Help, need posi.

[Rdub]

I have a 67 short step with the original 12 bolt ..... It has a 396 and I'm wearing out the passenger rear tire ...... I have the chance to get a 12 bolt posi from a 1/2 ton 81 Sub. at a reasonalbe price..... Will this work? Any fitment/shock issues or other changes needed to install in my 67?

[PICKMUP]

Well you will probably have to cut & weld on new spring perches and shock mounts. The ebrake cables may not hook up, and the front yoke is probably bigger than the 67.
Measure the width before you begin to see if it is close.
You will get a posi and better brakes! If you can do the work yourself...go for it. If you have to pay someone, get an estimate first.
Let us know how it turns out.

[Rdub]

Thanks Pickmup..... good points, my welding skills are limited so I would probably have it done..... considering cost, & better brakes aside, would it possibly make more sense to have positrac installed in the existing rear end?

[355]

Make sure your pinion angle is the same as the output shaft angle when you weld the new perchs. There is probably a thread in the FAQs that address this. Love my posi. Steve

[Psycho71]

Can't the posi unit in the newer rear end be used in the old one? I think it will fit from one twelve bolt to another if the axle splines are the same (30?). You would have to set up the gears again, or have it done, but no other changes should be necessary. Someone correct me if I'm wrong here? I guess it would depend on the cost of the burb rear end, and the cost to swap carriers vs. buying a new posi unit, and doing the gear set-up.



Jay

[cdowns]

well if you were to pay to have your original rear overhauled with new gears new posi seals bearings etc expect to pay in the neighborhood of $1000-$1200 so paying a welder to do the mounting brackets and having the driveshaft rebuilt and modified would give you the better brakes at a cheaper price in the long run but first make sure the width of the newer axel is about the same width of the original

[speedracer]

does the 67 have leaf or coils? if you have coils you'll run into problems with the trac bar

[Rdub]

Thanks for the replys guys and all the help... yes, it does have coils.... not any easy answers here.... the later model posi rear is $200 but, sounds like I may be better off waiting for a posi unit from a coiled spring, earlier model... what years should fit with little or no mods.... anything earlier than 67? Up to 72?

[Fastfun]

I had installed a posi unit with 3:43 gears new axles ,all the seals and used CPP rear disc brakes on my 72 and it cost about $1500.00. I very happy with the performance now.

[Livrat]

IMHO.. I would do it the easy way.. with a Powertrax Lock-rite carrier.. you just pull off your rear end cover drop out the spider gears and pop in the lock-rite posi.. it can be done with simple hand tools and a couple of hours time..
Heres a link to them at Summit Racing
http://store.summitracing.com/partde...5&autoview=sku

[JAMESCHURCH13]

Originally Posted by Livrat

IMHO.. I would do it the easy way.. with a Powertrax Lock-rite carrier.. you just pull off your rear end cover drop out the spider gears and pop in the lock-rite posi.. it can be done with simple hand tools and a couple of hours time..
Heres a link to them at Summit Racing
http://store.summitracing.com/partde...5&autoview=sku

What else should you replace when doing this? Would this make my silly 411 rear be a 373 posi?

[Livrat]

About all else you would need to replace is the cover gasket and the 90wt oil..
But no it will not make your 4:11 a 3:73.. the only way to do that is to change gears

[70short/step]

All the posi will do is make you wear out both rear tires instead of just the one! Just keep your foot out of the gas and save yourself some money.

[knsmodels]

Originally Posted by 70short/step

All the posi will do is make you wear out both rear tires instead of just the one! Just keep your foot out of the gas and save yourself some money.

but that ain't no fun!!!!!.......

[JAMESCHURCH13]

Originally Posted by knsmodels

but that ain't no fun!!!!!.......

Fo sho.

[Rdub]

Thanks for the tip Livrat, that's the kind of alternative I was looking for.... as far as "keeping my foot out of it", with the big block, it's extremely difficult to not to turn'em over from a stop light.... I really have to baby it, any moisture on the pavement, fergettabout it ...... not to mention the lack of fun factor! Anyway, thanks again for the comments, I'm going to look in to the Summit/Powertrax option

[Longhorn Man]

what's the point of a big engine if you don't have fun? If you wanted to limp from light top light you could do that with an inline blowing blue smoke and hittin on 4 cylinders.
Tail lights and tire smoke!

[70short/step]

You complain about 'wearing out' the passenger tire. Like I said a posi wont help your problem just cause you to wear out both tires. Now the way you wrote the question, it sounded like you wanted to stop wearing out a tire. The Big Block isnt the problem they way you are driving it is. Unlike what you said.....It isnt hard to "NOT" spin the tire. I have a Big Block and a Small block truck so I know what I am talking about. Yes you can have fun with it and still make it driveable without smoking the tire every time you leave a stoplight. My Small Block will smoke my big block the way it is built and I can drive it without wearing out the tires. If you are just asking will the later rear end fit in your truck, Yes it will but like other have stated here, It will need to be modified. Now if you want the tires not to spin so easily, change to a higher gear ratio. Of course a posi will help with a gear change, but just a posi alone wont do much good. It would be easier if you can find a complete posi rear end from a truck just like yours instead of making one fit. And if you never had a posi rear and you think you have problems on wet pavement now, Just wait until you light em up when it is wet with a posi!
And it is a lot more fun using money to buy other things than just tires!

[Rdub]

Hey 70 short/step, the complaint about the tires was tongue in cheek ..... I really want better traction and it seems like the people on here who have posi's really like them.

[70short/step]

Well the posi is just a start. Look at gearing and maybe a better suspension. My truck has a 4 link setup wih coil overs. Hooks up Great! But if you are a tight budget....look into gears and a posi. But even that will be expensive. Look around for a direct bolt in posi rear. I think that would be the cheapest for you. Good Luck.

[jimfulco]

If you decide to put the later posi carrier in your current rear end, make sure the carrier is compatible with your gear ratio. What is your current gear ratio?

You don't have to completely overhaul the rear end if yours is in good shape. You have to put your ring gear and side bearings (new bearings are highly recommended) on the posi carrier, and then the backlash has to be set, which shouldn't set you back too much if you do the scut-work & leave the backlash to a pro. Check the axles for grooves (grooves are bad, ng'kay) where the outer bearings ride, and use new seals.

And although you'll wear out both back tires now, it'll take them twice as long to wear out.