Need some advice on buying a jk 3.8 or tj 4.0

Big Max

Big Max

New member
I originally planned on trying to get a new JK but the stars have not aligned. I have had a tj with the 4.0 and it was a awesome jeep kinda wanted a jk but am a little concerned about the 3.8 engine. Only looking to spend about 15k I can get some really clean tj with 60k to 100k miles on them or there are a few jk with 70k to 130k on thim in my price range. Just wondering if the jk is worth the risk with the 3.8?
 
MR.Ty

MR.Ty

Token East Coast Guy
What risks have you heard about the 3.8? If anything it's underpowered but more reliable than the 3.6.

Edit: They do burn oil but not enough to warrant worry between oil changes.
 
Grubbicon

Grubbicon

New member
I personally dont think you will go wrong with either. My 07 has 73k miles on it and Ive had zero problems with it. Mine doesnt burn any oil like some say that do. If it was me personally Id get the one you like more personally. TJ parts are cheaper then parts for a JK so there is one plus there.
 
Big Max

Big Max

New member
Grubbicon said:
I personally dont think you will go wrong with either. My 07 has 73k miles on it and Ive had zero problems with it. Mine doesnt burn any oil like some say that do. If it was me personally Id get the one you like more personally. TJ parts are cheaper then parts for a JK so there is one plus there.
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Thanks I think it will probably come down to the lowest miles and the best condition just try to do some research.
 
Big Max

Big Max

New member
MR.Ty said:
What risks have you heard about the 3.8? If anything it's underpowered but more reliable than the 3.6.

Edit: They do burn oil but not enough to warrant worry between oil changes.
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I don't know a lot about the 3.8 but it seems like I have heard a fair amount of people that have had new engines put in because of problems.
 
jeeeep

jeeeep

Hooked
I have a 2010 over 120k miles on it and it's still going strong.

oil changed every 6k miles, transmission fluid changed every 30k miles unless I've been working it hard then sooner. been running 315's on it since 6 months new and 37's since march 2015

I'm geared 4.88 which worked great with the 315's, but it's slow with the 37's and I spend most the time with OD locked out because OD is just a joke on this transmission. I could gear swap to 5.13's but really hoping to get an LS swap soon.

I also have a 2015 sport and while it has more power which is nice, what I really like about it is the transmission. it's smooth, geared close and just makes it easy to drive.

IMO the auto transmission of the 3.8 is geared too far apart and it's work driving it. It feels like I'm pushing it along most the time and get worn out driving it long distances just from having to keep the gas on it.

I think a manual trans might be best for the 3.8.

ok. well, looks like I didn't need that 2nd cup of coffee :cheesy:
 
Big Max

Big Max

New member
jeeeep said:
I have a 2010 over 120k miles on it and it's still going strong.

oil changed every 6k miles, transmission fluid changed every 30k miles unless I've been working it hard then sooner. been running 315's on it since 6 months new and 37's since march 2015

I'm geared 4.88 which worked great with the 315's, but it's slow with the 37's and I spend most the time with OD locked out because OD is just a joke on this transmission. I could gear swap to 5.13's but really hoping to get an LS swap soon.

I also have a 2015 sport and while it has more power which is nice, what I really like about it is the transmission. it's smooth, geared close and just makes it easy to drive.

IMO the auto transmission of the 3.8 is geared too far apart and it's work driving it. It feels like I'm pushing it along most the time and get worn out driving it long distances just from having to keep the gas on it.

I think a manual trans might be best for the 3.8.

ok. well, looks like I didn't need that 2nd cup of coffee :cheesy:
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I am definitely going to get a manual transmission. Are the manual transmission the same in the 3.8 as the 3.6? I was pretty used to the 4.0 not having a lot of power.
 
thardy

thardy

Banned
The upside to going with a JK over the TJ is general size, as well as the chance that you will more than likely find the JK hasn't been abused as much as a TJ would. Or at least that's the experience I had when I was looking a few years ago. I ended up with a brand new 2014 sport because the payments weren't much more than buying a used TJ or JK with lower miles.
 
Big Max

Big Max

New member
thardy said:
The upside to going with a JK over the TJ is general size, as well as the chance that you will more than likely find the JK hasn't been abused as much as a TJ would. Or at least that's the experience I had when I was looking a few years ago. I ended up with a brand new 2014 sport because the payments weren't much more than buying a used TJ or JK with lower miles.
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I have seen a few tj that where stock and towed behind RVs with like 50 60 k on thim and you know those would not be torn up.
 
aldaman

aldaman

Member
Big Max said:
I don't know a lot about the 3.8 but it seems like I have heard a fair amount of people that have had new engines put in because of problems.
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Yes, some of the 3.8 burns / loses oil between oil changes. Part of the problem why some of the engines go bad is because they are close to running dry by the time the next oil change is made. So the Jeep may have only 1 quart left or no oil left in the crank case.

