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4.88 manual?

AcesandEights

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Rodeoflyer

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Yep, your gear chart seems pretty spot on ~2800 rpm at 80 in 5th gear with 37'' tires. That's cruising rpm for this little high strung 3.6 engine.

5.13 is ~5% more than 4.88's so really only about 100rpm or so.
 

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I don't want to hijack the thread, but given what I'm reading, 4.88 sounds possibly a touch overgeared for highway cruising - do you think 4.56 with 33s would be OK on the highway @ 75 mph?
As others have said it would be hard to ever say a manual is overgeared with the two overdrives. An old school 4 speed? Yes. But the Jeep cruises fine on the highway at 75-80. My little Subaru AWD Legacy spins 2,500 at 65mph so its even deeper geared.

The 4.88's give you a great starting point to put on those bigger tires and not feel the effects as much. I would definitely check the box if I was ordering a manual trans and the 3.6.
 

Rodeoflyer

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Absolutely.. I would have checked that box for 4.88's in a HEARTBEAT if they had been available when I purchased my Rubi.
 

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I got mine yesterday. Dang, like said above, first gear is *short*. I too was thinking that I could start in second, but the motor just doesn't seem to have enough low end torque to pull that off. I'm used to driving a 4.7 Stroker in my LJ, it has mountains of torque compared to this. But at speed it's as smooth as a sewing machine, never feels like it's over-revving on the freeway (what little I did, still in break-in).

With the 4.88's I found that if I want I can roast those 33's to the point that they won't be new when I switch to 35's next week. And low-range first gear, I'm calling it piss-low. You dump the clutch in first low, get out of the Jeep, take a pee, and get right back in because it hasn't moved anywhere. :)
 
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TriumphJeepster

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With the 4.88's I found that if I want I can roast those 33's to the point that they won't be new when I switch to 35's next week. And low-range first gear, I'm calling it piss-low. You dump the clutch in first low, get out of the Jeep, take a pee, and get right back in because it hasn't moved anywhere. :)
Question, I see you have the 2 dr rubi, same as I have on order. For around town driving, mostly stop and go, would you say you LIKE the gearing?
 

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Yeah, don’t fear the gear with the 3.6. It doesn’t start galloping until about 3000rpm anyway. I still have a usable 1st gear with 37” tires but can pretty much shift into 2nd as soon as it’s rolling.

The ratios aren’t great in the manual. It has a granny 1st, pretty good second but I’d like another gear between 2nd and 3rd. I’d happily give up 6th altogether for that. It’s pretty unusable under 80moh and I never drive that fast anyway. The great thing about the jeep is I’ve never gotten a speeding ticket it it lol
 

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Question, I see you have the 2 dr rubi, same as I have on order. For around town driving, mostly stop and go, would you say you LIKE the gearing?
So far I'm just doing around town break-in and finding that 4th is a gear I can stay in for a long time. Engine is happy to rev and it'll go down to below 35 MPH and still pull along. Almost like having - gasp - an automatic.
 

AVGeek99

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I have 35s with the stock 4.10s. I am plesantly surprised with how well it does. I was very worried that 6th gear would be unusable. But it does perfectly fine on roads that aren't too hilly, which is most roads where I live. I just took a road trip to Moab and I was very happy with how it performed on and off road.

That being said, I definitely would have gotten the 4.88s had they been available when I ordered my 2021. If I ever go to 37s I will definitely regear to 4.88s.
 

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jbcrane

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I'll chime in as a proud new owner of 4.88's in my 6-sp MT 4-door. It. Is. Awesome. You'll not regret it. No comment on running with 33's - but I'm on 315/70R17 KO2's (so a small-ish "35") and it's a perfect set up here in Colorado. I agonized between 4.56 and 4.88's. I have no plans to run 37's - but wanted to future proof him none the less. Been keeping him as light as possible but I know it won't last. When he starts getting heavier he'll be ready. Now he runs like a jack rabbit compared to the lugging-chugging stock 3.45's. Very happy with what I have. Proceed with confidence. And yes, did the Dana Spicer ring & pinion with master rebuild kits front and back - and added matching Dana nodular iron covers too. Looks great. Runs great - especially at altitude.
 

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Here's an update for those who might still be interested in a comparo... After driving the Jeep around town for a week with the OE 33" tires I had no real feeling that it was geared too low with the exception of first gear, which seems to be about halfway to the old "Granny Gear" that my F-250 has, which to me is a Good Thing as I want to be geared low for trail use. 6th gear on the highway at 2,500 RPM never seemed to be an issue with the V6, it's way smoother than the inline 4.7 I'm used to in my LJ.

