Best Limited Slip for 12-Bolt

[Irishpilot]

Alright guys,

Who's smart on the best Limited Slip unit for a 12-Bolt? Mine is currently a unlimited slip and I drag race the truck at the strip and I'm tired of the lack of traction. I use this truck weekly so it has to have some kind of street manners.

I know there are Eaton units, and some others, but I've heard there are clutch (most common) and geared. Any ideas or guidance??

[LONGHAIR]

If this is primarily a street driven truck that sees some racing, a simple clutch-type positraction is fine. Eaton being one of the more popular units because of it's strength and it's rebuildable.
Clutch-type models are the most forgiving and driveable. In everyday driving, most of the time, you will not even know that it's back there. The main exceptions being rain and snow. The back of the truck will be more likely to slide out on a turn. Any type of traction device will do that though, it is a function of the tires spinning together.

The "locker" type units are much more "harsh" in their action. You will know that it's back there in normal street driving. For all but the most extremem comditions, they are over-kill. The street manners take some getting used to, especially with a manual transmission.

[cdowns]

i used a MOROSO "brute force" posi the last one i used// it was a bit louded in announcing its presence but less aggressive than a detroit locker

[btullis99]

I run an eaton truetrac, its awesome. under hard power its locked up, but differentiates very well when driving around town. its silent, never needs rebuilt, and doesn't require special gear oil additives. this would be the differential I would recommend to anyone building up a diff.

[Husker]

I have Tru Tracs front and rear in My Jeep CJ and they work great
Ron

[Irishpilot]

I was looking at the Trutrac unit. Now I'm looking at which size gears for the truck. It has a TH350, so I'm thinking of either 3.42 or 3.73. Leaning more towards 3.42s as a good compromise between RPMs on the highway and acceleration.

Anyone have any thoughts on those gears?

[nlped]

I have an Auburn Pro w/ 3.42 gears. I love it!!! It has a TH350 in it and it runs out great at highway speeds. And the differential works flawlessly, I know it isn't rebuildable, but I have had the an Auburn Pro in my mustang (Driven hard...a lot) for a decade without issue!

[btullis99]

with a th350, i wouldn't go any lower than 3.43's. 3.73's or lower would make it a bear cruising down the highway. just my opinion.

[N2TRUX]

The 3.42s are great all around gears, especially with a non OD transmission. You really should factor in the peak HP/TQ range of your cam as well as the height of your rear tire. If your running a tall tire, the 3.73s are a better choice.

[LONGHAIR]

Since you mentioned drag racing in the OP I would say go with the 3.73s. You will run at a bit higher RPM on the highway, but it won't be that bad. If you have a taller tire, it might even be better to go to 4.10.

Some engine info and tire size would help with this.

[Irishpilot]

Engine is a 406 sb, 10.6:1 compression, alum intake and Etec heads, more info in my signature.

The wheels are 235/50R17 fronts and 255/50R17.

I have 4.10s in my 6-speed manual Corvette, and they are as steep as I'd want. I think with no overdrive and my tire size, 4.10s are too steep for street driving.

I sold my DD car before going to Korea, and the plan is to have the truck as hot-rod daily, so it will see more street that track, but I'll be racing enough. Here are some pics:

Truck at ride height on current wheels:

[mr.chevy]

wow what do you have in the suspension to make it that height. I am looking to lower my truck to about that height.

Looks really nice man!

[N2TRUX]

Originally Posted by mr.chevy

wow what do you have in the suspension to make it that height. I am looking to lower my truck to about that height. Looks really nice man!

From his sig "Air Ride Tech bags on all 4-corners."

[Irishpilot]

mr. Chevy, thanks. I've got 2.5" drop spindles up front with the bags, CCP sway bar. In back, the bags directly replaced the coils, drop shocks, CCP Trac Bar kit. Running 5 gal slip tank with onboard compressor, 8 valves for independent adjustments.

The picture shows it at ride height. It will go a bit lower, but I've got longtubes, so that is as low I as dare use on the road.

[Dynomutt]

What gear is in the truck now? I'd say use that as a baseline for your new gear if you can. I have a BB / TH350 and had 3.73's with a single spinner and I'm going back with 3.42 double spinner for better driveability (I hope). Won't be racing mine though.

[Rideto100]

I am brand new to this site and come from a rock crawling background with drag racing before that. I am not sure if you have looked into them but since you already have air ride I assume you have an air compressor set up of some sort. So with that being said why not look at the ARB air lockers? They are completely off without air to them and when turned on they are 100% locked up. I have never seen anyone using one in an application like this and have never understood why. I have used them several times and they are very streetable, and trust me when I say I have abused them and never had a single problem. Just thought you might give it a look.

[Irishpilot]

I also have a TH350 and single spinner with 3.73s. Right now I'm getting about 14mpg at 70 mph and somewhere in the 2500-2700rpm range. I think 3.42s would help the mileage but of course acceleration would suffer.

I'll look into the air lockers...never heard of them on a street truck. You are correct, I'm running an onboard compressor.