playbass

Just want to make sure my tranny is working correctly. I have the AW4 and at 70 mph I am pushing 2100rpms on the freeway. Is that about right for this transmission in overdrive (OD)?

thanks

black2000xj

your right on the money

i would assume you have 3.55 gears

playbass

Great! Thanks. I recently did a couple of drain and fills on the transmission, and I didn't really remember what my rpms were before doing that, I was thinking they were around 1800 before at that speed, but I could be wrong. Just wanted to make sure my overdrive was working correctly.

Just for my edification, what does 3.55 gears mean? It seems weird to me to think of "fractional gears"?

playbass

I have stock tires too, nothing fancy.

Lowrange2

3.55:1 is the gear reduction ratio in your axles.

playbass

Thank you, that makes sense now. I was thinking about it wrong.

Lowrange2

Check this out.

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

Select:

AW4

NP231

3.55 for gear ratio

Then your tires size.

Calculate.

All the way at the bottom is shows road speed at given RPM range.

playbass

Cool, yeah, looks like I'm about 200 rpms lower than what is listed on that sites calculator. Is that the "lockup" feature dropping the rpms a couple hundred?

Sorry for all the stupid questions, I just don't know how to verify all these features (overdrive/lock-up) are working on my transmission.

thanks

black2000xj

your jeep is working fine

the aw4 trans is a great transmission...takes a beating and still keeps going

best thing for them is a cooler...spend 50-100 dollars on a trans cooler and it should last a long time

heat is a transmissions worst enemy!

You shouldnt have any issues with it....other than fluid leaking..but thats about it

ksan0311

Ummm... i read this post, and my cherokee does 2,000 PRM's on 65 in the freeway.

could my transmission be stuck in overdrive??

(stock cherokee sport with stock tires in Drive)

salad

RPM difference of about 200 at that speed can be caused by variation in tires. The values written on the side wall are not necessarily accurate. However, it is more likely that your speedometer is off. (They're only accurate within about 3% or 5%) That site presents RPM values as if there is a direct drive for the gear - your torque converter must lock to accomplish this. If it wasn't locking you'd see more like 2800 or 3000 RPM and mileage would be really really bad and you'd likely be overheating.

Overdrive is 4th gear on an automatic transmission. It's called this because the output of the transmission is faster than the input (0.79:1 or 0.78:1) If you *AREN'T* in OD on the highway you have problems.

ksan0311

Oh... wasn't aware of the term on the gear.. thanks for the clarification salad