Dana Mode 20 Axle Tube Diameter?

I don't know the diameter, but when I bought my u-bolts, there was only one size. There are two sizes for the front because one of them actually has to fit over the diff itself while th eother one only fits around the tube. But the u-bolts on the back both fit around the tube, so they are the same size.

Yeah, I knew that. I wanted to get the order placed, but I'm gonna havta wait until I get back to the house and measure it.

That's what I'm telling you, there is only one size. Call the Order Desk and tell them you have an AMC20, and the ubolts will be the right ones.

By the way, it IS the AMC Model 20, not the Dana Model 20. Perhaps that is the problem with the guys on the Order Desk ...

You mean I should ask him to get out some AMC u bolts and have him measure them?

No, my bad, typo, here. AMC. The problem is the spring perches come with different diameter arches in them. You buy the size you need, not by application.

No. You should tell them you have an '85 CJ7 with the AMC20 rear axle, and this will drive you to the correct u-bolts without having to measure anything. The nut takes a 3/4" socket, it that helps.

I don't remember this. I replaced my springs a few years ago - do not get ProComp leaf springs if you can avoid it - and I replaced the spring perches at the same time. I don't remember two sizes of spring perches. That is, I think there are narrow springs and wide springs, and this would affect the perches, but the axle is still the same, so the u-bolts would be the same.

I don't have calipers large enough to measure accurate enough. But by using the "eye-ball across the tape measure" method I got 2 3/8". I have seen some expensive custom u-bolts that did not work right because the measurements were just a little off, so don't use my number as your final and only source.

Hey bill how about the size of an 81 narrow track, are they just as strong?

That's good to know, I haven't welded my tubes, was wonding if my lincoln mig 10 would do it, or should I get someone to do it for me, also does it have to be drained? I put in the one peice axles, but now that I have a detroit in there I keep thinking about spinning the tubes on it. And now with my new engine, (first run today), I have the power to do it, what a difference, may be able to pass someone on the hyway now.

I don't mean to be arguementative, but the U-bolts aren't what I need. I need spring perches so I may cut off my old ones from the axle tube to rotate my rear diff up to point at the new location of my NV4500 output shaft.

The perch is welded to the axle. The perches come in different sizes for the different diameter axle tubes. They said 2.5" 3" and 3.75" (IIRC) They are pretty much generic. I had ordered some last year (when I thought I might have time to actually work on the damn thing), but what I got were perches for a much bigger diameter tube and they wouldn't work. I measured my tube this weekend at 2.5" in diameter (don't I wish!). Thanks for trying!

Cool, my calipers said 2.5".

Interesting, Bill, my calipers said 2.5 inches. Hmmm.

Well now you have me wondering, will have to go out later and messure my

I'm sorry, I thought the request was for the correct ubolts. The perches are all the same on the axle side, the difference is the width of the springs. You keep asking about the diameter of the AMC 20 axle tubes, but there is only one size of tube. There are two sizes of springs though, so any difference in the perch has to be on the spring side, and will deal with the locatiion of the holes so the ubolts will be as close as possible to the springs.

OK, I get it.

I don't know what the diameter of the tube is, but I see where you may need to know it. What I have been saying all along is that if they look up the '85 CJ with the AMC20 axle, then they should know which perch you need after you tell them which spring you have. There are narrow and wide springs for the front, but perhaps there is only one size spring for the back.

They wanted to know the diameter of the tube, as they said, the perches are generic with the differences being the radius of the axle cutout. I guess they make them for many size tubes and you buy what you need, trouble was I didn't know what I needed. I do now, my calipers showed 2

Oh well, we all learn something new everyday. Thanks!

Now if I can just find an ARB freezer fridge in the middle 42 size in stock somewhere... I bought one from a fellow on ebay, he emailed me back and said he didn't actually have one, 4wheel supply advertised them as well and I just got off the phone with their rep, after an online order, and he said they didn't have them either, crap.

On 2005-05-09 14:47:15 -0500, Jeepers! said: Update: There is only one size of spring perch: 3" radius

!?!?!?!?!!!!!!!