JMortensen

Clean metal, prepped with brake cleaner. Most of the metal had been hit with an angle grinder + knotted wire wheel, so should have been plenty of grip available.

FWIW, I used Rust Bullet and scuffed and prepped and it did flake off in fairly large flakes. Could be my prep wasn't up to snuff, but I'm no longer a fan.

FWIW, I have an aluminum 5.3/T56 in my early 240. Pre swap was 49.5F / 50.5R with me in it, after swap is same weight within 2 lbs, but 52/48 with driver weight, so more front heavy. This is with the engine 1.5" from the firewall, but also has a heavy plywood splitter, heavy aftermarket PS rack gigantic wheels and tires, etc. With iron block should be closer to 54/46ish. You can make that handle if that's what you're after, just takes some working with alignments, etc.

There has to be some angle; the angularity is what rotates the needle bearings in the u-joints. Without the angle the power will be applied to the same few needles over and over and they will fail quickly. Occasionally you'll see this come up when someone makes their own mounts and decides to "fix" the driveshaft angles by not having any. Sounds good but doesn't work, unless you're running a torque tube without u-joints like a Vette or a 944.

There are some old threads on using laser pointers. I don't think you'll find a spec as to what the angle should be, but you will find some info on how to adjust. I am just horrible at math, so I did the laser pointer thing and basically shined lights from the diff and the trans on a piece of paper in the middle and then moved the trans mount until I could move the paper back and forth and the distance between the dots hardly changed at all. Basically held up the piece of paper, marked the dots with a sharpie, moved paper and tried to line up the dots again at the new location. When I got a minimum of movement of the dots, I called it good and welded up my engine and trans mounts to keep that angle. You can do this more accurately with trigonometry if you're less retarded than me. Regardless, my math avoidance workaround was successful, no vibrations with V8 offset to pass side, T56, R200, very short driveshaft (cyl head is ~1.5" from firewall) I want to say CTC on the driveshaft u/joints was 19". The problem with just the vertical angle measure is that the trans and diff might not be parallel to the center line of the car, and they are probably also not perfectly in line with each other.

I don't know what kit Z Car Depot is selling, but I've heard bad things about the cheapo RPM kits, and my friend had hers rebuilt 3 or 4 times due to bad synchros with that kit. It's been at least 20 years, so thinks may have changed, but I think factory Nissan synchros was the answer, the bearings in the cheap kits were fine buy synchro rings weren't up to snuff. EDIT--the other tricky part was the nut at the end of the mainshaft. Seems to have a propensity to loosen, despite being staked. My plan with mine was to tig weld the nut to the shaft in a couple spots and hope it didn't warp the shaft too much. Wonder if you might be able to tighten and then drill a hole and put a roll pin through to keep it from moving.

For now, since you still have the L, just get a 280Z shaft. It will be the right length, and you can try and match up the bolt pattern to your diff flange. IIRC the 280 diff has different bolt pattern than the Z31 R200. That NEAPCO part that Ben referenced is for when you get the big power motor in the car. Then you'll need to swap the transmission, and at that point you'll go to 1310 joints, use that flange and have a new shaft built. I think Ben's transmission uses standard American car stuff, so he probably has Camaro or similar slip yoke, that NEAPCO end on the diff side, and then a custom steel or AL tube in the middle. That's what I did on mine too (steel because it was cheaper and the weight difference was like 2 or 3 lbs), but you're not there yet. EDIT--Thinking maybe your 240 shaft will bolt right up to the R200? I remember there was one or two years that used 10mm bolts instead of 8mm. I think the rest is the same though???

That "cradle" from TTT looks insufficient to me as well. I'd run both if possible while working on a different solution. YMMV.

The thing that worries me most about any shortnose swap, Nissan or Ford, is the front mount. Any mount that attaches to the front of the diff and then to the strap holes in the chassis is insufficient, IMO. Having "arms" that are attached to the strap holes essentially gives the diff more leverage to rip the chassis apart, and we've had several members tear up the strap hole area of the chassis, which is probably the strongest part of the whole unibody. Needs to be a cradle that holds the entire diff, and attaches to the strap holes in front and the mustache bar bushings in the rear.

Checking backlash is simple but requires a dial indicator and magnetic base. You stick the base somewhere on the housing and aim the dial indicator at one of the ring gear teeth, perpedicular to the tooth face, then you just rock the carrier back and forth and watch the gauge. Good idea to do it in 3 places around the ring gear after as this also double checks that you have the ring gear on the carrier straight. I've never tried, but I'd bet you could get the bearings on with a hammer and a socket if you didn't have a press. Or, $150 is pretty reasonable cost to have it done. As far as the ebay auction LSD, looks like a 2 way. This video explains ramp angles, etc.

As to the different "ways": 1 way works on accel only, does nothing on decel. Usually found on FWD cars. 1.5 way works full power on accel, does a little on decel. Good for road racing, autox, canyon driving. 2 way works equally on accel and decel. Good for drifting, road racing, etc but going to be looser than 1.5. 1.5 way is the best choice, that said the Nissan LSD is 2 way and I've been using them forever for autoxing. Would rather have 1.5, but not worth it to spend the money and change it out for me. Be careful out there. Canyons are unforgiving.

If you're even moderately good with a wrench you can install an LSD. The tough part about differentials is setting pinion depth, and you don't have to get into that at all to put an LSD in. I did a write up on it:

Agree with Ben. It's all about the tires and the launch. If you're drag racing, spend the money and go 8.8 (I'd do that over 9 or R230). If not, the R200 is probably good enough but you really will need the chromoly stub axles to finish it off, at which point, you're coming pretty close to the cost of the 8.8 swap.

