Stock posi rear end or Eaton Posi Trac?

[dracko]

I drive my truck in the winter and could really use a limited slip rear end for those snow days. Truck is a 1964 with stock 3.73 rear end.

I did a few searches on here but couldn't find much info. If anybody is well schooled on these, I'd appreciate some advice. Like, what is the best option for a lsd swap? How good were the factory lsd units? Are they rebuildable, hard to find and what year posi's will fit in a '64 pumpkin?

Or would it be wiser to just buck up and buy a new Eaton positrac? Will my factory gearset bolt up to the eaton unit?

thanks in advance for any info

[LVPhotos]

I would go with the new gear style. No cluches to wear out.

[Snailed]

They aren't new at all, but I also like helical diffs like The TruTrac or Quaife and lots of OEM ones. They are great to drive since the tq distribution is generally smooth unlike some lockers and clutch types. I have had them in my last two year-round street cars and was happy even in very slippery conditions. Supposedly if one wheel is in the air or on ice they don't work but I have never had a problem on ice.

That said, for my truck I just bought a whole low mileage rear axle from a 90's truck with the GM govloc. It was $280 complete. Not the best or the strongest but it should be fine for the light duty towing and snow driving I plan on and the brakes are bigger. It's an open diff at speed so it should be good on slippery roads where directional control is more important to me than being able to accelerate.

[dracko]

Thanks for the info. I didn't know Eaton had 2 different lsd's. The truetrac looks like a killer design and about the same price as the positrac.

Still gonna consider getting a stock gm unit if the price is right, but if nothing turns up it looks like the truetrac is the way to go.

[1963c-10]

the 63 & 64 are 17 spline axles. posi units are out there but hard to come across. i have pics of one in my build thread. i can post the pics later here if you cant find them. 65 went to a 30 spline which is still produced. i have only seen nos/oem units for the 17spline posi & axles.

[dracko]

Whoa thanks for posting that up, I just assumed my '64 was 30 spline since the diffs are listed to fit 64-82 12 bolts. So i'll need to get some axles from a 30 spline 6 lug before the swap.

[Captainfab]

I would suggest first checking to be sure your diff still has the 17 spline axles. That is unless you are certain that they are original. While the OEM limited slip/posi's are good, by this time most will need to be rebuilt. The clutches alone are $150. Then if you need springs or spider gears, you are at almost the price of a new one. As long as you get the correct series of posi unit for your gears, they will bolt right up. Another option is the lock-right style of lockers. They may not be as smooth, but they are much easier to install. You do not have to remove the stock carrier.

http://www.summitracing.com/parts/pwt-1910-lr/overview/

I believe there are a couple other brands of this style.

[NEWFISHER]

I pull lock right's out of my rock crawlers because they are so loose and noisey, I can't imagine one in steert rig.

[rightpedal]

I just went through a rebuild on my 66 posi.

If you have a 30 spline here are some helpful links.

http://www.carcraft.com/techarticles...ted_slip_posi/

Toms youtube rebuild vid part 1

Tom's Eaton Posi Tune-Up Tutorial (Part One) -...

Part 2

Tom's Eaton Posi Tune-Up (Part Two) - YouTube

http://www.tomsdifferentials.com/

Eaton clutch style lsd have not changed for ever. You can covert the spring style to straight clutch if you chose to. It is a durable and cheap solution if you want to put the work into it. They work really well up to 400ish hp with decent tires If you are planing on putting serious hp/traction might want to think about a different setup.

Steve

[dracko]

Thanks alot for the input, good to hear from people with experience.

It sounds like searching for and rebuilding an old stock unit might not be worth the effort. I did some serious Googling and I kept hearing similar stuff about the lock rights...good for aggressive offroad but not really ideal for street use, especially snow and ice roads. Since this truck is a daily driver that will probably never have 1 rear wheel in the air...unless something terrible happens, lol, the detroit truetrac sounds like the way to go. Not to mention it supposedly will last a long time with no rebuild or special additives.

I'll definitely check the spline count but i'm almost positive the axles have never been touched....was an old farmer that had it before me and he never modified a thing. I don't think you can get a truetrac for 17 spline.

