This is my son's Jeep and I want it to remain stock until he becomes a lot more familiar with it (and even then, I will continue to recommend it stay stock). My ultimate guess is 80-90% road use with occasional light trails.
The issue is that cruising down the road at 75mph, we are turning nearly 3,000rpm. Larger issue is taking off from a stop (like a stop light), you have to shift about half way through the intersection due to high revs. It just feels like it is almost "granny geared". Like you should start out in second gear (but not quite)
I highly prefer the on-road manners of my Scrambler (258, T-5, 3.31 ratio, and 31" tires). Interstate driving I am around 2100rpm at 75 (and can easily downshift if I need power).
Add in the fact that my Scrambler (carburetor) gets 18-19mpg and his Unlimited gets 15-17mpg and the only real difference is the axle ratio...
My initial thought was to just swap out axles with someone who runs larger tires or prefers this ratio. What were the stock options? Is the 3.73 a desired ratio (I know in the CJ and Grand Wagoneer worlds it seems like everyone prefers 4.10 and 35"+ tires).
I am not familiar with the 6-speed as my unlimited is the 4 speed auto, however I don't think the added cost and work to regear to something deeper or taller is worth it if the jeep is going to stay stock. Ive read that most people have the same problem with first gear, ive even read some people just take off from a stop in second gear.
Ultimately it is your choice on if you want to drop a grand and a half to regear or do the work to swap out axles. My personal opinion is that its not worth it until, or if, he ever goes bigger tires. I just don't see the justification of spending all that money to remedy a small problem.
3.73 is not a ratio that few would want enough to bother swapping axles for. It'd be easier & cheaper to just go with a slightly larger diameter tire. You can go with a 31x10.50 tire with no lift or a 32x11.50 with a small suspension lift or perhaps a 1" body lift if you don't do tough offroad trails.
Edit: Exactly what size tires are installed now? Your RPMs seem a little high for 30" tires but I haven't done the math on that yet.
The 6 speed has a lower 1st gear than the other 5 spds so a sooner shift to 2nd is expected and not really an issue and the lower 1st is a plus off road
If you want lower rpm at highway speed and a faster speed at shift rpm in 1st just get larger tires
Since circumference is directly proportional to diameter if you want x% lower rpm in 6th gear at some defined vehicle speed you can accomplish that by increasing your current tire diameter by that same x%
However tires have to have room and you will loose some perceived power
Larger tires is not an option (until he is much more familiar with the rig). I have run larger tires and on-road it presents issues with hydroplaning (both on water and snow), wandering, and general "manners".
Larger tires is not an option (until he is much more familiar with the rig). I have run larger tires and on-road it presents issues with hydroplaning (both on water and snow), wandering, and general "manners". I am use to how a Jeep behaves and can anticipate when to drive slower etc. I would rather my son get more comfortable driving a vehicle that handles easier first.
As far as driving at 3,000 rpm, yeah, my Grand Wagoneer is that way; 3,000 rpm at 75mph. Personally, I don't like winding it out that much. One of the benefits to a more modern overdrive is the lower rpm range while cruising (while maintaining a lower ratio for starts). More realistically, I am just thinking MPGs. There is easily a 3 mpg difference in my carbureted '83 Scrambler and this Wrangler (the Scrambler even has larger tires and still gets better mileage). 3MPG may not sound like a lot; but, when you consider I will be driving the rig for a year before he does and I put between 20-30k miles / year on a rig...it adds up (quickly).
My hope was that someone who had the 3.09 ratio axles would want to trade and over a weekend we could swap them out... Is that ratio not very common?
As far as driving at 3,000 rpm, yeah, my Grand Wagoneer is that way; 3,000 rpm at 75mph. Personally, I don't like winding it out that much. One of the benefits to a more modern overdrive is the lower rpm range while cruising (while maintaining a lower ratio for starts). More realistically, I am just thinking MPGs.
you've got a misconception here about what your 4.0L should be doing on the highway.
I drove across the country this winter doing 65-80mph, turning 2.5k-3k RPM's all day for 2 days straight. Trust me 3k RPMs at 75 mph is perfect. That's exactly where you want to be.
You drop the RPMs much more and the engine bogs down and you can't maintain speed. That's the problem the 42RLE auto's have...they have a very tall OD gear, and the engine RPMs drop so much that the trans is constantly kicking down into 3rd when a bug hits the windshield.
In fact, I regeared my axles to 4.88s so that my 4.0L/42RLE could turn closer RPMs to that of a 6-speed with 3.73s. As far as MPG's go, I can get anywhere between 14-19mpg...all depending on how aggressively I drive.
Cruise control on, 4.0L/42RLE/4.88s/33s:
Remember, the Jeep has the aerodynamics of a barn. It needs to get the engine into the powerband just to push all that air.
Keep your foot out of it, drive like an old lady, keep up on maintenance, hypermile, and don't worry about 3k @ 75mph. Your best bet for mileage is keep it under 65mph.
This is my son's Jeep and I want it to remain stock until he becomes a lot more familiar with it (and even then, I will continue to recommend it stay stock). My ultimate guess is 80-90% road use with occasional light trails.