I owned an '08 for over 5yrs before I sold it and purchased a 2012 Rubi. When I had it I would always check the oil level every week and a half. On some occasions I would have to add a half quart before my next oil change. By doing that type of preventative maintenance I had no problems with the Jeep. :thumb:
 
Big Max

Big Max

New member
aldaman said:
Yes, some of the 3.8 burns / loses oil between oil changes. Part of the problem why some of the engines go bad is because they are close to running dry by the time the next oil change is made. So the Jeep may have only 1 quart left or no oil left in the crank case.

I owned an '08 for over 5yrs before I sold it and purchased a 2012 Rubi. When I had it I would always check the oil level every week and a half. On some occasions I would have to add a half quart before my next oil change. By doing that type of preventative maintenance I had no problems with the Jeep. :thumb:
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Thanks.You mean you should check your oil level one and a while! Haha yep I always check oil level on all my vehicles regularly.
 
aldaman

aldaman

Member
Big Max said:
Thanks.You mean you should check your oil level one and a while! Haha yep I always check oil level on all my vehicles regularly.
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Exactly, that is what I have always done on all vehicles I have owned and still do it to this day. I just don't get how some people complain about having to check their oil level even knowing their vehicles loses oil from time to time and wonder why there was hardly any oil left when going to do their next oil change....It takes less than 3mins and that's with having to add some oil into the engine...:naw:
 
Pyro1415

Pyro1415

New member
Big Max said:
I originally planned on trying to get a new JK but the stars have not aligned. I have had a tj with the 4.0 and it was a awesome jeep kinda wanted a jk but am a little concerned about the 3.8 engine. Only looking to spend about 15k I can get some really clean tj with 60k to 100k miles on them or there are a few jk with 70k to 130k on thim in my price range. Just wondering if the jk is worth the risk with the 3.8?
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Jk man. The 3.8 may be underpowered but getting a manual makes it a lot better. My engine was hydrolocked and still refuses to die.
 
albertmald9

albertmald9

New member
Big Max said:
I originally planned on trying to get a new JK but the stars have not aligned. I have had a tj with the 4.0 and it was a awesome jeep kinda wanted a jk but am a little concerned about the 3.8 engine. Only looking to spend about 15k I can get some really clean tj with 60k to 100k miles on them or there are a few jk with 70k to 130k on thim in my price range. Just wondering if the jk is worth the risk with the 3.8?
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I have both and I think the 4.0 on the TJ is much better than the 3.8 in the JK.
However, my TJ has a manual transmission, my JK is automatic. JK is 4 door and of course the TJ is 2 door. With that said, power, torque, and overall performance are significantly better in my TJ. I like the JK but if I had to do it again I'd buy one with a manual transmission. I just got a sweet deal on it and couldn't pass it up.

What everyone has said about the 3.8 is right. It is underpowered and may require monitoring with regard to burning oil. But that type of monitoring should be applied to all vehicles to ensure their longevity. With proper gearing and calibrating for size and gears with a flashcal or procal, the 3.8 on the JK does not run bad. And correcting the terrible shift points on the 3.8 is huge (at least it was for me).

With your price range, like mentioned by Grubbicon, I'd look at the price for parts. I was used to the price range for TJ parts and when I got into JK parts I quickly saw how much more I'd be spending. Also, you can find some nice TJs with low miles in that range. Finding them isn't too hard in California (selling mine with 80k). It comes down to preference and compromise, what fits you best will be up to you.
 
Shantz

Shantz

Member
Big Max said:
I originally planned on trying to get a new JK but the stars have not aligned. I have had a tj with the 4.0 and it was a awesome jeep kinda wanted a jk but am a little concerned about the 3.8 engine. Only looking to spend about 15k I can get some really clean tj with 60k to 100k miles on them or there are a few jk with 70k to 130k on thim in my price range. Just wondering if the jk is worth the risk with the 3.8?
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Welp, got into a major accident last year and totaled my beloved TJ that I spent 3 years building. Had a new rebuilt engine and tranny with less than 3000 miles on it... heart breaking so it was.

Bought an 07 JKU with 142,000 miles on it... yes you are reading that correctly. I picked it up for just under $16,000. Right off the bat I knew it needed a new transmission(rebuilt)... put about $10,000 into it getting it the way I want it... still a ways to go... but getting there.

I really hated the JKU at first but slowly grew to love it... best thing I ever bought... I look forward to the day I have it 99.9% done for life.
 
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