posted here on the forum if anyone wants to check it out.


Thanks in advance!

 

[KJlibertyBR]

????

 

[lfhoward]

What gears are you running in your solid axles? Gearing lower could provide the power you want without changing any of the drivetrain. Turning 40” tires is going to rob the power without lower gears.

 

[u2slow]

I hadn't driven an auto one until my work put me in a rental unit a few times. Ugh!

Our 2005 manual (6spd) lets you keep the engine in the powerband - just pick the gear for the speed you are going. The 3 selections for the auto just don't cut it.

 

[KJlibertyBR]

What gears are you running in your solid axles? Gearing lower could provide the power you want without changing any of the drivetrain. Turning 40” tires is going to rob the power without lower gears.

Hello. I’m using the 5.38 gear ratio, which is already pretty short. I’m thinking about adding a button to lock the torque converter, putting it at a 1:1 ratio in first gear. That way, it will spin the wheels more.





As it is now, first gear is too short and second gear is too long. When it shifts into second, the engine bogs down and can’t get the RPM up.

 

[eldredg]

Hello. I’m using the 5.38 gear ratio, which is already pretty short. I’m thinking about adding a button to lock the torque converter, putting it at a 1:1 ratio in first gear. That way, it will spin the wheels more.





As it is now, first gear is too short and second gear is too long. When it shifts into second, the engine bogs down and can’t get the RPM up.

You are likely to just bog down your engine more when pulling hard if you lock the torque converter. It doesn't just provide slippage for stopping with transmission in gear. It also increases torque power at low engine speeds to get you moving / keep you moving.

Google search "torque converter increase torque"
Response

"Yes, a torque converter does increase torque, a process called torque multiplication, which is essential for getting a vehicle moving. It achieves this through a combination of its fluid coupling design and a specialized component called a stator. The stator redirects fluid flow to the turbine in a way that adds to the fluid's force, creating a torque increase, especially at low engine speeds. "

 

[KJlibertyBR]

You are likely to just bog down your engine more when pulling hard if you lock the torque converter. It doesn't just provide slippage for stopping with transmission in gear. It also increases torque power at low engine speeds to get you moving / keep you moving.

Google search "torque converter increase torque"
Response

"Yes, a torque converter does increase torque, a process called torque multiplication, which is essential for getting a vehicle moving. It achieves this through a combination of its fluid coupling design and a specialized component called a stator. The stator redirects fluid flow to the turbine in a way that adds to the fluid's force, creating a torque increase, especially at low engine speeds. "

Yes, you have a good point. I know that if I lock the torque converter at 1:1 the engine will run slower, but that will happen in 2nd gear. My idea is to be able to use 1st gear with higher wheel speed. That way I won’t need to use 2nd gear.





In 1st gear the engine has plenty of power and feels strong, but when it shifts into 2nd gear it loses strength. The idea of locking the torque converter is precisely to make 1st gear longer.

 

[eldredg]

Yes, you have a good point. I know that if I lock the torque converter at 1:1 the engine will run slower, but that will happen in 2nd gear. My idea is to be able to use 1st gear with higher wheel speed. That way I won’t need to use 2nd gear.





In 1st gear the engine has plenty of power and feels strong, but when it shifts into 2nd gear it loses strength. The idea of locking the torque converter is precisely to make 1st gear longer.

Won't hurt to try it. Would be interesting to hear the results. First mention of it I've heard.