LUVTruck.com

Just picked up a cheap Ford 9" rear end. It's 28 spline and not posi.

What do I need to do make it posi or is it so expensive it's not worth the hassle?

Thanks in advance

It depends on what you can get away with. For dragstrip use only, you can install a spool. It wouldn't drive well around town.
A locker can get the job done but you might be annoyed with the clicking noise.
An Eaton posi center section is the smoothest but it comes at a price.

It looks like you're in the same boat as i'm in.

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Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

How will a spool not drive around town well? both axels spinning at the same rate of speed? Hnanding issues around corners?

Yep! The inside and outside tires in a turn will rotate at the same speed. The truck will feel like it wants to push straight (kinda).
After re-reading my post, It's a Trac-loc instead of an Eaton. A Trac-Loc is the "posi" factory unit. Finding a posi/28 spline assy is kinda rare. The best bet is to look at Broncos in the wrecking yards to find one.

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Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

Yea , a spool sucks around town period. Your best bet is a 31 spline 3.50 trac loc out of an late 70's-early 80's truck or Bronco .

Hi guys, Long time guest, new mwmber. On the subject of 28 spline posi units most os the latr 80's early 90's rears with disc brakes have a 28 spline posi. This would be the Explorers and Lincolns. You can also score
factory disc brakes this way.

I run a mini spool on mine around town all the time. The only time I can tell the difference is 60-70 mph curves. Blue Meanie was right it feels like you are being push to the ditch. Dont get me wrong I dont put the truck in a situation for a tight turn in a parking lot. Mini spool is cheap and gets the job done.

But late 80's/early 90's Lincolns and Explorers were'nt known for having big power. It's very possible to rip the splines out if you throw around 300 h.p. to it.
A posi/31 spline setup is the baseline for performance use. I'm running a 28 spline open diff with 2.75 gears so i can drive down the Hwy comfortably. The motor is pushing around 200/220 h.p. but the axle will survive because it wont hook up. I can ruin a tire in a week if i tried.
This axle assy is working just fine within it's limitations but later on, I may build another assy with at least 31 splines and a posi. I'll most likely go to an even stronger housing that holds the larger axle bearings. I'm not sure if it's possible to fit a 31 spline axle into the small bearing housing. That's another limitation of the 28 spline assy.
For V-6 conversions, a 28 spline assy would be perfect. Life was great when i still ran my 4.1 Buick motor.

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Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

I think they do make a special bearing to do this. I may be mistaken though.. it might be the other way around i.e. a small axle in a big bearing housing. Or maybe they have both, I will have to start looking and see if I can find the info again...

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Resident lurker

If I am going to spend the money to get the axles shortened (typically what does this cost?) + the cost of the rear end initially, I mine tis well buy the rear end that I'll need over the long run.

I have a 400 hp small block and not wanting to do a drag tubbing job just yet as this will be a daily driver for me. I just want a nice set of meats in wheel wells. What's the largest rims/tires combo we can fit in a 77 without having to cut the wells and start redesigning the frame?

Thanks for the help guys. Good in depth conversation.

I am also runnin a spool in my 8inch, and I really don't care for it! It does make things a little harder when making a u-turn or any kind of sharp turn for that matter. A u-turn for me now consists of a half doughnut

hyperwrx I was able to fit a 255/60/15 on 15 x 8 4" back space on mine. I have a 79' full size bronco, big bearing, 31 spline cut to 52". I run a 3.50 trac-loc . If i went into fraction on the back space I could probably get a little more tire in there, but 4" is pretty common. Still having trouble converting from standard brake line fittings to metric for rear brakes . I'm running 11" x 2" truck drum brakes. I traded out parts for the housing (about $25) and paid $475 for the axles to be resplined, housing narrowed , new bearings pressed on and leaf spring pads . I have yet to weld it in as I am not sure about pinion angle.

mini spool is the cheapest way to go but it sucks pitching a U but then again a lot of regular cars and trucks (like my old dually) dont turn a tight U anyway.

taking turns at lower speeds is what is really hard on things. there is the chance of pulling an axle which would destroy your rear quarter or worse if your axle and tire is bouncing around on the freeway.

you should be able to get a 28 spline trac loc for pretty cheap. I think I paid 300 for mine freshly set up with stock (motosport) 3.70 gears but you can find them for a lot cheaper in different gear ratios if you shop around. 4.11, 4.30, and around that area are more popular and tend to run more $$$

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1978 LUV Truck 2WD
450 "Small Block" Chevy
3.70 Ford 9
28x10 Goodyears

I am hunting hard for one on eBay or locally and coming up empty but will keep on hunting.

Dove season opens here in AZ on Friday so I know the truck will go on the back burner for a month or so. I wanna find this as soon as possible.

thanks for the input guys

do you know anybody in the LA area... somebody that frequents the Long Beach hi=performace swap meet? There is a guy there and all he does is sell center chunks all day long... all ratios, posi, peg leg, spool, whatever you want.

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1978 LUV Truck 2WD
450 "Small Block" Chevy
3.70 Ford 9
28x10 Goodyears

Last swap meet I went to @ houston raceway park . A dude was there with a lowboy full of axles . He had a 52" 31 spl 3.70 posi w/drum brake for $500 . I should have bought it . I paid more than that . to have my axle cut. I bought an open carrier with a 3.50 gear for $45 shipped and a 31 spline trac-loc for $110 shipped . Check the back lash first , install posi , and reset to origanal back lash . 3.50 posi $155 . 77',78',79' 4wd bronco and f-150 and some 82-86 broncos came with trac-loc. But junk yard hunts suck.

I did find out some info on getting 31 splined axles in a small bearing housing. YES! It can be done!!!
Bronco graveyard has axle assy's ready to ship And Pirate 4X4 shows that it's quite common. Dutchman also has a system to do that.
So as it turns out: if i get new axles made to length, I can order 31 spline assy's with CCR 207 bearings and i'll be good to go! I then can keep my current housing.

I wonder how long after i move will i be able to throw money on this?...

Can brake drums be redrilled to a different lug pattern?

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Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

Drums like the axles can be redrilled for a different bolt pattern, by the way i run a 31 spline 9" with a mini spool and mine is mainly on the street i just use my head when going around corners, i also have no problems drag racing the rear assy.

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1978 pro street step/side 455Buick, 4sp,4.11s, 31/18.5s

I am running a truck 11" an truck drum on mine . I re drilled it to 5 on 4.5 car pattern.