6-Speed 4.10s with 37s Need Some Help

[tjbrown23]

I need some help figuring out the best shift points. This is my first manual transmission vehicle and love it! I drove it stock Rubicon 4.10s with the standard 33in Wildpeak MTs over 2k miles, drove great and got acquainted with it. Just picked it up last week with the mopar lift and 37 cooper stt pros. I'm now struggling to find the best shift points with the new tires. Can you guys give me some tips or what rpm range you seem to be shifting with each gear?

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[DreamedofaJeepSomeday]

I need some help figuring out the best shift points. This is my first manual transmission vehicle and love it! I drove it stock Rubicon 4.10s with the standard 33in Wildpeak MTs over 2k miles, drove great and got acquainted with it. Just picked it up last week with the mopar lift and 37 cooper stt pros. I'm now struggling to find the best shift points with the new tires. Can you guys give me some tips or what rpm range you seem to be shifting with each gear?

I don't have larger tires or 4.10 gears. My Overland with manual is stock. So I can't help with the specifics you are asking for.

However, having driven many different vehicles with MT in my life, I think it is more just getting the feel for how much torque you have for given speed and acceleration rate. You will learn by doing.

 

[PDiddy]

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.

 

[tbaker]

You need to recalibrate your computer to the 37 inch tires you are running it will also recalibrate your speedometer I did mine but it’s an automatic and it made a big difference I would do that first before I did a regear I used the rough country recalibration kit to do mine it’s like 140 dollars

 

[Xxtavixx]

My 6mt with 35x11.5 is slow, youre probably feeling the near for a regear more a need to find new shift points

 

[tjbrown23]

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.

Yeah I went with 37x12.5x17 and I did loose a bit if torque but surprisingly its not bad. Around town and highway driving its liveable, interstate driving in the hills of WV it sucks. 6th is useless unless your downhill and coasting, 5th has no power to maintain speeds up hill so 4:88 gears are probably my best bet.

 

[DreamedofaJeepSomeday]

Yeah I went with 37x12.5x17 and I did loose a bit if torque but surprisingly its not bad. Around town and highway driving its liveable, interstate driving in the hills of WV it sucks. 6th is useless unless your downhill and coasting, 5th has no power to maintain speeds up hill so 4:88 gears are probably my best bet.

Since you live in hills, yes.

 

[tjbrown23]

My 6mt with 35x11.5 is slow, youre probably feeling the near for a regear more a need to find new shift points

It was never fast to begin with but its a little slower to pick up speed. I think my main problem was not staying in the gears a little longer. Just seems like I'm over reving the engine when its above 3000 rmp.

 

[PDiddy]

Yeah I went with 37x12.5x17 and I did loose a bit if torque but surprisingly its not bad. Around town and highway driving its liveable, interstate driving in the hills of WV it sucks. 6th is useless unless your downhill and coasting, 5th has no power to maintain speeds up hill so 4:88 gears are probably my best bet.

I would do it. It will make the truck much more enjoyable to drive. Which, for the money we spent on these trucks, it better be enjoyable. If I were you, I would go 5:13. It won’t cost any more and you will have a little more torque than stock. I have 35s with 4:88 on my auto gladiator and it is lovely.

 

[tjbrown23]

I would do it. It will make the truck much more enjoyable to drive. Which, for the money we spent on these trucks, it better be enjoyable. If I were you, I would go 5:13. It won’t cost any more and you will have a little more torque than stock. I have 35s with 4:88 on my auto gladiator and it is lovely.

I need to do some more research on 4:88 vs 5:13 I don't want to go too deep and lose the overdrive in 5/6 gears. I wasn't disappointed with the gearing on the stock wheels. And don't get me wrong it's not bad with 4:10s and 37s but in the hills of WV trying to stay 70-75mph is difficult.

 

[PDiddy]

I need to do some more research on 4:88 vs 5:13 I don't want to go too deep and lose the overdrive in 5/6 gears. I wasn't disappointed with the gearing on the stock wheels. And don't get me wrong it's not bad with 4:10s and 37s but in the hills of WV trying to stay 70-75mph is difficult.

yeah, look around on this forum. I think there is plenty of feedback on the 5:13 gearing. I said you should go 5:13 but is really up to your needs. I just know, you will love a regear.

 

[kahuna357]

Before you spend money on regearing, recalibrate your speedometer.

 

[tjbrown23]

Before you spend money on regearing, recalibrate your speedometer.

The shop forgot to recalibrate the speedometer before I picked it up, I plan to schedule it this week. From my understanding with a manual transmission this will only change the displayed speed to be accurate nothing with how it drives or operates is that correct?

 

[DreamedofaJeepSomeday]

I need to do some more research on 4:88 vs 5:13 I don't want to go too deep and lose the overdrive in 5/6 gears. I wasn't disappointed with the gearing on the stock wheels. And don't get me wrong it's not bad with 4:10s and 37s but in the hills of WV trying to stay 70-75mph is difficult.

If you were happy when you had 33s, then choose 4.88. This is based on the math: 37/33 * 4.10 = 4.60. The 4.88 gives a little more torque for the heavier tires.

If you'd like more oomph for those hills, choose 5.13, at the cost of a little less MPG.

 

[kahuna357]

The shop forgot to recalibrate the speedometer before I picked it up, I plan to schedule it this week. From my understanding with a manual transmission this will only change the displayed speed to be accurate nothing with how it drives or operates is that correct?

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.

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