4.88 manual?

[TriumphJeepster]

I just had to 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:

-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 absolutely 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 ~40 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 very 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.

Thank you for that write up. Looks like at least the 35's are in the near future for me.

I really dig the XR wheels, might just do some spacers and 35's in the short term. Drive that until out of warranty and get a lift.

Ugh. Choices. Thank you for making it harder =]

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[Go_Galt]

Thank you for that write up. Looks like at least the 35's are in the near future for me.

I really dig the XR wheels, might just do some spacers and 35's in the short term. Drive that until out of warranty and get a lift.

Ugh. Choices. Thank you for making it harder =]

We were surprised that 37" KM3s on these wheels (0 offset and 4.75" backspacing) did not rub at all on a stock 2-door Rubicon. You can turn full lock, backing up or moving forward, and do any kind of street driving, and it never rubs.

The tires did start to lightly chatter on the back of the rear fender liner when going up hill and articulating a small amount. That's to be expected, but I was impressed how one could do any kind of street driving with zero lift on these, if that was their goal.

 

[benny_rt2]

It will be awesome on the technical trails crawling in the rocks in 4lo, which is why it's offered. I wouldn't mind daily driving with that gearing in the JL. My TJ had 5.13 and 5spd manual on 33s before upgrading to much larger tires later. But for the year I was still on 33s with 5.13s I loved it. It was quite an experience.

But it is subjective and also depends on the trails. If you are in muddy trails with such low gearing, creeping along in 1st and 4lo, you'd be stuck alot.

 

[Chance_P]

Can anyone provide part # on these axles?

 

[AcesandEights]

DMS is the sales/option code if that's what you mean.

 

[TriumphJeepster]

Allright. For those wondering the 2 door with 4.88's is wildly impractical great fun. Rocket ship at sea level. Much smiling.

 

[n8billings]

Just ordered one today. Thanks for all the comments. They helped solidify my decision!

 

[wsly14]

Just ordered one today. Thanks for all the comments. They helped solidify my decision!

Awesome! I’ve put 2500 miles on mine so far and I think it’s a great gearing setup. Other than first, I wouldn’t want the gears to be any longer. If I have any momentum or downward slope, I use second gear to start out. It turns about 3,000 rpm at 80mph, which seems about right to me given the lack of low end torque the 3.6 has.

 

[n8billings]

Awesome! I’ve put 2500 miles on mine so far and I think it’s a great gearing setup. Other than first, I wouldn’t want the gears to be any longer. If I have any momentum or downward slope, I use second gear to start out. It turns about 3,000 rpm at 80mph, which seems about right to me given the lack of low end torque the 3.6 has.

Good to know. Now I play the waiting game…

 

[atmotocrosser]

I just ordered one too. Cheers to all those saving the manuals.

 

[TriumphJeepster]

At this point in a few hundred miles I am totally use to the 4.88 gearing. Wayyyy better than my old JK with 3.73 and 33's

 

[VAM4880]

Another 2 door with 6 spd and 4.88s. Got about 2,000 miles on it - real fun to drive...

 

[atmotocrosser]

Another 2 door with 6 spd and 4.88s. Got about 2,000 miles on it - real fun to drive...

Will you be going 35s is 37s in the near future?

 

[VAM4880]

Will you be going 35s is 37s in the near future?

I thought I would go right to 35s, but right now I am happy with the 33s. Drives better than I thought It would. And it is great checking out what others have done to their jeeps - so I think I’ll wait a bit before doing anything.

 

[Go_Galt]

I just got back from two weeks in Colorado and Utah in the 2-door manual on 4.88s and 37" K02s. I did Red Cone, Black Bear Pass, Imogene Pass, Fins and Things, Hell's Revenge, Poison Spider, Top of the World, Elephant Hill, and a couple others I'm probably forgetting.

For people wondering about manual + 4.88 + 37s:

-Highway driving with this setup does indeed suck at high elevation and/or on steep grades. 5th and 6th gears are distant memories in these situations. 4th actually worked very well for passing and maintaining speed in a lot of cases, but I frequently needed third to maintain progress up hills. You're going to be working a lot. If I lived in an area like this, and was dead set on 37s with a manual, there's no doubt I would want 10-20% deeper gearing for quality of life purposes.

-Slow, technical rock crawling is still very, very good on 37s, thanks to how short 1st gear is. It's absolutely not a chore to start out in the middle of a tough obstacle with the Jeep sitting at a precarious angle. You can easily two-foot drive at idle with the clutch and brake to crawl and then subsequently hold yourself on obstacles.

-That said, for the toughest/steepest slow obstacles, there were still plenty of situations were I wanted a little slower crawl speed and a little more wheel torque in 1st gear. This was easily done by leaving the clutch partially/half engaged while you climb a ledge or negotiate an obstacle at idle. While I found this easy to do, and it wasn't abusive to the clutch, it's definitely a case where 10-20% deeper gears would make things a little easier.

-On 37s I found myself kind of 'between gears' in certain situations. First would be simply too slow, while second didn't give quite enough wheel torque at low RPMs, mandating you keep the RPMs and speed a little higher than you'd ideally like. There were a lot of situations where I found myself thinking that shorter gearing would allow 2nd gear to be more useful in more slow/technical situations.

Overall, this setup on the 37s is "perfectly usable", and I'm very happy with it, but it's "not ideal". IMO 5.13 or 5.38 would allow:
-First to crawl a tad slower for the absolute toughest obstacles
-Second to be much more useful in more low-speed situations (I'll bet second would be your ideal go-to on of 80% obstacles, if it were 10-20% shorter).
-Much better manners at high altitudes

Hope this helps anyone considering 37s.

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