Regearing, where does the power come from?

[Coldtoes]

Zf850 for tranny nvg240 for transfer case

ha! Here I was expecting to enter every value for every gear. Now i see you can just choose from a drop down, that sure simplifies it. Thank you!

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[Animal]

This looks like a data heavy site which is very much my kind of site, however to use it we need to know a whole ton of numbers. I expect somewhere in this forum they can all be found if you dig enough and are lucky, but do you happen to know any of these already or know any of the threads that would have them?
Also, it has a field for "under drive", is that the same thing as a doubler?

Underdrive is a doubleler. Just leave it set to none. For transmission dodge 850RE and transfer case np241/nv241/nvg241 should get the numbers you need.

 

[Stuntman Mike]

Instead of regearing, a turbocharger might also be a good measure to cope with the bigger tires ...

 

[JTGuy]

Just made an appointment for Dana Spicer 4.88swith the REM polish for Nov 27. In at 8:30 done by lunch. No break in or oil change needed with the polish.

 

[Fly-by]

2107rpm, or 2700 rpm at 90mph. 4.88s are a good combo for 37s. The guys suggesting 5.38s for 33s are off their rocker if you ask me. 3300 rpm in overdrive on the freeway? Hard pass.

To be clear, Im not suggesting it to anyone but rather doing this to my own vehicle. I live at the base of a long forest service road that connects to a couple thousand miles of logging roads where this vehicle will see most use. Good torque in second and third from 20mph to 55mph is the priority. For my infrequent highway trips there is a grade that requires 4th gear with 4.10s which puts me at 3250 already, so I won't be running higher rpms than I currently do. I would rather have a 5 speed plus a granny gear than a 4 speed and two useless overdrives. If it doesn't work out I can just slap on some 37s.

 

[Lunentucker]

Here's a much simpler tool.
https://www.rocky-road.com/calculator.html

Personally, I would probably install a Banks or similar and try that before regearing. Rory says 4.1 is the perfect ratio for an off-road vehicle, because you're retaining good mass on both sides.

 

[Badunit]

Edited. I deleted my reply because some posts came in before I finally hit "post", including the reason why 5.38 gearing was being chosen. 5.38 seems a little too deep to me but I'm not driving those roads so I can't really say. Might look at 5.13 or 4.88 instead, though.

 

[ecidiego]

torque multiplication = butt dyno.

/thread

 

[AmishMike]

I'd have to see it to believe it that 4.10 is quicker 0-60 than 5.38 with all other factors being equal. That doesn't make sense.

In many years of land speed and drag racing, I have seen things like this. Yes, counter intuitive but it can happen. Maybe there was an extra shift that caused a lag, maybe there was a de-rate situation, maybe the 10th planet didn't align with Aquarius, who knows.

 

[Wheelin98TJ]

In many years of land speed and drag racing, I have seen things like this. Yes, counter intuitive but it can happen. Maybe there was an extra shift that caused a lag, maybe there was a de-rate situation, maybe the 10th planet didn't align with Aquarius, who knows.

It's a turbo. Makes it a little confusing when we're talking about Gladiators.

 

[Zachanadandy]

It's a turbo. Makes it a little confusing when we're talking about Gladiators.

The gladiator isn't a unicorn, it's a jlu with a bed. Last I checked the ecodiesels have a turbo too? Our other jlu is a 3.6L on 39s and the 4.56 gears are good. Again, short of 40+" tires I wouldn't go lower than 4.88s in any JT/JL regardless of engine. If you rarely drive over 70mph, there's not much penalty for gearing super low. I tend to drive faster than that in the dirt when out in the desert so I'll pass on the super deep gears.

 

[RavensEyeOffroad]

leverage the gears provide to turn the tires.
the driveshaft has to turn x times to get the tire around once.
the bigger the tire size the more turns it takes. maybe only by .25 of a turn now but this adds up.
Changing the axle ratio gets it back, close or better than stock.

 

[AmishMike]

5.38's on 33"s is too much gear for most of us. He stated that he is off road 75% of the time, it might make sense then.
Being used to big-block pickups, I did not like 5th or even 4th gear on the highway pulling my 16' 2460lb. camper. Then I realized this is a high revving small V6 and it was running where it needs to.

This chart is from 4wd. It is rpm at 65 mph in a 1:1 gear. What is important is the relationship between gears. Typically, you want a little more mechanical advantage as you move up to bigger tires, lift etc. so you would welcome more rpm..

 

[AmishMike]

Trans gear ratio

Effective gear ratios

A/T

M/T

A/T

M/T

A/T

M/T

A/T

M/T

A/T

M/T

A/T

M/T

A/T

M/T

rear ratio

3.73​

4.1​

4.56​

4.88​

5.13​

5.38

​

1st

4.71​

5.13​

17.57​

19.13​

19.31​

21.03​

21.48​

23.39​

22.98​

25.03​

24.16​

26.32​

25.34​

27.6​

2nd

3.13​

2.63​

11.67​

9.81​

12.83​

10.78​

14.27​

11.99​

15.27​

12.83​

16.06​

13.49​

16.84​

14.15​

3rd

2.1​

1.53​

7.8​

5.71​

6.2​

6.27​

6.66​

6.98​

10.25​

7.47​

10.77​

7.85​

11.3​

8.23​

4th

1.67​

1​

6.23​

3.73​

5.77​

4.1​

7.61​

4.56​

8.15​

4.88​

8.57​

5.13​

8.98​

5.38​

5th

1.28​

0.81​

4.77​

3.02​

5.25​

3.32​

5.84​

3.69​

6.25​

3.95​

6.57​

4.16​

6.89​

4.36​

6th

1​

0.72​

3.73​

2.68​

4.1​

2.95​

4.56​

3.28​

4.88​

3.51​

5.13​

3.69​

5.38​

3.87​

7th

0.84​

3.13​

3.44​

3.83​

4.1​

4.31​

4.52​

8th

0.67​

2.5​

2.75​

3.05​

3.26​

3.44​

3.6​

This shows effective gear ratios in each gear vs. rear end ratio. (No accounting for slippage)

According to this chart, 6th gear with 5.38's will be slightly lower rpms then 4th gear is for you now. If you can live with your current 4th gear being the top gear, then you are all set!

 

[Ted404]

The one thing you must think about when changing tire size is you kind of already re geared it. It’s called roll out. If your one turn of your drive shaft from the factory moves you 1 foot (not real numbers) when you add 10% in tire size you will add roll out distance the gearing simply corrects this distance closer to factory. Now your Speedo is correct again too and in cases like mine you get to use 7,8 gear again on the highway. Not to mention lower strain on your motor and transmission

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