Datsun 521 Transmission Puzzle

[JackSun]

Hello everyone,

 

I'm new here so you'll see me coming here more and more often. I've been enjoying the Datsun pics and info on this great forum.

 

I've got a 1971 521 and when I got it a few months ago (April) it was slightly leaky, when I brought it home, and it was an altitude difference, it bled out. When it ran, the exhaust smoked plenty, between the mess underneath and inside w/ oil, grease, mud and grime and the smoking which told me it needed a new head gasket, I decided to pull everything out and clean it all up and reassemble w/ new gaskets and seals.

 

I found the rear end of the transmission where the shaft output was frayed and warped. It was some strange damage that I can't seem to find anything online about such a problem for comparison. I took it to a buddy who's a transmission expert at the auto dealership I used to work at and he has not seen damage like it. The big question was of course whether it was critical or not. The coconscious was yes but who knows how long the truck got by like this, it still seemed to retain lots of oil in the gearbox area when I drained it. Over the past few months I've searched for replacement end/output area housing for the transmission. It's broken and frayed where I think a collar would have held a seal. I've no considered finding a whole other tranny but all searches prove fruitless. I suspect now that maybe this transmission is similar to the ones in the later 620 but I don't know for sure, as diagrams, pictures and info on 4 speed manual transmissions in 1971 521s seems very limited, I very frankly don't even know what model of transmission I'd be looking for, if I were to get another.

 

I've talked about the possibility of getting a machine shop to McGyver something up so dirt does not get up in there. Maybe it's not as bad as I think it is as the truck ran before without but something obviously tells me a gapping hole around the shaft in the back of the transmission won't work for long. I really want to avoid replacing it to begin w/, gears and all check out fine. As tempting as it is to hotrod this and drop a non stock engine and tranny in it would defeat the original purpose of this truck as a practical little economy fix'r upper get around town working truck. Plus I don't really have the equipment or know how to do all the cutting or non stock custom modifications.  :geek:

 

Long time Datsun Z owner, just now getting into the trucks and learning the ropes.

 

I'd like to post photos of the kind of damage I'm trying to describe but I've yet to discover how to post photos here on this forum. I looked at the how to instructions, posted here but it seems that it might only work if I had a photobucket or some kind of pic sharing site. I just wanted to keep it simple and attach images of the truck from my computer.

 

Anybody w/ any insight or advice into this crazy transmission mystery would be much appreciated. :confused:

 

Thank You :thumbup:

[MicroMachinery]

I don't know what advice to offer in terms of repairing yours, but I will say that the later 620 pickups have a different transmission that wouldn't be as simple as you might think. As far as size, the 521 and the 510s of the same era utilized the same transmission case, but the gears were somewhat different. Also, if you were to find a 510 trans that you wished to make work, you would need to remove the output shaft flange from the 521 trans(you'll need to remove the retaining nut), install a freeze plug(40mm, I believe) into the hole where output shaft protruded, along with some RTV to keep it sealed. It just slips into the output of the 510 trans, but doesn't bolt down like the 521 does(hence the plug to keep the oil in).

[bananahamuck]

These are what Micro is speaking of ,,, The top 2 are early 510 and the bottom is 521 ,,except you can't see yolk/output thing in picture. 620 trannies (except for very early ones) are longer.

 

mixing and matching to make one non rattling/clanking leaking trans







 

 

 

 

What part of this is frayed?  Seal or the Aluminum housing

 

I realize yours has yolk on it but i don't have picture of one of those without effort on my end.

 

 

And a Oreilly`s u-joint was installed

 

[JackSun]

Thanks for the help so far. A friend found an online manual. Looks like a F4W63. It looks like what I'm really after is the extension housing, lots of seals out there but nothing for the housing part.

[JackSun]

The frayed part is the aluminum housing. The seal is gone, it's like it was broken off. It's very strange.

