What is the stock rearend setup specs, and.......

[BAMC1369]

What is the stock rearend setup on a 71?

I have to look agin but i think i have a 10 bolt and was looking in to a posi unit. Right now i'm Running a basic 400sbc with a th350 nothing mean but i would like to put in posi for street use. Im not looking to change out the hole thing but just a simple replacement. What options are out there for a simple swap?

[BAMC1369]

I guess thats a stupid question.

[monte70car]

Depending on price you could go with a powertrax unit which replaces the spider gears and you dont have to worry about shims or backlash. The powertrax unit acts like a posi when taken a turn the inside wheel unlocks and allows you to turn, once straight and you get on it both wheels lock in place. If you want to change gear size a reg. posi like eaton would be a good choice but you'll need tools to set up the gear.

[BAMC1369]

I'm happy with the gear set up i have now, i'm not even sure what it is but just want to some posi in there for a little traction. I guess my only goal with the car is drivability and i would like to smoke this 88 Trans Am my buddy has just to shut him up. I think he would take my off the line with his posi other than that his car has a lot of low end and not much high end.

[CrazyDavey]

probably somethng like this Matt. There are a couple of other brands but this is the basic idea...Dave..

 

http://www.summitracing.com/parts/ETN-19557-010/

 

[monte70car]

powertrax I was thinking something like that. I have one in my 12 bolt rear end and am very happy leaving two 50' black marks about 20' long.

[BAMC1369]

Both look like good options Thanks guys. I'll have to save a little befor i go that route but at least i have an idea.

 

Dose any know of a cheaper option like somethinkg i could go to the junk yeard for?

 

i'm not planning on doing this but when i had my 72 chevy pickup i think the welded the gears together so they were allways locked. Everytime i took a turn the tires slipped a little.

[CrazyDavey]

yeah Matt, locked is not too good for the street. You could go with a spool which is cheaper but you still have that issue of going around corners. Save your money and do it right, no junkyard stuff, you'll just end up having to redo it...Dave

[Andy's Auto]

Welded spiders can be dangerous. They work great for mud trucks, just not for drivers. Your Monte most likely has an 8.2 in it wich is marginal at best when built. They did make an 8.5 28 spline, but although generally cheaper than a 12 bolt, they are tough to find. A 12 bolt is an easy find, but they do cost. You can usually find a nice 3.31 posi for around a cool grand, but if you plan on tearing it up in the future with more power, that in itself will need an upgrade.

 

What I have done on most of my 12 bolts is simple. I buy the 12 bolt open diffs for around $3-400. Add a new Eaton posi, new gears, a rebuild kit and a good set of either Strange or Superior axles, and for around $1800 large, you have a very hard to break diff.

 

My reputation in town is the affordable horsepower guy. Took a deposit on a 540 going into a 71 Shovel. After talking to said client in depth about which end of the car I was going to build first, I refunded him. A bone stock 3.55 12 bolt will NOT hold 550 at the rear wheels. If only for a moment.

 

Andy

[BAMC1369]

So i was looking into all of my options and i think i'm going to go with the Powertrax unit. I found it on jegs.com for cheep and reading up on it, it sounds like its easy to install and only takes about an hour.

 

I've read some people with 10sec cars using these and i guess they hold up good.

 

this is the one i was looking at Jegs powertrax.