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I have a set of meaty 35x15R15 Swampers that I want to run on my truck. Problem is, the stock 3.55 gears with open diffs really bog down my engine. I have looked at many different gear charts and they are all pretty close to the same. I'm looking for real world experience with what gear sizes and differentials you guys have run with success. I hardly ever get my truck up to 60 mph and I do not treat it like a race car.
This is what I am thinking of doing. Since I don't see highway speeds much at all, I'm thinking 4.56 gears. I know most charts say 4.11s will be fine with 35s but I don't want to strain my engine at all. I am also thinking I want a full spool up front since I don't use 4 wheel drive unless I am offroad, in the mud and rocks. For the rear I want to use a limited slip for the ease of normal driving. I am slowly rebuilding a 460 but that won't be finished any time soon. Plus, changing the gears will be faster and cheaper in the short time. What is your advice? Is 4.56 gears too deep? Will a full spool cause me issues?
I had 4.56 with 36” swampers and it was too much gear. I run 4.10/4.11 on my early bronco with 35’s and it works really good. I would suggest 4.10’s. With that said I have 3.55s on my f350 supercab with 325/60r18 tires with are roughly 34s and it doesn’t strain the 400 at all…. Are you sure your motor is ok?
If you are at the point you are thinking a spool in the front (I run one in my Bronco) you will be disappointed with a rear posi. It will let you down when you need both tires spinning most. I would suggest a locker in the rear. The on street the locker isn’t that bad in my bronco and they show less effects the longer your wheel base is.
In my '06 Jeep Wrangler (turbo 4.0) I run 4.88's with 37's. For several years though, I ran 35's and really liked it. Granted it has an OD but if you're really staying around 60, then it wouldn't matter too much. With that said, you will probably appreciate 4.56's way more than the current 3.55's. A coworker is running 4.56's in his '89 K5 with a stock 350 and 35's and loves it. Cruises all over the place well.
Some more charts to consider. There is some chart discrepancy.
I run a spool in the rear and a locker in the front of the Bronco. NOT a pavement rig at all, and it does have it's trail handling differences for sure. Sorry no advice for the ratio.
I've seen these charts before. Other charts say that 4.11s are the correct gears. But, I am leaning more on the 4.56s. I just don't want to regret going too low of a gear. Also, I don't want to regret running a full spool up front.
^This. Too many people think that throwing a steeper ratio into the rear axle is going to be a cure all. It comes with a lot of undesirable tradeoffs. The input torque is the real problem.
One thing to take into consideration is down the road when you upgrade to the 460 will you be needing any kind of stall in the torque converter and to not have your cruise RPM range in the same RPM range as the stall in the converter. If that makes any sense? Regardless my vote would be 4.56. My truck came stock with the 4.10 ratio and with 35's it was not very impressive at all with a stock 351 of course the 460 will be a game changer. I run detroit lockers front and rear and it drives just fine on the highway.
You do not want a spool in the front. If you ever do use 4wd because it's slick, a spool in front is gonna force the front tires to spin / slide unless the truck is going perfectly straight. A spool can very easily put you in a ditch then. If one front tire is on flat and the other has to climb over a rock or go through a deep hole, again something is going to slip or spin as the spool allows absolutely "0" differentiation in wheel speed. A locker in the rear would work, but no way would I run a spool up front unless strictly a mud truck.
3.50 gearing should be fine, 4.11s will be noticed, 4.56s will be miserable on a highway. Do you not have a low range in the transfer case?
I have low range and it works just fine. My concern is that when I was running with the 35s a few weeks ago, there was a huge loss in power. My 351M with 3.50 gears are not liking the bigger shoes. I will be regearing the axels in the future no matter what.
@tbear853 - I can see that spool causing those issues. I have lived in northern states for about half my life now and the snow would be my only issue that I can think of. But if it's going to slip in snow/ice with a spool, wouldn't it act the same with a locker? When one wheel slips, a locker will engage the other wheel causing both wheels to apply a pulling force.
Has anyone ever run a spool up front that can verify any issues? Or am I going to be the Ginnie pig?
I have a spool in the front of my early bronco and I’ve had no issues with it in the snow. The front end will push when turning tight but once you figure it out and get used to it it’s not an issue. I do wish I had an air locker just for tight turning on the trails but that’s not worth the $ to me.
A healthy engine, 3.55 or 4.10 gears and 35’s would be no problem. I’d only do 4.56 if you think you’ll go to 36-38” tires later on.
I think you'd be fine with 4.10s, but are 4.30's an option to split the difference? If you ever think you'll step up to a bigger tire than the 35's, go with the lower gears. While a front spool isn't ideal if you ever need to use 4WD on the street in slick conditions, you just leave one front hub unlocked so you only have 3wd and the front won't fight itself nearly as bad. I've only driven something with full Detroits front/rear and it wasn't an issue, but it was a big heavy truck and you did had to pay attention to how you drove it in certain conditions.
What axles do you have? If you have a front 44, you might want to upgrade shafts and ujoints with 35's and a spool if you'll mostly be using it off-road.
I think you'll be fine with 4.56s for that area. There isn't that much high speed driving there. People could be saying lockers could be talking about selectable lockers where you can turn them on and off. That's what I'd like to do for my setup. I think a great setup would be a Truetrac limited slip in the back and an electric locker in the front. I've read lots of good experiences with Truetracs front and rear if you want an uncomplicated, less expensive setup but less capable in lifting wheels off the ground situations.
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