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Troublesome Tranny Tale


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I bought a 620 a few months ago and a 280zx 5-speed a week later and my next couple weeks were all laid out in front of me. I've never done any major work on any cars I've owned, but that's partly why I bought the truck :). I got lucky and was able to use my girlfriend's parent's garage (and her dad's tools).

 

First I decided to open up the 5-speed and see how it looked (partly just because I wasn't straight on how everything worked). Getting it apart was an adventure in and of itself... bent a forged wrench getting the front cover off. First bad thing happens: the residual fluid had apparently dripped off the top of the driveshaft while it was stored and the whole top side rusted. The 1/2 gear selects and rings were badly pitted and all of the gears had at least some mild rusting but looked OK. Should have stopped there and demanded a refund... *sigh*. Putting it back together was fine, except I was too anxious and didn't order a new front cover gasket. I kept the old one and sealed it with a little Right Stuff so I don't know if the shim that was in there is big enough.

 

Getting the 4-speed out was a piece of cake, I drained the fluid, sawzawled the tailpipe, removed the driveshaft, loosened all the bolts, no prob (I think DatDoug did all the hard work for me). I even wrestled it out without all that much of a problem, I don't know how. But getting the 5-speed in? Ouch. I only had a floor jack, and I must have spent an hour trying to fit it in between the torsion bars. Finally with my gf's dad's help, and only after putting it in almost upside-down, I got it into place. Then *WHAM*, my knee spasms and locks while I'm supporting the tranny entirely with one arm. Totally random, and it hasn't happened since I was 12, but it took the entire night to relax straighten out.

 

Well, the rest went pretty well, except the muffler place didn't have any joints and so they just welded it back together and I'm going to have to cut it the next time I take it out.

 

Test drive! eeeeeeEEEEEEEEE, eeeeeeeeeeEEEEEE, eeeeeeeEEEEEEE... FUCK!

 

It whines like there's no tomorrow. I guess the gears with the rust were't fine after all. Now it's been a month and I can't stand it! A little bit more of my soul dies every time I accelerate... I bought some MoS2 and some new gear oil, but no change. The 2nd gear syncro is fucked too, I have to hold it just outside of 2nd for a second every time I shift into it.

 

Even worse, it's got the shortest 5th gear ever, and combined with a truck's differential, I basically cruise at 45 mph down surface streets in 5th. And I bought it for road trips!!! ARGHHH! Oh yeah, and my gf's parents moved, so even if I had the money, and a new 5-speed, I wouldn't have a place to swap it out. *curls up in fetal position on floor*

 

It was pretty fun though, all in all. :D

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1) the first thing that goes out on a 280Z/280ZX transmission are the 2nd gear syncros. I drove mine like that from 132,000 miles to 232,000 miles until the rest of the tranny let go

 

2) Short 5th gear is the same as a Datsun truck's short 5th gear. You got a 1979 Z tranny or earlier. Should have tried for a 1980-83 which had a lower rear gear in the car so 5th gear in the tranny was taller.

 

Sorry to hear that it whines. Use thicker oil! :D

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They won't rust just sitting. This one was outside and must have filled with rain water. If it was rusty at the top it was stored upside down. The bearings are probably rusty too and causing the whine. Any way to take it back and get another?

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I syncro isn't a big issue for me -- not yet, it's the whining I can't stand.

 

I don't think it's the bearings that's making the whining sound, because only 1st, 2nd and 3rd gears whine. I think it was just stored for a really long time and the oil slowly dripped off of the top of the gears. That, and maybe the speedo pinion or switch was not sealing it from the outside.

 

On a side note, I bought this from a kid in Renton and he said that it shifted fine, and was in good condition -- obviously not the case. How can I go about making sure it's decent next time?

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On a side note, I bought this from a kid in Renton and he said that it shifted fine, and was in good condition -- obviously not the case. How can I go about making sure it's decent next time?

 

Drain the tranny, if rusty water comes out start walking, if the oil looks like yogurt but is grey, start walking, unscrew the bottom 'bung'. It has a magnet that collects metallic powder and filings. All trannys will have some black metallic 'paste' but if it has gear chunks (even small ones)...... start walking.

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Drain the tranny, if rusty water comes out start walking, if the oil looks like yogurt but is grey, start walking, unscrew the bottom 'bung'. It has a magnet that collects metallic powder and filings. All trannys will have some black metallic 'paste' but if it has gear chunks (even small ones)...... start walking.

 

Hu hu.......you said BUNG!

images.jpg

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Funny thing about the 4-speed, I thought I could swap out all of the gears and the synchros into the 5-speed... I only realized after I pulled the countershaft bearing that it's all one piece and can't be used in a 5 speed. shit. Anyone looking for 4-speed parts?

 

I really just want to get a new 5 speed. Does anyone have a post '81 280zx 5-speed they'd like to sell to me? :rolleyes:

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Sounds like my tranny. It makes a whines in the same gears, its been doing it since in installed it.. I took the speedo gear out because I thought I had the right one... I didn't.... When I pulled the gear out a bunch of metal shavings fell out :eek: My fix is turning up the tunes :D My Ipod broke a few days ago :( so I may be installing a new tranny to :D

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I threw a '81 ZX 5spd (the one with the numerically low OD) in my 521. LOVE the overdrive.

Then I swapped to a 3.90 rear end from a 720. That may have been a bit too much. :blink:

At 3k rpm, I'm doing about 72mph. She'll cruise real nice at that speed, too. But as soon as I hit a hill, it's either WOT or downshift.

But 4th gear seems too high revving for me. Don't want 4k rpm at 55mph!

 

And I'll probably be swapping trannys again this year. My input shaft bearing (I think) is bad, and is noisy as all hell. And the gears whine :D

 

Anyway, my 2 pence.

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Even with 4.88s and a 4-speed you aren't turning 4K at 55. Not even at 60, unless you're running clown car tires. My Mom's '73 620, all stock (4.88s and a 4-speed) just bumps 4K at 65MPH. Sounds like it's revving through the roof but that's pretty much in the L16's happy range (until the cam went flat, but that's another issue). I've had several tachs in the truck, I almost never saw 4000 on the freeway (at 70 the front tires wanted to float).

 

But 3.90s and a ZX overdrive... be turning just over 2300 RPMs at 60. WAY off the power band. Downshifting to 4th only pops it up to 3100.

 

I have the ZX trans in my '76 KC with an L18, but the stock 4.375 rear (same as a L-series 521). 35MPG highway, but it's gutless. Like merging on the freeway with a 4cyl Chevette (ok, not that bad. BTDT).

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You're right. 3000 @ 55. Sorry :o

And it IS way off the band. It'll pull hills at 75mph in 5th, but at 55mph it's chugging pretty bad. But cruising flat straights it's pretty happy at ~65mph.

I'm trying to decide whether to just find a cam with better torque, or to find a 4.88 rear gear.

Thankfully it's an L20, so it's got some midrange grunt. Call me strange, but I don't like pushing this motor to high rpm.

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