matt_w

How would that cause it though? Wouldn't all the current go directly from the battery to the frame at the point of contact?

I pulled my dash to install new gauges, and I happened to notice that a large majority of the ground leads (to the gauges, a few switches, etc) are melted. The wire is still there, but all the insulator is melted. One of the big connectors on the side got melted because a ground wire running through it got so hot. How did this happen? I wonder this as I go through and repair all the damage. Did someone connect the battery backwards or something? One incident happened awhile ago where the battery slid on the tray while it was being driven and the positive lead arced out on the frame and the entire battery caught fire. I don't think that would have done this, but maybe it did? 1973 240z

Thanks for the help everyone! palosfv3, the stock weld ends right before the area where it looks like the weld is "torn", so I don't think (I hope) rewelding that part is necessary. I've put a patch over that covers the damaged part along with 1.5" on either side of unbent rail. The steel I used is 1/8", so it should _hopefully_ help keep the structural integrity. I've only tacked it into place, I'm going to test-fit the V8 to make sure there are no clearance issues before welding it on. http://matt.loadedregister.com/picz/240_frame6.jpg

Well I took some measurements, and everything seems pretty square. There was some spray-on rubberizer over the whole area, where someone had obviously tried to "patch" it. When I scraped that off, it really looks gouged up pretty bad. I'd like to know how they managed that. Maybe a mishap when they were swapping in the 280z engine? here are some better pics. http://matt.loadedregister.com/picz/240_frame3.jpg http://matt.loadedregister.com/picz/240_frame4.jpg http://matt.loadedregister.com/picz/240_frame5.jpg I think I may end up welding a plate over that area so it looks better.

Thanks for the reply! You mean measure the length that the TC rod normally spans right? How much variation can I put up with? Is there any worry about the frame twisting from suspension force if the frame is dented in like it is?

Ive pulled the engine out of my 240 and have begun preparing the bay for a v8 swap. I noticed that one of the front frame rails is dented in at 2 places, almost like someone was beating on it with a hammer. The damage is located right above a compression rod mount (see pictures). The rails themselves still look straight (from the top side), and I've welded in the Bad Dog Frame Rails lower down. Do I need to worry about fixing this? I'll be putting in an engine with a sizeable amount of torque. How would I fix this anyways? Weld a thick plate over the dented parts? http://matt.loadedregister.com/picz/240_frame1.jpg http://matt.loadedregister.com/picz/240_frame2.jpg

I moved the ring gear 10 mils closer to the pinion and there seems to be way less slop when I jiggle the ring gear around. I should have it driveable again this weekend, hopefully the clunk is gone!

I think you may be right, as I've pretty much exhausted everything else. When I did all my measurements when setting up the rear end, I found that I needed a 10mil shim to account for the smaller size of the posi unit. I bet I put it in on the wrong side

Hmm...Do you think the rear springs could be causing the noise? I was just toying around with the rear, and I noticed that several of the coils are compressed and touching eachother (when I push from the side, I can feel that they are binding on eachother). I am running the Eibach lowering springs for the 240z, but I have an R200 with an additional 20 pounds or so from the LSD. Converting to rear discs, removing the spare tire and rear bumper should have freed up some weight though. I wonder if it's normal for them to be so compressed?

I swapped out both halfshafts with some untouched ones off a 79ZX, and it's still knocking Also, I emptied out the differential fluid (It's been about 2-300 miles since I put in the LSD and re-shimmed it). There was a noticeable amount of fine metal flakes in there. Is that expected? I would guess it would be, but who knows. I'm running out of ideas. Short of something being fubar inside the diffy, the only other thing I can think of is the driveshaft not liking the slightly different angle of the R200, and going into some kind of weird vibrational mode.

Wow, thanks for the quick replies. The diff mount is newish, I didn't swap it when I put the new diff in. I know, I know, I really should have. I put the LSD into the diff myself, and did a complete backlash/runout check after, and adjusted the shimming. It definitly doesn't rub anywhere, and all the teeth look to be in good condition. I also don't have the rear sway bar in right now, and the e-brake cables have already been adjusted for the lowered suspension to not rub. I happen to have 2 spare halfshafts, so I think I'm going to swap out one at a time to see if that fixes it. I think John S might be onto something with the ujoint theory. I may not have pressed them in perfectly when I rebuilt my halfshafts.

Finally had more time to look at this problem again. It seems to be the same frequency whether I'm turning left or right. One other thing I noticed is that the knocking goes away under 5mph. Checked closely anything that would be touching the mustache bar, half shafts, or diffy. Do you think it's possible that the LSD could be causing it? I've never heard of one causing an issue like this, but who knows.

