Gears

[Braxton]

Hellio all, I have an 88 Shortbed Pioneer with a 4.0 @139,000 and a rebuilt AW4 tranny. I am currently runnung 31's with intentions of going to 33's. I drive mostly city and highway with not too much serious off roading, my question is will 4.10's be enough gear for highway speeds or should i go higher like a 4.56. i need highway speeds and the current gears just suck down the gas when I'm heading up I-70 in CO. Any imput is appretiated.

[flint54]

4.56 is lower gear than 4.10, resulting in higher engine RPMs and your fuel use will most likely go up.

 

Top gear on your AW4 is 0.75. 31 inch tires at 70 mph with 4.10 should give 2334 rpm

and the 4.56 gear you propose should give 2596 rpm. For 33 inch tires it's 2192 rpm using 4.10

and 2438 rpm using 4.56, if I've pushed all the buttons correctly.

[Braxton]

So going with 4.10s would increase the power felt at the wheels while helping a bit in the fuel use department. In your opinion would you suggest 4,10 then?

[jpnjim]

I wouldn't do the swap expecting a MPG improvement with 31's.

 

Do it for the improved acceleration, feeling of power,

and in anticipation of the tire size jump later,

but don't bank on getting better MPG with 31/4.10's or 4.65's vs 31/3.55's.

 

 

Look at it this way,

for sake of argument assume that 3.73's are the perfect all around ratio for MPG with 31's.

(probably not true, but I bet it's close).

 

If you do a ton of highway, and live in Florida (no hills),

31/3.55's, or even 31/3.07's would likely give you better gas mileage.

 

If you live in a high altitude,

do a ton of city driving, and there's hills everywhere,

31/4.10's, or even 31/4.56's would most likely give you better numbers.

 

Once you jump to 33's, 4.10's would probably be close to an ideal ration, with average conditions.

High altitude + lots of hills (you said Colorado, right?)

4.56's would be a better compromise.

 

 

 

 

 

FWIW, I like taller gears for my daily drivers:

 

Renix 4.0L/5spd 31/3.73's was my favorite combo,

HO 4.0L/AW4 31/3.55's a close second (more power and auto shifts made up for the slightly taller gears).

 

Renix 4.0L/5spd 31/4.56's wasn't as fun as I thought it would be (hitting 3rd gear by the time you hit the other side of an intersection gets old).

Might not be as bad with the auto (since you're not doing the shifting),

 

would probably be a ton of fun with a High Output/auto:

more power at the top of the RPM band to put all that reving to good use.

 

Either way tho, 31/4.56's can get buzzy at freeway speeds

[Eagle]

4.56 is lower gear than 4.10, resulting in higher engine RPMs and your fuel use will most likely go up.

 

Top gear on your AW4 is 0.75. 31 inch tires at 70 mph with 4.10 should give 2334 rpm

and the 4.56 gear you propose should give 2596 rpm. For 33 inch tires it's 2192 rpm using 4.10

and 2438 rpm using 4.56, if I've pushed all the buttons correctly.

You're close.

 

I make it 2440 RPM at 70 MPH for 31s and 4.10 gears, and 2713 RPM for 4.56 gears.

 

With 33" tires, revs drop to 2292 with 4.10s and 2550 with 4.56s.

 

Considering that a stock vehicle with AW4 cruises at 2230 RPM at 70 MPH, for a truck that's going to be used mostly for highway the 4.10s will be as close to stock as you can get. But ... the 33" tires have a lot more inertia to get rolling, so it may not feel as quick when accelerating.

 

2550 RPM at 70 MPH is not excessive, by any criterion. If you're going to regear with new gears, by all means get the 4.56s. But it'll be a lot less expensive to find junkyard axles already set up with 4.10s.

[JeepcoMJ]

to be honest, I LOVED my truck with 4.0 HO, aw4, 7" lift, and 4.10's on 33x10.50 bfg a/t's.

