So I'm considering changing the trans in my Jeep for either a granny 4spd manual for a stupid-low 1st gear(will net me 100:1 crawl ratio with stock D300 gears...) or an auto, TF999 seems to be the easiest to swap with minimal issues. Another potential plus for the granny 4spd is I might have room for a doubler to keep DS lengths close to now(NV3550 and D300).

This is all behind my 4.0 in my 03 TJ.

As for auto vs manual that is for myself to debate with myself over... what I want to know is can I safely run my 4.0 at ~3200 rpms for hours at a time? I DD my Jeep(a whopping 2.0 mi to work and back including coming home for lunch:laughing:) but more importantly I will be driving it to and from the trails anywhere from 4-8 hours away on the highway. I have no problem being sorta "limited" to 65mph... that is about as fast as I want to take it.

So are there any known issues with a 4.0 running hot or any oiling problems(oil blowing out dipstick tube?) or any other kinds of long-term issues like ridiculous wear or anything when being run at these kinds of RPMs?

It would also comfort me to hear any stories of you guys running high(er) gear ratios in your axles with non-OD transmissions on the highway for extended periods of time and/or regularly seeing 60+ mph. :p


edit: for reference with my NV3550, 40" tires and 5.86s I'm only turning about 2300 rpms on the highway at 60-65.

And yes I know I can drive on the highway in 4th gear to get an idea of what it will be like... it's loud(exhaust) but am more interested in any long-term problems it may cause.

You'll be fine. When I was "done" with mine, I was turning around 3k humming along at 75 no problems on the HWY. This was 5th gear(ax-15), 35" tires, 5.38's. Sometimes I would kick it to around 3200 for miles non-stop cruising 80 just to keep up with flow of traffic. The engine will take it. Just keep all fluids/filters clean and fresh. Just the normal maintenance and your good. Of course, all things mechanical needs to be tip top of course. But you already know about that. And when Im crusing, I am averaging 7in/hg on the guage:smokin:

So I'm considering changing the trans in my Jeep for either a granny 4spd manual for a stupid-low 1st gear(will net me 100:1 crawl ratio with stock D300 gears...) or an auto, TF999 seems to be the easiest to swap with minimal issues. Another potential plus for the granny 4spd is I might have room for a doubler to keep DS lengths close to now(NV3550 and D300).

This is all behind my 4.0 in my 03 TJ.

As for auto vs manual that is for myself to debate with myself over... what I want to know is can I safely run my 4.0 at ~3200 rpms for hours at a time? I DD my Jeep(a whopping 2.0 mi to work and back including coming home for lunch:laughing:) but more importantly I will be driving it to and from the trails anywhere from 4-8 hours away on the highway. I have no problem being sorta "limited" to 65mph... that is about as fast as I want to take it.

So are there any known issues with a 4.0 running hot or any oiling problems(oil blowing out dipstick tube?) or any other kinds of long-term issues like ridiculous wear or anything when being run at these kinds of RPMs?

It would also comfort me to hear any stories of you guys running high(er) gear ratios in your axles with non-OD transmissions on the highway for extended periods of time and/or regularly seeing 60+ mph. :p


edit: for reference with my NV3550, 40" tires and 5.86s I'm only turning about 2300 rpms on the highway at 60-65.

And yes I know I can drive on the highway in 4th gear to get an idea of what it will be like... it's loud(exhaust) but am more interested in any long-term problems it may cause.

I think your math is wrong, unless you are running a 4:1 kit your crawl is about 80:1 with a Granny 4 speed. You RPMs at 65 mph in 4th gear, with 40" tires and 5.86 gearing, would be 2600 RPMs, well with cruise range of the 4.0. That 4.0 doesn't really have the nut to turn tires that large so you are gonna be down shifting on hills alot. Also, what are you doing on the highway with a rig running 40 inch tires?

Here play with this, I used this so much in my builds to play with gearing and drivetrain choices it wasn't funny.

Enjoy
http://www.grimmjeeper.com/gears.html

I think your math is wrong, unless you are running a 4:1 kit your crawl is about 80:1 with a Granny 4 speed. You RPMs at 65 mph in 4th gear, with 40" tires and 5.86 gearing, would be 2600 RPMs, well with cruise range of the 4.0. That 4.0 doesn't really have the nut to turn tires that large so you are gonna be down shifting on hills alot. Also, what are you doing on the highway with a rig running 40 inch tires?

Here play with this, I used this so much in my builds to play with gearing and drivetrain choices it wasn't funny.

Enjoy
http://www.grimmjeeper.com/gears.html



Whatchu talkin' bout Willis?

6.69(NP435) x 2.61(stock D300 gears) x 5.86(my axle gears) = 102.3 final drive

FWIW that is the calculator that I used... it's been in my favorites for a while. And it is damn accurate for what I have now. I'm turning 2300 rpms in 5th on the highway, and in 4th gear roughly every 500 rpms = 10mph. 40 = 2000rpms 60 = 3000rpms etc etc.


And I drive it on the highway because I built it to be my daily driver again... Drives fine up to 70:flipoff2:

Bump. Anyone else?

I run at around 3000 rpm with no problems, and I've driven my jeep cross country, 24-30 hrs straight.

Here play with this, I used this so much in my builds to play with gearing and drivetrain choices it wasn't funny.

Enjoy
http://www.grimmjeeper.com/gears.html

good link!

Whatchu talkin' bout Willis?

6.69(NP435) x 2.61(stock D300 gears) x 5.86(my axle gears) = 102.3 final drive

FWIW that is the calculator that I used... it's been in my favorites for a while. And it is damn accurate for what I have now. I'm turning 2300 rpms in 5th on the highway, and in 4th gear roughly every 500 rpms = 10mph. 40 = 2000rpms 60 = 3000rpms etc etc.


And I drive it on the highway because I built it to be my daily driver again... Drives fine up to 70:flipoff2:

I fucked up the gear ratio when I put in the numbers. You must have alot of money to be able to afford tires. When I was on 37s I had to park that bitch because I don't think I was gonna get more then 10, maybe 15k on my IROKs. I was debating getting some street tires, but the economy fell out shortly after that and that was the end of that project.

I fucked up the gear ratio when I put in the numbers. You must have alot of money to be able to afford tires. When I was on 37s I had to park that bitch because I don't think I was gonna get more then 10, maybe 15k on my IROKs. I was debating getting some street tires, but the economy fell out shortly after that and that was the end of that project.

I live 0.5 mi from work... my commute is pretty minimal:laughing:

I just want it highway drivable so I can get to trails... no room or means for a tow truck and trailer.

One day:rolleyes:

Did a 2600 miles trip across 2 countries in december all at 2900-3200 RPM in my cj-7 with the 4.2L with over 165K on it. Never burned a drop of oil, and it averaged 14MPG, even with the stupid carter carb sputtering the whole way. I was pretty impressed.