Build a 28 spline or swap a 31 spline?

[shr3dd3r 09]

So I have a Cummins 4bt in my 2000 4x4 ranger. It has 4.10 gears and at some point soon I'd like to re gear to 3.07/3.08 to keep the 4bt in it's power band and still be able to cruise 70-75 around 1800-2000 rpm. I have 33 inch tires currently.

So I can either re gear my stock open 28 spline rear end or buy a 31 spline explorer axle and re gear that one and swap it in.

My question is can the 28 spline axle be upgraded to handle more horsepower/torque? Or is it best to just swap a 31 spline in it? I realize most people just do an axle swap, but if I do that I STILL have to swap the gears to a ratio that will have to be aftermarket to really get it where I need it.

Are there kits out there to really build a 28 spline axle? Is it worth it vs. buying a 31 spline and swapping gears? The max power it will see is 200hp/450ft-lbs if I ever decide to add an Intercooler and mod the fuel pump. I'd guess right now it's around 130hp/300ft-lbs with my modest upgrades.

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[pjtoledo]

I just did a quick search on car-parts.com for 2000 Explorer axles. they list 3.27 gears as an option for 6 cylinder models.

that appears to be worth checking out


you didn't say which 28 spline you had, 7.5 or 8.8 yes, some 2000 4x4s did come with 7.5 rears. I doubt they are the best behind a diesel.

 

[scotts90ranger]

a fully upgraded 28 spline would probably about equal a stock 31 spline axle... I've done stupid things to my explorer axle and the only thing I broke was a plug weld and twisted a tube... 4 low first gear 5.13 gears with a 2.3L turbo WOT at 6000rpm during a tractor pull with an aussie locker and too much axle wrap...

 

[shr3dd3r 09]

a fully upgraded 28 spline would probably about equal a stock 31 spline axle... I've done stupid things to my explorer axle and the only thing I broke was a plug weld and twisted a tube... 4 low first gear 5.13 gears with a 2.3L turbo WOT at 6000rpm during a tractor pull with an aussie locker and too much axle wrap...

Mine is a 28 spline 8.8.

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I'm not sure what would be best. I suppose I could always buy a 31 spline axle, build it, and the. Just swap it in. Would be less down time as well.

 

[shr3dd3r 09]

I just did a quick search on car-parts.com for 2000 Explorer axles. they list 3.27 gears as an option for 6 cylinder models.

that appears to be worth checking out


you didn't say which 28 spline you had, 7.5 or 8.8 yes, some 2000 4x4s did come with 7.5 rears. I doubt they are the best behind a diesel.

Mine is a 28 spline 8.8. I'll have to look into that. I didn't think they ever came with anything taller than 3.55. Then again I'm also limited by aftermarket ratios for my D35 SLA front end.

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[shr3dd3r 09]

My truck with everything I've done to it probably weighs about 4,000 pounds, with 285/75r16 tires (33x11.5). Max power I'll probably ever make is 200hp/450ft-lbs. But all that torque is made at 1600-2000 rpm. Cruising speed 1800-2000 rpm.

Can a built 28 spline 8.8 support this combo, or is the 31 spline the way to go?

I'm leaning toward just buying a super cheap 31 spline and spending some time building it. Then when it's ready I can toss it under the ranger and sell the old axle. Maybe that makes more sense.

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[fastpakr]

You may not even need to build the 31 spline axle. I'd throw in a 3.27 limited slip from an Explorer and see how it holds up.

 

[shr3dd3r 09]

You may not even need to build the 31 spline axle. I'd throw in a 3.27 limited slip from an Explorer and see how it holds up.

My truck is 4x4. I have yet to find a 3.27 aftermarket ratio for a Dana 35 SLA standard rotation front axle. Unless the center section can be swapped over from an explorer as well. When I last checked the tallest ratios available were 3.55 and 3.08 or 3.07.

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[4x4junkie]

Torque is really what breaks things, not HP.

450ft-lbs w/33" tires IMO is very good reason to swap to 31 spline (there's not much you can do to strengthen your front axle besides SAS though).

3.08 was a somewhat common factory ratio in 2WD 4.0L trucks in the mid-'90s. See if you can find a set of used OEM gears from someone who's upgraded theirs (or maybe a cheap used axle to pull a set of gears from). Failing that, other options are to swap 31-spline shafts into your 28 spline housing (however they need to be custom aftermarket shafts to fit the smaller wheel bearings), or get a set of 3.08 aftermarket gears to put in a 31 spline Ex axle.

 

[shr3dd3r 09]

Torque is really what breaks things, not HP.

450ft-lbs w/33" tires IMO is very good reason to swap to 31 spline (there's not much you can do to strengthen your front axle besides SAS though).

3.08 was a somewhat common factory ratio in 2WD 4.0L trucks in the mid-'90s. See if you can find a set of used OEM gears from someone who's upgraded theirs (or maybe a cheap used axle to pull a set of gears from). Failing that, other options are to swap 31-spline shafts into your 28 spline housing (however they need to be custom aftermarket shafts to fit the smaller wheel bearings), or get a set of 3.08 aftermarket gears to put in a 31 spline Ex axle.

I'm not too worried about the front handling much power. 4x4 is used sparingly anyway. This truck doesn't go wheeling. Mainly a commuter with the occasional 4x4 use if and when it ever snows in Alabama. I'm thinking more and more just to buy a 31 spline axle and swap the gears. At least I can do that and still drive my truck in the meantime.

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[shr3dd3r 09]

So I pulled a 31 spline 8.8 out of a 2000 explorer to swap into my ranger. It has 3.27 gears which I think is slightly more desirable than the 3.08 I had originally intended on putting in. However, after searching online it looks like the only aftermarket ratios offered for my front differential are 3.07, 3.55, 3.73, and up... Does anyone make a 3.27 ring and pinion set for the 1998-2011 ranger IFS front end (dana 35 SLA)? Older gears from the TTB Dana 35 will not work. If not is custom gear cutting an option? Or am I doomed to eventually have to swap to the 3.08/3.07 rear/front combo so I can someday use my 4wd?

 

[85_Ranger4x4]

Grab the front pig out of the ‘00 Explorer too. Everything will be all matchy-matchy.

 

[shr3dd3r 09]

2000 explorer, disc brakes, 2wd. I didnt think the 4wd or AWD explorers had 3.27 ratios. In any case I don't think 3.27 was a factory D35 IFS ratio.

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[shr3dd3r 09]

I think the best course of action at this point will be to swap the 3.27 ratio axle in and see how it drives with that ratio (front driveshaft removed). Then I can decide if I can live with swapping to either 3.08 or 3.55, which are the two closest ratios available for my front differential. It's not likely I'll ever truly need 4wd since I drive it on the street in a state that sees little to no snow. But I'd still like useable 4wd at some point, but it looks like I will be limited by what's available for my front end.

 

[pjtoledo]

per Rockauto, 2000 Explorer

Dana 7073591X ( Ford # F57Z-3222-AA ) 3.27 ratio

only 1 left, and it's expensive at $414.79

they also state carrier break between 3.31 and 3.54