 

it was a very nice combination. I had plenty of power, couldn't really get stuck, and I was getting 17.92mpg around town, and up to 23mpg highway depending on if I was doing 65 or 75. I got better mpg at 75.

 

my gas mileage decreased by 1mpg when I put 35's on it...but I also stayed out of the skinny pedal when I was not driving it purely to screw around.

 

 

I'd be comfortable with 4.10's and 31's for a small time...but I'd be getting the lift first, then the gears and tires. accumulate all of the parts, and do the whole swap in one go...

[Braxton]

The junkyards out my way want gold for rusted crap so getting a set of Axles from there is pretty much a no go. I currently have a 2 inch budget boost that I'm pretty sure I'm going to stick with for a while. I'm looking to go gor as much flex as possible with as little lift as possible, kinda like the whole Lower 40 idea. As for the gears I have a guy who will install new gears and carriers for $560 out the door. Not really one of my skill sets was going to take the Comanche in next week but wanted to try to get a general feel for the gearing that would work best for me.

[JeepcoMJ]

The junkyards out my way want gold for rusted crap so getting a set of Axles from there is pretty much a no go. I currently have a 2 inch budget boost that I'm pretty sure I'm going to stick with for a while. I'm looking to go gor as much flex as possible with as little lift as possible, kinda like the whole Lower 40 idea. As for the gears I have a guy who will install new gears and carriers for $560 out the door. Not really one of my skill sets was going to take the Comanche in next week but wanted to try to get a general feel for the gearing that would work best for me.

 

 

you are maxed on flex with 31" tires at 2" lift.

 

4.5" will clear 33's with trimming. you're gonna need to reconsider your options.

[HOrnbrod]

As for the gears I have a guy who will install new gears and carriers for $560 out the door. Not really one of my skill sets was going to take the Comanche in next week but wanted to try to get a general feel for the gearing that would work best for me.

 

That's not a bad price for regearing, especially w. the loaded carrier, but I'd verify what gear set mfg. your guy is going with. Original Dana Spicer is the best, with Yukon being #2. Personally, I'd avoid the rest, especially Superior as I've been reading lots of negatives on their products lately.

[Pete M]

I didn't see mention of what rear axle you have. Do NOT spend any cash on upgrading a Dana 35. Find a worthwhile axle (44,8.8,8.25) and invest you money into something that will last. :thumbsup:

[Braxton]

Sorry, o have the D30/D35 combo in the truck right now. The cheapest I have been able to find a D44 for is around $450 bucks. That plus the gears and getting the mounts for the 44 to mount to my truck is more than I paid for the truck, plus I don't know anyone in the state that would not charge me an arm an a leg for the fab work.

[jpnjim]

Sorry, o have the D30/D35 combo in the truck right now. The cheapest I have been able to find a D44 for is around $450 bucks. That plus the gears and getting the mounts for the 44 to mount to my truck is more than I paid for the truck, plus I don't know anyone in the state that would not charge me an arm an a leg for the fab work.

 

Here's a good page on 8.8's:

http://www.therangerstation.com/tech_library/Axles.html

 

4.10 geared 8.8's are really common in junkyard Explorers,

I bet an online junkyard search would find one close by.

 

 

Then,

if you have not already,

consider becoming a member of a local 4wd club.

 

That's almost a sure fire way to find new 'friends with welders' who don't mind burning some perches on for you in exchange for beer. :cheers:

 

Once that's done, all you need is a 4.10 geared D30 (either have your gear guy swap gears in your, or better yet, use the junkyard search to find a complete 4.10 D30 out of a 4cyl XJ).

 

Done. :thumbsup:

[Pete M]

car-part.com can help finding junkyard parts :thumbsup:

[flint54]

LKQ and Pick&Pull around here have flat rate price for axle assemblies regardless of type. I paid $90 for my 8.25 out of a 2000 cherokee, in prime shape. Several of those, but could not find any Dana 44's though.