do axle ratios need to match? - 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 > Jeep CJ Forum > do axle ratios need to match?

FS: Jeep Fog Light LED Bulbs! Several Brightness Options! SPARTAN LOCKERS are on sale BIG TIME at ROCKRIDGE 4WD!Yukon Ultimate 35 axle kit for c/clip axles with Yukon Zip

Reply
Unread 06-30-2012, 06:21 PM   #1
shadoow
Registered User
1985 CJ7 
 
Join Date: Nov 2006
Location: Granbury, Texas
Posts: 465
do axle ratios need to match?

saw another thread on here discussing axle gear ratios & it sounded like front & rear axle ratios may not have to be the same.

i've got an 85 cj7 w/258. Front is a dana 30 and rear is a dana 20. Both have 3.31 gears. I'm looking to replace the dana 30 with used/rebuilt one & am wondering if I need to get a 3.31 axle to match the rear. If not, what ratios would work for me?

shadoow is offline   Reply With Quote
Unread 06-30-2012, 06:27 PM   #2
FLynes
Web Wheeler
 
FLynes's Avatar
1976 CJ5 
 
Join Date: May 2010
Location: San Angelo, Texas
Posts: 2,800
They must match. You can get away with .01 or so difference, i.e. 3.54 and 3.55, 4.10 and 4.11, etc...
__________________
Fred
Retired Army Guy

High Plains Drifter
1976 CJ-5
Lime Green
Black Wellington Vinyl Bench Seats
258 I-6 1bbl
T-150 3-Speed
3.54:1 Open Gears

Grammar Test
FLynes is offline   Reply With Quote
Unread 06-30-2012, 06:33 PM   #3
B52dude
Registered User
1999 TJ Wrangler 
 
Join Date: Oct 2010
Posts: 344
Well, technically, if you run different sized tires in front and back, you could use different ratios in the axles. But you generally don't see that. Nor do I recommend it. Because it will look dumb.
__________________
[QUOTE=Ripper3494;10936705]i think we should chase him around with yjs, its like being chased by zombies, slow, crippled but for some reason still scary as heck lol[/QUOTE]

Red Jeep Club #614
B52dude is offline   Reply With Quote
Unread 06-30-2012, 09:23 PM   #4
80cj
Web Wheeler
 
80cj's Avatar
1980 CJ5 
 
Join Date: May 2002
Location: Hawaii
Posts: 5,796
Quote:
Originally Posted by FLynes View Post
They must match. You can get away with .01 or so difference, i.e. 3.54 and 3.55, 4.10 and 4.11, etc...
Ford used 3.54 front and 3.50 rear for years with no problems.
80cj is offline   Reply With Quote
Unread 06-30-2012, 09:28 PM   #5
mopar346
Registered User
1984 CJ7 
 
Join Date: Aug 2011
Location: Quincy, Florida
Posts: 2,656
You guys are nuts they don't need to match as long as you don't put it in 4WD and lock the hubs everything will be fine, you can run any ratio with any other.

Manufactures have run them a few hundredth off front to rear for years, still not sure way.
__________________
Careful your character's showing
mopar346 is offline   Reply With Quote
Unread 07-01-2012, 12:01 AM   #6
Skerr
<*////><
 
Skerr's Avatar
1985 CJ7 
 
Join Date: Sep 2008
Location: White Springs, Florida
Posts: 8,877
If you are replacing the D30 with another D30, and the gears are still good, you could swap them into the new axle. What's the problem with the current D30?
__________________
Kerrdog
Go Fish! <*////><

But the right word at the right time... "Hey, give me a little hug!" That's the difference between lightning and a harmless lightning bug!
Skerr is offline   Reply With Quote
Unread 07-01-2012, 12:12 AM   #7
80cj
Web Wheeler
 
80cj's Avatar
1980 CJ5 
 
Join Date: May 2002
Location: Hawaii
Posts: 5,796
In answer to the OP's original post, yes you would have to get another 3.31 axle because there is no other ratio available in a D30 that is close.
80cj is offline   Reply With Quote
Unread 07-01-2012, 12:46 AM   #8
firewalker909
Ok, one more.
 
firewalker909's Avatar
1973 CJ5 
 
Join Date: Jan 2011
Location: Yucaipa, California
Posts: 378
The way it was explained to me at mek-a-nik school, the higher gears were used in the front to create a pulling action, as opposed to a pushing action from the rear. Supposed to be more stable off road.

There was a guy at my school in Phoenix that had replaced his gears in the rear of his Toyota pick up with a higher gear set. He literally climbed all the hills in Deer Valley backwards. Don't remember off hand what the ratios were, but pretty sure the guy had a screw loose anyway.
firewalker909 is offline   Reply With Quote
Unread 07-01-2012, 12:49 AM   #9
80cj
Web Wheeler
 
80cj's Avatar
1980 CJ5 
 
Join Date: May 2002
Location: Hawaii
Posts: 5,796
Quote:
Originally Posted by firewalker909 View Post
The way it was explained to me at mek-a-nik school, the higher gears were used in the front to create a pulling action, as opposed to a pushing action from the rear. Supposed to be more stable off road.

