6-Speed 4.10s with 37s Need Some Help

[Hardhead]

It's all software driven, recalibrate then you decide. No matter what I tell you people on here will want to argue. If you were happy with the shift points before you went with bigger tires, I would recommend 4:56 gearing since you have a rubicon with a 4:1 transferase and you were happy before the larger tires.

Shift points in A manual transmission are software driven ?

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[kahuna357]

Shift points in A manual transmission are software driven ?

Depends on your interpretation. If you are going by speedometer versus tach then yes. Thanks for proving my point.

 

[tjbrown23]

Depends on your interpretation. If you are going by speedometer versus tach then yes. Thanks for proving my point.

I see where your coming from and it would make a difference if you shifted based on speed alone. I have been primarily using the tach and engine noise to dictate shifting and the speed difference is quite easy to calculate fast. I'm finding I am off +7 in the 70s, +5 in the 50s, +4 in the 40s and so forth. I was just curious if other engine settings were based on speed/rpms that would potentially change such as throttle, intake, and what not. I could imagine in the automatics recalibrating the speedometer would be day and night different.

 

[PDiddy]

Depends on your interpretation. If you are going by speedometer versus tach then yes. Thanks for proving my point.

I don’t remember ever shifting by anything but engine noise, except for when I was first learning to drive a stick. Even then I used the tachometer.

I have never heard of shifting by the speedo. What happens when you have a heavy load or are going up a steep hill? You just shift too early?

 

[PDiddy]

I see where your coming from and it would make a difference if you shifted based on speed alone. I have been primarily using the tach and engine noise to dictate shifting and the speed difference is quite easy to calculate fast. I'm finding I am off +7 in the 70s, +5 in the 50s, +4 in the 40s and so forth. I was just curious if other engine settings were based on speed/rpms that would potentially change such as throttle, intake, and what not. I could imagine in the automatics recalibrating the speedometer would be day and night different.

I just went to 35s and regeared to 4:88 and have not recalibrated anything yet. I’ll be getting it done next week. So far there is no difference in how the vehicle shifts. Seems completely
Normal. It just has more pep. It will be interesting to see if there is any difference when I do get it calibrated. I don’t think there will. Just my mpg and speedo will be accurate.

But, you should get it calibrated. You never know what you don’t know. I waited because I wanted to do the recalibration at once. Jeep service chargers for it and I don’t want to pay twice. Once for tires then again for the regear.

 

[Hardhead]

Depends on your interpretation. If you are going by speedometer versus tach then yes. Thanks for proving my point.

If you shift by speedo, then you should not be driving a manual ?

 

[Hardhead]

I just went to 35s and regeared to 4:88 and have not recalibrated anything yet. I’ll be getting it done next week. So far there is no difference in how the vehicle shifts. Seems completely
Normal. It just has more pep. It will be interesting to see if there is any difference when I do get it calibrated. I don’t think there will. Just my mpg and speedo will be accurate.

But, you should get it calibrated. You never know what you don’t know. I waited because I wanted to do the recalibration at once. Jeep service chargers for it and I don’t want to pay twice. Once for tires then again for the regear.

how do you like the 4.88 with the 35s. you driving a manual?

 

[Renegade]

Shift points in A manual transmission are software driven ?

We are all part of the Matrix, so EVERYTHING is software driven!

Actually I’ll weigh in on this. The automatic will make adjustments based on speed and load, so reprogramming is more important. In a manual, all its doing is changing the speedometer readout. I think 4.88 or 5.13 would both offer sufficient improvement. 4.88 should be fine as long as you don’t eventually wind up on 40s...

 

[PDiddy]

how do you like the 4.88 with the 35s. you driving a manual?

I guess I should have mentioned I have the auto. I went with 4:88 because o tow a large travel trailer and wanted to not just get the torque back to stock, I wanted a little more. My RPMs are at 2200ish at 70mph.

so far I love it. Nice and peppy.

