Options for posi?

[bigmoe]

My 65 has a square body rear end under it. It's a weekend cruiser, not a racer. It has the gear ratio I like (3.42) but it's a one legger. It spins that one tire like I'm on ice. What are my options to convert it to posi and what is most practical with good driving characteristics and easier for me to do? I've never set up gears for lash. etc.

[SkinnyG]

I am a HUGE fan of the Detroit TrueTrac limited slip for street vehicles. It is almost invisible in operation, but totally works.

I put one in my '77 C10 and LOVED it. I put one in my V8 Firefly and it's probably what kept me out of the ditch.

I WILL put one in my '61 when the time comes. I love them.

[bigmoe]

I did some searching around and the Eaton application chart says the Truetrac is only available for the 12 bolt for 3.73 and up ratios (I'm 3.42). However their Eaton Posi IS available though for 2.76 - 3.42 ratios. The Eaton Posi evidently is the real deal, actually used by GM factory muscle cars in the past. Not sure about installation difficulty though.

I also found the Powertrax 9207883005. They call it a "drop in" locker with "easy diy" and doesn't effect ring and pinion settings.

[SkinnyG]

Hmmmm.... that's disappointing. Powertrax sell a "helical diff" too, but also 3.73+.

You're not going to be happy with a "drop in locker", also known as a "Lunchbox Locker." It's a mini Detroit Locker "ratcheting" differential that replaces your differential gears. Noisy and a bit unpredictable on/off throttle. I recommend Lockers for dirt, drift, or drag; not street. Easy to install, yes. But you might not love it.

An auburn diff uses cones, which is similar to later factory limited slips. They are relatively smooth, but not rebuildable.

Your basic clutch-type posi might be your best bet, given the options. It will work fine, and I'm sure you will be much happier with it than the locker.

As for install, you will need a press to put new carrier bearings on. You don't have to touch the pinion at all, but try the factory carrier shims and then check the backlash with a dial indicator, then visit your local rear-end shop for some different shims to get good pre-load but the correct backlash. Or just take it to a shop you trust and pay the man (much safer).

[bigmoe]

Thanks Skinny. Good advice.

[Jackson's Dad 64 C10]

I just forked over $2800 last week to get the 12 bolt truck rear end back from my transmission/rear diff shop. They went through and replaced everything in the rear. I went with 3.73, a TrueTrac, all new seals, ring and pinion and a 1350 yoke. It's just sitting on stands right now waiting to go back in (then we have to finish building the rest of the truck), so it will be a while before I can say how happy I am with the experience. I've read/heard nothing but positive comments about the TrueTrac, so that was enough to push me in that direction.

[mongocanfly]

Moe... what trans do you have and tire size..3.42s and 3.73s arnt that far apart....
You may really love 3.73s with a locker..
I'd say trutrac as well if you could use it.

[bigmoe]

4L60e, 255-60-17. I'm liking the 3.42 ratio. I'll likely pick up an Eaton posi but I'll wait till the Can/USA border opens to regular folks. (hopefully soon!) I'm just over the border in Canada so if I get my stuff sent to a US friend and go pick it up I save a bit on shipping and brokerage. It adds up over time.

[SkinnyG]

Summit ships free to Canada on orders over $300.

[mongocanfly]

With the od trans and 29-30in tire, youd be fine with 3.73s if you wanted to go that route and get a trutrac..
My 99 with 4l60 had 3.73s...it was a nice setup...
Nothing wrong with keeping your 3.42s though..my 13 truck has 3.42s....
Only about 200rpm diff between 3.42s and 3.73s with your setup at 65mph...

[88Stanger]

I am not sure if this is any kind of help, but I was looking at what gears to put into both my C10's and new posi carriers. What is learned is that with the 12 bolt "truck" rearends there are two carriers available, one that goes up to 3:42 gears and lower and the other that goes from 3:73 and up. Due to what I want, fun and cruising, one has 4L60E with LS and 352hp to rear wheels and then the other is 383 storker with Muncie 4-Speed I have both with complete new everything from axles (5 lug) to posi and gears with 3:42. I really like the gear, fun but able to go on the highway. Cost about $1400.00 total with buddy install, each.

[bigmoe]

Well I ordered an Eaton 19587-010 for 2.76 - 3.42 gears ($345) and I also got a rebuild kit with gears and races and some shims, etc ($89). I usually do all my own work but I know a guy in town who is good with rear ends so I'll likely get him to do it.

[bigmoe]

Got the posi installed today by a friend with a local shop. Should be way better traction. No more one wheel peel! Never got to try it out. Had to rush home because it was threatening to rain on my shiny paint, lol.