There is no debate, go 4.88 gears (my review)

[Alanscott_1]

I heavily debated between 4.88s and 5.13s on my JT with 37s and the shop that did my install highly recommended going with the 5.13s.

I’m in the process of driving cross country at the moment and once I started getting into the hills and steeper grades the benefits of the 5.13s became immediately apparent. Still averaging 18mpg overall.

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[FLUndertaker]

I heavily debated between 4.88s and 5.13s on my JT with 37s and the shop that did my install highly recommended going with the 5.13s.

I’m in the process of driving cross country at the moment and once I started getting into the hills and steeper grades the benefits of the 5.13s became immediately apparent. Still averaging 18mpg overall.

5.13 all things!

 

[Bonanza]

I just ordered 4.88s. Will report back once I install them. I have 37s.

 

[shrinkhead]

so I am going to keep the 4.10s for the 37s for now as I want to see how the HEMI does with those gears and tire size. I worry getting to short gears though the 4.88s are most certainly not. Would not do anything shorter with my HEMI which spends a lot of quality time in 4Lo. Curious what the rpm range was for most of you with the 4.10a between 65-75 and what it is with 4.88s?

 

[be77solo]

The 3.6 doesn’t mind screaming all day long most of the power band is high in the rpm range. Even a Jeep Engineer said that it needs to be reved Often.
ill share this
This post was on Bob Is The Oil Guy. Thought you all would like to read it.

Nice! As an former Pentastar design engineer I am slightly bias but the engine is really high quality. Few points from the development using tens of millions of dollars in analysis and testing regarding the oil and durability..... The lighter oil was chosen mostly for fuel economy BUT engineering is the science of compromise. You help one thing but hurt another. A thicker oil will reduce timing chain and tensioner wear because the center timing chain idler doesn't go fully hydrodynamic till about 1650rpm on 5w-20. So, a thicker oil will lower that number slightly and with general loads/speeds the engine spends a lot of time around 1500-1750 rpm with the 8 speed. So thicker oil is a win there. Additionally, the earlier engines had what was called the "McDonald's Arches" in the idler bearing which was intended in making a more uniform distribution but in actuality acted as a knife edge. This design was changed around 2014 to a smooth bearing. So overall timing chain issues will likely follow the 2011-2014 engine years more than 2014+. Where you lose.... The head is very complicated with a Type II valve train. Meaning lots of things to pressurize and pump up at start up. A thicker oil didn't do so well here (on long sit times +cold start) and contributed to a overall increased engine wear especially in the head and cam bearings. Last point. This engine needs occasional WOT runs if you want it to last. Granny cycling is bad for it. So bad for it we actually created a new granny cycle test during the cylinder #3 misfire issue. The highest wear is in the valve guides, because of tight valve stem seals (for emissions, reduce oil burn). They basically dry out. When you go WOT/high rpm/load you get some fresh oil in there and this keeps the wear down. Thicker oil might not help this condition but we also change the valves/guides/seals in 2014+. Not sure the impact. Cheers! Kevin PS. Turn off stop start and do not run e85 if you are concerned about engine wear. Eats the engine alive.

I have no idea who this engineer is, but rest his soul, that was a great read and I DO drive the shit out of my 3.6 manual, so seems it will live forever! Great read.


Gears, I'm in the 5.13 camp all day long. That's where I'm going.

I'm that now old guy that put 4.10's and Nitrous on an S10 back in the day..........

 

[seven30]

I have no idea who this engineer is, but rest his soul, that was a great read and I DO drive the shit out of my 3.6 manual, so seems it will live forever! Great read.


Gears, I'm in the 5.13 camp all day long. That's where I'm going.

I'm that now old guy that put 4.10's and Nitrous on an S10 back in the day..........

+1 on that! Keep the oil fresh and don't baby it. What color was that S10?

 

[be77solo]

+1 on that! Keep the oil fresh and don't baby it. What color was that S10?

RED of course ha

Hard to believe was 20+ years ago.

 

[Bbannongmu]

I have no idea who this engineer is, but rest his soul, that was a great read and I DO drive the shit out of my 3.6 manual, so seems it will live forever! Great read.


Gears, I'm in the 5.13 camp all day long. That's where I'm going.

I'm that now old guy that put 4.10's and Nitrous on an S10 back in the day..........

check it out. - 5.13 vs 4.88. Thanks @Jt-wrx for the idea and collaboration.

 

[Jt-wrx]

I have no idea who this engineer is, but rest his soul, that was a great read and I DO drive the shit out of my 3.6 manual, so seems it will live forever! Great read.


Gears, I'm in the 5.13 camp all day long. That's where I'm going.

I'm that now old guy that put 4.10's and Nitrous on an S10 back in the day..........

Great read indead. Would love to know his thoughts on extended running above 3000 rpm where the dual stage oil pump is running 70-80 psi vs the single stage running around 33 psi? I tend to tow in 4th gear at 3000 rpm and 65 mph and it's just before the dual stage oil pump kicks in. I'd have no issue bumping it up a mph or two and run the dual stage if that was deemed healthier for engine? Gut just tends to think i should stay on stage 1 for some reason. I'm that old guy that lowered a yj in the 90's, also in my instagram page.

Gread video work JTRSPARTACUS! I suppose i could have wiped the dust of my gauges before filming my parts lol.

