Gears? - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Full Size Jeep Forum > Gears?

Jeep speedometer gears at rockridge4wdDana 30 Truss for your TJ, LJ, ZJ, and XJClayton Off Road JK Long Arm Upgrade Kits!

Reply
Unread 04-10-2013, 10:34 AM   #1
rabbott1
Registered User
1985 J-Series Truck 
 
Join Date: Apr 2012
Location: burlington, ky
Posts: 95
Gears?

Does anyone know what the stock gears were in 1985 J-10? How to identify what I have, and the best gearing to run with 35's? Never really messed with this kind of stuff, and don't know what has been done to this truck. Besides doing some hunting and fishing I am mostly going to be driving street and highway. Sin I know.

rabbott1 is offline   Reply With Quote
Unread 04-10-2013, 10:50 AM   #2
pleontks
Registered User
1976 J-Series Truck 
 
Join Date: Apr 2010
Location: Whetstone, Az
Posts: 1,130
there should be a tag on the diff, held on by th bolts for the diff cover. That should have your ratio on it. There should also be one on the front diff, if the one on the rear is missing. It may just say '3.54' or whatever, or it may be like '43 16' and you get to do the math yourself.
__________________
Beauty is in the eye of the jeepowner.
pleontks is offline   Reply With Quote
Unread 04-10-2013, 03:48 PM   #3
timgr
Registered User
1975 CJ6 
 
Join Date: Dec 2012
Location: Medford, MA
Posts: 463
An '85 should have an AMC Corporate axle in the rear (the M23). Look here for the axle codes: http://www.jeeptech.com/axle/amc20.html

The front axle should have a tag, as mentioned. Likely it's 3.31 or 2.73, by 1985.

Re "the best" gearing, for off-pavement the higher the number the better. But you may have to compromise to get acceptable engine speed on the highway. Decide what engine speed and highway speed you want, then use one of the online calculators to find an acceptable gear ratio. http://www.novak-adapt.com/knowledge/gearing.htm - for example, 35s at 65 mph and 2500 RPM is about a 4.10 axle ratio.
__________________
1) '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps. 2) '82 J20 360/T18/NP208/3.73, KOs, 7600 GVWR 3) '75 CJ-6, 304/T15, PS, BFG KM2s, soft top 4) '95 VW Golf Sport 2000cc 2D
timgr is offline   Reply With Quote
Unread 04-11-2013, 09:20 AM   #4
rabbott1
Registered User
1985 J-Series Truck 
 
Join Date: Apr 2012
Location: burlington, ky
Posts: 95
What if someone has changed them already? Is there a way to tell what they replaced them with? Are the gears themselves marked? Or do you just count the teeth?
rabbott1 is offline   Reply With Quote
Unread 04-11-2013, 10:42 AM   #5
CSP
Registered User
 
Join Date: Aug 2002
Location: Colorado
Posts: 12,078
The ring gear will have a stamp on the outer circumference that gives the tooth counts. Do the math and it will tell you the ratio. You'll see something like 41-10 (4.10 ratio) or 43-13 (3.31).
CSP is offline   Reply With Quote
Unread 04-12-2013, 11:33 AM   #6
rabbott1
Registered User
1985 J-Series Truck 
 
Join Date: Apr 2012
Location: burlington, ky
Posts: 95
Thanks everyone!
rabbott1 is offline   Reply With Quote




Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.