Dana 20 hear ratio

[wag86]

Hi Guys, looking for a reduction of the gear ratio in the Dana 20 axle. It’s now 1:354 and i guess 1:331 ( available at BJ’s ] will have good effect. Has anyone got experience with this? Do i need more than a pinion and gear set, like new bearings? And What to do with the front axle, anything needed there? Like switchable hubs?
Thanks all!

[Stuka]

I am going to assume you mean the AMC 20 rear axle? A Dana20 is a transfer case used in 63-79 FSJs.

For the ratio, that would be 2.73:1 standard for 80+, and 3.31:1 with the tow package. 3.54's were only an option on 79 and older FSJs.

What size tires will you be running? This will determine what gears you want, which then will tell us what parts you need. Will you be having a shop install them?

Oh, and front and rear HAVE to be changed at the same time.

[1979bettywhite]

I have a Dana 20 in my CJ as well . The transfer case version that is. But also an AMC 20 rear axle.

From my understanding, any time you change gearing, you need to reset the pinion. Which also per my understanding, if you don't have a lot of experience, you should leave that up to someone who does.

Just curious as to why you might want to go from a 3:54 to a 3:31. Would not think it would have that great a difference. Now going from 3:54 to 2.73 would. But I would not think most would want to do that as it would make things more sluggish for you.

Also, if you change one set of gears you have to change the other. So you would need to do both the front and rear at the same time. So you are now looking at some $$$ for a slight gear change.

Here's a good chart to go by when it comes to ratios versus tire size:

https://www.4wheelparts.com/off-road/ge ... meter.aspx

3.54 is a pretty solid all around ratio. I have it in both my CJ and FSJ and it turns 33s just fine. Do I want to rock crawl with it? No. But it gets around fine.

[wag86]

Thanks bettywhite for the chart! And yes i am referring to the dana 20 rear axle . I understand now that transferring to 1:2.73 makes more sense. I’m not looking for off road use, only on rpm reduction on the highway.. is there a way to get around having to change the front axle too by mounting locking hubs and simply disengage the front wheels permanently?
Thanks again!

[440sixpack]

not how I'd do it but it would work. all you'd have to do is remove the front drive shaft.

[Stuka]

The rear axle isn't made by dana, it was made by AMC.

Yes, you technically you could remove the front drive shaft, and drive in 2wd only. BUT, if it was ever shifted into 4wd full time on accident, it could destroy the transfercase.