Gear Ratio....what to do.

[Michael]

Okay I am getting close to doing gears what gear ratio has worked best with 33's for all that have done them.

for sure detroit rear
detroit truetrac up front

I am driving this to the trails....so it has to be halfway normal on the highway. Say 70mph
TIA.

[waggin'ear]

I've got 3.54 gears in my J10 with 33's. This makes it very highway friendly at 2500-2600rpm @ 70mph.

I've also got a 65:1 crawl ratiodue to the granny gear, where your's will only be about 45:1 if you count a 2:1 reduction for the torque converter.

I would say 3.54-4.1 would keep you between 2500-3000 rpm @ 70 mph.

3.73 best compromise probably

[Amc71601]

I've got 4.09's and 33's it really winds the motor up around 60 to 65 when I had 3.54's it seemed kind of sluggish If I changed my gears again I would probably go with 3.73's

[Ralph]

If your OEM setup involves 3.31 gears and 235/75/15 tires, you would have almost identical engine RPM range with 33x12.50x15 tires and 3.73 gears. This tire/gear swap also makes it unnecessary to correct the speedometer.

[KYJ10]

I would suggest 5.13's, cause your gonna eventually be getting some 38's. I mean, buy next year you'll be asking about 1 ton axles swaps and 38's. Wait and see. It all ends up that way! smile.gif

[viscacha]

I agree with KYJ10. It’s best to figure out what you’ll end up with in a couple years.

The stock 3.73’s I have are great with my 33” MTR’s, but when I had 31.5” tires it was really nice. I have 4.10’s for my new setup and will prolly be running 37” MTR’s after the conversion. It would have been nice to go up in the 5’s, but I would have to buy a new detroit locker for the rear since the one I already have can only go to 4.10’s.

The other nice thing about 4.10’s is they are readily available just about everywhere where lower gears aren’t. That could be important if you break something away from home and need parts.

If you haven’t used Grimm’s calculator try it at this url. It will answer all your questions and you can do side by side comparisons. :cool:

http://www.dfw-tx4wd.org/gears.html

[ April 15, 2004, 01:34 PM: Message edited by: AZ J20 ]

[robselina]

consider spending your money on more beef unless you're absolutely sure you don't want anything bigger, but I vote 3.73s for anything that's on the street.

[badaboom]

Yah 3.73
I would have went 3.92 but they were not available
for the AMC model 20. If you are running dana 44 F/R the 3.90/2 gear ratio may be available.
Good Luck

[Heimeken]

more road 3.73, more off-road 4.10

[AM JEEP]

What about running 35" MTR's on a '78 J10 360. Stock it had 3.54:1 gears.

[Michael]

Thanks for the replies. I do about 90% offroad and 20% road...which is when I drive to the trail. do the math...lol. Now I am getting miss information about one thing. How tall a gear can I run without changing the carrier/case? Thanks again.

[Ralph]

The carriers in your Jeep will accept ring gears for ratios up to 3.73. The next available ratio for a Dana 44 is 3.92; you would have to swap carriers if you go to 3.92 or numerically higher gears.

[Grantshire]

AM Jeep,

I am running 35" Goodyear MT's and just swapped out my 3.54's for 4.56's (I also currently have the 16% OD in my part-time MileMarker QT conversion). Boy, what a difference!!! Before, it was like starting in 2nd gear. Now, I have acceleration like you would not believe. I can comfortably run 65-70 mph (no long trips yet) without overheating or stressing the engine (its a built 360). I was going to go with 4.27's but decided an OD transmission or larger tires down the road made more sense if the 4.56's seemed to low. I am glad I went with the 4.56's.

[jeepsr4ever]

hey badaboom 3:94's are and 3:44's