tire sizes...axle sizes

chef717

Basic User
City
clearwater
State
fl
#1
i here so much conflicting information about this subject. i'm running an amc20 and a dana30 on 33's. eventually i'll step up to at least 35's when i can afford a rubicon sping over. it's my understanding that as you go up in tire size it puts more pressure on your axles and it's best to step up your axles. SOME people in my club swear that my current axles will handle the bigger tires with minimum issues. NONE of them wheel a scrambler. i need some SCRAMBLER input !!!
 

MarknessMonster

Amiable Jeeper
City
Western
State
CO
#2
I would suggest that you'll be fine with 35x12.5's, but you might experience more strain on your junk if you get into any wider tires. The AMC 20 is a fine axle and strong enough to run 35's. What ratio are you running in your axles? Why do you want taller tires?

I've found the best combination of tire in the BFG 33x9.50 MT's, but they don't make them anymore. Mine are mated with 4.10's in the AMC20 and D30. They are excellent in both mud and snow, as it allows the light-weight CJ8 to dig, as the tread width is only about 6". However, I've also got 39x15's MT's hooked up to a D60 and D70 with 5.89 gearing, as this tire size starts to push limits on axles. This tire is good for the farm where I don't want to dig into my furrows, as the vehicle tends to float on the surface of the ground; they are awful in the snow.
 
8

81_cj8

Guest
#3
I've been told the amc20 does well with 33's and may need 1-piece axe shafts if you want to move up to 35's. I used to have 33" tires on then I stepped up to 35" and got the shafts too just to be safe and make everything that much stronger. I've heard that welding the axle tubes + 1-piece shafts makes the axle really strong..i've yet to get the tubes welded though.
 

Bogged

CJ-8 Member
CJ-8.com Member
City
Sydney
State
NS
#4
Truss it, weld it, 1 piece axles and you'll be set. They are a strong diff initially, just poorly cobbled together.
 

chef717

Basic User
City
clearwater
State
fl
#5
i'm running 410 gearing. lockrights front and rear. someone else suggested trussing the rear so i'm guessing that it's a good idea. the guys i wheel with the most run 37's and 38's and push me to the limit. i want to go spring over when the all mighty dollar gives me the ok and i think 7 inches of lift on 33's would look kinda funny. i DEFINITELY could use some more ground clearance as my u bolts and transfer case skid plate get hung up the most.



here's the guys i wheel with...





it sounds as though i may be able to stay with my current axles...sure would save me a lot of money !!!
 

PetesCj-8

CJ-8 Member
CJ-8.com Member
City
slatington
State
pa
#6
This is it right here. Get the tubes welded and throw in some 1 piece axles , something like Superior from Quadratec for about $270.If cash allows throw a lunchbox locker in there while the axles are out. I believe 4 wd hardware sells a truss for the Amc20. Then you'll be good to go. Gearing for 35s should be between 4.56 and 4.88.
Truss it, weld it, 1 piece axles and you'll be set. They are a strong diff initially, just poorly cobbled together.
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Biloxi
State
MS
#7
Put a Warn Full FLoat conversion on the rear and never worry about busting a shaft again:thumbsup: And if you do, pull it out and keep on rolling:rolleyes: And you dont have to worry about pressing on and off wheel bearings and shimimng the axles.

Front Dana 30, put some chrome molly shafts with the bigger u joints in and you should be good. There is a guy in my club that runs a 30 front with a Detroit (which broke, and is now welded together like a spool) with chrome molly shafts, backed up by a Fuel Injected LT1 and pushing 37 inch tires, no problems.

By the way, my 78 CJ-7 runs rear 20 with Warn full float, Detroit, 3:73 gears and 33" Swampers. My front 30 has an Aussie Locker installed in the factory open diff carrier, chrome molly shafts with the Dana 44 size U-joint, and the internal spline Warn hubs (like on a Dana 44) with the same 33" Swampers. I drive this thin on the highway to the trails, wheel it, and drive it back with no worries. As long as you dont try the super crzy kamikazee stuff you shouuld be good. I am running a modified 304 backed up by a granny gear T18, so I do put some torque through this set up.:thumbsup:
 

chef717

Basic User
City
clearwater
State
fl
#8
i knew you guys would have some good input. it sounds like welding axles is the wat to go vs lockers. i won't TRY to go out and break the lockers i have... but if it happens i know my next move. thanks for the help !!
 
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