So I just got my car back on the road, and part of the upgrade was the 4x4 calipers up front, a rear disc conversion, braided brake lines, and the bigger master cylinder (this is on a 73 240z). When I go to press the brakes, the pedal goes in about 2-3 inches (I'm assuming this is an adjustment problem), and then the brakes come on REALLY strong. The pedal only goes maybe another 1-2 inches down and I can't push it in at all anymore, but it's still quite a bit ways from being all the way in. It's a little annoying because it feels like the brakes are either "off" or "on!!!!!", with not much room in between. I did play around with the plunger length a little bit (the plunger that goes into the master cylinder) when I swapped to the bigger one. So I guess my questions are: How do I adjust it so the brakes come on as soon as I push in the pedal? Why can't I press the pedal down all the way when the car is running? (I can when it's off)

Unless it's something wrong inside the diffy, it almost HAS to be a halfshaft if it's clunking at that frequency doesn't it? The ujoints I got for the halfshafts have those long grease fittings, I wonder if one of the joints is bumping against those? Perhaps under deceleration, the suspension changes just enough that the angle change of the half shafts is causing the ujoints to rub against the fitting. I'll look under there tonight and see.

Sorry, I meant the frequency is like something is hitting a halfshaft, not the driveshaft.

Thanks for the replies thus far. I've played around with it a lot more and have more info. First of all, here is my setup: Tokico struts, eibach springs. new ujoints/rebuilt halfshafts R200 rear end with OBX LSD All bushings replaced with poly Some of the obvious gotchas that I've checked: Ebrake cables rubbing on driveshafts Mustache bar bolts (I used loctite on them) Exhaust (about 1/2 inch of clearance between exhaust and rear end) halfshaft clearance while suspension is under load The knock only happens when not accelerating. So either coasting in neutral, or not giving it any gas. It sounds like something is hitting a driveshaft as far as the frequency that it happens. It's not super loud (somewhat muffled), but it's there. Also, to answer softopz, the springs are about 1/4" from the end of the insulators. This is what Eibach recommends.

I just finished putting my 73 back together. New springs/struts, an r200 with an LSD. When driving it slowly, I don't hear any noise, but once I let off the gas (doing about 5-10mph, haven't gone faster yet) there is a clunk clunk clunk sound. Not a very fast one, maybe one clunk per wheel revolution. The only suspicious thing I've found is that the rear end is about 2mm away from that torque arrestor strap mounting bar. I also jacked the rear end up in the air and let it run in 5th gear. There was a lot of vibration coming from the driveshaft it seemed like. Is it possible that the rear end is slightly off angle? Or does it sound like the problem is something else? edit: It's more of a "knock" than a "clunk". I tried grinding down the ridge in the torque arrestor mount to give me more than 2mm clearance, but that didn't fix it.

I've tried it both ways now, and the rear end is lower either way. Also, I think 2003z is just confused, because the 001 part number (which he says to put in front) is the shorter spring according to that classiczcar thread...

Mine are installed correctly, but the rear is still about 1.5 inches lower than the front. Has anyone tried the replacement "donut" from MSA to fix it, or are there any other tricks?

Looking at the pictures of your welds makes me nervous. Did you have any problems with burning through the floor? I believe the floor pans are 20 gage, and my frame rails are 12 gage. After some more thought yesterday, I was thinking the easiest way to do it would be to use your bolt idea to bring the old frame rails inline, and then spotwelding the new rails to the old ones by way of filling in the bolt holes. I realize you didn't have that luxury because your old rails were gone.

It was a helpful post (although the pictures aren't working). Im leaving most of the stock rails on (except around the T/C mount) , so I think the 2x4 approach may work better.

I got a set of these, didn't see much info on here about the 240z-specific ones. Has anyone installed them on here yet? From the pictures I've seen of the 280 rails, it looks like those mount to the side of the old rails. These mount to the part of the old rails that is tack-welded to the floor pan. The problem I'm having is that my frame is buckled slightly, so the front and back of the new rails are flush against the old ones, but the middle is off by about 1/4 of an inch. Anyone have any suggestions for this?

One of mine is 15 1/8, and the other is 14 1/2. The control arm bushings on the 14 1/2 side look like they are torqued back slightly, so it looks like the arm on that side needs to be replaced. Wonder if it came that way from the factory?

Thanks! Were they both the same length?

Really? No one can help?