Jk 3.8 ???

K9guy

Well-Known Member
Joined
Oct 21, 2006
Location
Beckley WV
I passed on the tj I found , had some vin/title issues. I have found a few 07-09 Wranglers (jk) and I know hardly anything about the 3.8 so please weigh in with the options/ experience with this motor please.all are just over 100,000 one was as much as 150,000.

they seem to be really fair priced even the Rubi’s .
 
I have heard nothing but bad things about the 3.8. When I was looking I did find a ton of 3.8 jks with "new engines" To me that was a red flag. I keep searching for a quality tj but for the stupid money people are asking I might as well buy a 2012+ jk
 
I had zero problems with my 3.8. Ran it well over 150K miles. In fact, its the CTB giveaway jeep. The ONLY thing about the 3.8 is for some odd reason it likes to eat waterpumps, but they're about a 5 minute job after you do it once. It's an old pushrod v6. Treat them right with routine maintenance and they seem to live a long life. I also still own a 3.6L JK and while it develops more horsepressures, they're way up in the RPM range. The 3.6 also sucks for a lot more failing sensors that may be easy or a huge pain.
 
I have a 3.8 JKU automatic with 116k miles. I have a rear main seal leak (probably upper since it only leaks while running). Other than that, it's rock solid running. People who talk down on them are usually directly comparing against the 3.6 or talking bad because other people have too. I'm assuming the 3.6 IS better.
 
I've had a 2007 JK with the 3.8 since January. Bought it with over 175k miles. It's got no power, but I'm running 35's. Common problems I've found and heard about are

Upper oil pan gasket (was already done)
Valve cover gasket (not a terribly hard job)
Lower intake manifold gasket (pain in the ass but I'd never been that deep before)

I'm looking at a transmission rebuild in the next few months as well. Not sure if that's common or not. I suspect it's never had fluid changed.

With that age, just expect that bearings and seals and gaskets are gonna need to be taken care of.

Other than the common issues I've read about and tackled, I'm happy with mine. I mean it'll never get out of it's own way but hey, that's just more reason for an LS swap down the road, right?
 
ShimShim said:
I've had a 2007 JK with the 3.8 since January. Bought it with over 175k miles. It's got no power, but I'm running 35's. Common problems I've found and heard about are

Upper oil pan gasket (was already done)
Valve cover gasket (not a terribly hard job)
Lower intake manifold gasket (pain in the ass but I'd never been that deep before)

I'm looking at a transmission rebuild in the next few months as well. Not sure if that's common or not. I suspect it's never had fluid changed.

With that age, just expect that bearings and seals and gaskets are gonna need to be taken care of.

Other than the common issues I've read about and tackled, I'm happy with mine. I mean it'll never get out of it's own way but hey, that's just more reason for an LS swap down the road, right?
Click to expand...
If you have an automatic and are running the stock 3.73 gears, the lack of power is the transmissions fault not the engine. The gearing of the RLE42 is stupid for the 3.8. I forgot to mention that I regeared my axles to 5.13 and it still drives 75-85 on the highway.
 
willness33 said:
Could also be 3.21s.
Click to expand...

Southern_Transplant said:
If you have an automatic and are running the stock 3.73 gears, the lack of power is the transmissions fault not the engine. The gearing of the RLE42 is stupid for the 3.8. I forgot to mention that I regeared my axles to 5.13 and it still drives 75-85 on the highway.
Click to expand...
According to my VIN, I've got 4.10 gearing. I can do 75 to 85 on the highway too. But by the time I get that fast I've reached my destination.

Not to hijack the thread, but if I'm having the transmission rebuilt, can they fix the gearing to something more appropriate for the 3.8? Or is it easier to re-gear the axles?
 
My 07 Sahara beach Jeep also had the factory 4.10 and rear LS option (07 was the only year this was an option on a Sahara)

ive got 170k on it. I’m the 3rd owner and know the first two very well. It’s had one water pump and valve cover gasket. Zero other issues BUT it‘s had routine maintenance it’s entire life.

since there‘s so much negativity about the 3.8 motor the prices are good compared to the 3.6 JKs. If I had to buy another JK I wouldn’t hesitate on a 3.8. Could always do a LS swap if the 3.8 goes south.
 
Last edited:
ShimShim said:
According to my VIN, I've got 4.10 gearing. I can do 75 to 85 on the highway too. But by the time I get that fast I've reached my destination.

Not to hijack the thread, but if I'm having the transmission rebuilt, can they fix the gearing to something more appropriate for the 3.8? Or is it easier to re-gear the axles?
Click to expand...
Never known anyone to regear an automatic, but I suppose its possible if the OEM makes different gears for it. Regearing the axles is much more common, lower cost, and wouldn't mess with the transmission computer.
 
The 3.8 is not a horrible motor IF you don't have one that has a porous block. The biggest fault of the 07-11 JK's is the 42RLE and it's gear ratios. Coupled with the gearing of the differentials at normally 3.21 or 3.73 (I know you said you had 4.10's) made it an anemic drive.

A well maintained 3.8L that doesn't consume oil can go a long time. Gear it to 5.13's it will do decent on the highway and nicely on the trails.

Personally, I still prefer the 3.6L with the NAG1 but I can't speak poorly about a solid 3.8L. The performance issues are not it's fault.
 
jeepinmatt said:
Never known anyone to regear an automatic, but I suppose its possible if the OEM makes different gears for it. Regearing the axles is much more common, lower cost, and wouldn't mess with the transmission computer.
Click to expand...
Re-gearing the diffs is the long term goal. But the mention of the gearing on the 42RLE had me wondering. I'd never thought of re-gearing the trans, but since it was gonna get rebuilt anyway I figured I'd ask.
 
jeepinmatt said:
Never known anyone to regear an automatic, but I suppose its possible if the OEM makes different gears for it. Regearing the axles is much more common, lower cost, and wouldn't mess with the transmission computer.
Click to expand...
We have a turbo 350 that the trans guy have made 1st out of a 700r4 work in( may be off on the actual parts he swapped). Made for a lower first gear in a drag car I helped with.
 
snappy said:
We have a turbo 350 that the trans guy have made 1st out of a 700r4 work in( may be off on the actual parts he swapped). Made for a lower first gear in a drag car I helped with.
Click to expand...
The 700 with the right parts was a hell of a transmission. Super low 1st and great OD. I have built several very quick cars with them included.

As the the 3.8 wasn’t it the same as the minivan engine?

To not buy a TJ means you miss out on the thundering 100hp at the wheels and constant rust prevention of everything aft of the rear main seal 😂
 
Back
Top