I use the heck out of it and drive my manual transmission jt like a sports car a lot, i oil change like clockwork every 7500 kms (4600 mi) as that's been about the point i notice the ole pentastar lose some of it's zip zang from previous pentastar ownership. I run synthetic 0w as recommended. I feed mine premium also, i did cat back exhaust, hauk offroad snorkel, and something about a high compression high performance v6 just says i should probably feed it premium, we really do drive it like a sports car, you'll see on my instagram page, we take people on all the time lol, it's never been more fun to get taken to gapplebees than in a lifted jt on 37's with 4.88's and a stick. Especially when we have to make em work for it. I do think we surprise a few folks. I've taken a couple previous gen chev v8's half tons to gapplebees that thought they were going to walk the lifted Jeep, i know the 8-spd would be faster but for me it's all about the smiles per miles and that means manual transmission with a motor loud enough to hear.

 

[hjdca]

Great read indead. Would love to know his thoughts on extended running above 3000 rpm where the dual stage oil pump is running 70-80 psi vs the single stage running around 33 psi? I tend to tow in 4th gear at 3000 rpm and 65 mph and it's just before the dual stage oil pump kicks in. I'd have no issue bumping it up a mph or two and run the dual stage if that was deemed healthier for engine? Gut just tends to think i should stay on stage 1 for some reason. I'm that old guy that lowered a yj in the 90's, also in my instagram page.

Gread video work JTRSPARTACUS! I suppose i could have wiped the dust of my gauges before filming my parts lol.

I use the heck out of it and drive my manual transmission jt like a sports car a lot, i oil change like clockwork every 7500 kms (4600 mi) as that's been about the point i notice the ole pentastar lose some of it's zip zang from previous pentastar ownership. I run synthetic 0w as recommended. I feed mine premium also, i did cat back exhaust, hauk offroad snorkel, and something about a high compression high performance v6 just says i should probably feed it premium, we really do drive it like a sports car, you'll see on my instagram page, we take people on all the time lol, it's never been more fun to get taken to gapplebees than in a lifted jt on 37's with 4.88's and a stick. Especially when we have to make em work for it. I do think we surprise a few folks. I've taken a couple previous gen chev v8's half tons to gapplebees that thought they were going to walk the lifted Jeep, i know the 8-spd would be faster but for me it's all about the smiles per miles and that means manual transmission with a motor loud enough to hear.

Yeah, what you said... burning rubber in 1st with the Clutch all the way out with 37s, acceleration like a V8, 4:88 or 5:13s (what I have) make a huge difference in acceleration, and if you drive the stick like you stole it, you can give any truck on the road a run for it's money from stoplight to stoplight. It's tons of fun. The gears made me really appreciate the V6 motor and all it can do with decent gas mileage and huge tires.

 

[DanW]

I have no idea who this engineer is, but rest his soul, that was a great read and I DO drive the shit out of my 3.6 manual, so seems it will live forever! Great read.


Gears, I'm in the 5.13 camp all day long. That's where I'm going.

I'm that now old guy that put 4.10's and Nitrous on an S10 back in the day..........

I believe he is still with Stellantis. He's a good dude and has all kinds of insight into this great engine.

I did 4.56 on my JL/manual and it is absolutely perfect with 35's. We just did a 3k overlanding and off-roading trip to Vermont and whether on the highway, dirt roads, or tough trails, it's just right. I can take hills and pass on the highway without downshifting. It runs about 2450rpm at 75mph with 35" General Grabber X3's.

 

[shrinkhead]

so after a couple days with 4.10s and 37s with the 8-speed it’s obvious that 4.10 works really well as a no frills daily driver and off road as well but it’s not great. so it needs to change. now the question is 4.88 or 5.13…leaning towards 5.13 to optimize rock crawling.

 

[DanW]

so after a couple days with 4.10s and 37s with the 8-speed it’s obvious that 4.10 works really well as a no frills daily driver and off road as well but it’s not great. so it needs to change. now the question is 4.88 or 5.13…leaning towards 5.13 to optimize rock crawling.

I think with the auto 4.88 would be the sweet spot. If you've got a Rubicon, crawling won't be an issue, at all.

But its just an opinion. I'm running 35's with 4.56 gears on my JL Rubicon with a 6 speed. My brother's Gladiator Rubicon does well with 35's, 4.10 gears, and the 8 speed. If I had that rig, I'd go 4.56 with 35's and 4.88 with 37's, just from driving it and mine around quite a bit. He's been to Moab and never had a complaint with the 4.10's and 35's with that Rubi 4:1 transfer case.

Just my 2 cents.

 

[JTPatriot]

so after a couple days with 4.10s and 37s with the 8-speed it’s obvious that 4.10 works really well as a no frills daily driver and off road as well but it’s not great. so it needs to change. now the question is 4.88 or 5.13…leaning towards 5.13 to optimize rock crawling.

I have 4.88's and 37's I would not want to go any lower as cruising on the highway at 75 is around 2300 RPM's with the hemi

 

[shrinkhead]

I have 4.88's and 37's I would not want to go any lower as cruising on the highway at 75 is around 2300 RPM's with the hemi

I got used to the 4.10s with the HEMI. so new gears will only come with new axles.

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