What is my stock gear ratio? - JeepForum.com
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post #1 of 11 Old 05-23-2019, 09:11 PM Thread Starter
weider1717
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What is my stock gear ratio?

Guys, I have looked online and nothing really says point blank what gears I would have.

1978 golden eagle
304
3sp

I have 35" tires on it now and I know the past two owners the gears are what was in it stock it was only lifted and big tires put on very recently. My thought was I'll need to re-gear but whatever is in it does pretty good turning the 35's you wouldn't be crawling with it too good but otherwise not bad at all plenty of power but I may still re-gear.

thanks

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post #2 of 11 Old 05-23-2019, 09:41 PM
Superjeep3
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This is what I found. I hope it helps.

https://www.automobile-catalog.com/auta_details1.php

Looks to be 3.54 stock with 4.09 being an option.
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post #3 of 11 Old 05-23-2019, 10:03 PM
RiverandSand
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You should have an AMC20, there should be stamped letter(s) on the right rear side near the diff cover. Jeeptech under the Amc20 tab has the code breakdown. Of course that's if the gears haven't been changed by a PO.
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post #4 of 11 Old 05-23-2019, 11:49 PM
ddawg16
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Or....jack up one tire....spin the wheel and count driveshaft turns.

Don't forget to multiply by 2. With one wheel blocked, the DS will turn half as fast.

Say you have a 3.00 ratio....that means your driveshaft turns 3x for each turn of the wheel. With a standard diff, if you block one wheel, then 3 turns of the ds means 6 turns of the wheel.

Since it's easier to turn the wheel vs the DS....use a piece of chalk....mark a line on the DS (I like doing it at the pinion for reference)...mark a spot on the wheel (I like using the body side as a ref)....then turn the wheel.

You don't have to be exact.....the real world ratios are not very close.


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post #5 of 11 Old 05-24-2019, 04:01 AM
keith460
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I'm pretty sure the axle ratio's available for 1978 were standard 3.07 and optional 3.54. You can check the letter code on the right side of the rear axle cover, stamped into the casting just to the left of where the axle tube meets housing.


Standard X = 3.07
Trac-Lok Y = 3.07
Standard A = 3.54
Trac-Lok N = 3.54

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post #6 of 11 Old 05-24-2019, 06:17 AM
jeepdaddy2000
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Ya know, you may just want to drop the rear diff cover and do a tooth count.


This will give you a positive answer.


It will tell you if there are any other issues in there. Things like a bad LS or chunking of the axle/side gears.


It will let you see if a PO has installed anything else in there.



It will put fresh 90WT into the diff.

Regardless of what the stock gearing is, 35's are gong to require at least 4.11 or lower gears (transmission dependent)


Might think about a set of one piece axles as well.
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post #7 of 11 Old 05-24-2019, 07:23 AM
BrutusBlue
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What’s your rpm at any given speed? easy to calculate your ratio without lifting a finger.

Otherwise, pop the diff cover.
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post #8 of 11 Old 05-24-2019, 09:25 AM Thread Starter
weider1717
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Thanks for the replies!

3.54 is what I was finding online also but someone on here told me it was wishful thinking that I probably has I think they said 2.73 or 3.31. So, I thought I would ask.

When I am back home I will be sure to check out the stamp code first and go form there, thanks!
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post #9 of 11 Old 05-24-2019, 09:30 AM
jp360cj
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Most likely 3.54s, which were standard. 4.10s were optional. IMO, it would be best to pop the covers, verify the tooth count, inspect, and fill with fresh fluid. This will also give you a chance to check the diff for a limited slip/locker.

77 CJ-7- AMC 360, Edelbrock cam, MC2100, Fenderwells, CJ T18/D20, Chevy D44/EB 9" rear, Trutrac f/r, 4.11, SOA, 1.25 lift shackles, 35x12.50 BFG KM2s, Shackle Reversal
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post #10 of 11 Old 05-24-2019, 01:26 PM
John Strenk
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One last way to check is to put a chalk mark on the drive shaft and just push the jeep forward one wheel revolution and count the turns of the DS.
If it turns 3 and 1/2 times it's probably 3.54
If it turns 4 times then it's probably 4.10.

No jacking up
No removing a rear cover
No trying to read a rusted ID label.

Not that those are not good ways
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post #11 of 11 Old 05-25-2019, 02:10 AM
80cj
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Quote:
Originally Posted by keith460 View Post
I'm pretty sure the axle ratio's available for 1978 were standard 3.07 and optional 3.54. You can check the letter code on the right side of the rear axle cover, stamped into the casting just to the left of where the axle tube meets housing.


Standard X = 3.07
Trac-Lok Y = 3.07
Standard A = 3.54
Trac-Lok N = 3.54
3.07 came out in 1980 and I believe that was the only year it was used in CJ's. Optional for 80 was 3.54.
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