View Full Version : welding limited to posi
08-07-2001, 02:03 AM
Does anyone out there know what when or where I would have to weld in the rear end to make a limited slip into a posi ?? any helpis appreciated
08-07-2001, 09:22 AM
welding will only work on the dirt tracks.
It will break with a strong engine on the street.
08-07-2001, 03:49 PM
A posi rear end typically uses clutch packs to apply pressure to both axles to prevent one from spinning faster than the other until enough force is applied (such as going around a corner) to force the clutch to slip, allowing the inside tire to rotate more slowly than the outside.
A limited slip differential typically uses a cone-type affair to achieve the same results as a posi. The big difference is that a limited slip will "break loose" sooner than a posi, and it is also much quieter on the street.
To answer your question, technically, it is impossible to make a limited slip into a posi by simply welding anything, since even a posi is not a locked (or "solid axle") differential.
wileys_farm is entirely correct to caution you about welding your differential on the street. In fact, I can't believe people are still willing to try this!
The reason you should not run a welded differential (and also the reason they are banned by all drag racing sanctioning bodies, although I believe a few of the smaller circle track sanctioning bodies may still allow it on dirt tracks, but not on asphalt) is that it puts a tremendous strain on the carrier and the axles. If you are using a GM type of differential that uses C-clips to retain the axles (like a 10 or 12 bolt), it is entirely likely that the axle will break at this weakest point, thereby releasing your tire, wheel, brake drum, and a 2 or 3 foot long piece of axle to go whereever the heck it wants to go. It's first stop is usually your rear fender, where it will chew the heck out of a lot of sheetmetal.
If that's all that happens, consider yourself lucky. If an axle breaks at high speed, the car will swerve out of control and could kill someone else, or your broken parts could hurt or kill someone.
For anyone still wanting to experiment off-road with this type of modification, you would weld the spider gears to the carrier so that they cannot rotate independently of each other. The surfaces to be welded must be completely clean of all differential lubricant.
Considering that a spool can be purchased for under $100, and a good used posi differential can be had from a wrecking yard for that price or less, I would suggest trying those routes before you start burning coat hangers.
76 Mustang II
01-18-2002, 02:41 AM
if you're SUICIDAL that's one way to kill yourself. There will be less danger to others around you if you just fill up your tub. ONLY an idiot would weld differential parts. REMEMBER: TRASH IN, TRASH OUT..... buy the right parts, and BE SAFE..... I want to beat you at the track..... NOT CARRY YOU OFF OF IT!!!!
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