The issue is that cruising down the road at 75mph, we are turning nearly 3,000rpm. Larger issue is taking off from a stop (like a stop light), you have to shift about half way through the intersection due to high revs. It just feels like it is almost "granny geared". Like you should start out in second gear (but not quite)
I highly prefer the on-road manners of my Scrambler (258, T-5, 3.31 ratio, and 31" tires). Interstate driving I am around 2100rpm at 75 (and can easily downshift if I need power).
Add in the fact that my Scrambler (carburetor) gets 18-19mpg and his Unlimited gets 15-17mpg and the only real difference is the axle ratio...
My initial thought was to just swap out axles with someone who runs larger tires or prefers this ratio. What were the stock options? Is the 3.73 a desired ratio (I know in the CJ and Grand Wagoneer worlds it seems like everyone prefers 4.10 and 35"+ tires).
I've got the 6 speed as well but am running 33s on 4.10 geared axles. So really we should be turning about the same rpms... With that said I typically have to shift to 2nd in the middle of an intersection and I know the little automatics behind me hate it but that's just how it is. I don't turn 3k rpms on the highway but I rarely go over 65 because even though I'm 20 I drive like a grandpa most of the time. With that being said I do turn roughly 2600 rpms at 65 so I could see how you'd be close to 3000 at 75. Only thing you can do is what Jerry said above and buy bigger tires or you could eat the cost of of a regear and be the first person to go to a numerically lower ratio on a stock jeep... or do like me and slow up.
Swap in a 5 speed tranny, taller 1st gear and taller OD gear, that will help both your rpm related problems.
If you are adamant about swapping with someone else, keep in mind that all the 3.07 geared TJ's were equipped with the less than stellar Dana 35 rear axle as opposed to your much more desirable Dana 44.
I guess there is the extremely rare chance you could find an Australian TJ with a D44 and 3.07's but they are not a direct bolt-in swap for yours.
Swap in a 5 speed tranny, taller 1st gear and taller OD gear, that will help both your rpm related problems. If you are adamant about swapping with someone else, keep in mind that all the 3.07 geared TJ's were equipped with the less than stellar Dana 35 rear axle as opposed to your much more desirable Dana 44. I guess there is the extremely rare chance you could find an Australian TJ with a D44 and 3.07's but they are not a direct bolt-in swap for yours.
I ran my previous TJ at 3K rpms on the highway for many miles, the 4.0L engine doesn't mind it at all. Many car owners have problems with those rpms, they're just not used to seeing that rpm since they run small tires in lightweight cars that don't require that high of an rpm so 3K rpms scares some of them.
Of your son is such a novice driver why is he doing 75mph?? Is that the speed limit in your area? When I first got my TJ I didn't drive over 65mph and I had 8 years driving under my belt. As for gearing, why not start off in second? 1st gear in the 6spd is like a granny gear, you should be able to skip it in most situations.
Look into upgrading to a taller tire but keep the width at stock 9.5"... tires made for rain/snow now should perform better as far as hydroplaning than the GSA's the factory put on it. Also, take him out in it A LOT in varying road conditions and teach him all the little things you have learned driving Jeeps. You may be impressed with how good of a driver he becomes!
I guess from the standpoint of a 20 year old kid in college and having driven a jeep since I was 15 under my learners permit... you've just gotta realize you're driving a jeep and not a sportscar. I've had 33s on my jeeps ever since I've owned both of them and have got to say that neither handled better or worse on the highway with a 2" lift and 33s than when they were stock... besides my old tj X that 3.07 gearing which drained the power out of it. So don't be afraid of of a slightly taller for safety reasons, because as long as he drives like he's got some sense it wouldn't matter if he was on 40s (don't put 40s on it). If you don't trust him with a jeep on 31s or 32s you shouldn't trust him with a jeep on 30s.
Like mentioned before, if you want to regear by swapping axles you'll have to give up your D44 for a D35. That would be enough to keep me from doing it. To my knowledge 3.73 was as high (numerically low) as you could go in a TJ/LJ D44.
This is my son's Jeep and I want it to remain stock until he becomes a lot more familiar with it (and even then, I will continue to recommend it stay stock). My ultimate guess is 80-90% road use with occasional light trails.
The issue is that cruising down the road at 75mph, we are turning nearly 3,000rpm. Larger issue is taking off from a stop (like a stop light), you have to shift about half way through the intersection due to high revs. It just feels like it is almost "granny geared". Like you should start out in second gear (but not quite)
I highly prefer the on-road manners of my Scrambler (258, T-5, 3.31 ratio, and 31" tires). Interstate driving I am around 2100rpm at 75 (and can easily downshift if I need power).
Add in the fact that my Scrambler (carburetor) gets 18-19mpg and his Unlimited gets 15-17mpg and the only real difference is the axle ratio...
My initial thought was to just swap out axles with someone who runs larger tires or prefers this ratio. What were the stock options? Is the 3.73 a desired ratio (I know in the CJ and Grand Wagoneer worlds it seems like everyone prefers 4.10 and 35"+ tires).
Honestly, treat 1st gear like a granny gear and take off in 2nd. Yes you may need to slip the clutch a tiny bit more but you'll also have to shift one less time. I've owned 2 6 speeds and did just that with both. No problems.
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