 

[tjbrown23]

We are all part of the Matrix, so EVERYTHING is software driven!

Actually I’ll weigh in on this. The automatic will make adjustments based on speed and load, so reprogramming is more important. In a manual, all its doing is changing the speedometer readout. I think 4.88 or 5.13 would both offer sufficient improvement. 4.88 should be fine as long as you don’t eventually wind up on 40s...

That's what I figured with the speedometer, but after driving it again last night I think eventually I will regear to 4.88s. I think if you live somewhere flat you'll be fine with 37s and 4.10s but I seem to always be either lugging it around or downshifting and cruising at 2800 rpm. If I do 60+ its not bad but staying at 55 is not enough for 5th gear to make it up any slight grades and holding speed. My next question is will I experience an increase in mpg with a regear specific to the manual? I'm thinking it would minimal but more enjoyable to drive and be able to cruise low in the power range.

 

[hjdca]

The 6th gear on our manual JTRs is higher than the 8th gear in the auto JTRs -- I think about 200 rpm or so higher at the same hwy speed. Manual gear ratios (5th - .81, 6th - .72). Auto gear rations (7th - .84, 8th - .67)... So, our hwy rpm with the manual in 6th gear should be slightly higher than the automatics -- but, we do not have a torque converter. Personally, I live in the mountains and am leaning towards 5:13s for when I install my 37s.

 

[tjbrown23]

The 6th gear on our manual JTRs is higher than the 8th gear in the auto JTRs -- I think about 200 rpm or so higher at the same hwy speed. Manual gear ratios (5th - .81, 6th - .72). Auto gear rations (7th - .84, 8th - .67)... So, our hwy rpm with the manual in 6th gear should be slightly higher than the automatics -- but, we do not have a torque converter. Personally, I live in the mountains and am leaning towards 5:13s for when I install my 37s.

Have you done any research on what 5.13s would be like at +70mph for 5th and 6th? I don't want the truck to be running hard on the interstate.

 

[mstrav73]

I think your best bet would be to regear the truck to 4:88 or 5:13s. I know it’s another $1600, but it’s going to remove that struggle in shifting and make it feel peppy again.

Those tires are about 15lbs heavier than you stock ones. Assuming you went with the 12.5 width, not the 13.5 width coopers. That’s a heck of a lot more weight per wheel that’s eating up the torque.

those rims dont look stock so it could be way more then 15lbs from the tires. It will def need to rev several hundred rpm higher then when it had the stock 33's

 

[tjbrown23]

those rims dont look stock so it could be way more then 15lbs from the tires. It will def need to rev several hundred rpm higher then when it had the stock 33's

The wheels are AEV Salta for the JK I loved the simple look and no fitment issues. The only difference from these vs the ones designed for the JL and JT is roughly 1/2 more offset. From my research they are only 9 lbs heavier than the stock grey rubicon wheels. The tires on the other hand are 77lbs vs stock 61 so I'm plus 25lbs per corner total. I have noticed running it out around 3300 rpm is about right before it was 3k. I just don't like where 55, 45 or 35 mph fall in the gears, I seem to be close to either 3k rpm in a lower gear or under 2k in the next. With this being my first standard my only reference is stock with 33s. Stock I was always running 2200-2500 rmp. Is it alright to be cruising around 3k rpm?

 

[hjdca]

Have you done any research on what 5.13s would be like at +70mph for 5th and 6th? I don't want the truck to be running hard on the interstate.

3000 rpm is when the computer increases the oil pressure for high rpm running. You can see it on your own gladiator if you turn on the oil pressure gauge. Mechanically, the objective is to stay under this 3000 rpm threshold for long hwy driving in your highest gear - 6th for the manual. I believe with both 4:88s or 5:13s you will always be under 3K rpm on the fwy in 6th..., so, .... probably best to go by your needs - flat terrain... or mountains and towing.

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