Technical Vintage-style Altered build: Open dif, or limited slip?

Brad
I suppose that your uncle is no longer around to ask. I may very well have run welded spiders that was a popular mod. if you uncle was serious it is doubtful that he ran an open rear end.

 

Some friends and I ran an FED in the late 70's to mid 80's. It was built in about 1972, had a 220" wheelbase. It had an 8 3/4 open mopar with 3 series gears. It ran 8.60's consistently with an alky injected big block. It always hooked up, spun both tires due to the light car weight, and, as it has been said here, intertia. If you're going to run an 8 3/4, it's simple: set up one center chunk w/a spool, one that is open. Test. Decide.

 

When I ran C/D in the late 60's and early 70's we used an open rear and so did everyone else. If one tire hit a slick spot it would just spin and not make the car go sideway's . The problem with an open rear is breaking the spider gears and the pin . That's what will come through the housing and hurt you . Please put a spool in it .

 

OH, I see the problem here. The facts dont match everyones common perception and therefore the facts must be wrong.

I would think that onyone who had a street car with decent power but not much tire bite has been able to spin both tires at some time. Try driving on ice for instance.
Now, take into account the short nearly even length axles with a high torque motor and relatively little traction compared to todays standards. Easy to see how both tires could/would spin.

An open diff does not mean both tires/axles wont spin, just that they are not locked together. Even a tightly shimmed open diff is just that-a shimmed open diff. They work ok, better when the have slipped enough to build heat, grow and stop slipping.
But not something I would want in a short wheel base car myself.

MASRacing does have a good point however. Spider gears coming apart or bearing cap failure can be catastrophic. THus the Chrisman plate on the rear of most FED diffs. to help keep your own parts intact.

 

Chrisman's deal was the whole rear end spinning out of the chassie and not somthing comming out the cover.

 

I was mistaken. I Thought Chrisman had a bearing cap failure causing him harm. No disrespect meant, thanks for setting the facts straight.
None the less, the plate/covers welded on the housings were to reduce bodily harm if internal parts tried to exit.

 

You know what? I would run a spool in a full width altered rear.
With all the junk thrown in here, I forgot my intent.
Not to persuade either way, just to inform.
Some times I get caught up with those who look for an argument.

 

why not go real hard core old school, put a spool in it, drill the housing full of holes and use open gear grease on the ring and pinion. Anyone remember the Modifications Unlimited Fiat alterned our of, I think, Maryland back in the day?

 

HAHA, there were atleast two early FEDs at the Epping NHRA reunion on display with swiss cheese style banjo rears.
Was that fiat blue with flames? by any chance?

 

Wow.I stand corrected,and I think I need to throw out an apology to a few people for being so stubborn about what I "thought",and mistaking it for what I "knew"....
If your eyes and ears aren't open all the time,you're missing out on learning stuff,and this is a case of me talking when I should have been listening.
Thanks for sharing the knowledge guys.And thanks for being somewhat diplomatic about it.

Scott


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IT could have been cap failure to cause the gears to lock at which the momentum rotated the rear end, thus the requirement of more bolts ,thicker mounting flanges, and a antirotation plate. 4 - 3/8" bolts and 1/8"plate are not enough

 

Our Altered is 96"wb. 59 Olds rearend with a spool.To getdown the track in a short wheelbase car with a spool ,staging straight is critical.

 

i accept monetary compensation for such infractions


its all good, no apology necessary

 

We have a ford 9 inch with a Strange spool and axles in our altered, it drives well,I ran spools in all of my dragsters front and rear engined, never had a problem