WOT, Redline Passing Power (Downshift Observations) at 65-70mph, From 8th Gear, With 4.10 VS 4.56 VS 4.88 VS 5.13 Gear Ratios

[Jeep Dude]

My ride is a 2019 Wrangler Rubicon Unlimited, on KO2 37's, with a Metalcloak 2.5 lift, and a few other goodies like full metal skid plate(over 100 pounds) etc.

It is my daily driver, so I do drive on more dangerous, 2-way roads, where traffic speeds are about 65mph, and passing power is important around the 18-wheelers.

If you are driving an anemic car, with subpar passing power over 65mph, it can be a butt puckering experience. I also love rock crawling on the weekends up in the mountains, and driving up extreme vertical incline gravel roads, sand dunes, etc.

Now to the question, that has been putting me off from re-gearing for the longest of time. I have read many posts on this forum, about which regear ratio is the best, and ultimately it seems to boil down to personal preference, so I don't want this discussion to turn into a , my 4.88 is better than your 5.13 and vice versa type of thing.

I want this to be a comparison of various re-gearing ratios, including stock, with real world acceleration observations from owners, on WOT, kick-down passing power with the 8-speed auto, 37inch and larger tires, at speeds over 65-70mph, and preferably with the 3.6L (unless the 2.0L owners are experiencing and observing what it is that I describe here)

I must say that I'm a bit surprised, that I have not read more discussions, on the 8 speed automatics ability or disability, with a significant regear, to be able to downshift(kick-down), from 8th speed to 4th speed, or basically a low enough gear, that will allow the Pentastar to hit REDLINE, while attempting a WOT pass around a huge truck at speeds over 65-70mph.

I have heard and even seen on youtube, owners with 5.13 gears, and I THINK even with 4.88's on the 8-speed, with 37 inch tires, and the 3.6L, completely lose its ability, to downshift to a proper gear, that would provide optimum FULL POWER for passing, even when attempting to manually downshift it. To reiterate, with stock 4.10 gearing, on an exact same setup, the auto 8-speed will downshift at WOT, regardless if doing over 65-70mph, to a low enough gear, that will allow the RPM's to stay in the 5000-6000rpm zone while passing, and achieving full power while WOT.

With higher re-gearing, at least with the 5.13's, this does not seem to be the case. It will NOT downshift to an efficient enough gear, to allow for maximum passing power at those aforementioned speeds. This to me is a deal breaker, and quite disconcerting.

I noticed that Jeep added 4.56 gears on the Xtreme Recon package, which makes me ask two questions in regards to this choice. Did Jeep reprogram the auto transmission (glitch), to allow for good power WOT downshifts at higher highway speed passes? Or is this the "sweet spot" gear ratio afterall, for those who fit the criteria i basically humbly tried to describe above? Will adding 37 inch tires, to the xtreme recon package, with the 3.56 gears, and 8-speed auto transmission, still allow for identical type of downshifts, as with stock 4.10 Rubicon gears, on 37inch and larger tires?

I hope my question is clear enough to understand, and the dilemma I'm having about which re-gear project to do in the future, if any at all. It's not like I'm dissatisfied with the 4.10, nor am I desperate to replace it, not by a stretch of the imagination. Clearly, my perfectionist side seeks a higher numerical gear ratio, for the obvious reasons, that need no explaining.

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[Chocolate Thunder]

https://www.jlwranglerforums.com/forum/threads/3-6l-8-at-37”-4-88-or-5-13.63486/

 

[Jeep Dude]

https://www.jlwranglerforums.com/forum/threads/3-6l-8-at-37”-4-88-or-5-13.63486/

Yup read it already. Thank you for that. However it doesn't answer my direct question at all. I think there were a mere 1-2 posts, that mentioned [Banned Site]'s experiences, but it ended there. As far as i'm concerned, those posts did not answer anything at all.

Waaaay too much "noise" in that thread.

I don't care about yada yada yada, like top speed, and fuel economy, and acceleration from a dead stop, and what is your rpm with cruise control on @75mph, and.....

All I care about is a SPECIFIC discussion, addressing my question, about full passing power, WOT downshift capability from 65-70mph. I don't want to take away, what the stock 4.10 is already providing, WOT downshifting wise, at those speeds.

Like I wrote earlier, this road is dangerous enough, so I need to make an educated decision on this specific question alone. That thread you linked does not cut it sorry to say, although it it does provide plenty of other types of interesting information, on the topic of re-gearing.

 

[BradyW]

This doesn’t answer your questions but my 392XR has no trouble downshifting at 65mph or 85mph if you go WOT. It will get to the 110mph limiter quickly and easily and sound very angry, in a good way. There doesn’t appear to be any transmission issues or glitches with the 4.56 gears in the 392XR.

