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Now what

Now what
driver007

driver007

Senior Jeeper
Posts
610
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1
Location
Canada
Vehicle(s)
1981 cj5 304 v8, 300 Dana,model 30 Dana and model 20 AMC rear end
I have the model thrity diff out of my 81cj5. I plan on rebuilding it for now. If I run a 9.5 by 31 tire would I need to change my gear it is 2.73. I use it on back roads and trips into the city 20 miles on the highway. I would like to keep the highway speed but still do some humble 4x4ing. It has the AMC 304 so lots of power.
 
I would think that with the AMC 304 and 31's 2.73s would be fine and if all else fails on the tail you always have 4l. Depending on what Transfer Case you have quadtrac on some i think dont have a 4l. Also not sure what modles came out with that Transfer Case , I'm no expert by far. My jeep had 33's no lift and 2.73 and the AMC 258 i6 / 4.2l and 4l was a must on the trail, till i Put in 4.10 Unless you plan on putting bigger tires and a lift on I would think the 2.73 would be fine. Just my opinion.
 
Gear Calculator

Check that out...

I have a AMC 304 with T-15 3 speed and Dana 20 . My Ratio is 4.27 with 33" tires.

Plan on swapping in a granny Low T-18 or SM465 for the granny gear in the future, but for now, the ratio I have going is awesome for light trail riding and a little more aggressive wheeling.

I would recommend changing your ratio a little, but it really is all up to you... And you may be able to retain the current ratio in the diffs while still increasing your crawl ratio...

How does it do in 4L now when you take it on the trail and put it up against a small challenge? If you find it's hard to clime something or "lacks power" I would recommend changing gearing.

What do you currently have? Tranny, and Transfer Case , we know already you have the 2.73's and 31's... I ask, because if you want to still keep your current gearing, you may be able to do a tera low package for your t case and gain your low crawl ratio there instead too...

That above link is one of them out there that will allow you to play with options a while before making a decision...

:chug: Plenty of options :cool:

~ JR
 
Since you have the axle out here is a link on how to put a zerk into your axle to repack the bearings I don't know how good of a job it would do but its something to read and look at. Easy Bearing Repacking
 
Nice article 86CJ

It's for the rear axle.

The Dana 30 can take the zerk in the hub.

I would recheck the 2.73 ratio though. I think they only went to 3.07s.

Most popular was the 3.73 ratio.
 
After getting some crude of it the gearing is 49-18 or 272. What will this combo be like? And thanks for the tip on grease zerks
 
300 Dana Transfer Case and the 4 speed tranny witch is the weak link but will have to do tell it breaks down
 
73CJ said:
Nice article 86CJ

It's for the rear axle.

The Dana 30 can take the zerk in the hub.

I would recheck the 2.73 ratio though. I think they only went to 3.07s.

Most popular was the 3.73 ratio.
Click to expand...
your mistaken, 2.73 is the most common factory gear ratio for the later cjs, 3.73 factory gears are almost unheard of with the exception of 4cyl jeeps, then I think they are actually lower than that.



Droooiiddd 2
 
I would get 4.11 gears. What tranny do you have? If you have an Overdrive you could even go a little lower than that. If you have or plan to swap in a granny low such as a T-18 you could go much taller than that.
Check out this chart and shoot a gear ratio in the green.
_35422.jpg

Edit: What tire size do you have now? Going to 31 inch tires may not make a big jump. You could install the tires first to see how you like the gearing. In the '80s the gearing was very tall. If you swap out the tires and decide to get lower gears then get 4.11.
That's my 2 cents.
 
Last edited:
I double checked the tag and it said 272 49-18. There just seems to be no info on that gear option. I will count it when I open it up after I sand blast it.
 
49 crown 18 pinion. 49 divided by 18=2.72
 
Sorry Busadave9 Old age taking my sharpness away. Hard to say the tack is a small one hard to see standing still let alone at speed. I went for a couple of ripps and went in restore mode. I wanted to get the steering fixed etc to much wobble to keep it at 65 one thing leads to another. I will have to wait and see what rpms are after and then make a better informed choice on gearing. For now it will work. It is just the fact that I have not seen that gear combo talked about anywhere
 
Irregardless of what they are now 4.11 gearset will give you about 2900 rpm at 65 mph. I would think that should work out. Regearing can be a big job or if you have someone else do it, it can be expensive. I would first get the tires then decide if you need lower gears.
 
If I regeared I would have to consider a axle swap to a better axle hate to regear then do it all over in a couple of years. Your right I will get it up and running then figure out needs etc
 
Unless you plan on getting tires over 36 inches tall your stock axles should do fine as long as you get one piece axles in your AMC20 rear.
 
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