So if I recall correctly, Eagles were available with 2.35, 2.73, 3.08, and 3.55 gears from the factory, depending on engine/transmission or if it was sold with the towing package or sold in the mountains.
I was told by a former AMC|Jeep technician (cruiser54 for those who know, RIP) that the AMC I6 engines (232, 258, 4.0) were all designed to run 1000 rpm for every 24 mph in high gear. So 1000 rpm at 24 mph, 2000 rpm at 48 mph, and 3000 rpm at 72 mph. Assuming a 205/75R15 (27.1" diameter) and a non lock up converter or a 1:1 transmission ratio, you're looking at 2823 rpm at 72 mph with 3.08 gears and 3245 rpm at 72 mph for 3.55 gears. Either of those are good options for these cars. Both of which are also available in many Jeep XJ Cherokees, which have a near bolt in rear axle. See my rear axle thread for more on that.
When I told people that I was going to run 3.55 gears in my car (which is on 225/75R15s, or a 28.3" diameter), I was pretty much told not to do it because it would be way too much rpm for the car, even though the math says it should be decent. I went ahead and regeared the front axle to 3.55 and swapped in a Chrysler 8.25 with 3.55 gears. I previously had 2.73 gears. I wasn't terribly concerned about highway rpm because I never drove faster than 60 mph in the past. Having done the swap, I actually started using the car as more of a daily driver because it's so much more fun with the deeper gears. And it behaves so well on the highway. I have ran 75-80 mph several times lately and the car doesn't mind it at all. I also did not notice a drop in mpg, in fact, mpg seemed to improve (I live in a rural area, so most of my driving is at 60 mph on county roads). The drivability improved greatly in town too because the car didn't have to work as hard to get moving. My car is a 258 with an automatic. It now also has an NP231J, but it did not when I first changed gears.
In summary, don't be afraid to give these cars some better gearing. The car is so much happier, the mpg improved, and it's way more fun to drive.
Personally, I'd absolutely go with 3.55 gears again with the same size tire. With a smaller tire though, I think 3.08s would be good, especially if you spend a lot of time on the highway. If a lot of your driving is in town, don't be afraid of 3.55s.
What are everyone else's thoughts on gearing?
hi, last year I converted my 84 sedan from the stock 2:35s to 85 2:73s with Shift on the fly. Big difference, very happy with the change. 3:08 would be better, but I'm good for now, good luck, gz
Quote from: amcfool1 on July 29, 2024, 11:39:10 PM
hi, last year I converted my 84 sedan from the stock 2:35s to 85 2:73s with Shift on the fly. Big difference, very happy with the change. 3:08 would be better, but I'm good for now, good luck, gz
I'm sure that did make a big difference. I can't imagine how anemic these cars seem with 2.35 gears.
Anemic is one way to put it. 2:35 gears do make it a bit boring, however it is still far more fun to drive than everything Les we have.
Quote from: Taylor on July 30, 2024, 08:20:01 PM
Anemic is one way to put it. 2:35 gears do make it a bit boring, however it is still far more fun to drive than everything Les we have.
That is very true!
Just to complete your list of options, 3:31 was available in 1981 only (I believe) for high altitude, automatic transmission cars. I'm pretty certain my Kammback has the 3:31 gearing.
hi, afaik, the 3;54 set is hard to find, as it came mostly on the 4 cyl cars.
Quote from: vangremlin on July 31, 2024, 11:35:08 AM
Just to complete your list of options, 3:31 was available in 1981 only (I believe) for high altitude, automatic transmission cars. I'm pretty certain my Kammback has the 3:31 gearing.
Interesting! I bet those are a nice happy medium between 3.08s and 3.54s.
Quote from: amcfool1 on July 31, 2024, 12:26:42 PM
hi, afaik, the 3;54 set is hard to find, as it came mostly on the 4 cyl cars.
Thank you for the info!
Quote from: 89 MJ on July 31, 2024, 11:25:46 PM
Interesting! I bet those are a nice happy medium between 3.08s and 3.54s.
Thank you for the info!
I like 'em! ;)
You're welcome!
Hello, I know this is an old thread but where did you buy your new gears from for the front? I have an 8.8 with 3.55 gears ready to go in the rear but trying to figure out what i need for the front is driving me crazy. I dont know if new gears will fit, or if they need to be some special long pinion version or what. if you are still out there let me know what you bought!
Quote from: spacedust on October 01, 2025, 05:40:43 PMHello, I know this is an old thread but where did you buy your new gears from for the front? I have an 8.8 with 3.55 gears ready to go in the rear but trying to figure out what i need for the front is driving me crazy. I dont know if new gears will fit, or if they need to be some special long pinion version or what. if you are still out there let me know what you bought!
I'm still around! I bought new Yukon gears off of Rock Auto.
Were the Yukon gears from Rock Auto specific to the Eagle? If so what your did you specify for the order? I too would like to change my hearing.
Thanks,
Taylor
Quote from: Taylor on October 01, 2025, 07:44:32 PMWere the Yukon gears from Rock Auto specific to the Eagle? If so what your did you specify for the order? I too would like to change my hearing.
