stock 3.55 gears w/ 30x9.50x15's

96 4.0 w/ auto tranny and 3.55's --
ok, I searched, and found a lot of 'will 30's fit my stock suspension?'... etc type questions, no help there. What I'm wanting is a straight forward answer from someone who went from the stock 225/75's with 3.55 gears, 4.0, auto tranny to 30x9.50x15's, as to wether there was a noticeable loss of power with this tire size and 3.55 gears. I know all 30's do not measure the same, nor do 225's, 235's, etc, some are 29.5, 29.6, and some 235's are 29.0...... Right now I have some off brand cheapo 225's on there with sidewall bulges and leaks that need replacing, and when I spend the money, I'd like to go up to 30's if it won't bog me down. This Jeep will spend most of it's time on road, with the occasional foray down the trail, so I don't want to lose highway driveability. With that said, I'll be putting on a 2" BB, and I don't want mickey mouse looking 235's if I can help it.
Again, I'm not worried about rubbing, clearance, flexing, etc, just performance results. Thanks!

i dont think you will notice a huge loss of power, i am running 3.55's with my 35's right now until i got money to regear this summer

35's ? wow, I know that hurts. I was into YJ's until the babies started coming, and I ran 31's with the stock 3.07's for a year or so, and I would have to get out and push it uphill on the x-way.

yea, its not fun

I ran 235's before hand, and 30's later. The steel rims I used for the 30's were significantly heavier, so the power loss was quite noticeable. If you can keep the rolling weight lower, with alloy rims the power loss would be quite a bit less noticeable.

But realistically 235 works out to 28.8 inches So you are talking a difference of 1.2 inches total difference in height.

citRon said:

What I'm wanting is a straight forward answer from someone who went from the stock 225/75's with 3.55 gears, 4.0, auto tranny to 30x9.50x15's, as to wether there was a noticeable loss of power with this tire size and 3.55 gears.

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Slightly out of your specs, but...

I'm running 245/75R16 Goodyear MT/Rs at the moment on the stock 3.55:1 gears with an AW4. These tires have an (approximately) 31" diameter. Was there a noticeable amount of power loss? Yes, but possibly where you might not expect it.

Off the line starts are... Smoother. There isn't the neck-snapping urge that there was before, but pace is good right up to about 60mph. Where I've really noticed the difference is at freeway speeds - acceleration through the gears isn't as good above about 55mph, and a couple of test runs up to 80mph showed that it starts running out of puff much sooner than previously - somewhere around about 72mph or so.

Long, gradual uphill gradients caused more locking and unlocking of the torque converter than before along with the odd additional downshift. Not so much that it's a problem, but on mountain roads there's no more using drive until you hit a level stretch: put it in third and save it from constantly hunting. The effects I'm describing will likely be less noticeable with the smaller-diameter tires you're talking about using, but they will be there.

Put it this way: it's fine for what it does right now, but I know 4.10s are in my future. The next time I have to tow something is going to be interesting.

Citron,
I've got an '89 Limited that I bought with 235's and factory alloys. I've since traded up to 30's on Wrangler alloys with no lift. If I flex the suspension a lot the rear tires rub but nothing major. There is a difference in power off the line and climbing hills but it's nothing major. Downshifting into third for hills is the cure for the hunting.

Works for Me!
Cherokid.

I have the same setup you are looking at--3.55, auto 4.0 and 3" lift w/ 30" BFG AT's. The tranny tends to shift too early, and on freeway hills it is noticable--but still can do 75/80 without difficulty. I have Rusty's airtube and exaust which help a bit. I'm looking to upgrade to 31's and 4.10 gears within the year. I would recommend 31" w/ a 3" lift.

I've got 3 inches of lift, a ton of extra steel, and 255/70-16's (30x10.00) on an '01 4.0 Auto 242. Power has not been an issue, but mileage is suckin. Around town I'm hurting to get 14 mpg. On the highway, it'll do 16-17? Prior to the added weight, the 30's would get me 16 round town, and 19 on the highway. I'm really carrying around a lot of weight, and I think that is half my problem.
If you are interested, I'm considering jumping up to 32's, and would entertain any interest in my rims/tires!!! Stock Limited 5 spoke aluminum wheels 16x7 with 255/70-16 Goodyear MTR's with 9/32's tread left (new is 19/32, so slightly less than 50% left)..........................:sunshine:

thanks, I'm going to stick with my stock 'sport' lots-of-holes-in them 15x7 rims.

hman333 said:

i have noticed a huge loss of power, i am running 3.55's with my 35's right now until i got money to regear this summer

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fixed