ok i have a 7.25 that i've been looking for a posi for, for a while and i dont have to money to get a bigger rear and have already put money in rebuilding the 7 with 3.55 gears. i was wondering if any one have heard of or thought of a way to convert open to posi with out welding spyders together, i'm looking to remove the spyders and some home pin or do something.

anybody????

Now this is old school, VERY old school,like front engine dragster old. I have never done it but guys shimmed the spyders till they locked tight on 8 3/4 open rears for a home made spool, locker, what ever you want to call it. I am sure it takes alot of trial and error. I am not sure how long it lasts or if I had the guts to try it.

It is not hard to do...
Just doube-up the shims that go behind the side & spider gears.
For even more "drag" on the spider gear assembly, you can install a motor cycle valve spring in-between the two spider gear faces, then push the cross-shaft thru the spring to hold it in place.

If done "right" the spider / side gear will be locked solid when the unit on the bench but you will hardly feel the added friction in operation.
A tightly shimmed open diff will spin both wheels in a straight line and on wet surfaces. It will not do drifter type slides or doughnuts.

I find that doing this mod turns the gear oil black faster and in the case of a 7 1/4, will break weak spider gears.
DD

do if i'm going to try to shim the spyders tighter i should start stocking up on spyder gears for when they break?? by doing this will i get enough of a posi ish rear to when running slicks at the strip i will hook hard.

A "hard hook" and a open carrier 7 1/4 don't "mix".
Save yourself some trouble and find a stronger rear axle assembly to work with.
DD

yeah i know i'm working on tring to get a 8 1/4 or 8 3/4 but dont have the $$ right now. i already rebuilt the 7 with 3.55s and did new brakes and all that stuff. really want to find a 7 1/4 sure grip, bought one years ago but it was completly distroyed.

Thanks Doc, I was hesitant on that post thinking that most would have thought I was nutz!!

I am just as "nutz"... seeing that I tend to go "out of my way" to try a lot of those "who knows" ideas... just to end-up with broken parts... but now I know.

I will say that a tightly shimmed "open" 8 3/4 works pretty well.
I am currently running one, a tightly shimmed 3.07 ratio and it reduces the amount of one wheel "sit there & spin - no forward movement" type action.
The tight spider shimming also reduces the amount of backlash in the assembly so there is not a loud "clank" when putting the car in gear.
The big difference... the 8 3/4 open carrier and spider gears are a lot bigger and stronger then the 7 1/4 parts.
DD

yeah i'm probly just going to leave mine alone cuz i know its weak, i will continue search for cheaper 8 3/4, i screwed up years ago, had the chance to get a full drum to drum brand new everthing 3.55 posi 8 3/4 at carlisle for 800 bucks.

That still is the going price. Found one at MATS swap meet for $700. PM me and I can get you the guys # I think he will ship.

hey thanks alot but i just found a posi unit for my 7 1/4, with brand new clutchs,ring/pinion,bearing,axle bearings.

So it takes just one additional shim under each gear? And where do you buy the shims? I may need to try this.

Rick

Just weld it together to make a spool. Circle track guys have doing that since about 1930.

I have a lot of side gear shims if you need a couple.
DD