Gear ratio

[86jpcj7]

Does anyone know what gear ratios came in cj7s?

My jeep is a 1986 jeep CJ7 Laredo .

 

[Saddle Tramp]

In 1986 common CJ ratios were 2.73 and 3.31. Look for a tag on the housing cover, the ratio should be coded on the tag.

 

[NorthwestCJer]

Already said, is correct. 4 cyl models will be 4.10's.
86 year did receive Dana 44 's and some AMC20 's in the early models.
There will not be a tag on the AMC20 . letter code stamped into the housing beside the diff cover. You can google search this code for gear ratio.
Jeep Axle: AMC 20
However, it could have been changed by previouse owner.

 

[PaRenegade]

Don't trust code stamps or tags. Previous owners could have changed them. Rotating the wheel one full turn while watching how many turns the driveshaft turns is the only sure way to tell. Wrap the shaft with masking tape and mark a vertical starting point. It will be close to one of these. 2.73,3.07,3.31,3.54,3.73,4.10,4.56
If it is a round cover it's an AMC20 axle. A few of the later 86 models got Dana 44 's thrown under them.

 

[86jpcj7]

How good is amc 20s?

 

[Kilo19]

Need to be trussed and reinforced. But not a bad axle after that

 

[86jpcj7]

Ok thanks everyone. Now just gotta make some money to get them trussed.

 

[Petescj]

The first thing a AMC20 needs is the 1 piece axle conversion.The next weak spot is is the tubes are a little thin and pressed into the centersection. If you are a good welder youll be fine. There are people on here better qualified to explain that process than I. A good truss isnt a bad idea either depending on how hard your going to wheel it. It really depends on that. Some people skip over upgrading the AMC20 and go straight to an axle swap like a Dana 44 or Ford 8.8. That depends on various things like how hard you wheel and how much cash you have. For all I know you need portal axles.

How good is amc 20s?

 

[Old Dog]

I agree, the 3 main things the 20 needs is
1 piece axles, so you don't strip a hub,
the tubes welded to the center section, so you don't twist a tube,
and a truss, so you don't bend a tube.
Just ask me, I've done all three.

As saddle tramp said most later years of cj's had 2:73 gears stock.
They were thinking about gas mileage instead of wheeling.

 

[Petescj]

Your my hero.

I agree, the 3 main things the 20 needs is
1 piece axles, so you don't strip a hub,
the tubes welded to the center section, so you don't twist a tube,
and a truss, so you don't bend a tube.
Just ask me, I've done all three.

 

[Petescj]

And actually its all "4" cause you ened up with the 8.8 after that.

I agree, the 3 main things the 20 needs is
1 piece axles, so you don't strip a hub,
the tubes welded to the center section, so you don't twist a tube,
and a truss, so you don't bend a tube.
Just ask me, I've done all three.

As saddle tramp said most later years of cj's had 2:73 gears stock.
They were thinking about gas mileage instead of wheeling.

 

[Tommy]

I have an '81 CJ5 with a AMC 258 i6 / 4.2l and an AMC20 rear end. The 2 piece axle has never given me a bit of trouble, I know it only takes once, in over a dozen trips through the Rubicon and other tough trails. Mostly do rock crawling and desert runs. I don't keep my foot in the throttle but you can't run the Rubicon while babying it either. Just my 2 cents. My brother spun his but he had a V8 and was hammering it. It guess it depends on what you are going to do with it and how you are going to drive it.

Tommy

 

[Old Dog]

Tommy, all I can say is ...the jeep Gods must be watching over you.

 

[mtnwhlr]

I've never broken one either but I think it's because they are rusted together

 

[thiswontbetooexpensive]

I've never broken one either but I think it's because they are rusted together

Now that's what I'm talking about! Sounds like we have related vehicles.


This won't be too expensive Dear! That's what I keep saying. Over and over again.

 

[PaRenegade]

Glad to see the AMC20 isn't getting the typical bashing that gets regurgitated on some sites. Once the weak point of the 2 pc. axles is overcome it's really not a bad axle. And then it can be further improved as mentioned, by welding the tubes and trussing it. Two things that aren't needed on 80% of Jeeps.

 

[wm69]

Glad to see the AMC20 isn't getting the typical bashing that gets regurgitated on some sites. Once the weak point of the 2 pc. axles is overcome it's really not a bad axle. And then it can be further improved as mentioned, by welding the tubes and trussing it. Two things that aren't needed on 80% of Jeeps.

Yep. I'm running Superior axles, but haven't ever welded or trussed mine. To me axle upgrade is a must-do, but welding and trussing isn't neccessary unless you're going big on tires or engine and really doing some wheeling/rockcrawling.

I'll probably weld my axle tubes when I pull the rear axle to put in my truetrac, but only because it will be easy to have it done with the axle out. Probably don't need it with my use of the Jeep (hunting, farm roads)

Don't have any intentions of trussing.

 

[86jpcj7]

Do you think the AMC20 will roll 33s good through mud and little crawling?

 

[Petescj]

Sure will depending what gears you have. Like was said earlier the 2.73s wont but if your ratio is 3.31 or numerically higher you'll be fine. Ultimately youd like to have 4.10 , 4.27 or 4.56 for 33s.

Do you think the AMC20 will roll 33s good through mud and little crawling?

 

[86jpcj7]

I have an '81 CJ5 with a AMC 258 i6 / 4.2l and an AMC20 rear end. The 2 piece axle has never given me a bit of trouble, I know it only takes once, in over a dozen trips through the Rubicon and other tough trails. Mostly do rock crawling and desert runs. I don't keep my foot in the throttle but you can't run the Rubicon while babying it either. Just my 2 cents. My brother spun his but he had a V8 and was hammering it. It guess it depends on what you are going to do with it and how you are going to drive it.

Tommy

What size tires do you have?