Edit: rightpedal: I hadnt' seen your post yet, that rebuild doesn't look too bad, finding one for a decent price might be another story

[61_FL_Apache]

I had a 3.08 Eaton posi in my 94 Caprice 9C1.. Mine was not on the best shape due to years of abuse. On a Caprice related forum, most guys were moving away from the Eatons. I don't remember what was recommended then.

[dracko]

Thanks for the info Apache, maybe those were the clutch type units? these helical units are supposedly maintenance free and don't require any special additives.

So will any 30 spline 6 lug chevy axles work in my '64 rear end? or are there different diameter/length axles over the years?

[1963c-10]

Heres a few pics of the 17 spline Eaton posi for you Dracko. I do see them on ebay from time to time rebuilt for $300-$400

[dracko]

Thanks man, that looks like new. How does it perform? lock up pretty good when ya start spinning? The truetrac is definitely pricier and i'm not sure if I need to buy that install kit they sell too, its like an extra $100.

[1963c-10]

I haven't installed it yet. Its going to be one of my winter projects. Im dropping in a big block that I've been working on for sometime now and wanted a little more strength under the rear.

[61_FL_Apache]

I think my Eaton was the clutch type. It use to slip and chatter a bit

[Sharps40]

I'd love to put an eaton posi in my 65. But, what I'd really like to hear is the no balony truth from drivers of posi equipped C10s....do they do sudden doughnuts in the rain in a tiny curve if a gnat hits the fender or.....do they do a nice job of putting traction to the ground....do ya have to baby em in turns or what? Seems the only things folks have to say is hearsay and old tails about how nice it is to lay two black stripes and more hearsay about being Pit Manuvered by rain drops/heavy foot/and sideways bird turd impacts on the fenders.

So, what is it.....good upgrade or DANGEROUS FOOLISHNESS on the part of a daily driver with a lil I6 motor?

[rightpedal]

I did mine like Tom recommends. Nothing squirrely or weird in the rain.

I spent about $220.00 all said and done on the rebuild.

Draco axles up to 66 in the 6 lug and up to 72 in the five lug. Don't know on the 67-72 6lug 9 but i cant imagine they would change. You have to redo the panard bar location if you switch to a complete 65-66 rear end.

steve

[1963c-10]

Rich, Ive driven plenty of posi cars and trucks and I've never had any issues. Everything from work trucks w/6cyl to my 69 chevelle ss w/built bbc and I've never had any issues with them in rain or any other driving conditions.

[Sharps40]

Good. Sideways flying pollin particles causeing a Pit Manuver wipe out on wet roads must be more of that innerweb crap then. Sorta like "All Chevy C10 I6 Flywheels will accept the Chevy Astro Van 11" clutch kit" NOT! (but an S10 flywheel will and it'll bolt to a 250 engine too, we proved it.) Nice.....now I gotta think hard bout gettin a posi for John Lee.

[1963c-10]

Much easier to find a posi for your 30 spline axles than the 17 splines

[Sharps40]

Yep, plus the fine spline is a durn site stronger than the corse spline on the 63/64s. But an I6 prolly won't bend the splines up too much, coarse or fine.

[1963c-10]

I'm not so sure on the spline count being much stronger or not, 17 spline was standard in the corvettes for a long time and many high HP cars off the GM line

[Sharps40]

Fine spline/thread, etc, is always the stronger...greater area of contact. Its why small screws for guns are always NF, maximum strength, much more so than the NC. Its also a significant part of tranny input shafts, T5 for example, fine spline on the 300 hp rated ones, 14 spline on the V6 and 4s....etc.

[Snailed]

Originally Posted by Sharps40

Good. Sideways flying pollin particles causeing a Pit Manuver wipe out on wet roads must be more of that innerweb crap then.

Ha! I hear that about lockers but never clutch or cone LSDs and not helicals either. I have only driven any significant miles on spools, helical, clutch/cone and viscous and the helicals and clutch types are very well behaved if the preload is reasonable. I would guess that's probably why nearly every vehicle manufacturer sells cars and trucks with these types to use in all conditions.