So then I switched to a set of 35's, and after a week of the exact same driving patterns my opinion is that the 4.88's are really *meant* for 35's. First is still a mini-granny but you do need to start in it from a standing stop simply because the V6 doesn't have the low end that I'm used to in my LJ. 6th now is something I use on the highway, the engine seems perfectly happy to stay in 4th or 5th around town up to about 45 MPH. I live at 5,800 feet above sea level so I may never know if the V6 is any peppier down low. It averaged 18 MPG on it's first tank of gas on the 35's, though that included about an hour on I-25 the other day, typical for me. I corrected the speedo/odo using the J-Scan app.

For my uses this just feels "right", better than the OE 33's.
 

jbcrane

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So then I switched to a set of 35's, and after a week of the exact same driving patterns my opinion is that the 4.88's are really *meant* for 35's.
Agree completely. Haven't taken him up the Eisenhower Tunnel yet but am looking forward to his first run (well, as much as you can look forward to driving I-70...). But really can't wait to get him up in the San Juans this Fall. That's where the fun's at.
 

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Just took delivery of a manual JLR with 4.88s.

It's a little idiosyncratic, but I love it.

First is so short that you don't need to apply throttle when engaging it in 2-Hi. In a lot of situations you can start in second without excessively riding the clutch. I still only start in second occasionally though.

The large ratio difference between first and second makes it a little jerky when shifting. It's something you'll have to learn/ get used to. When you match revs well, it's smooth.

On the OEM 33s the vehicle is an absolute BULLDOZER in 4-low. On flat ground, you can idle against the brake, with the brake pushed to the floor, and it will not stall. You can two-foot drive it on obstacles with the throttle and the brake, or with brake and a little clutch modulation. It simply will not stall on any trail with a rating below 'difficult'.

I'm going to 35s soon, and while I think 35s are probably better suited to 'normal' street driving with this setup, I'm so impressed with how the manual, 33s, 4.88 combo drives off-road.

ETA: These observations are all near sea level. Hope this helps.
 
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Go_Galt

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I just had the unique opportunity to drive my '22 manual JLR with factory 4.88s with 37s.

A friend had a set of 37" BFG KM3s on Teralfex Nomad wheels waiting to be used, and he let me mount them up and rip around town for a couple hours. So I got to drive the 4.88 manual combo on 33s, 37s, and then back to 33s, back-to-back-to-back.

My observations on 37s:

-First is still plenty short (Probably not surprising). The Jeep still happily pulls forward from a stop by just engaging the clutch, no throttle needed. You can still back out in reverse with no throttle as well.

-Crawling on flat ground in first gear 4low, I *still* could not make the Jeep stall by standing on the brake. It will actually shudder now when idling against a mashed brake pedal like this, but still feels like a tractor that refuses to stall in 4low.

-Can still crawl up small undulations in terrain in 4low, in first, second, and third gears with *no* throttle input. Just engage clutch and it happily walks up.

-Driving around town feels much more natural and intuitive on the 37s. With the 33s the Jeep is manic in first gear and only slightly less so in second. While this is fun and kind of charming in a weird way, I absolutely prefer how it drives around town on the 37s. The 37s calmed it down to the point that it feels like a normal progression through gears now.

-Still pulls very well around town. First will still get you off the line like you're spring-loaded, second still pulls with a surprising amount of authority, and third will easily get you going up to freeway velocities on an on-ramp. Third and Fourth are still great 'around town' gears for quick accelerating and then cruising at ~45 mph at low RPM.

-With respect to the above note- THIS surprised me the most. I assumed the 3.6 Pentastar would feel like a dog around town on wheels+tires this big and heavy. I assure you on 4.88s it is not. It still revs freely up to the RPMs that it likes to make power, and never felt burdened/overworked. I still had to consciously make sure I wasn't speeding on 45 mph roads, because running through the gears is still so effortless.

Conclusion:

-I am extremely sensitive about changes in manual driveability when going to big tires. I initially assumed there was no way I was going to 37s, even with these 4.88 gears. If 37s affected driveability, made low speed crawling difficult, or mandated using the clutch in a mechanically unsympathetic manner, I wouldn't touch them with a ten foot pole. Seriously, I'd rather die of ball cancer than be forced to abuse a clutch because of big/heavy tires.

-After driving these 37s around town for a couple hours, I have NO reservations about setting up my JLR like this. If there's anyone that would admit 'this sucks badly on 37s', it would be me. I wanted to hate it. I loved it. I'm 100% getting 37s now.

-These observations are with a pretty heavy wheel and tire combo. These Teraflex Nomads are ~75% heavier than OEM Rubicon wheels, and 37" KM3s are something like 15 pounds per corner heavier than a 37" K02. It's possible you may be using a lighter 37" wheel/tire combo than what I drove here.

-These observations are all close to sea level (roughly 1000'). If you're at elevations where the Pentastar is known to be asthmatic, and you need to pass semi trucks uphill in the mountains, I can't speak to that. If you have a 4-door with several hundred pounds of 'overland' gear on it, or a trailer, I can't speak to that.

-What I can tell you is that 4.88s turning 37s on a light, minimalist 2-door at low elevation is awesome.

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