I6 or V8

[daniel.99.tj]

I have a 99TJ with 6 in's and 35's with 4.56 gears front and rear that I use for a daily driver and wheel on the weekends, but only have a 4cyl. It really isn't that bad, but I would like to do better than 55mph and use 5th gear sometime. I want to upgrade the motor to something that has some good power, but doesn't really kill my pockets with gas. I know a lot of people that have the I6 4.0L and like it just fine, but I'm wondering if it's enough for the tires and gears. I've heard a few people say that a small V8 mid-range hp and torque wouldn't be to bad on gas because of the Jeep being light. I just wanted to get some inputs from some one that knows more than me.

 

[Bounty__Hunter]

Don't waste your time on a I6 swap, you'll have another run of the mill 6cyl jeep with a hacked up install, something you could trade up to cheaper and easier than swapping. Go for the GM 4.3L or a 350. The vortec 4.3L v6 is a hell of an engine.

When shopping for drivelines, look for the entire engine/transmission/transfer case package to keep adapter costs to a minimum.

 

[daniel.99.tj]

Thanks for the input. I'll try and do something original, cost permitting.

 

[Collin the Hen]

I love sixes. They have a lot of torque, yet they don't use a ton of fuel. The Vortec is an excellent engine. You may be able to get more info on a 4.0 swap, though. I guess if you wanted to stay cheap you could just beef up your four. There are a lot of people one this sight who can help with your four.

 

[daniel.99.tj]

Thanks, I looked into the 4.3L vortec but can't find anything on the swap. I don't have a lot experience and don't really know any one to fabricate motor mounts or anything else thats comes along with a motor swap.

 

[Collin the Hen]

I'd say to just modify your current engine. It would probably be cheaper than a swap. Like I said earlier, there are a lot of people who like their four and would be more than glad to help you. You never know, you may learn to love it.

 

[Bounty__Hunter]

4BangerJP.com - Index if you want some 2.5L mods.

 

[daniel.99.tj]

I have a intake, header, and a good exhaust aready on it. What else could I do, I understand the price advantage with mod on the 2.5, but is it really worth it. I read in another thread that my gears may still be to high, and need to go lower than 4.56. Off the subject, I need to replace my front drive shaft, do yall know of anywhere that is cheap but make a good product.

 

[Bounty__Hunter]

4.56 is too tall of a gear for 35" tires under a 2.5L 5spd. If you do the match, 5.13 to 5.38 gears get your performance back close to stock, putting the RPM band close to where it was from the factory. I run 5.38 in my 4banger with 35" tires and I love it, can even accelerate uphill in 5th.

Of course you can't go any lower than 4.88 in stock TJ axles, you would need at least D44's which is a pricey proposition in a TJ.

 

[daniel.99.tj]

How will that affect my gas milage?

 

[Bounty__Hunter]

I get between 15-18, with a best of 21, running 35" and 36" tires, so I'd say not at all. You get the benefit of getting the engine back in the correct rpm range so it's not struggling like it does with tall gears.

 

[daniel.99.tj]

Thanks for all the info. Would I need to swap the transfercase and transmission if I put D44s in. I would like to eventually do that, but would it be necessary to do that first.

 

[Bounty__Hunter]

No, you can leave your transmission and transfer case alone, as long as you select a front D44 with drivers side diff, like a Ford or late-model Wagoneer.

I run a Waggy front d44 and Isuzu Rodeo rear d44 so I'd have matching 6-lug wheel pattern and 4whl disc brakes. If you want to keep the 5x4.5" lug pattern, find an XJ rear d44 and convert a Waggy front d44 to that lug pattern using Ford parts.

 

[dave123]

Not to disagree with everyone, but since your jeep had the I6 offered as well, if you can find a doner vehicle with the same setup, then I would think it would be a fairly easy swap. Since it was a factory option, I would not think it would be a "hack job" like it would be with a V8. I prefer V8's, but if you could get the doner jeep cheap, then it would not be very costly. Assuming you like the rest of the Jeep, and just want some more power, I would think this would be better than starting over with an original I6. You can improve the 4, but more torque comes from more cubic inches! I doubt your milage would change much, as the 6 would not be working as hard.
just my .02