gear ratio

[reptile610]

So Im going to get a new set of wide tracks Sunday for my jeep.these axles have 2.72 gears in them. I have the little iron duke engine w/ soon to be 31s on it.what gears should I switch to? I was thinking 4.10s

 

[diddy2003]

What's wrong with your current set of 3.73 axles? I just came from 31 inch tires and 2.73s. Such a terrible match up. I really hated it because the motor was lugging everywhere and I had to avoid hills when I could. I have an extra set of 3.31s I would do before that with 31s. The 2.73 is a terrible gear IMO.

 

[reptile610]

What's wrong with your current set of 3.73 axles? I just came from 31 inch tires and 2.73s. Such a terrible match up. I really hated it because the motor was lugging everywhere and I had to avoid hills when I could. I have an extra set of 3.31s I would do before that with 31s. The 2.73 is a terrible gear IMO.

They're narrow tracks, the front is drums, and the rear is welded

 

[diddy2003]

They're narrow tracks, the front is drums, and the rear is welded

Oh, that makes sense then. 1982s had wide tracks, along with front disks, so I was confused. I just put 4.10s in my jeep. In the 5 miles I went with the 31 inch tires on it I would not recommend that for any jeep seeing a lot of street duty. Too short of a gear with my 176 Transmission . 33 inch tires helped. Do you like the 3.73s?

 

[reptile610]

Oh, that makes sense then. 1982s had wide tracks, along with front disks, so I was confused. I just put 4.10s in my jeep. In the 5 miles I went with the 31 inch tires on it I would not recommend that for any jeep seeing a lot of street duty. Too short of a gear with my 176 trans. 33 inch tires helped. Do you like the 3.73s?

I currently have 33s and its way underpowered but I think I'm having quite a few different problems. I wanna go down to 31s for sure. 3.73s aren't bad I just figured the 4.10s would suit my 4 cyl better

 

[Incommando]

Gear Ratio Calculator

Go there and enter you numbers to see where you would wind up.

4.10's were a very common factory ratio for the 2.5 and with the stock 27-28" inch tires in XJ's, YJ's, etc... and should work well in a CJ with 31's.

SR4 /Dana 300 with 3.73's:
crawl ratio: 34.27
RPM's @ 35: 1415
RPM's @ 65: 2628

SR4 /Dana 300 with 4.10's:
crawl ratio: 37.67
RPM's @ 35: 1555
RPM's @ 65: 2889

The T-176 is the same due to its 1;1 high gear.

Not a huge difference between the two ratios. If your jeep had a Transmission with an Overdrive , like a T-5 for example, your 65 MPH RPM with 4.10's and 31's drops to 2080. That would be a worthwhile swap while you were in there...

 

[AussieCJ7]

I currently have 33s and its way underpowered but I think I'm having quite a few different problems. I wanna go down to 31s for sure. 3.73s aren't bad I just figured the 4.10s would suit my 4 cyl better

My Iron duke came from the factory with 4.10's and ran it for years with 31's it now has a 4.0L and 4.56 on 33's

I personally would not go any numerically lower (higher ratio) than 4.10 but if you are going to keep the iron duke long term then work out what tyre size you want and set it up for that so I would be looking at putting in 4.88's and running either 33's or 35's at most

Do it right and Do it once

 

[jasonmark1993]

Screw it man go 5.38s

 

[AussieCJ7]

Screw it man go 5.38s

Can you get them for a AMC20 to suit his rear axle ??


You are dead right going to Dana 44 or D60 rear then go the deepest set of gear you can get and get some weight in the iron duke fly wheel Jason Bunch had some good idea's in his YJ when he was competing with the 4 pot screamer

 

[reptile610]

Can you get them for a AMC 20 to suit his rear axle ??


You are dead right going to D44 or D60 rear then go the deepest set of gear you can get and get some weight in the iron duke fly wheel Jason Bunch had some good idea's in his YJ when he was competing with the 4 pot screamer

with a max speed of 30mph? don't think so. im building my jeep in 2 stages right now. stage one is get it running correctly in about 3-4 years i'll be buying my own house and then im pretty much going to start from the frame and go from there. but living in a rental home and having no garage access really limits me. i have a friend who can let me use his shop for a weekend to do my axle swap but thats about it. figure im going to run 31's or 235's but just want to know what a good gearing is for mostly street use. when i get done with college and actually have money i wanna swap in Dana 44 's and a v8 and a T-18 i was thinking.

 

[AussieCJ7]

with a max speed of 30mph? don't think so. im building my jeep in 2 stages right now. stage one is get it running correctly in about 3-4 years i'll be buying my own house and then im pretty much going to start from the frame and go from there. but living in a rental home and having no garage access really limits me. i have a friend who can let me use his shop for a weekend to do my axle swap but thats about it. figure im going to run 31's or 235's but just want to know what a good gearing is for mostly street use. when i get done with college and actually have money i wanna swap in dana 44's and a v8 and a t-18 i was thinking.

4.10 is your answer then IMHO

 

[reptile610]

4.10 is your answer then IMHO

Yeah that's what I was thinking. Thanks for the help guys