posi unit for 9 inch rear

- Welded spider gears. Although I have done it myself I advise against it. Without getting into a lengthy explanation I'll just say it is potentially unsafe. For that reason welded spider gears are not permitted by many racing sanctioning organizations.

- A drop-in mini-spool is relatively cheap, but not too strong.

Both of these options result in a permanently locked diff. Not what you want on a street car.

 

Yea, I know folks that have preloaded the spider gears and I think there was even an article in one of the magazines about it years ago.

But if it worked right, no one would be buying all of the different locking rearends. Of course, someone is gonna come on here and say they've been running one for 20 years and they work perfectly.
Larry T

 

Had a Detroit in my 56...took a beating and still in use by the new owner.

 

For a street going vehicle, especially a light one, and/or one with a short wheelbase, I cannot recommend a Detroit Locker, unless you like throttle steering, and involuntary lane changes.

Torsen has been sucked up by a giant Japanese manufacturing conglomerate. Good luck finding one for a 9". You can; however, get the next best thing, a Detroit TrueTrac. They can be had for under $500.

 

It would be cool to hear what this 66nova dude ever did?

 

Couldn't be happier with my TruTrac. It stands up to my 1.30 60' times, but behaves like an open diff when cruising around town. I'm sure my drag radials are lasting a lot longer without the scrubbing, and now its almost effortless to make a tight radius u-turn. Much easier to push the car by myself in the staging lanes too. The car now seems to coast forever when i slip it out of gear. I'll never put another locker in a street/strip car.

Something that seems to get lost in the fog is the fact that lockers and spools can be dangerous when something goes wrong. Probably the most common of drag car accidents is a car suddenly making a hard turn when it loses traction or power at one or the other rear tire. That scenario is much less likely to happen if the car has a typical street differential instead of a locker or spool. If you blow a hose off and wet a tire down with a TruTrac, it behaves more like an open diff without sending you into the wall. Some people don't like that about the TruTrac, especially for off road or winter driving, it's little help propelling the vehicle when one tire has no traction.

 

good post and thank you for sharing actual experience

 

Think I will be buying a true trac after reading what I have read!

 

If you are only going racing once in great while I'd get a posi. I've had a 9" locker and I didn't like how it drove. I like the clutches-style posi it had before, and I liked the spool I did after.

 

I am a believer in the Tru Trac. I have one of the Torsens in a Miata that we autocross. One tire on dirt and the other on pavement, dump the clutch and both spin like a spool. Around town or up in the air, the diff acts like an open. The only draw back to racing the Torsen/TruTrac is if one wheel goes airborn, it is an open diff. No torque steer, noise, bumps or anything goofy. Great diff.

 

My under costruction '31 "A" roadster on '32 rails has a 9" equipped with a
"Power Trax" locking type unit made by Richmond Gear. Supposed to be a sorta "civilized" version of Detroit Locker.
Got it from a friend who had it in a "40 tudor, which he used as a daily driver in city traffic. I never rode in it, but his story was that it was decent on street. Anybody had any personal experience with one?
Sorta think I would have bought a True Trac if buying new, but I guess I'll see how it operates when I get on the road!
He's a trusted old friend, and offered it in trade on a frame I needed to sell or trade, so I think all will be OK, just a bit concerned since the "A" is quite a bit lighter and shorter than that"40 it was in.
Dave

 

Powertrax is a drop in version of the "Detroit". It was called the Lock-right. They are "softer" than the Detroit and quieter. They still can be interesting to drive. Used them on CJ5 type rigs. The outside tire unlocks and ratchets faster than the inside power tire. The inside wheel has the power while the outside is freewheeling. Moderate power makes the rig want to go straighter, more power will slip the inside tire until it reaches the speed of the outside tire and then drives the two at the same speed. While turning you will hear and feel bumps. Lift on the throttle and the car will pull inside slightly on a corner.

Don't give up on it yet, I used the lockers on sloppy suspensioned short wheel base lifted jeeps. It made the drive interesting but not hairy. On a lowered tight suspensioned rig it may be awesome! One big plus is ultimate traction! You will never have one wheel spin!