1976 280Z Restoration Project

[Zed Head]

6 hours ago, wheee! said:

Mines an '83 (I think)... I prefer the top end cruising over the tire squealing...

Edit: I just looked back at page one of the thread and realized I called the tranny a 78... even though I was sure it was an 83...! Is there an easy way to tell from the outside of the transmission?

The very easiest way is to look at the exhaust system hangers.  The 81-83 ZX transmissions have one, the early 5 speeds have two, one on each side.  The early 3.321 1st 5 speeds came with a 3.54 ratio rear.  Here's an 83 ZX 5 speed...

 

 

[wheee!]

Well this pic spells early model...

[wheee!]

Good friend Taka stopped by and brought me a gift! What a nice guy..!

Pedals complete!

 

Edited August 9, 2018 by wheee!

[Zed Head]

2 hours ago, wheee! said:

Well this pic spells early model...

I think you'd be fine with a 3.7 rear.  Yours has a 3.321 1st gear.  3.7 x 3.321 = 12.29.  With your cammy engine a little more ratio might make it a nicer drive from a stop.  And with a smooth running engine even the four speeds are pretty nice at higher RPM.  I got my 5 speed mainly because my engine was running rough and I didn't realize it.  High revs seemed to be working the engine.  After I got a better engine with better parts I often forget to shift in to 5th. 

You won't really know until you get it on the road.

[7tooZ]

16 hours ago, Zed Head said:

I think you'd be fine with a 3.7 rear.  Yours has a 3.321 1st gear.  3.7 x 3.321 = 12.29.  With your cammy engine a little more ratio might make it a nicer drive from a stop.  And with a smooth running engine even the four speeds are pretty nice at higher RPM.  I got my 5 speed mainly because my engine was running rough and I didn't realize it.  High revs seemed to be working the engine.  After I got a better engine with better parts I often forget to shift in to 5th. 

You won't really know until you get it on the road.

Hey ZED

So you factor the two numbers to get a result of 12.29. How would I use that number? Is there a optimal number to measure to?

Thx something new to learn.

Don 

[Zed Head]

It just gives you the final ratio of the transmission/differential combination.  I use first gear because that's where people notice ratio problems first, taking off from a stop.  Passenger cars are usually around 12 because their tires are the same size.  A truck would have much higher ratio.

Nissan went to a 3.9 when they changed first gear to 3.062, and ended up in the same general spot.  They went to a much higher number with the heavier 300ZX.

Early 280Z (2975 lbs) - 3.54 x 3.321 = 11.76

Late 280ZX (2824 lbs? [probably 1979]) - 3.062 x 3.9 = 11.94

1989 300ZX  (~3000 lbs?) 3.321 x 3.9 = 12.95

Got some weights from the internet and they don't really fit.  So who knows why they changed the ratios.  

Edited August 9, 2018 by Zed Head
Added some internet weights

[7tooZ]

Interesting. I have never seen that before. I am going to go back and look at what my early 4 speed and diff was. Thanks for the brain tease


72 body and block, everything else 71, Tokico springs, Illumina, R180 CLSD, 83 close ratio, 3.90 gears, Ztherapy SUs, BRE 15X7 Libre wheels and BRE front spoiler.

[7tooZ]

My apologies for stealing the post for a moment


72 body and block, everything else 71, Tokico springs, Illumina, R180 CLSD, 83 close ratio, 3.90 gears, Ztherapy SUs, BRE 15X7 Libre wheels and BRE front spoiler.

[wheee!]

All good. I’m in for the conversation!

[wheee!]

So I have still been picking away at things but not a lot during the nice weather. I have been spending some time with the grandkids and the wife while the sun has been out. I few developments to report though:

1) I have decided to leave the R200 CLSD as is. The 3.70 ring gear is going back on as I do not trust a redrill of the 3.90 ring gear to fit the larger M12 thread versus the M10. Not worth damaging a ring gear if I can live with the 3.70. The CLSD will go back in with fresh paint and seals, then I will rebuild the 3.90 as an open diff for now. That means I have to prep the new R200 diff case and housing for paint. This is not too big a job but...

2) I tried to powder coat the stripped and blasted finned R200 diff cover with chrome powder coat. The blasting and powder coating went on flawless and I had pre-baked the cover to help cleanse the porous cast aluminum. Didn't work... The cover came out of the oven like a bubbly wrinkle coat from all the off-gassing. arrghhh. Now I had to start over, media blasting fresh hardened powder coat off the cover!! Three times the work of a regular painted cover. No pics of the disgusting powder job after baking.

3) Took a few days to help out the son-in -law get a car ready for resale. A 99 Camry with low kilometres but a little bit of body abuse. Needed a new front bumper and some paint detailing. Spent about 8 hours sanding and polishing the clearcoat on his car, then painted his replacement bumper from a jobber in town. I was happy to do this because I wanted to test my paint skills. The results were excellent considering I painted outside on a cool day with no paint booth etc. The clear went down like glass. Raw urethane black bumper was sanded, primed with flex primer in grey, degreased and sanded with 600 grit, sprayed with 3 coats of urethane base coat gold and then three coats of urethane clear. Very happy with the results and this gives me great confidence in spraying the rest of my car when the time comes.

4) Plan going forward is to paint the diff cover with an anodizing silver engine paint and the diff itself in an engine enamel black. I hope to have it reassembled and installed in the next couple of weeks. Hopefully by then, AZC will have the rear brake brackets I need to get the car down on its wheels and I will finally have a rolling chassis again after 3 years of rotisserie!

Edited August 27, 2018 by wheee!

[wheee!]

So I tried the paint out on some scrap metal to see the anodized effect. Crap. 

I decided to go give powder coat another try. This time I heated the part to 400 degrees and then placed it on the powder coat rack. I then sprayed powder on the hot part to avoid the off gassing. I am happy with the results and can live with this. 

[ksechler]

Nice work on the Camry.  I think you're ready to give the z a go.  I can't wait to see the finished product.  Nice job on the diffy cover too!