From slip to posi? Best bang for the buck?
 

Hey guys I am constantly debating what to do with my slip differential rearend.

I have a sb400 350th trani and a .308 slip differential rearend.

I dont really mind the .308 gears but I do not like the slip differential.

I want a posi!

I ask the guys at the fab shop how much it would cost to turn my rearend into a posi track and beef it up a bit. They said probably around $1800 and I about fell in the floor.

What do you guys recommend? I want the rearend to be pretty new and relialbe since my trani and motor are.

So should I turn mine into a posi?

Buy a posi and have it rebuilt?

I want it beefed up a little too because I'm going to be throwing better than 550lbs of torque at it.

Thanks guys!

Re: From slip to posi? Best bang for the buck?
 

I've been looking at these for a while. Seems like a no-brainer installation.

http://www.summitracing.com/parts/PWT-1910-LR/

Re: From slip to posi? Best bang for the buck?
 

I like the True-Track units. They cost a bit more, but they're tough and smooth. If your not re-gearing, you just need the True-Track and an install kit. If you follow the directions, it's really a DYI project. You can do it for about 700 bucks.

Re: From slip to posi? Best bang for the buck?
 

I have a basicaly brand new limited slip 3.08 10 bolt with 6 bolt axles from my 1986 4x4. The guy I bought the truck from just had it completly rebult with a new limited slip unit. I have yet to take off the cover but I got concerned when I turned one axle and the other one turned the opposite direction. Anyway the guy spent $1200 (I have the receipt) to have it done which was about 1/2 labor. Just installing a posi should be less than $650 if you do it yourself.

Re: From slip to posi? Best bang for the buck?
 

$1,800? Dollars or pesos? Run away, run far away!

If you have the mechanical ability, you could do it yourself. One of the ratchet lockers would be the easiest way, but won't get you a new gear ratio. A posi on those 3.08 gears is kinda, well, you just won't be happy. At 550ft lbs. you'll likely want to do some other work to the rear end while you're in there. Maybe a new gear ratio? A carrier replacement type posi unit? Assuming it's a 12bolt? if you go this deep you might as well throw some new bearings and seals in that dude as well. Basically a drum to drum rebuild.

It really all depends on how deep into it you want to get. I did my first differential build a few years back (a 12bolt). With some good instructions from Richmond Gear's website it really wasn't that hard to do. I did it all in a day, a long day, and was back on the road that night. You'll need a mag base and dial indicator and a good set of calipers, but they won't run you too much and they're cool little tools to have around for other stuff as well. Aside from that, basic garage tools and a good amount of patience will get you through it. It's not rocket science.

I pulled the whole rear end out of my truck when i did it, and I think it made it easier for a first timer. I still think when i do the next one, soon, I'll yank it out too so i ain't trying to do it while laying under the truck.

After a little thought, i guess $1,800 isn't aweful for having someone else do it. The posi unit, a quality one, would be anywhere from $500-800, then the gears, bearings, shims, seals, basically everything in a Master rebuild kit. Then labor and warranty, and yeah I could see the high price tag. But I sure ain't ever going that route again.

Re: From slip to posi? Best bang for the buck?
 

Hello neighbor,

Lot's of good info given in this thread, I've been pondering much the same info as you have. Which shop did you talk to for the price quote? Austin drivetrain?

Re: From slip to posi? Best bang for the buck?
 

Junkyard? I have seen posi units for around $150 at junkyards and swap meets. "when I turned one axle and the other one turned the opposite direction." Never seen a posi do that. NEVER take a strangers word for anything unless your buddies will vouge for him.

Re: From slip to posi? Best bang for the buck?
 

i run a 308 rear and put a eaton unit in, brand new cost about 700$ fitted and it runs real nice

Re: From slip to posi? Best bang for the buck?
 

I have GM 12 bolt posi units in my and my Son's trucks. They have 3.73 gears and the combination works well with the OD trannies that we put in. Both trucks have Eaton posi units in them. My 91 DD also has an Eaton posi unit with the 3.42 gears that it has.

Re: From slip to posi? Best bang for the buck?
 

I got my Eaton LSD new for $400. You will need new bearings which will add to the cost.

Re: From slip to posi? Best bang for the buck?
 

Psycho71
I dont think I'm ready to tackle the rearend yet. I'd hate to drop all that cash and mess it up.

As for the .308 gears I'm still unsure if I should keep them. With the 350th trani and a sb400, I Almost have to stay with high gears because I'm afraid with a .373 posi I may run out of throttle. I had a .373 posi once before and I would bang out at 115 mph at 5500 rpms. That was in my old '66 chevy short wide with basically a stock sb400 stock 350th and stock .373 gears. Plus on the street it seems like my tires were doing more spinning than the truck was moving. Once again though I had a stock suspension as well with some big fat redneck tires on it so I'm sure that was a lot of it. (High school... Oh the memories... haha)

To be honest I really dont remember. It wasn't Austin drivetrain I dont think.... I'm open to any suggestions though. I'm new to the area.

Re: From slip to posi? Best bang for the buck?
 

I'm dumb so that part kind of confused me...

The Powertrax Lock-Right and Performance Lockers' straight-line performance is equal to a solid spool axle, yet automatically unlocks to allow full differentiation in turns.

?

How does that work? So it is a posi when you need it to be and a slip when you turn....?

If so that may be something I would buy. IF IT WORKS!

Re: From slip to posi? Best bang for the buck?
 

This style of locking rear end is a good selection, however it is noisy as the dogs snap into place. That is why I chose the Eaton setup.

Re: From slip to posi? Best bang for the buck?
 

Here's an explanation. It's long-winded and a little awkward, but he gets to it eventually.