Tire Size verses transmission

[VaGent]

I need some help guys in figureing something out as I am kinda new to to all this swapping stuff.

I just switched out the front & rear springs in my 1990 Bronco II & installed 1991 Explorer front & rear springs. I did this because the rear leaf springs were sagging as most of them do. I gained exactly 1 1/2" in the rear & now the Bronco Ii is setting level all the way around which is what I wanted the end results to be. I am not using any kind of lift kit at all. I just ran across a "steal" on a set of 31X10.5X15 BFG AT radial tires & wheels & couldn't pass them up for $200.00. They only have like maybe 1000 miles at most on them. The guy who had them took them off his Bronco full size & went with 35" tires instead as he didn't like the looks of the 31" tires. Anyway, where's my question.

Can I put these 31X10.5X15 tires on my Bronco II without having to use a lift kit & will the transmission work OK with them. Keep in mind the transmission is a newly rebuilt A4LD out of a '91 Explorer 4X4. The engine in the Bronco II is a 2.9 V6 that runs pretty strong. It only has 76,000 miles on it right now. I am going to be swapping it out later this summer when I get the money to a 4.0 V6 along with changing the automatic over to a Mazda 501R 5 speed. I am not into any crawling or bogging at this time & will be driving the Bronco II on a daily basis to & from work & out on the open highway. I just don't want to tear up the A4LD tranny right now by using larger tires until I can do the swap to the 4.0. Any help would be appreciated greatly.

 

[metalmacguyver]

you will be fine with those tires. i am pretty sure that you wont have any rubbing. if you do it will be absolutely minimal and only happen under more extreme conditions. the mazda transmission that you mentioned is the M5OD-R1. IMHO BFGs are the best "off road" tire that you can get for a daily driver. they last a long time and dont make noise like large lug tires do.

 

[pimtool]

If he took the wheels off of his full size, they will not fit your B2.

 

[VaGent]

Thanks for the replies everyone. The wheels I am not planning on using as they will not match up to my Bronco II hubs & I was aware of that when I bought them. The wheels are the factory chrome steel wheels with the centers & are in really great shape. The guy that sold the package to me is very particular about keeping everything in great shape. They are off of his 1996 Bronco. I plan on selling them to anyone who might want or need them.

I was worried about the tires rubbing or putting too much stress on the A4LD even since it has just recently been rebuilt. And thanks for clarifying the Mazda tranny too. I have two of them & they both need to be rebuilt which I am planning on doing later.

I am also planning on swapping out the stock rear to a 8.8 with disc brakes since I already have Explorer front & rear springs under it now. Trying to decide if I want to lift it at a later date of not. Money is tight everywhere & prices are high so I am trying to do everything I can myself. I can twist a wrench, open a cold Bud & say a few choice words so I think I am going to be in good shape. Thanks again for the info. Just a side note. I have lots of BII & some Explorer parts if anyone is interested. Hit me up at d4000@comcast. net if you need anything.

 

[4x4junkie]

What axle gear ratio do you have? This is what actually matters when it comes to your transmission (and engine) relating to tire size.

31s are not much above stock size though. Chances are you'll be fine if you have 3.73 or 4.10 gears (4.56 would be the ideal with a 2.9L though)

 

[derekj]

I run 30" tires on my truck with a 2" lift. The 31's might rub a little in the back on full flex but otherwise mine only rub on the sway bar on full lock. I have a freshly rebuilt A4LD in my truck with 3.73 gears and it seems to be fine.

Derek

 

[VaGent]

I have 3.73 gears in mine too. Wasn't sure if using 31s was too tall a tire to use with it & the tranny. Since I am new to all this, is gas milege going to suffer? I get around 16 in town & 21 open road running 237/75/R15s now. This is driving it as normal as I can with traffic like it is on I-95. Sometimes 50 & then sometimes ????? whatever it takes to go with the flow. Can't wait to put the 4.0 in it & the 5 speed.

 

[VaGent]

I forgot to add that right now using 235/75/15s I am measuring 32 1/2 inches from the ground to the center of the wheel wells front & rear using the Explorer springs.