[datson4life]

I don't know what advice to offer in terms of repairing yours, but I will say that the later 620 pickups have a different transmission that wouldn't be as simple as you might think. As far as size, the 521 and the 510s of the same era utilized the same transmission case, but the gears were somewhat different. Also, if you were to find a 510 trans that you wished to make work, you would need to remove the output shaft flange from the 521 trans(you'll need to remove the retaining nut), install a freeze plug(40mm, I believe) into the hole where output shaft protruded, along with some RTV to keep it sealed. It just slips into the output of the 510 trans, but doesn't bolt down like the 521 does(hence the plug to keep the oil in).

Ok i skipped the freeze plug part, im leaking fluid everywhere, went from stock 521 4 speed to 710 4 speed, i dont understand the freeze plug part

[MicroMachinery]

The yoke will have a hole straight down the middle where the 521 output shaft protruded through, and was secured by a nut. Now that you've removed the nut, and you're using a shorter output shaft(one that isn't threaded), there will be an open hole for the fluid to migrate past the splines then out the hole.The hole can be plugged with a 40mm freeze plug(or "expansion plug"; the ones like in the side of your engine block). We just did this on my buddy's 521, with a 510 trans that I gave him. It will look like this:

 

As opposed to this:

[datson4life]

Ohhhhhhh, thank u very much, i will get to it asap so i can finally drive it lol

[datzenmike]

 

All of these are F4W63 4 speeds. They could be from a '68-'73 510 sedan or wagon, an early 620 truck up to '74, and 710 or the A10 cars. None are definitely for a 521 as they don't have the bolt on spline pictured here...

 

 

... but they will work when plugged as MicroMachinery showed.

 

If you want the exact same gear ratios, then the 510 wagon or the early 620 is desired. The car ones don't have as a low a first gear, but will work just fine.

 

If just looking for a replacement tail then any old F4W63 will do including the earlier 520 with the J13 engine.

[JackSun]

Lots of good info here. Thank you I've been thinking about the modification alternatives over the past few days. This gives me a better idea of what to look for. Biggest challenge so far, and this is to be expected is just simply finding the right stuff to work w/. Datsuns are so few and far between in the this part of the country, thus so are parts. Without shipping a transmission from elsewhere, options seem limited. The most abundant in Colorado are old Z parts. I located a '72 521 in the middle of nowhere which could be a suitable parts donor, once in a blue moon a mini truck related deal comes up for sale in Denver. It's tempting to go after a cheap donor, since nobody else wants them, just so I'd solve the tranny issue (providing it's trans is not compromised at the extension housing) and have an abundance of parts for other unforeseen but potential problems. Minus the situation of additional truck carcass outside taking up space. I want to walk into some guy's garage and buy a stand alone transmission that will work w/ some mod work but even those alone are rare here. Also rare, people here who have much knowledge on Datsun related stuff. Unlike Cali, just not much Datsun help period. I have one buddy whom works at the GM dealership I used to work at, whom back in the day worked w/ them, he sent me entire online manuals. I'm truly out in no man's land on this one without this forum.

 

It's a crash course fun and interesting learning experiment, playing around w/ the 521 but also a headache where I live, guess this is what happens trying something different, this is a truly a one Datsun town. I'll keep at it and get this solved sooner or later.

[JackSun]

I should say by "abundance" - actually the largest inventory you'll find in the state (which is only an handful) is old Datsun Z parts, so for many other obscure/rare models found regionally, I'm SOL or up the creek without a paddle if I expect to find these parts locally. :rofl:

[datzenmike]

A later long tail 620 or 280z/zx and Maxima 4 or 5 speed is also an option it just won't drop in. If you got one cheap you would need to mod the rear mount and shorten the front driveshaft. Once converted over you could replace it forever with Z trannys.

[datson4life]

The yoke will have a hole straight down the middle where the 521 output shaft protruded through, and was secured by a nut. Now that you've removed the nut, and you're using a shorter output shaft(one that isn't threaded), there will be an open hole for the fluid to migrate past the splines then out the hole.The hole can be plugged with a 40mm freeze plug(or "expansion plug"; the ones like in the side of your engine block). We just did this on my buddy's 521, with a 510 trans that I gave him. It will look like this:

 

As opposed to this:

I have one of the expandable rubber ones, do u think it will hold, or should i get the normal pound in ones?