 

[Jeep Dude]

In the perfect world, I'd rip my engine out, and drop your 392 in, and all would be solved , but this is not a perfect world

Enjoy your 392XR, Congrats!

 

[Headbarcode]

I've been poking around the shorter gear topic, and have read about the 8-speed not dropping as many gears with say 5.13's compared to what it did with factory 4.10's. Pure hypothetical thinking tells me that there must be some protective programming involved. The computer seems to prefer being further down in the meat of the power range, so less downshifts would be needed to hit that same rpm range with shorter gears.

 

[BuffaloBill]

I don’t have the same setup you’re interested in (mine is diesel, 35”, and 4.10), but personally I enjoy manually shifting the transmission sometimes. I don’t typically do that on the highway so much, but would do so if it wasn’t giving me the passing power I wanted.

If you did get the gear ratio best for the conditions you’re interested in, and it didn’t downshift as you’d like it to while passing, would you consider manually downshifting? Slapping the lever to the right and working it forward, etc?

 

[Gaffer]

Does this help?

 

[Jeep Dude]

I don’t have the same setup you’re interested in (mine is diesel, 35”, and 4.10), but personally I enjoy manually shifting the transmission sometimes. I don’t typically do that on the highway so much, but would do so if it wasn’t giving me the passing power I wanted.

If you did get the gear ratio best for the conditions you’re interested in, and it didn’t downshift as you’d like it to while passing, would you consider manually downshifting? Slapping the lever to the right and working it forward, etc?

Good question, but you see, even when you DO manually downshift it, it simply WILL NOT ALLOW YOU TO DOWNSHIFT TO THE PROPER GEAR FOR OPTIMUM POWER!

There are a couple of videos on youtube demonstrating this quite clearly, and dare I say, quite disturbingly.

I don't expect much feedback in this thread, because I do fear, for the obvious reasons, that what I'm asking about, is something best shoved under the rug, and forgotten about, a "buzz kill" if you will

 

[BuffaloBill]

Good question, but you see, even when you DO manually downshift it, it simply WILL NOT ALLOW YOU TO DOWNSHIFT TO THE PROPER GEAR FOR OPTIMUM POWER!

There are a couple of videos on youtube demonstrating this quite clearly, and dare I say, quite disturbingly.

I don't expect much feedback in this thread, because I do fear, for the obvious reasons, that what I'm asking about, is something best shoved under the rug, and forgotten about, a "buzz kill" if you will

Ok, sorry. I didn’t know it would prevent a manual downshift!

 

[XtremeRetard]

Well I can say the 3.6L XR JLU with 4.56 gears and 35's drives like my wifes cherokee 3.2L v6.

That is to say, its not fast. Though if you keep your foot on the floor it will kick down and rev out ok.

I suspect if overtaking power is required you might be better off upgrading to the 392

 

[XtremeRetard]

Im trying to get my wife to tell me she wants my 3.6L XR so I can go 392...

 

[CarbonSteel]

I guess I would question why IF 4.88s or 5.13s and 37's (depending on tire OD) brings the ratios back in line with 4.10s and 33's why there would be such a difference in passing.

I have 37's and 4.88's (wish I would have gone 5.13's) and have skid plates, winch, lift kit, axle skid, LCA skids, trusses, etc. and I have not experienced anything weird when trying to pass. It typically does not drop below 5th, but it typically did not do that with 4.10's and 33's either.

 

[4xFUN]

I have a very similar setup except on a JLR: 3.6 non-eTorque, 8 speed, 37" KO2's, 2.5" lift, skids, steel bumpers and winch. I used a taser to set tire size and gear ratio and have put a couple thousand miles on her since regearing. I find when merging on the freeway and punching it (WOT) she drops gears and revs to redline way too easily and too often. I plan to remap shift points when/if I install the Edelbrock Supercharger sitting in my garage and if I decide not to use the Edelbrock, then I will do the Livernois tune and they also remap the shift points as part of the tune.

 

[damageinc321]

I guess I would question why IF 4.88s or 5.13s and 37's (depending on tire OD) brings the ratios back in line with 4.10s and 33's why there would be such a difference in passing.

I have 37's and 4.88's (wish I would have gone 5.13's) and have skid plates, winch, lift kit, axle skid, LCA skids, trusses, etc. and I have not experienced anything weird when trying to pass. It typically does not drop below 5th, but it typically did not do that with 4.10's and 33's either.

So why do you regret not getting 5.13s? I'm trying to choose 4.88 or 5.13, my area is mostly flat and I don't do much highway driving but when I do it's for 8hrs for periodic road trips. I would like to regain the acceleration like stock and maybe improve some mpg's. I have 2018 jlur with 3.6 auto with 37's and 3"lift with Rocksliders and steel bumpers. I currently get 14mpg avg. I might go to 38 or 39s but not 40s.

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