Metal scraping sound

[FatDatSun]

I get a metal scraping sound, sounds like... the hulk running with a building support beam dragging on the ground.

 

I've tried keyword searching on here.

Maybe I missed it but i couldnt find anything. If there is a fix can someone forward me it. Details below.

 

Sound only come when #A letting go of gas at higher speeds in higher rpms (letting go of gas at low rpms doesn't make the sound) ,#B: shifting down to slow to decelerate and car tugs (down shift causes it to make the sound until at a full stop, unless, I hit the gas alittle. If I hit the gas here it stops) and #C: when over small pot hole, bumps when at slower speeds (only over the imperfect road while driving slow [slowing trying to not bottom out on dead shocks atm] When back on smooth top there is no sound until #A and #B happens again)

 

4spd trans/ turned town torsion bars alittle, and rear blocks. Everything else is stock and waiting on parts to come in to change them out. Every bushing and moving part for front suspension is on order except control arms. 

 

Goal for the car: go down the road safe (suspension), add rotors (with complete brake components along with raising upper shock mounts), rebuild motor (l20b), delete everything not needed for climate control and replace with vintage setup climate underdash. And rewire. All in those order. For everything else use Visa.

 

If I am starting topics and questioning in the wrong section please let me know. I apologised in advance.

 

 

 

 

[thisismatt]

Hmm.  Check the carrier (center) bearing on the two piece drive shaft?

[datzenmike]

Well down shifting and or using the engine to slow the vehicle causes the nose to 'dive' and the rear to lift. As you don't mention this happening when braking it probably is in the drive train.

 

First inspect the entire exhaust system and pull on it to see if it's possible that a pipe or the muffler is rubbing the driveshaft or... anything. Sometimes it's something simple, and maybe the pipe has hit the ground and  bent. Engine torque will twist the engine and move the exhaust.

 

 

From the description I would say to inspect the three U joints and the center support at the rear of the front driveshaft. Try to force the driveshaft side ways and up and down at 90⁰ to rotation at all three U joints. There should be NO looseness or slop. All you should feel is it turning. You may need to grip in front and behind the U joint to detect any slop.  

 

 

 

 

The bearing inside the center support is probably OK but the rubber 'doughnut' tends to rot away. If this is the case the driveshaft will be unsupported and can 'flop around'.

 

 

Check the rubber transmission mount is secure bolts tight. Shifter not rubbing the hole in the tunnel.

 

 

Damn, Matt you're fast.

 

Wouldn't hurt to check the differential and transmission fluid levels. If you have not changed the oils in the last 3-5 years, nows the time.

 

 

 

 

 

 

 

 

[FatDatSun]

Center support - center support bearing aka "donut" now on order! The one on the car got ate by Homer Simpson.

[datzenmike]

It might come with a bearing, I don't know, but there's only been one confirmed case of the bearing being bad. It has almost no load on it and allows the driveshaft to spin inside the 'doughnut'. It's a bother to change it. I would save the bearing and just change the 'doughnut'. Hell I had a bad doughnut and wrapped a strip of rubber conveyor belt around the driveshaft and clamped it in. It worked so well I forgot about it for 3 years till I took the drive shaft out.

[FatDatSun]

I thought about clamping it with a belt so it hangs center. I might do that for the mean while. I ordered the whole part (donut and bearing) but, part is already on order and with lifetime warranty, part was only 55 dollars with lifetime. A little elbow grease and learning experience doesn't hurt. Thanks for the info. I shall remember to take pictures to add to this when I work on it for future ratsun repairers.

[FatDatSun]

Update: used a serpentine belt and hose clamps. 1 year later, still running on same belt and hose clamps instead of support bearing. Hooraa