K so I'm new to this jeep thing and sending a lot of money on this project!! I've got an 83 cj7 with the inline 6 and a weber carb. My mechanic said it's got 3.73 gears when he installed the lockers. I don't know how to tell the transmission but it's an automatic. I've converted the suspension to the ome 2.5 lift and it's got 15x8 wheels on 31s. I plan on going off-road and trail riding along with driving in town. Need ideas on larger tires when I have the 1 inch bl this week and I don't want real wide tires but want it to flex without rubbing bad. Gonna put dura trac tires on her. Let me know if y'all have any ideas for this newbie!!
I agree with Matt about the 32s. Any bigger is going to minimalize your gearing.
Generally speaking, the shorter the tire, the better the tractive effort. The problem is life is full of compromises; shorter tires mean less ground clearance. Taller tires do give better clearance but you start losing any advantage your gearing has for you.
Another thing to consider is if you go to LARGER tires (not so much a small increase in size) you put more spinning mass at the corners of your Jeep. That means you now need beefier brakes to slow or stop. And you need to beef up your steering and suspension. You're messing with the designed geometry of your vehicle when you make radical changes.
I get a kick when guys say something stupid like the steering shaft is a lousy design, or the Jeep engineers didn't know what they were doing.
Yes they did! But when you alter your vehicle to outside their design parameters, don't be amazed when stuff breaks!
I'd rather be lost on the trails than found at home!
your transmission is probably the TF-999, 3 speed auto.
your automatic tranny acts as a torque multiplier. proper range selection in the transfer case and you should be fine with the 3.73 gears and tires in the 30-32" range.
in the tires you want, you're pretty much limited to 31/10.5Rx15. the only other option are their 33/12.5R15 and they might be too tall and wide for the lift you have without modifying your fenders some.
1966 CJ5A, mods are coming
1966 Wagoneer, bone stock
32's might be perfect for your setup. I've gone just about everywhere I want to go in the Colorado high country with my 3" Black Diamond lift and 32x11.50x15 Cooper STT's.
258 cu. inch six, Team Rush ignition upgrade, T5, Dana 300, Superwinch lockouts, Black Diamond 3" suspension lift, greasable shackles, poly bushings, JKS quick discos, 32x11.50x15 Cooper STT's, American Racing 23 15x8 alloys, Uniden Pro 520XL CB radio, 2' adjustable tip Firestick antenna, Viair 460 onboard air system
The 31" tyres are a great fit with your rig and gearing. 31x10.5x15 is a very common size and will not alter the gearing much from factory which came with 29" tyres, a 7% differnece in ratios for 32". The 32s are 10% and 33s are 14% (if they actualy measure those diameters, many tyres are only notionally the size on the sidewall).
It doesn't sound like much but if you used to cruise at 2400rpm, you will now be trying to do that at 2,200rpm, 2150rpm or 2060rpm. That is a big drop for 33" tyres and you will bog down, and with a 3 gear auto you may find it dropping to 2nd a lot.
You can overcome this by regearing but those big rotating masses on the corners will in any case slow you down. As said above, it is a series of compromises.
Here's a pic of my 76 CJ5 with 32x11.50-15 TSL/SX tires on 15x8 wheels. Jeep has a 2.5" BDS lift, EnergySuspension poly body mounts (no lift), and close to stock 3/4" ConFer Shackles:
Bear in mind, that in the above pic, the roll cage, windshield, and a few other parts haven't been assembled, but it's pretty close to total weight and ride level right now.
I've got 4.56 gearing, so I'm looking into mounting larger tires exclusively for street use. From my measuring, I should be able to stuff 33x10.00-15 tires under it, all depending on what the actual mounted diameter is. I wish someone made a 35x10.00-15 all terrain, but I haven't been able to source one. Of course turning radius on my narrow track axles will suffer, as the front tires will hit the sway bar in the front, and the springs in the rear. So adjusting the steering stops is mandatory.
If your 83 is stock, you've got wide track axles: Dana 30 front and AMC 20 rear. You will have less turning radius issues than us that are running narrow tracks. Going to large tires also creates additional stresses on them. Since you will be staying at 32"-33", they both 'should' hold up fine. I would definitely consider 1-piece axle shafts in the AMC 20.
If your CJ has 3.73 gears, that 'should' be a good compromise gearing for 32-33 inch tires for street use. IMHO, 4.10 gearing would be the way to go if the 33 inch tires measured a true (or close to) 33 inches diameter.
Also, it's been my experience that automatics are a bit less stressful on drivetrain components than manuals.