Axle ratio question

[Harley]

I know this was covered in the past but can't seem to find exactly what i'm looking for.

I have an 86, 2.5L, 4spd, 2wd and I'm wondering what ratio it has?? The tag is gone and I havent gotten around to pulling the cover off to check the stamp. Is there any other quick way to tell?? via VIN possibly?? it has a smooth round cover and the bolts are torx if that helps.....

Also, is it worth keeping or should I swap it out with something else?

[Geonovast]

Round, as in circular? Possibly an AMC 20... I've never seen torx bolts on a diff cover.

 

You should have 3.55. The 2.5/4 speed combo generally came with 3.55 axle gearing.

 

You can check the ratio by jacking up one rear tire, putting the trans in neutral, and spinning the tire twice, and count the number of times the driveshaft spins. If it spins just over 3 1/2 times, it's 3.55. If it spins just over 4, it's 4.10.

[Harley]

Yeah circular, i've never seen torx either thats why it threw me off. They appear to be factory too. If i knew how to upload a pic i would post one to show it

[jpnjim]

CJ model 20's sometimes used torx bolts.

 

MJ M20 all got 4.10's,

 

so if your diff cover looks like a pith helmet,

it should have 4.10's.

 

Other than the M20's,

1986 was a weird year, even the factory literature doesn't specify what combo's got which gears. :dunno:

[btm24]

Here is a help on what it may be:

My new Solid diff covers have torx bolts but thats an after market cover :dunno:

 

Brandon

[ride172]

It's an amc 20.. mine had the torx bolts on it. Just changed my gear oil and got 12 new hex bolts for the cover.. the torx size is 40.. broke torx bits getting them off..

[Harley]

It appears to be an amc20....those good or bad? Whats the pros and cons? I'm gonna keep it 2wd so it won't ever see much offroading

[Harley]

anybody know what the markings on the top of the housing are??

N

428

5105

Thats what I can see so far. also looks like theres a row of numbers near the cover edge. can't make em out though

[btm24]

It appears to be an amc20....those good or bad? Whats the pros and cons? I'm gonna keep it 2wd so it won't ever see much offroading

 

Its better then a dana 35 and 8.25 but not as good as a dana 44 or a ford 8.8. Also from what I under stand, after market parts can be hard to find. Oh and I think but am not sure that it should have 4:10 gear ratio.

Brandon

[Eagle]

It appears to be an amc20....those good or bad? Whats the pros and cons? I'm gonna keep it 2wd so it won't ever see much offroading

 

Its better then a dana 35 and 8.25 but not as good as a dana 44 or a ford 8.8. Also from what I under stand, after market parts can be hard to find. Oh and I think but am not sure that it should have 4.10 gear ratio.

Brandon

There are some who would argue that it's better than a Dana 44. It has a larger ring gear. The downside to the AMC 20 is that it's heavy, and it has less ground clearance than the D44. It isn't difficult to find lockers and such for it -- it was used in a lot of vehicles over the years.

 

If you have it -- consider yourself lucky. BTW -- it should also have 10" x 2-1/2" drum brakes, which are significantly larger than the standard 10" x 1-3/4" brakes on the D35.

[ride172]

should have told you this too. the gear ratio is stamped on the flat area on the rear of the axle next to the diff cover. I think its on the the passenger side, you may have to scrape some gunk off. But if it has 4.10 it will be stamped "C" if 4.10 limited slip it will be stampd "CC". There is a chart around here somewhere that has the letter code broke down, I used it to find out what I had. If it is stamped something other than "C" and you can't find the chart, post it up and someone will be able to tell you..

[Eagle]

1986 was a weird year, even the factory literature doesn't specify what combo's got which gears.

Yes it does. Not the sales literature, but the FSM has a chart:

 

4WD

 

I-4 . . . 4-spd = 3.31 - 3.54 - 4.10

. . . . . 5-spd = 3.54 - 4.10

. . . . . Auto == 3.54 - 4.10

 

V-6 . . . 5-spd = 3.54 - 4.10

. . . . . . Auto == 3.54 - 4.10

 

2WD was the same. Footnote says 3.31 was available only with a fuel economy package.

 

I don't know if I believe this chart or not, though. I have an '86 XJ hulk out back that was a V-6 with automatic, and the axles are 3.73s.

[Harley]

I scrapped and cleaned where tge numbers should be abd the only markings on it seem to be the ones i mentioned earlier on the top of the diff

[ride172]

It's not on the top. It's there, if you got the 20 its stamped on there. It's not a very big letter, smaller than half inch. Flat spots, perpendicular to the ground, on the rear of the axle, 3 o'clock and 9 o'clock. It's there, its only removable with a grinder.

[Harley]

Yeah i know where it should be but theres nothing there!

don't ask me why or how.

I'm guessing nobody knows ehat the markings on top are for???

[ride172]

They are probably casting numbers. I'm in my garage looking at my axle. The stamp is right on the edge where the tubes are welded in. Pass. side.

[ride172]

"Identifying the gear ratio of an AMC 20 is a bit tricky. Dana axles normally have a tag on the left of the diff cover with the gear ratio at the time of build. The AMC axles have a code that has to be looked up in a table. The code is stamped on the housing boss to the left of the diff cover right near the axle tube. Good part about the stamp is it tends to stay readable longer than the tag, but you have to know the code. Since there are conflicts between what a code means for a narrow track and what it means for a wide track, don't count solely on the code to identify an axle. Bring a tape measure or know the source of the part." (I'm pretty sure where it says to the left of diff cover they mean pass. side, because that is where mine is stamped.)

 

Wide Track AMC 20

Code Gear Ratio Diff Type

D 2.73 Open

DD 2.73 Trac-Lok

B 3.31 Open

BB 3.31 Trac-Lok

A 3.54 Open

AA 3.54 Trac-Lok

H 3.73 Open

HH 3.73 Trac-Lok

C 4.10 Open

CC 4.10 Trac-Lok

(The letter code is different for narrow track 20's, the mj axle is a wide track)

 

See the X? That is where the stamp is located.

 

Looking at the info I have, I can't find what ratio "x" is :dunno:

[Harley]

[Harley]

FINALLY got it figured out. turns out somebody did some grinding and damn near rubbed that letter code off. I cleaned it, hit it with black spraypaint, and lightly sanded it. then it started to show. I know the insides have never been changed and the magic code is a C now acording to what ive read, thats a 4.10, widetrack, open, amc-20...... now that I know exactly what I got is that a decent axle or should I look in to swapping it with something else???

Give me your thoughts

 

Thanks

[mnkyboy]

You have one of the strongest axles jeep used,I would leave it alone.

[ride172]

 

You had one too many image tags.. I would pull the cover and take a look. Mine was pretty rusty under the raised spots on the cover between the bolt holes. This was due to the diff gasket. It only seals the inside of the cover, not around the holes. I got a new gasket for 9 bucks (you need the gasket) and then used rtv around the holes and raised spots.

[Eagle]

.... now that I know exactly what I got is that a decent axle or should I look in to swapping it with something else???

Give me your thoughts

 

As already posted:

There are some who would argue that it's better than a Dana 44. It has a larger ring gear. The downside to the AMC 20 is that it's heavy, and it has less ground clearance than the D44. It isn't difficult to find lockers and such for it -- it was used in a lot of vehicles over the years.

 

If you have it -- consider yourself lucky. BTW -- it should also have 10" x 2-1/2" drum brakes, which are significantly larger than the standard 10" x 1-3/4" brakes on the D35.

Keep it. It's a great axle.