Any reason NOT to use a welded diff for drags?

Limited slips are expensive for my next challenge car, but welded ones are not. Any reason not to swap in a welded one for drags? RWD car with drag slicks.

For some reason I'm thinking there might be some NHRA rule against welded diffs, but spools are pretty cheap.

Welded are both heavier and weaker than a spool. I would imagine a weldy would blow up real nice when squeezed between a lot of torque and a lot of traction.

What diff are you using?

Second gen RX7

The offroad guys do okay with welded diffs. An SBC in a CJ7 with welded diffs isn't that horribly uncommon. I think it's all about penetration.

I'd do it.

Seen many a welded diff over the years. Seen them let go big time, too. For instance, the one that was in the Jensenator when I got it was welded and used for road racing. And I do believe it exploded. Off road the tires can slide/spin easily on dirt, leaves etc but on asphalt, not so much.

If you pull the diff out of the carrier and stick weld it (thus keeping crap out of the carrier) then reassemble you should be all right. For a while. I sure wouldn't trust it long term, though.

I say stick weld because as racinginc215 says it's all about penetration. Clean the dickens out of everything, crank the stick welder up wide ass open, then weld in 8 spots.

We welded the dif in our SCCA road course cars (280Z) Worked great!! The down side was getting it to turn but you had to toss it more. The other down side was it caused other things in the suspension to brake. Adding additional reinforcement and or making new heavier duty parts eventually solved the issues. Once sorted it worked very well.

Derick Freese wrote: penetration.

giggidy

do not weld with it in the case or axles/stubs installed.

the redneck that i bought my k5 from welded the diff with the axles still in it, and the axle let go from the heat weakening it. it twisted and let go.

I say stick weld because as racinginc215 says it's all about penetration. Clean the dickens out of everything, crank the stick welder up wide ass open, then weld in 8 spots.

^this.

I'll be welding the diff on my little plymouth truck. Not until it needs the traction, though.

The ring and pinion will break long before the diff will.

I was told to always weld with the axles in, so you can ensure that the side gears aren't off-center. Hard to do with this kind of rear, though.

I'm a pretty big time drifter (I do enjoy all forms of motor sports, not just a drift kid) and tonns of people weld their diffs.

Very low failure rate unless they are 5+ years old or you don't fill them with fluid. surprise!

Best thing to do is pull the pumpkin, heat up the diff, and weld it like that

~Alex

patgizz wrote: do not weld with it in the case or axles/stubs installed. the redneck that i bought my k5 from welded the diff with the axles still in it, and the axle let go from the heat weakening it. it twisted and let go.

The axles should never see enough heat to damage them.

Just so you know, don't weld the carrier.

You want to weld the spider gears together. I have had the best luck with SS welding rod, at the proper amperage, using multiple passes.

I had a welded diff in a Back 40 car (field racer). It lasted exactly one afternoon of racing before it let go. That was probably less than 50 miles on dirt and grass.

That said...I am not the one that did the welding and the diff was welded with the rearend still assembled.

I read a website were a guy mentioned not to weld anything together...but to fill the valleys on the spider gears so that they can't turn. Makes sense to me. Might be worth a shot.

Clem

had a welded diff in my first dirt oval car, one where you depend on tire stagger to get around the corner under power. The diff let go and it was an instant trip into the wall..

read a website were a guy mentioned not to weld anything together...but to fill the valleys on the spider gears so that they can't turn.

That sounds a lot less likely to fail... good idea!

1) NHRA illegal, period

2) if you break an axle, the other one will still be under power, period

3) most people don't do it 'right' and it ends up popping

I drove a FWD car with one and it was a bear.. if you can find.. well anything else, use it!

+1 on the drifters. Near as I know, there's no [commonly] available spool for the 240SX differential, so they're just about all weldies.

However, I imagine the stress on a diff that's being drifted is MUCH less than the stress on a diff during a drag launch.

Also, don't do what Donny Don't did:

ReverendDexter wrote: +1 on the drifters. Near as I know, there's no [commonly] available spool for the 240SX differential, so they're just about all weldies.

This makes me want to draw up a spool for a 240sx and find a shop to do a run of them...

Hmmm....

Clem

http://www.google.com/images?q=you%27re+doing+it+wrong!&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&source=og&sa=N&hl=en&tab=wi&biw=1440&bih=710

My main experience is with GM rear ends, especially the weak 7.625 rear ends. I tried welding 2 diffs before I got it right on the 3rd one. Works fine on dirt, was heavily warned against using it on asphalt. It puts a serious strain on rear end parts when turning. Slicks make it even worse. I've tried a few different methods. Welding up the valleys in the spider gears just takes the heat treat out of them and they shatter almost instantly under any kind of pressure. I would look into other alternatives, but if you're dead set on trying it, look around on the internet. There's a bunch of pics and info from people that have done it. Rule #1 - everything must be CLEAN, CLEAN, CLEAN before welding. Good luck.

I've had welded diffs (lincoln lockers as we call them) on Jeeps before. I had a Dana 30 front axle, a GM 10-bolt front axle and a full-floater 14-bolt rear axle. None failed on me, but I wasn't particularly rough on them. I had a friend do the welding on all three. He MIG'd the spider gears with the carriers and shafts still in the housing. Gear oil is flammable, by the way... so be careful.

My concern would be more about the overall strength of the differential, axles and gears than the strength of the welds. On my 10-bolt I broke outer u-joints, but never had any problems with the welded spiders.

In addition to spools, there are mini spools which replace the spider gears (as opposed to the entire carrier). These tend to be cheaper than a full spool, but I've never tried them myself.