i have a 10 bolt 7 5/8 rear end in my 88 formula what are the pros and cons of each posi unit?? need to do something my stock unit is bout shot sometimes spin both tires but most of the time its just a peg leg sucks!!!!

 

pros of the eaton unit:

rebuildable

clutch type diff (means car still drives if worn out, it just acts like an open diff)

same style posi as old chevy muscle cars

---the eaton is the one I want, i just need the funds.

powertrax I know nothing about.

 

thanks tom maybe we can roust up a group purchase??

 

The PowerTrax requires an open carrier. It's advantages are:
1) It's a locker, not a clutch-type limited slip.
2) Can be installed with ordinary tools in an open rear.

Disadvantages:
1) Noisy around corners (clicks).
2) Can't be installed in a posi carrier.

If you have a posi now, you'd have to get an open carrier and have it installed properly. Then, you could install the PowerTrax. Since it costs about the same as a new posi carrier, you'll have to spend as much putting in the PT as you would an Eaton (unless you set up your own gears).

I like the way it performs on the track in the '57. I don't much like the way it drives on the street or in the pits, but I also used the heavier springs when I installed it. I almost went with the street springs when I put it back together last week after the gear swap, but chickened out and kept the strip springs in.

 

With the street springs it corners just like a normal car. Nobody knows mine is a locker, until I tell them.

 

in my summit i don't see a powertrax for our 10 bolt only the8.5 inch and up. but since this is a locker doesn't that mean it can't get worn out liek a eaton witch has clutches??? thanks

 

Like I said, I chickened out. I knew it worked where I wanted it to, wasn't sure that would be the case with the street springs although I figured it would be quieter.
Check PWT-1930 (26-spline) and PWT-1931 (28 spline) on their website (www.summitracing.com, do an "Enter your Summit Part Number" search).
No clutches, correct. I've had mine in for a year, it looked very good when I had it apart last week. I expected some kind of wear, rounding of teeth, something. Found nothing like that.

 

Would you recommend that I take it apart again, and put the street springs in? My main use is at the track, but it's not trailered, I drive it there (and occasionally to work on Fridays), and I have to make some pretty tight turns in the pits.

Will it lock as hard in a straight line? Or, at least, as reliably?

 

well now i am confused as to what i have i thought it was a regular stock posi unit. so what one would i want to replace the one i have?? since i sometimes spin two tires and at times it will only spin one.

 

You're probably going to have to pull the cover and find out. Eaton posis are availible in either 26 or 28 spline for the 7 1/2. Eaton is my choise for the street. You WILL need to know what spline axles you have. I wouldn't order anything till you pull an axle, rearend may have been changed before. When I had a set of 342s in pegleger, it would lite both tires. So you can't go by that. I know for sure it was an open carrier too.

 

i jsut put richmond 3.73 in it last fall. it had i think 3.23 or a 2.08 and the 10 bolt is a 7 5/8". and i think its a 28 spline if i am not mistaken. but it looks like an eaton carrier thats in there. how cani tell what i have if its posi or just an open rear end?

 

If you have an eaton, I'll have clutchs and plates behind the springs in front of the axle gears. They are replaceable, so are the springs. Eaton DOES NOT recomend synthetic gear lube on their carriers. If you have an eaton and are running synthetic gear lube, drain it and use standard gear lube with GM friction modifier before you buy another carrier.

 

I pointed that out to the AMSOIL tech people. Their response was something to the effect of: "That's interesting. We have a lot of people using AMSOIL with Eaton units, without a single reported problem."

There have been some fly-by-night synthetics out there in the past. And, it took Lawn Boy about a decade to admit synthetic 2-cycle oil wasn't causing failures. Eaton seems to be slow to come around as well. The U.S. OEMs resisted it for years because their cars wouldn't wear out as quickly. The Japanese taught them a lesson about what people expect once they get used to quality - now they're doing synthetic factory fills.

 

im not saying ihave an eaton now i just meant it looks like one. so how can i tell if i should buy the eaton or the power trax?

 

If you have a posi carrier right now, the PowerTrax will not fit it. To use the PowerTrax, you would have to convert it back to an open carrier, which means a complete gear setup, and then install the PowerTrax.

The locker works great in straight-line acceleration - that may be a reason to consider it. But, if you do primarily street with some strip driving, it makes a little more sense to just get your current piece rebuilt, or get an Eaton or other posi carrier.

FWIW, since I had the 3.73's installed last week, the PowerTrax seems to be a little quieter. The shop didn't want to mess with it, so I took it out before I gave them the rear, and installed it after they installed the gears. New axles, bearings, and gear lube were done at the same time, so one of those may have affected the clicking noise. Still works great, though.