Rear Axel Hopping

[Djmayle]

I have a welded diff on my 1990 240sx. When I'm making turns I feel like my ass end is hopping all over, not like the normal shim from the tires. I lifted it up yesterday and all my subframe bolts are tight and replaced my tires. Does anyone know what it may be?

[s14boy]

... its your welded diff i would recommend taking it out for a stock one or go read up about a welded diff before you crash it.

-Mike

[Djmayle]

But I'm used to the feeling of the welded diff. This is different, it's more aggressive. Imagine a welded diff with 5x the violence. It just started 2 days ago after I was putting it sideways more than usual. I'm just confused.

[PrimeDirective]

Is your subframe cracked?

[boxerpicker]

you have solid diff and subframe bushing? if so then youre fine. its pretty normal

[zerodameaon]

Go get a replay/gopro/your phone and stick it up under there and see if you can record what's going on. You say your subframe is good, what about the rest of your suspension? You were drifting after all, something could be loose or bent.

[driftminds13]

Check your subframe bushings, axles, rear control arms etc. Something back there is in need of replacing/changing/fixing. As they mentioned above, do you have solid subframe bushings?

[thefro526]

Like everyone else said above, check your subframe bushings. Having a welded diff will accelerate the wear of those bushings, especially if you're beating on the car, once they fail, you lose the (relatively) smooth 'chirp' of a welded diff and it's replaced with more of a clunk.

If your bushings are good, then check everything else, bushings, arms, bolts, etc. It could also be that one of your axles is loose or going bad, my two way was 2x louder, if not worse, when one of the axle nuts had come loose.

[ShadowMan]

The Ultimate Guide to Suspension and Handling: Part Six, Adding Negative Camber (http://www.motoiq.com/MagazineArticles/ID/1781/PageID/2539/The-Ultimate-Guide-to-Suspension-and-Handling-Part-Six-Adding-Negative-Camber.aspx)
If you have your stock/rubber bushings, chances are they've taken a beating and this bushing deflection is part of your problem (page 2, top picture), but it could be any combination that anyone has mentioned above. The idea of mounting a camera under there is a good idea, that or get on a creeper and have a friend tow you around while you look at it from underneath. J/K, don't do that.