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LS1 / T56 Update # 47


Phantom

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Well, something on the car has finally gone south. I've got about 20,000 miles on it since the conversion and now I have some seriously bad noises coming from the back of the car that are speed related, not engine rpm. It also is causing some vibration and I get a jerky feeling on accelleration or in sharp left turns.

I've been under the car twice now and have not been able to find any loose bolts or nuts or any indications of misalignment / rubbing anywhere. I pulled out the FSM last night - last resort is always to read the manual - right? I think I may have figured it out.

Anyone want to hazard a guess as to what the problem may be?

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Ring and Pinion, maybe? Check the sway bar mounts and make sure one hasn't broken... I'd get it on a lift and inspect it closely... Get lots of light under there and check every bolt and nut on the rear suspension, including the strut housing bolt, the strut to top hat bolt and the assembly bolts to the strut tower. Check the control arm bolts and the spindle pin bolts, along with the rear wheel bearings... Do all this for both sides, and check the Mustach bar mount nuts, along with the front diff mount bolt...

 

Mike

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Ring and Pinion' date=' maybe? Check the sway bar mounts and make sure one hasn't broken... I'd get it on a lift and inspect it closely... Get lots of light under there and check every bolt and nut on the rear suspension, including the strut housing bolt, the strut to top hat bolt and the assembly bolts to the strut tower. Check the control arm bolts and the spindle pin bolts, along with the rear wheel bearings... Do all this for both sides, and check the Mustach bar mount nuts, along with the front diff mount bolt...

 

Mike[/quote']

 

Ring & Pinion - thought about that but sound/vibration doesn't sseem right. Will check that out if I don't find the problem elsewhere.

Strut Towers - checked

universal bolts - checked

control arm bolts - checked

differential mount / mustache bar bolts - checked

Driveshaft bolts - checked

Modified torque tube bolts - checked

signs of rubbing - checked - none

 

Read Factroy Service Manual - oops - bearings that rotationally lock inner & outer half shafts together "should be lubricated periodically" Hmm - 28 years and 220,000 miles - is that periodically?

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Diff problem when accelerating or decelerating = ring and pinion.

Diff problem when turning = spider gears in the carrier.

 

At least that's usually the way. This might help:

http://www.ringpinion.com/content/technicalhelp/default.asp?pid=109

http://www.ringpinion.com/content/technicalhelp/default.asp?pid=110

 

I don't imagine that it's the halfshafts needing lube. What you're lubing in there are the ball bearings that allow the halfshaft to extend and compress. But the lube doesn't come out of them, and I pulled a couple apart and they didn't look like they needed any attention whatsoever. The grease didn't smell burnt and they were working fine. Pretty easy test would be to pull the halfshafts off and extend and compress them. If it's frozen or doesn't move smoothly I'd just replace the whole shaft.

 

Assuming the halfshafts are good like you said, I'd be looking at the diff or the wheel bearings, because suspension doesn't make noise according to speed.

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I did the basics first. Lifted both rear wheels, loosened and retorqued the lug nuts. Didn't fix the problem. Took the car in and had a top end dynamic balance done. Tires run really smoothly now but problem is still there.

 

Rear wheel bearings were replaced on both sides about 30,000 miles ago. When they were bad the noise went away when I was in a corner. That doesn't happen now and this is a different noise/vibration than I had then. I don't think it's bearings but I will recheck them.

 

The car goes on a lift the end of this week. Right now I'm thinking it's either the half-shafts or the differential but will go through everything after the transmission again just to be sure.

 

In the meantime I'm an unofficial JSR member.

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Well, so much for my second post on this thread. Turns out one of my Spicer 'Brute Force' u-joints had given up. The drivers side half-shaft had one missing a chunk of steel. Since they had only about 20,000 miles on them I have to attribute the failure to the severe axle hop I induced more than just a few times during that 20K. I couldn't see it it just looking at it - eveidently it was on a side away from me. The joint didn't rattle or appear damaged until rotated then it manifested a little abherent behavior which led to a closer inspection and the discovery of the missing piece. It was replaced with another half-shaft with a used Datsun universal on it so I won't be doing any extreme stuff for a while. I now have to decide if this was a fluke and just rebuild my old half-shaft with new u-joints, or do the CV conversion.

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bill, i'm using the 280zxt cv joints with the adaptors ross has at modern m'sports. when one of the rubber boots split while i was at watkins glen [just a few weeks prior to the convention] i discovered that no one makes parts for them anymore. too bad i found this out after i converted. luckily i was able to get them rebooted. they also inspected the cv joints [great shape] and relubed them prior to the reboot.

 

i'd go with the 300zx cv conversion. the place that did the [above] work said the parts for the 300's are plentiful and more common and they don't anticipate they'll go away anytime soon...fwiw.

 

of course, there's always the questionable clutch footwork / driver input that caused the failure...lol

 

david

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