"A bit much" is somewhat the goal here, plus luckily I don't highway drive often at all. That is a good consideration too though, thanks
Question about re-gearing
- Thread starter tlord
- Start date
"A bit much" is somewhat the goal here, plus luckily I don't highway drive often at all. That is a good consideration too though, thanks
It really can’t hurt to regear to 5.13. That’s as deep as you can go in a non-Rubicon with factory axles.
The 42rle overdrive ratio 0.69 sucks, so for now just hit the OD button every time you shift out of Park and you’ll find it a bit peppier.
You can dismiss his suggestion. Anyone who argues against 3k rpm at 75mph has never had a TJ that can begin to get out of it's own way. The difficultly with the 42rle is getting that in the first place.
At the end of the day it is still limited by it's 190hp, 30% driveline losses, narrow 3200-4500 powerband and 5200 red line. In turn made worse by the 4 speed auto and it's excessively tall OD.
But put another way between 2750 and 3250, each 250 rpm is gaining about 10hp on tap taking you from 125hp at the crank to ~135hp at 3000 to around ~145hp at 3250. You lose 30% of that in the driveline, so 87 - 102 at the wheels.
If you want to make meaningful changes in the numbers on that power curve (I posted above), you've got to look at forced induction, increasing displacement by stroker crank, or swapping the motor. And you still might want or need the numerically higher gearing to have the power where you want it. For instance sizing a turbo on the smaller side might limit peak hp, but bring peak torque down to 2000rpm or lower making a wider power band and giving much better mid range power and response. Banks sidewinder was a good example of this. Increasing the hp number from 87 to 102 will have the same effect on acceleration whether you get there by gearing or power adders. Except the power adder route can mean you end up with much more than 190hp peak. It's going to be a bit more expensive when you factor tuning, but having someone install gears is not exactly cheap today. When you're putting $3k-$6k into a 20+ year old TJ without addressing all the age rotted suspension, leaking seals, etc... you've got to reality check yourself. You will never get that back at sale.
But put another way between 2750 and 3250, each 250 rpm is gaining about 10hp on tap taking you from 125hp at the crank to ~135hp at 3000 to around ~145hp at 3250. You lose 30% of that in the driveline, so 87 - 102 at the wheels.
If you want to make meaningful changes in the numbers on that power curve (I posted above), you've got to look at forced induction, increasing displacement by stroker crank, or swapping the motor. And you still might want or need the numerically higher gearing to have the power where you want it. For instance sizing a turbo on the smaller side might limit peak hp, but bring peak torque down to 2000rpm or lower making a wider power band and giving much better mid range power and response. Banks sidewinder was a good example of this. Increasing the hp number from 87 to 102 will have the same effect on acceleration whether you get there by gearing or power adders. Except the power adder route can mean you end up with much more than 190hp peak. It's going to be a bit more expensive when you factor tuning, but having someone install gears is not exactly cheap today. When you're putting $3k-$6k into a 20+ year old TJ without addressing all the age rotted suspension, leaking seals, etc... you've got to reality check yourself. You will never get that back at sale.
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I did change my gearing, did some bolt on mods netting 10 hp here, 6 there and 8 here. And I've driven it a bunch coming to the conclusion that I just want alot more power.
The challenge I run into is the lumbering RV or truck on our increasingly busy 2 lane mtn highways doing 45 in a 65. I've got the 5 speed NV3550 and when you dig through those numbers, you can get more power to pass by downshifting to 3rd, but run into the 5200rpm redline at 80mph before completing the pass. You can go wide open in 4th, but you're limited to ~75hp on that curve at 45mph, taking too long to accelerate out of the hole. You need to be able to accelerate from 45 to at least 85mph quickly to complete such a pass safely IMO. I typically hit 90-95 mph briefly making a pass in my wife's twin-charged wagon or more in my car.
You can solve this problem with the 4.0L with a bigger cam and higher psi springs (and some other work and tuning) to raise redline from 5200 to say 7000rpm making the pass in 3rd gear starting at 3000rpm. You will be starting the pass at ~135hp at the crank. For my tires and gearing, it would increase speed at redline from 80mph to 107mph with projected peak power (crank) in the 275-320hp range.
You can also solve this by increasing displacement and compression and thus power in the bottom end of the curve. Now stay in 4th gear, make roughly equal power at 2000 rpm to the example above and complete the pass at 85mph at 4000rpm with a max speed at 5200 rpm of 111mph. Peak power would again be in the 275-320hp range.
Of these builds, option 1 should cost around $3-6k. Option 2 $7k and up.
I personally do not like the sound of the 4.0L at 4500+ rpm and don't want to find out what a 4.0L at 7000 rpm sounds like from the drivers seat of a TJ. Other people would love this and that's cool. My other car's 3.8L NA boxxer 6 sounds awesome to me at it's 7250 redline. Production variants of this motor platform rev to 9000rpm. I'm not against high rpms in an engine designed around it and I like cruising at 85mph in 6th at 3300 rpms in that car. Personally I find a lower rpm while cruising in the TJ more enjoyable.
We live in a world where there is rarely a single "right way" to do something.
The challenge I run into is the lumbering RV or truck on our increasingly busy 2 lane mtn highways doing 45 in a 65. I've got the 5 speed NV3550 and when you dig through those numbers, you can get more power to pass by downshifting to 3rd, but run into the 5200rpm redline at 80mph before completing the pass. You can go wide open in 4th, but you're limited to ~75hp on that curve at 45mph, taking too long to accelerate out of the hole. You need to be able to accelerate from 45 to at least 85mph quickly to complete such a pass safely IMO. I typically hit 90-95 mph briefly making a pass in my wife's twin-charged wagon or more in my car.
You can solve this problem with the 4.0L with a bigger cam and higher psi springs (and some other work and tuning) to raise redline from 5200 to say 7000rpm making the pass in 3rd gear starting at 3000rpm. You will be starting the pass at ~135hp at the crank. For my tires and gearing, it would increase speed at redline from 80mph to 107mph with projected peak power (crank) in the 275-320hp range.
You can also solve this by increasing displacement and compression and thus power in the bottom end of the curve. Now stay in 4th gear, make roughly equal power at 2000 rpm to the example above and complete the pass at 85mph at 4000rpm with a max speed at 5200 rpm of 111mph. Peak power would again be in the 275-320hp range.
Of these builds, option 1 should cost around $3-6k. Option 2 $7k and up.
I personally do not like the sound of the 4.0L at 4500+ rpm and don't want to find out what a 4.0L at 7000 rpm sounds like from the drivers seat of a TJ. Other people would love this and that's cool. My other car's 3.8L NA boxxer 6 sounds awesome to me at it's 7250 redline. Production variants of this motor platform rev to 9000rpm. I'm not against high rpms in an engine designed around it and I like cruising at 85mph in 6th at 3300 rpms in that car. Personally I find a lower rpm while cruising in the TJ more enjoyable.
We live in a world where there is rarely a single "right way" to do something.
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