31 or 35 Spline - Detroit or Spool??

VintageIronFab · Post by **VintageIronFab** » Fri Sep 20, 2019 2:01 pm

Hello All,
I’m going to put a 82 Bronco 9” in my 96 Bronco - Cheryl Project. The housing is getting sandblasted, Explorer discs getting used and all there is now is determine the differential. I’ve narrowed it to 2 routes.
—Route 1: stock 3rd member with 4.88 gears with the $200 31 spline used NASCAR Detroit lockers and the factory 31 spline axles with new wheel studs.

—Route 2: In my 95 F150 Marilyn Project I have a nodular 4.88 gear, full spool, 35 spline. Now I want a 5.13 gear in my F150 because it’s now setup for 37” vs 35” tires. So the 4.88 geared with spool would go into the Bronco.

So costs - I’m figuring for Route 1 its looking at about $650 with new axle bearings and wheel studs. Route 2 is $500 for complete axles, and I would need to replace the third at about $850. Now I’m guessing I could sell the stock axle shafts and stock third member for about $200ish. So the costs are about $600 vs about $1350 - $200 in rebates so about $1150. The biggest deal is do you want a spool or a Detroit?? I guess I’ve always contended that a Detroit is a spool except at certain times. Anyway I’d love to hear some opinions!

ChaseTruck754 · Post by **ChaseTruck754** » Fri Sep 20, 2019 4:52 pm

I've been quick to shout the same about detroit vs. spool. Spool is all on, all the time no matter what til it breaks something. They are cheaper than detroits, but I like detroits.

VintageIronFab · Post by **VintageIronFab** » Fri Sep 20, 2019 7:47 pm

Well Steve what’s your opinion?? All new or all used and some new??

ChaseTruck754 · Post by **ChaseTruck754** » Fri Sep 20, 2019 8:45 pm

It all depends on how much you care to throw at it, and how bad you'll abuse it. Plus I guess how badly you really want to re-gear Marilyn.

My $.02 is 31 spline stuff costs a lot less & you have most of the stuff. Use the 4.88's from Marilyn in the bronco with the detroit & run it til it breaks. IF it breaks... You that way get lower gears for Marilyn & don't spend a heap on the bronco

Tchajagos · Post by **Tchajagos** » Sun Sep 22, 2019 4:18 pm

It kind of depends on the tires size and engine power too. 37s and big power you will want 35 spline. Stock motor and 35s, 31 spline should be fine. A spool is great for offroad. If you plan on any on-road driving a spool is kind of a pain. Do the explorer brakes just bolt on the ends or what? I don’t think I’ve heard of this on a 9” before.

tcm glx · Post by **tcm glx** » Sun Sep 22, 2019 6:26 pm

I hated the Detroit in my Bronco. Went to a Limited slip and loved it. Just didn’t like the characteristic of it unlocking, particularly on Baja highways. Just me maybe. Never had an issue with the Detroit Limited Slip.

hobbyturnedobsession · Sun Sep 22, 2019 8:02 pm

My Detroit was unpredictable. Mash the throttle and it'd go left or right. In the dirt if you let off the throttle in a small slide the rear end would unload and you couldn't tell which way you were going. Climbing hills t was amazing. Parking lots sounded like I was doing donuts and I was just getting out of the parking spot.

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robertcrav · Post by **robertcrav** » Tue Sep 24, 2019 12:26 pm

I liked the detroit I had in my old Bronco, I drove it daily for years

funinthesun95 · Post by **funinthesun95** » Mon Sep 30, 2019 7:51 pm

I think I have a detroit on the shelf. If you want to think about it while looking at one. Text me I will send It out to you.

I need to check spline count

mobil1syn · Post by **mobil1syn** » Mon Oct 14, 2019 4:00 pm

ARB

when im in the dezert my ARB is open 90% of the time. i found that with it locked it pushes a lot, so i just leave it off. stock 351, 4.88s and 35s. ive had spools (welded diffs) in other trucks and they did the job but after getting an ARB i dont think ill have anything else. coming from a rockcrawling, there are times two tires spinning actually hurt you.

the other thing about the ARB is being able to toss the keys to anyone and not have to worry about them looping it out because of the spool or the detroit randomly deciding to hookup.

yikes · Post by **yikes** » Tue Oct 15, 2019 6:14 am

Detroit = less tire wear for street driving. Works great in the dirt. Rarely fails. No air. No electronics. Simple. Effective. Cheap. Long lasting.

I've been running a Detroit for the last 12 years or so in the Yeti. Zero issues. Don't experience too much load shift in turns. No problems on Baja highways. It's always been very predictable...one hand steering on curvy roads. Many of the issues guys have come from imbalanced tire pressures and steering set ups. If your steering geometry is solid and the front end is in good shape (ie no loose heims or ball joints), it will drive nice.