There was a guy at my school in Phoenix that had replaced his gears in the rear of his Toyota pick up with a higher gear set. He literally climbed all the hills in Deer Valley backwards. Don't remember off hand what the ratios were, but pretty sure the guy had a screw loose anyway.
Guys who run mud a lot do that and I imagine it would work well in soft sand too but don't forget to disengage 4WD when you get on a high traction surface.

Last edited by 80cj; 07-01-2012 at 09:36 AM.. Reason: for get corrected to forget
80cj is offline   Reply With Quote
Unread 07-01-2012, 04:52 AM   #10
colojeepguy
Registered User
1970 CJ5 
 
Join Date: Jan 2010
Location: Colorado Springs CO
Posts: 1,093
Quote:
Originally Posted by 80cj View Post
Ford used 3.54 front and 3.50 rear for years with no problems.
I had a '66 F-100 with that setup. It was a great ol' truck, but I used to have to stop & back up to get it out of 4WD.
colojeepguy is offline   Reply With Quote
Unread 07-01-2012, 04:59 AM   #11
hp_lovecraft
Registered User
1981 CJ5 
 
Join Date: Sep 2009
Location: Maine
Posts: 986
I had a CJ5 years ago that the PO swapped in another axle with mismatched gears.
I didn't know any better and just ran it anyway. I had no problems offroad, but it would bind and be nearly impossible to get out of gear. If I hit a hard surface, the tires would hop and skip.

For the OP, maybe you will be fine in the shortterm, but its going to put more strain on the driveline. Eventually something is going to go.
hp_lovecraft is offline   Reply With Quote
Unread 07-01-2012, 07:12 AM   #12
Skerr
<*////><
 
Skerr's Avatar
1985 CJ7 
 
Join Date: Sep 2008
Location: White Springs, Florida
Posts: 8,877
Quote:
Originally Posted by colojeepguy View Post
I had a '66 F-100 with that setup. It was a great ol' truck, but I used to have to stop & back up to get it out of 4WD.
Ditto!
__________________
Kerrdog
Go Fish! <*////><

But the right word at the right time... "Hey, give me a little hug!" That's the difference between lightning and a harmless lightning bug!
Skerr is offline   Reply With Quote
Unread 07-01-2012, 09:41 AM   #13
80cj
Web Wheeler
 
80cj's Avatar
1980 CJ5 
 
Join Date: May 2002
Location: Hawaii
Posts: 5,796
Quote:
Originally Posted by hp_lovecraft View Post
I had a CJ5 years ago that the PO swapped in another axle with mismatched gears.
I didn't know any better and just ran it anyway. I had no problems offroad, but it would bind and be nearly impossible to get out of gear. If I hit a hard surface, the tires would hop and skip.

For the OP, maybe you will be fine in the shortterm, but its going to put more strain on the driveline. Eventually something is going to go.
I ran into the same situation back in the 70's with a 70 CJ-5 that I bought and was told it had 4.88's. As it turned out, the front was 4.88 but he broke the rearend and subsituted a 44 from an M38A1 which was 5.38. Very difficult to get out of 4WD and the slip yoke splines on the front drive shaft were very loose. Ended up getting my money back.
80cj is offline   Reply With Quote
Unread 07-01-2012, 03:24 PM   #14
shadoow
Registered User
1985 CJ7 
 
Join Date: Nov 2006
Location: Granbury, Texas
Posts: 465
Quote:
Originally Posted by Skerr View Post
If you are replacing the D30 with another D30, and the gears are still good, you could swap them into the new axle. What's the problem with the current D30?
gears are probably shot. The pinion yoke wiggles around in the housing and i've seen metal bits in the oil i drained. Didn't take a close look when i did the oil cause i hadn't yet found the pinion wiggle. I had recently got the jeep & was going thru doing fluid changes.
Besides the gears, i'm concerned the housing may be internally damaged.

thanx all for the info on gear ratios. Guess i'll continue my search for a 3.31 replacement.
shadoow is offline   Reply With Quote
Unread 07-04-2012, 09:06 PM   #15
FLynes
Web Wheeler
 
FLynes's Avatar
1976 CJ5 
 
Join Date: May 2010
Location: San Angelo, Texas
Posts: 2,800
Hopefully this helps you:

http://www.ebay.com/itm/Jeep-CJ7-CJ-...5d187e&vxp=mtr
__________________
Fred
Retired Army Guy

High Plains Drifter
1976 CJ-5
Lime Green
Black Wellington Vinyl Bench Seats
258 I-6 1bbl
T-150 3-Speed
3.54:1 Open Gears

Grammar Test
FLynes is offline   Reply With Quote
Reply
Thread Tools


Suggested Threads





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.