RPMs at what MPH?

[Wheelie]

There seems to be an endless supply of charts on the web showing rpms when choosing tire size vs gear ratio... that’s great info , but is there one that states (at what mph the chart represents????)

It doesn’t help me to know what rpm it is if I don’t know the mph...I’m looking at .... I’m pulling out the 3.07’s 0n the wifes mall crawler TJ, with 33” tires to regear and from what Jerry and several others suggest are 4.56 gears ... but I’d like to compare the rpms at say 60 mph with the 4.56 vs the 4.10... so any link to a chart showing specs at that speed would be very helpful.. her Jeep is a 1997 4.0 5 speed ... thanks

 

[JDS123]

http://www.grimmjeeper.com/gears.html
Should be all you need right there.

 

[jjvw]

3k rpm at 75mph is a good goal.

Your tire size for the calculator is the height of the hub x2. Nothing else is accurate.

 

[ranger101]

4.88’s, 4.0, AX15 transmission, 35’s and I see 2800rpm at 70mph. Ideal cruising speed for me.

 

[Jerry Bransford]

4.10 is slightly undergeared for 33" tires when you have the 4.0L engine and 5-speed transmission, go with 4.56. I made the mistake of only regearing to 4.10 when I had 33" tires and within a few days of driving knew I had made a big mistake of not going with 4.56 as more experienced Jeepers recommended.

 

[Steel City 06]

There are also intermediate ratios like 4.27 or 4.30. They're not as common but a lot of manufacturers like Spicer offer them, though often only for the Dana 44 and maybe the Dana 30.

Personally, I would go 4.88 with 33s and the 5 speed manual. That will get you close to the 3k @75 target. 4.56 would also be acceptable, especially in flat areas.

5.13 would provide more torque, but at the cost of a little fuel economy and a bit of extra noise. 4.88 would probably be a better choice than 5.13 unless you plan to go to 35s.

I plan to go to 4.88 with 35s, but I have the 6 speed transmission, which has an OD gear which is not as tall as the 5 speed transmissions.

 

[TJ2]

31" tires 1750 rpm for 65 mph

 

[Chris]

3k rpm at 75mph is a good goal.

Your tire size for the calculator is the height of the hub x2. Nothing else is accurate.

X2 to this.

 

[Wheelie]

She won’t be driving 70-75 mph , that’s why I’m looking for charts geared at 60-65 mph... if I’m doing the ratio chart jodimcfrodo suggested I’showing a4.56 to be running 2201 rpms in 5th gear at 60 mph... that can’t be right can it????? Sounds way low

 

[JDS123]

She won’t be driving 70-75 mph , that’s why I’m looking for charts geared at 60-65 mph... if I’m doing the ratio chart jodimcfrodo suggested I’showing a4.56 to be running 2201 rpms in 5th gear at 60 mph... that can’t be right can it????? Sounds way low

That is about right for 33's with 4.56's and your transmission. If the Jeep won't be going much faster than 60, 4.88 is a perfectly fine ratio. I liked my 4.56's with 33's. No complaints even in the mountains. 4.88's would have been nice as well.

 

[jjvw]

She won’t be driving 70-75 mph , that’s why I’m looking for charts geared at 60-65 mph... if I’m doing the ratio chart jodimcfrodo suggested I’showing a4.56 to be running 2201 rpms in 5th gear at 60 mph... that can’t be right can it????? Sounds way low

What did you enter for a tire size?.

 

[MutantNinjaTJ]

My 6 speed, with 33's, does 75mph at 3000rpm with 4.56's

 

[Wheelie]

That is about right for 33's with 4.56's and your transmission. If the Jeep won't be going much faster than 60, 4.88 is a perfectly fine ratio. I liked my 4.56's with 33's. No complaints even in the mountains. 4.88's would have been nice as well.

ok . I thought I was doing the chart wrong.... sounds good then , I’ll shoot for 4.56’s then , if she encounters hills she can downshift if needed . 4th gear says it will be 3018 rpms .. thanks for the help

 

[Wheelie]

What did you enter for a tire size?.

33 , although the actual may be 32-32.5” —-33 will get me an idea on the gears of choice....

 

[Wheelie]

Thanks again for the help guys, she only just tools around town and nearby towns, so she only runs about 60 miles an hour, if she needs to go somewhere on the interstate she will take one of her other vehicles so it looks like I will be getting a set of 4.56s for her

 

[jjvw]

33 , although the actual may be 32-32.5” —-33 will get me an idea on the gears of choice....

No. Measure your hub height and double that number. Your actual for the purposes of the calculator is closer to 31".

 

[JDS123]

No. Measure your hub height and double that number. Your actual for the purposes of the calculator is closer to 31".

For 60 mph, the difference between plugging 31 in and 33 is 142 RPM. I'm sure he will be happy either way with 4.56's for just around town.

 

[Steel City 06]

My 6 speed, with 33's, does 75mph at 3000rpm with 4.56's

That would be about the equivalent of 4.88 on a 5 speed due to the OD ratios (0.84 on the NSG370 versus 0.79/0.78 on the AX-15 and NV3550)

 

[jjvw]

For 60 mph, the difference between plugging 31 in and 33 is 142 RPM. I'm sure he will be happy either way with 4.56's for just around town.

He was doubting the numbers he got and he put in the wrong numbers. I told him (twice) how to get accurate numbers.

 

[Wheelie]

Be

No. Measure your hub height and double that number. Your actual for the purposes of the calculator is closer to 31".

Ok , official hub height to center 16 1/4 inches X 2 + 32 1/2
"