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Old 02-16-2009, 03:08 PM   #1
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engine replacement..6 cyl. or 4 cyl. and transmission too?

I have a 95 YJ and have come into a little bit of money and would like to update my engine. I have a 4 cyl with 121K and the ax5 tranny. If I were to update what would be the suggestive approach.

Does upgrading to a 6 cyl from a 4 cyl cause problems?

Is a transmission upgrade needed in either upgrade?

What kind of costs could I be looking at?

I live in Massachusetts, any recommendations of credible installers?

Thanks for letting me call on your experience!! Thanks guys!

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Old 02-16-2009, 03:15 PM   #2
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yes, new trans needed. ax15 or nv3550 were bolted to the 4.0 from the factory, those would be easiest.

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Old 02-16-2009, 04:09 PM   #3
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I would upgrade. If you have the 2.5L now why not throw in a 4.0. The 4.0 and AX15 combo is a good combo. If there is nothing wrong with you 2.5L why not look at upgrading other areas of your drivetrain. Axles, lockers, gears. Just my 2 cents. Alot of guys will talk crap on here about the 2.5L but I have one and with 2nd gear and 4 lo, I can make it over and through MOST anything that the 4.0L guys could.
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Old 02-16-2009, 04:13 PM   #4
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Quote:
Originally Posted by Fire Hart View Post
Alot of guys will talk crap on here about the 2.5L but I have one and with 2nd gear and 4 lo, I can make it over and through MOST anything that the 4.0L guys could.
this is true, off road it is great, and its reliable. i had one. the only shortcomings are on the street, hi way, and in sand.
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Old 02-16-2009, 04:46 PM   #5
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And its great when you pull someone thats stuck and go yep my 4 banger does it all
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Old 02-17-2009, 07:18 AM   #6
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Thanks for the inpuit guys. It's actuially my daily driver. I get 65 mph at around 3100 RPM so not too bad. The 4 cyl has been very good to me. The tranny i think could use an upgrade though for the highway driving and the fact I run 32's for sneakers.
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Old 02-18-2009, 04:15 PM   #7
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what kind of mpg's are you getting?
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Old 11-27-2009, 09:42 AM   #8
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I've been thinking about upgrading from a 4cyl to a 6cyl at tax time. I went out of town for Thanksgiving - I tanked up, reset the trip odometer, and got directly on the highway. After 40 miles, I was already down to less than 3/4 tank. Seems kinda sad, ya know??
Would the 6 do any better for gas mileage, since 70mph seems to be a lot of work for the 4cyl?
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Old 11-27-2009, 09:49 AM   #9
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Ill take the 4 banger
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Old 11-27-2009, 09:58 AM   #10
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In town, the 4 isn't so bad. I don't have any power issues, and the mileage is fair. Highway driving in the Jeep isn't so much fun though.
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Old 11-27-2009, 10:30 AM   #11
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Why does everybody worry about gas mileage??? If your worried about that; buy a rice burner. Jeeps aren't known for mileage. I have a 01 TJ & a 90 YJ. Most full sized pickups get better than either. As for the original question; JP mag points out it is better to sell the 4 banger & buy a 6 cyl Jeep. They have proven it will cost you more to swap all the neccessary parts than to just buy a whole Jeep. I'm not knocking the 4 cyl. They have pulled me out before. They just don't have that much power on the road if you are running a modified Jeep.
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Old 11-27-2009, 10:42 AM   #12
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I've got a rice burner (sort-of....a Focus ZX5 - for sale!!) and I still enjoy my Jeep more.
I just get kinda concerned that the 4cyl is working too hard on the highway at 70mph (legal speed limit on I-64 and the WK Parkway). It's not overheating or anything like that, but I know it's literally got nothing left to give at those speeds.

As far as gas mileage goes, I just wonder if the 6 would do any better since it wouldn't have to work as hard at those speeds.

And with the work that I've put into my '99 4cyl, I'd rather keep it than to sell it and start over, since I have the inability to leave anything stock. Other than this power issue, I love my Jeep. It's been good to me, and I don't wanna sell it.
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Old 11-27-2009, 10:55 AM   #13
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Stay off the highway,drive the back roads .take your time ,have fun

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