Gearing question...

[krejr]

Ok, I'm getting a 6" lift in the mail hopefully this week, and I want to get bigger tires, probably 33's. I'm told that I should probably change my gearing. If I change to 33's or 35's, what amount of change from the stock gearing needs to be done? What is the stock gearing on an '87 GW, and on an '88 GW. If the gearing does need to be changed, what is the process? Should I just change the gears, or should I buy one with the correct set up already done? Also, I know the difference between NT, and WT, but which vehicles came with an axle that I could use for a WT in case I decide to do the SOA? I know, lots of questions....sorry. I'm just trying to soak up all the information I can from the most experienced crowd I know on the subjects.

[krejr]

Oh, also, when you guys give me a number for the gearing....I'll have no idea what it means. I'm guessing it's a ratio of some kind, but what to what?

[89grand]

Let me try and answer this without forgetting anything. First, G-Wags more than likely have 2.72:1 gears unless it has the tow package then it has 3.31:1 gears. If you like the power and rpm's your truck currently develops then your gear ratio needs will be simple, if you get a tire that is 15% bigger than what you have currently then you'll need a gear ratio that is 15% lower than what you have now. So if you are running 2.72's and are happy with them then a 15% lower gear will be like a 3.23. If you want more low end grunt then you have now then you'll want to go even lower like 3.73:1. I would keep your current axles and just have new gears installed, keep in mind that if you are running 2.72's then 3.73's are the lowest gear you can use while still using the same carrier in the differential.

I'm not exactly sure about the question of what axle to use in a Wide Track if you want to go SOA. You can use the stock axle in whatever you want to do a SOA to, you just have to have the spring perches moved and other mods done to it. A SOA is a lot of work, fab work and stuff and isn't for everybody. Get more info on this before you even seriously consider it. A SOA should not be used with 6" lift springs. The gear ratio is how many teeth are on the ring gear versus the pinion gear. Lower gears generate more engine rpm's at any given speed. Bigger tires have the same effect as raising the gear ratio which is why many people install lower gears after getting bigger tires. The higher the ratio number the lower the gears. 4.10: gears are "lower" than 2.72's. I hope this helps some.

[krejr]

That helps a ton! I'm sure if I would've taken an auto mechanics class in high school rather than extra math classes, I would have known this a long time ago. I really appreciate your input. Thanks!

[89grand]

You're welcome. Keep in mind that a 6" lift is a big lift. If you combined a SOA with it you'd be rediculously high. If you stay around here long enough you'll learn a lot. Pretty soon you'll be answering questions too instead of just asking them.

[ March 11, 2004, 06:32 AM: Message edited by: 89grand ]

[FSJ Thing]

Originally posted by 89grand:
You're welcome. Keep in mind that a 6" lift is a big lift. If you combined a SOA with it you'd be rediculously high. If you stay around here long enough you'll learn a lot. Pretty soon you'll be answering questions too instead of just asking them.This is exactly right! When I came here I thought that because I knew alot about Dodge trucks that I'd be FSJ savvy too. Boy was I wrong! Fortunately, it didn't take too long for me to get educated on exactly how much I didn't know! Two years later, I'm still learning, but I think I have a good grasp of how much I know versus the plethora of what I don't now. :D I agree with the 6" + SOA being way too much lift, it would be next to impossible to get a good driveline angle with out serious extreme driveline modifications. I did an SOA on my first FSJ, and I won't do it again. It's a great way to get alot of lift with alot of flex but in my opinion, it was more that $500 worth of trouble and frustraition and chasing misc parts. I'm sure it would be easier a second time around, but even so, I don't see me doing another SOA anytime soon.

[jode]

Some, (but not all) Cherokees came with WT and ALL trucks came with WT. I think that if you have the means, swapping to WT is a great idea. The added width will help to offset the increased center of gravity that your lift gives you. HOWVEVER, it will leave you looking for some way to get your tires back under cover. Here in ID (as in many states) having your tires hanging out in the wind is a ticketable offense. The cool thing a bout an axle swap is that you can kill several birds with one stone. Setting up gears is not a garagable project as it requires special tools and expertise that most people don’t have. So if you can buy a set of WT axles with the right gear ratio, then you are like 2-3 steps ahead. In fact, I’m going to have a set up for sale in the not so distant future, and they do come up for sale on a fairly regular basis here on the forum…Blt2Krl sold a set of totally refurbished WT axles (already set up for SOA) not too long ago, and I am sure more will come up later. It is an option to consider.
As far as changing gearing, 89G’s response was great and quite thorough, but you may want to consider that if you increase tire size by 15%, you may want to lower your gears by more than 15%. It depends on how you’ll be using the rig. IF you think it will be a mean offroad rig with 33s and 3.73s, think again. You’d probably want 4.10s or so (if your focus was offroad) and if you EVER thought you might want more meat (bigger tires) then you would prolly want to go with even lower gears like 4.56 or 4.88. Granted, if you lower your gears too far, it kinda makes your rig un-street-friendly, but that is where you have to decide what your use for the rig will be. Personally, I’d rather run a bit higer RPMs on the freeway in order to be able to have a better low-range crawl ratio. So I guess what I am getting at is that the forum can only take you so far in your search for info on gears….you’ll need to sort out all our BS to find the final gear ratio that fits your personal driving needs. And, it is expensive to regear, so you’ll want to make the right decision the first time.