Deacceration shake/rattle from the drivetrain somewhere.Help NISTECH

[youngmanvr4]

Couldn't fit year and model into title. 90 240sx with 92 engine (DOHC swap) and 92 transmission (auto to manual swap).

Time to work out the next bug. When going 55+ mph and I let up on the gas I get this very loud noise (it sounds like a rattle or vibration type noise) and it shakes the car. It feels like its coming from somewhere in the drivetrain (from under the drivers). It doesn't feel like its coming from the front of the car, either the mid or rear of the car. It doesn't happen right when I let up on the gas most of the times, it take a couple seconds for it to start. The noise slows down as the engine speed does. I can make it do it at lower speeds sometimes (like 40 mph and under). But most of the time its not as bad at lower speeds as to higher speeds.

I'll be taking my car out to Cali (a 1,800 mile drive) and I just want to make sure it will make it out there. I mean I can fix it when I'm out there for 3 months I just need to make sure it will be ok for almost 2,000 miles. Could it be the carrier bearing? I just bought the driveshaft from a guy like 2 months ago.

Does anyone know what the problem might be? If you have any questions that might help you figure it out just ask, I'll try to relay what the car is doing the best I can. Thanks, Nate

*EXTRA TIPS* 1. At 70+ mph the noise isn't there til I slow down to about 67 or so to about 50 mph it really makes the noise. But almost never above 70 mph.

2. I have a SSauto Chrome dual cat-back and where the resnator is it looked like the driveshaft might touch it. It was about 5mm or so of travel room til it would rub it. Could it be this?

3. When slipping the clutch when starting out at a stop light and seemed to want to make sort of the same noise/feel at a lower volume. It seemed like it wanted to do it more when slipping the clutch and turning at the same time. But going straight it would do it sometimes too. But then other times I would try to make it do it and it would do it.

[AZhitman]

I'd def get up under there and see if it's a simple matter of something touching (exh on body or on driveshaft)... First thing I thought of was rear diff, though.

As you're decelerating, and it's making the noise, does it go away if you put your foot on the gas and lightly "match" the car's speed (not accelerating but just maintaining)? If so, it's likely a bad diff.

[youngmanvr4]

Hey Greg,

Yea if I just lightly step on the gas it goes away right way. Like you said matching the cars speed it goes away.

So does that mean the diff. is going bad? I did want to get a 2 way LSD (Kaaz) when I get better at drifting but I might need to get it sooner then I was thinking. What all would I need to replace? Another words if I bought a Kaaz LSD is their anything else I'd need to make the noise go way.

Will it last to Cali (1,800 miles)?

Could it also be low fluid level? Right now I'm in Houston, Tx from now til sunday, then I'll get back next week and be home for like 3-4 days then we'll leave for Cali for 3 months and I need to know if it will make it. I'll put a LSD in there when I get out there if thats the problem.
Modified by youngmanvr4 at 12:52 PM 1/9/2006

[AZhitman]

Doubtful it's a diff fluid issue... Bet the diff is taking a crap.

I wouldn't trust it for 1800 miles, but then again, I drove on a bad whining diff for 20K miles...

[youngmanvr4]

Well I'll give it a try. Think its to risky? The only other thing I can do is maybe have it shipped out on a semi (we have 22 semis going out there) and I'm sure we'd have room on one of them. But I'd rather not do that.

[youngmanvr4]

Greg, I started a thread about it but do you think I should go ahead and get a LSD even though my drifting isn't good yet?