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

[noodles]

Yup just got 4.88s installed on my JT Overland running 35s. Night and day!

Sponsored

 

[aevgladitorrubi]

So, the debate, at least for me, is settled

I watched all the videos. Scrubbed all the forums. Checked all the pricing too.

Like a lot of us, My JTR rides on 37 mud terrains on a mopar lift. For everyone who says the 4.10s are fine with this kind of set up, you are right. You can get down the road just fine, no surging, reasonable power. Its also true that doing so comes with a lot of gear hunting on the highway. But its seriously not an issue, you’ll just spDend a lot of time in 6th going down the road.

But, as decent as the 4.10s are with allowing you to get down the road, the 4.88’s are a game changer, and its not even close.

Elite Offroad here in Birmingham did a great job dropping in some Dana Spicer 4.88 gears and master install kit on my JTR this week. We used a Superchips Flashcal to dial it in. This thing will never be a hellcat in terms of pep but it moved itself with way more ease with the new rings. Very peppy, and more importantly, super smooth at part throttle. The jeep also uses all its gears and settles in to 8th without bogging. It shows off the strengths of this 8 speed well, up hill downshifts arehandled crisply and the engine never lags or bogs.

All of us have different driving styles. But for me, on the highway running 70 on flat ground i could achieve 20mpg running 2100 rpms. Pic below confirms what I saw.

We’ll put it on a trail after the break in period but I am expecting greater control off road and also less need for 4 lo on average trails here in the southeast. Hope these notes help any who are trying to make a decision. Zero regrets here, its really a no brainer and highly recommend.

I am assuming you are gas? What would you do if you had a JTRD on 37s-- 4.56?

 

[Rusty PW]

I am assuming you are gas? What would you do if you had a JTRD on 37s-- 4.56?

4.10's would put you back equal to the 3.73's with 33" tires. If you offroad a lot. I would go with the 4.56's.

 

[Bbannongmu]

I am assuming you are gas? What would you do if you had a JTRD on 37s-- 4.56?

I'd say consider 4.56. here is why in rough numbers

37" tires are roughly 12% larger than stock 33 tires (37s aren't really 37 but 33s are really 33 either so its theoretically a wash for percentage)

3.73 x 1.12 (12% lower gear) = 4.1776 (no such ratio exists. Rounding down to 4.10 could work but remember you have additional unsprung weight to account for too)

good luck!

 

[Tommyd]

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 haven’t dogged my truck very much. Every once In a while I will rev it up. I have 12,000 miles on it now. Is it to late to start “runnin” her more and more? Should I switch back to 0w20 instead of 5w30 then as well?

 

[AmishMike]

@Tommyd it’s never too late to flog your engine!
Yes occasional WOT pulls are good, like on an on ramp or playing in mud. Remember they do have a rev limiter
The other thing is to get it in higher rpm to kick in the second stage of the oil pump. If you watch the gauge it will jump from 30-70 psi.
I hate to admit this but yes switch back to the 0-20. I stay with Mobil 1 but pick any good brand and stick with it.

Sponsored