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HybridZ

clunka clunka in my drivetrain


HICKL

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Car=76 280, sbc, t5 tranny, r200 diff.

 

That being cleared up, I have developed a light clunking somewhere in my drivetrain. It is fine under hard accel or decel, but shows up under no load "coasting" type situations. Sounds like it is coming from the rear end, does it regardless of gear, u-joints seem tight. What do you guys think? :(

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Does it do it when you lightly get on and off the throttle? If yes then drivetrain and suspension checks are in order.

 

First place to check is always the front diff mount. Need a jack to really check that correctly. Have known guys who got clunks from loose suspension bushings. After that I would check the strut bolts, both the isolator and strut rod nut. My Z had such a clunk. Turned out the D shaped hole in the isolator had rounded out allowing the strut rod to wobble (very dangerous. It almost wore through the rod.). Also check the gland nut for play. I also had clunks comming from loose bolts attaching the diff to the mustache bar. Finnaly check all the drive and half shaft bolts are tight. Basically torque every nut and bolt in the rear end.

 

Another possiblity is excessive backlash in the diff.

 

If it does it going up hill at a steady speed, drivetrain/suspension slop is probably not it. Look for things like exhaust pipes hitting the floor boards, loose parking brake cables, loose fuel lines.

 

Good luck.

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I fear that it is diff backlash. I just did a coilover install and the sound which was there before did not change so I think I can safely rule out anything loose in that area. It does it under light decel or accell like you mentioned. Under load in any direction it is fine. How much play/rotation should the driveshaft have with the rear wheels locked?

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The R200 I got out of a JY has noticeable backlash. With the car in gear and the back wheels off the ground, I can move one of the wheels a degree or so before I hear a light clunk and see the other wheel move.

 

Don't know what is excessive, but mine has held up well. To get around the clunk on mine I just turn up the radio. :D

 

Maybe someone else knows the correct answer.

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pulled the pumpkin last night and found that the little roll pin had sheared that holds the larger pin in place in the spider gear assy. I guess that would make some noise :-D

 

Yes Myron, you were right.

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Do you ever get wheel hop with your car? I had a 383 5-spd S10 Blazer that had the same problem. It would wheel hop and bust the retaining pin for the spider gear cross-shaft. It made a really weird noise as the pin worked it's way out and started hitting stuff in the diff like the end of the pinion. :shock: Eventually installed LSD and reworked the suspension to get rid of the hop.

 

Doug

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