70 240. When I put it on the rotisserie, I found the firewall splitting from the cowl, rust.

Totally agree, and thought I'd throw my $.02 in as well. Re: front strut bar, I did my own about 20 years ago and I've relayed the experience many times, but after installing I took a test drive on my favorite curvy road and nearly drove off the inside of the road because the front end responded so much better. Night and day. People tend to think that the strut bars hold the strut towers apart, and it might do that when you go over bumps, but when turning the load comes in at the bottom of the tire which pulls the top of the strut tower out, reducing neg camber. So strut towers help to preserve your static neg camber setting under load and that's why the front end grip is much better. Learned this out of a Porsche Owners Club magazine where they had tattle tale dial indicators on the struts and did some skid pad testing before and after. From personal experience I would suggest that the Z chassis is VERY weak in beam loading (fore/aft). When I used to put my car on jackstands I'd set them under the TC rod boxes and I could literally watch the front end droop about 1/2" under the weight of the motor and hear the metal creaking. When braking at 1g and the forces trying to both pull the front strut towers forward while simultaneously folding the car in half around the firewall are much greater than the static weight of the motor. I'm not convinced that subframe connectors do a whole lot to help, either, even though I have them on my own car. There needs to be a strong load path between the front and rear struts that prevents a lot of flex under braking. To that end, any well designed cage for a Z should connect the strut towers front and rear, IMO. Can be done through door bars, or with bars down the center of the car, but I think it's a shame to build a cage and not take advantage of the opportunity and I always shake my head when I see a car that has main hoop supports that don't connect at the strut tower. I'm also increasingly convinced that I did my front strut/firewall supports in a suboptimal way, and that an X from the strut towers to the dash bar with the V's connecting at the firewall is a better way to go than a V to the middle of the dash bar like I did. Eliminates the need for the bars down the middle of the car to connect the front and rear struts. This encroaches on the space above the engine and might make it harder to get the engine in and out, so I'd do a bolt in V in the engine compartment and weld it in on the interior side.

I have a very similar setup from the strut towers to the center of the dash bar. The center of the dash is not the optimal place to terminate those bars. There isn't any structure there, it's the middle of a span, no node. I made it a node and sent the load to the diag in the main hoop and then down to the rear strut towers in this sort of arrangement >---< and that works better. It also is pretty similar to a wood model Herb Adams shows in the book Chassis Engineering. Dr Sideways (can't remember his real name) has a similar dash bar and he did it better, with an X between the main hoop and the door bars and a V to the rear struts. Precludes passengers though.

You might want to check the crossmember for cracks. Plenty of ITS racers end up cracking the front crossmember that holds the diff mount with a weak 6 cyl.

I did a FAQ post on diff clunks that might help. Sounds like you've been over the most common causes. On the tires, make sure they're dynamically balanced with weights on both sides of the rims (if needed). I've actually had the OWNER of a tire shop tell me that his tire balancer does a dynamic balance with weights only on the inside of the rim. He told me it was a dynamic balancing machine, and therefore only did dynamic balances, even if weights on one side. Dumbass. Just on the off chance--I had a weird issue with what I thought was a balance issue on my Z, turned out to be a slip on wheel spacer from the auto parts store with a pilot hole that was .005" or something like that too small ID. It LOOKED like it was on flat against the hub but when I tightened the lugs it would warp and cause what felt like tire balance issues. Finally switched to lugcentric spacer from www.colemanracing.com and that solved it. dpracing.com carries good spacers too.

I made shorter CV shafts for this purpose. Stopped making them maybe 10 years ago, but gave the technical drawings to www.modern-motorsports.com and Joe over there still makes them. http://www.modern-motorsports.com/z31-half-shafts.html On my own car I made custom LCAs that were 1/2" longer than stock (did this before I made the shafts).

A rare triple post!

My understanding, which has been reinforced through conversations with an engineer who works on automotive safety systems, is that a 3 point is designed to let your torso rotate which is what prevents you from submarining and sliding out under the lap belt. A 4 point doesn't let your torso rotate, which is why you need a 5 or 6 point to keep you from sliding out under the belts in an extreme accident. 4 point is actually less safe in a front end collision than 3 point. FWIW, having rolled a car (went over many times, BTW) while wearing a 3 point, my experience was that the shoulder belt fell off of my shoulder and I ping ponged my head on the roof and door frame as the car went over. It was not fun, but my passenger and I managed to walk away with VERY minor injuries. Cheated death for sure. The pass side of the car took all the hits and my friend realized the roof was getting closer to his head, so he put his hand on the roof and leaned the seat back mid roll! So if you're the 1 in a billion person with that kind of presence of mind, 3 point might be safer in a rollover with no cage. If you're just going to scream on the way down like I did, scream something to the deity of your preference and hope that works is my advice... Regardless of the aesthetics, that seat design sucks. Get something non-sucky. There are lots of seats with a channel in the bottom corner so that a standard lap belt will not be held away from your pelvis.

Ride the brake and gas up to the line. Re the blues, my friends were running 510s, but I recall they didn't do much until hot like the R4. Maybe I'm wrong, maybe they upgraded the compound since the 20th century.

I went with Hawk Blacks based on Coffey's recommendation. He was saying they work on the big tracks and at autocrosses, although I think he ran at Willow Springs a lot which is not hard on brakes. So far I can confirm that they work at autox without heating up. Hoping they'll be OK on the track with some big ducts. Back in the late 90s I was running Porterfield R4 and friends were running Hawk Blues. Both had to get warm before they worked. Not safe on street.

So you had brake temp issues? Boiled fluid or just cooked pads? Want to go out there this year, have more power and weight than you with 12.2 vented rotors and working on good 3" vents in the front.