[datson4life]

Oh nevermind, just read u put (or expansion plug)

[datson4life]

Nope,expandable one is negative, ill keep at it tomorrow

[datzenmike]

If it truly IS rubber the trans oil will soften and dissolve it.

[datson4life]

Ur right datzenmike, plus it wont fit, double fail

[datson4life]

Thanks for info fellas, should be dalying it soon now

Sorry for thread Jack

[JackSun]

The good news is I have found a 510/521 transmission for sale thanks to a friend whom sent me the link of one for sale. The guy is getting rid of it for a reasonable price, took a look and the extension housing is intact. My next option was going to be what King Rat recommended. Z trannys as that's about the only thing that can actually be found physically where I live, to which without dissecting or seeing it run in a vehicle I have no idea what condition the gears inside are in. W/ this one I'll have the housing covered and I know I have good gears on the one I have already, on the replacement, some are slightly rusted, of the ones that can be salvaged I'll just keep the duplicates for spare parts. Seems like a sure plan.

 

This was a rare lucky find indeed. The guy whom found it also saved my bacon on my Z car, or I should specify, saved the dealership's bacon on that one, I just waited for it to work before snagging it off the B lot and for employee discounted pricing. He was the only guy in an entire GM car dealership that could solve the problem w/ my '83 ZX. - It took what seemed like an army of GM certified technicians to bumble and tumble around w/ the 280ZX for a few months (September - November 2010). The dealership was duped into the deal and found themselves stuck w/ it unless they could make it run. Load and behold the guy whom just located my transmission also located the needed replacement part (an ECM unit) and made the Z run, the others just cried and whined about never making run. He's a life saver.

 

The first problem is was an obvious one (An army of GM technicians + Datsun 280ZX = Something that sounds like an intro to a bad joke)

[datzenmike]

If replacing the 521 4 speed be sure to replace the rear output seal. It's easy, only $5 and put some oil or grease on it before slipping the spline on.

[Oregon_PLG222]

Which year 5 speed from a z car works?

[Oregon_PLG222]

Does a Borg-Warner T5 transmission from an 82-83 Datsun 280zx fit in a 521?

[DanielC]

Any transmission off any L engine will bolt on to a L-16 .   Keep clutch, pressure plate, throwout bearing, AND COLLAR with the engine.

the 521 originally had a shorter transmission.  To accommodate a longer transmission, the rear transmission mount will need to be modified, the drive shaft shorted, and a yoke that fits the transmission you are using need to be mated to the 521 driveline.  the speedometer cable may need to be changed to a longer one.

[datzenmike]

None of them 'work' if you mean 'drop in'. The 521 4 speed is 26" long. A 280z or 280zx non turbo 5 speed is 31.5" long so the driveshaft will need to be shortened and the rear mount modified.

 

The FS5W71B 5 speed was introduced as an option on the '77 280z and the 620 truck. It came with three gear sets... wide*, mid** and close*** ratios.

 

'77-'78 280z**

'77-'78 620** '79 620*

'80 720 2wd*

'79 290zx** '80-'83 280zx non turbo***

'78-'80 810**

'81-'84 Maxima**

 

All these 5 speeds are the same length and will bolt to any L series engine.

 

Does a Borg-Warner T5 transmission from an 82-83 Datsun 280zx fit in a 521?

 

 

If you saw one you wouldn't ask. They are longer than the FS5W71 and larger around, specially at the bell housing end. It was only used on the standard 280zx turbo cars. The output spline is different than the 521's driveshaft also.

 

FS5W71B...................................................... FS5R90A (Borg/Warner T-5)

 

[Oregon_PLG222]

Thanks for the great information. You guys are the best! I have read pages and pages of pages of posts about the 5 speeds and 521's. So much that my head hurts and I can't keep it all straight.

 

I found the borg transmission on craigslist this morning cheap (like $60) and wasn't sure if it was one that works.