Thanks,
Taylor
I don't think they were Eagles specific, but I did order them under an Eagle for vehicle option.
What gear ratio are you changing from?
If you have 2.72 or numerically higher you will be able to re-gear your front axle without issue. However if you have 2.35 gears like I did you will need to find another axle to re-gear. The carriers and housings are specific to the Eagle and have a different offset than the Jeep carriers. You will need an axle with at least a 2.72 gear ratio to have any success at going to 3.54 gears.
I ordered mine from rockauto as well. I got the Dana branded gears part #2020585. 3.54 gear ratio.
Hey I really appreciate the responses guys. I'm not positive what I have for gears but in guessing it's 2.35 unfortunately. I don't seem to have a diff tag, is the easiest way to tell by pulling the diff cover? Or is there a way to tell visually from the outside?
This should help there is a letter stamped into the rear axle on the right side of the diff cover that indicates ratio.
(https://amceaglesden.com/guide/images/f/f0/9axles011.jpg)
There should be a standard tag on the front axle but it will be very hard to see as the diff is very close to the front cross member.
Thank you for the info 5speed! I don't use forums much but so far you guys have been awesome help. I'll check when I get home, funny that I just replaced the pinion seal and didn't even see the stamp.
Well I have a 1982 disco with J stamp so I should be good to buy the same gear set from rock auto since mine should be 2.73:1. Woot!
Are gear swaps doable for the average backyard wrencher? Did you guys get an install kit when you did yours?
I have regeared 4 different axles and it is doable. However I would get a quote from a local shop and if you can afford it have them do it. The first one I did took me about a week to get just right. Also don't try to regear it while the axle is still under the car. Do it on a workbench or with the axle removed from the car on some jack stands on the ground.
If you do it your self I defiantly recommend buying an install kit. I thought it would be cheaper to just buy the bearings I needed but ended up spending more to get everything I needed individually than what the kit cost.
I'm no expert mechanic but I would consider this job beyond my capabilities. Maybe watch a couple videos on YouTube a see if you would be comfortable doing this job.
Good luck!
I would say it's a little complicated for the average guy. It takes a lot of time and precise measurements (we're talking thousandths of an inch) and you need to have a hydraulic press as well. If you're comfortable with all of that, go for it.
Thanks guys! Sounds like I should probably leave this one to the pros although ironically I have machining experience so I've got dial indicators and experience in the right tolerance department and actually have a hydraulic press too! I'll pull the diff even if I do bring it to a pro, it sounds like that's definitely the way to go. I found a couple of diffs in the junkyard, I might grab one since it's a 3.07 non disconnect. I assume the non disconnects can hold more power.
Quote from: spacedust on October 04, 2025, 10:28:09 AMThanks guys! Sounds like I should probably leave this one to the pros although ironically I have machining experience so I've got dial indicators and experience in the right tolerance department and actually have a hydraulic press too! I'll pull the diff even if I do bring it to a pro, it sounds like that's definitely the way to go. I found a couple of diffs in the junkyard, I might grab one since it's a 3.07 non disconnect. I assume the non disconnects can hold more power.
If this is a car that will see a lot of highway use, you might actually want 3.07s. It sounds like you could swap the gears though. Maybe watch a few videos on D30 gear swaps and see if it's something you think you can do.
I watched a few videos and of course they made it look super easy, in realty I can tell that it takes some serious patience. I'm going to poke around and check to see what my local shops will charge.
Long term I actually am hoping to engine swap it. I was talking to a fella down the road that LS swapped his Eagle and I even found a Tahoe doner. His drove really nice and and his had 3.73 gears so I think 3.54 gears would work nice for me. It'll drive decent now with the inline 6 and if I do ever LS swap it then it will also be decent. Plus my 8.8 already has 3.55 gears that I don't want to change.
Are you guys happy with the gears you chose or would you do it differently now?
I went with 3.54 gears and for the most part am happy with it. Biggest problem is the fact that I am now turning too many rpms to spend any real time on the interstate because I don't have overdrive. If mine were a car that was going to stay with the factory 3 speed forever, I would wish I went with 3.07 gears. Because my car will probably end up with overdrive in the future, I am glad I went with the 3.54s. I also usually don't end up over 60mph.
I like the 3.54 gears in my car. However I do have the T5 manual transmission. It has overdrive and at 60 mph I am running 2200 rpm. At 80 which doesn't happen very often it is about 2900 rpm.
I found this gear ratio calculator that was very helpful in choosing the gears I did. You can compare what you have now with the new setup.
https://www.grimmjeeper.com/gears.html (https://www.grimmjeeper.com/gears.html)
Do you guys daily drive your eagles?
Quote from: spacedust on Yesterday at 09:20:19 AMDo you guys daily drive your eagles?
Sure do. About 120 miles per week.
Quote from: spacedust on Yesterday at 09:20:19 AMDo you guys daily drive your eagles?
Yes I switch between my Comanche and Eagle. Usually get about 150 miles a week on one or the other. Daily driving I never get above 60 mph.