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New to CJ-8

#1
Just purchased a 1982 CJ8 with lots of modifications - most not that great. But I'm slowly bringing it back to life.
I'm having the standard speedometer issue and my mechanic says it's the speedo gears. I'm running 35s and a dana 30 rear end. Any idea how I determine my gear ratio? It's a 1982 CJ8.
Thanks
 

93_Fummins

CJ-8 Member
CJ-8.com Member
#2
The most accurate way is to pull the differential cover and count teeth, or look for the stampings on the ring gear for tooth count. Seeing as it's new to you, it wouldn't be bad to go ahead and do that just to inspect what everything looks like, check if there are any traction aids, and put fresh fluid back in.
 

FLCJ8

Legacy Registered User
#3
I'm having the standard speedometer issue and my mechanic says it's the speedo gears
What is the issue?

If you're trying to determine the appropriate speedo gear to use to correct a MPH discrepancy the best way to do that is use a GPS/app and compare the percentage the speedo is off from the GPS reading, check your existing speedo gear and adjust the tooth count by that percentage.
 
#4
The most accurate way is to pull the differential cover and count teeth, or look for the stampings on the ring gear for tooth count. Seeing as it's new to you, it wouldn't be bad to go ahead and do that just to inspect what everything looks like, check if there are any traction aids, and put fresh fluid back in.
Ok I'll try that. Can't hurt. Thx
 

John N

Addicted....Ex-SOA VP
LIFETIME
CJ-8.com Member
SOA Member
#5
BTW... the rear is am AMC 20, the front diff is a Dana 30, if they are the originals.
Welcome.
 

sevensandeights

sevensandeights
SOA Member
#8
Welcome! As mentioned above there should be a letter stamped on the rear of the diff housing - this would indicate what the factory gears were. However, with 35s it would be hard to imagine the diff gears weren't changed at some point. Most Jeeps came with 2.72 or 3.54 gears with the 6 cylinder engine. Some came with 3.73s. Many of the 4 cylinders came with 4.10s. Regardless my guess would be that the gears aren't stock with 35" tires so the best way is to pull the diff cover and count - good time to check for wear, change the fluid and see if someone installed a locker.
 
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