First question for anyone that knows:

My son's 6 of '71 ('72) 240 is getting an R200 with a 3.9 ratio. When I went to service and make sure of the gear ratio, I found this:

The main large ring gear is stamped with the 39:10 ID but what I don't get is the smaller internal gears; they're welded together. Is this a LS differential that has been "cured" of potential breakage?

Secondly:

I bought a T5 to replace the four speed. I think I should have bought a non Borg Warner five speed "Type B" instead, but I'm not sure. From what I've read through many a thread and blog in order to avoid sounding like a whiner who doesn't want to do the work, was that a T5 is better matched with a 3.545 rear ratio, or 3.7. The assumption that first and second gear will burn rubber too easily was met with approval from my son; strong approval. But I'd like to know any other concerns anyone may know. Is first gear going to red line the turbo we're putting in too quick? Second as well? I believe I've understood this potential as one of the drawbacks... I guess I could let him blow the motor and learn some more valuable lessons...

The T5 is identified under the shifter with these markings: R1, then under that 13-52-066-903, the the Borg Warner markings. Under that but forward bolted to the housing is a metal tag reading: 052-004 space 24379 (I can't read what the number is above this on the tag...). Above on the top of the middle housing reads Basic 1, 13-51-097-901. Lastly, on the front section top reads 6Z 791

From what my son found on a link provided by another member, I believe, is that this BW was made for the 1983 turbo.

We are putting in an '83 turbo.

Thoughts and feedback are much appreciated.

BTW:

Here are some additional photos of the build:

Ummm,

you posted this on hybridz right? CZCC is an awesome site, but the better wealth of knowledge on swaps is on Hybridz.

Looks like the diff has been welded, might want to google pro's and cons on that.As I posted in Hybridz, have you addressed the issue of the driveshaft and the diff flange? Yes a 3.54 would be better, but you seemed insistant that you weren't going to do a diff swap! Where's the diff if you have everything else from the zxt?

IMHO, the 3.90 would be a mistake with that trans or with a turbo motor-especially both.

Don't worry-it only costs time and money-

The answers to the same questions on Hybridz were all pretty good. They'll be about the same over here. The new question about blowing the motor is kind of moot. It just depends on how the driver drives it.

Going by the number you quoted from the Tag Id plate, its a T5 from a late 82 or early 83 Turbo 280ZX.

The ZX turbo came with two versions.

The first one (code E) had Ratios 3.50, 2.14, 1.38, 1.00, 0.78 and reverse 3.76.

The second version (code J) had ratios 3.35, 2.08, 1.38, 1.00, 0.78 and reverse 3.15.

There was a third version released in Germany for the last 4 months of production, so Im guessing it wont be that one:bulb:

The code E has a very low first gear. Both are not really close ratio when compared with the 280ZX N/A 71B transmission which is 3.06, 1.86, 1.31, 1.00, 0.77 and reverse 3.03

You should be able to check which one it is.

You keep quoting the casting numbers, but they don't tell you much in the end, nothing really. The ID plate and the ratios are the only way to find out which one it is. Identifying and Assembling a T5 5 Speed

BTW Your mustache bar is mounted upside down.

You caught the mustache!!

We got her in

Zed Head :

What's the biggest drawback to this combination? It seems to be a pretty nominal concern in the scheme of things. These items were purchased from someone as a package; so the choices of rear end, motor and T5 were all what another wanted and couldn't afford to put together. I have been trying to teach myself the whole z thing ever since.

And I didn't get any response from anyone at Hybridz on the welded differential. Do you know why this was done or if this was a limited slip?

Not an LSD.

The T5 is heavier than a 280ZX "B" tranny by many, many pounds.

Sell the T5.

Try the diff. Likely you might not be pleased using it in a street car.

Chas,

thanks for the info, didn't realize there was 2 versions of the BWT-5 in the USA(didn't read that on hybridz:)) I will have to see what version I have.

To the OP, do you have the right DS for this set-up ?

The welded differential will be skipping the inside tire in every turn. Parking lots will be noisy, and the tires will wear prematurely. Unless you put a lot of extra power in the car, an open differential will be a better choice. There are LSD differentials that can be made to fit, which is what is needed on a street car.

Welded differentials are for drag cars and extreme off-road trucks.

And I didn't get any response from anyone at Hybridz on the welded differential. Do you know why this was done or if this was a limited slip?

I see that you did get back in to your Hybridz thread.

On the welded diff - it just makes it easier to "get sideways" and impress the crowd. That's it, in a nut shell. Its only purpose, for a street car.

I'll be in the hunt for a ds

Already read up on that thread and saved links -- thanks for this site

Got to have it shortened, or the end fitted onto, etc

So is it a general consensus that I should look for a Type B 5 speed? The BW is that much heavier and undesirable? Quite a few threads saying differently but I'm the student here...

You might want to start reading up on the 71B if you decide to go that route. Nissan had three versions in the 280Z/280ZX. A so called "wide ratio" in the 280Z and two almost identical (5th is different) "close ratios" in the ZX. They also came in other models like the 720 truck series, which had three versions.

This thread is running atm and will give you a good starting point. http://www.classiczcars.com/forums/engine-drivetrain-s30/52177-gearbox-id.html

Chas