720 Diesel tranny interchangeability?

[primer grey]

Hi there,

I am new here, but y'all seem to have all the information about the questions I have...

 

I've got an '82 720 with the sd22 diesel in it. The tranny has failed, in that it has busted through the cast aluminum piece (front, inside the bellhousing) that I've seen referred to as the "bearing retainer" or just the "front cover"...

 

anyway, I may be up a creek here, as I know the bellhousing is unique to these motors & they've become scarce as hen's teeth around here, but, I've heard that all internal components are interchangeable, and wondering also about that front retainer piece.

 

I've found a 280z 5-speed for sale, & I am wondering if you think I could use the internal components of that tranny to rebuild this one, & then can I cap it off with the Bearing Retainer from the Z tranny.

 

I've seen pictures, and they look like the same part. Any experience with this?

 

Thanks in advance,

Mc.

 

[ggzilla]

The front part of the tranmission which includes the bearing retainer and the bell shape is named by Nissan the "Front Case"

 

Yes, you can use a front case from a 280Z, but then it will only fit an L-series engine, no longer will it fit the SD-series engine.

 

One thing you could do is take both 280Z and SD22 front cases, cut each in half and weld the two desired sections back together. This sort of thing has been done many times, the key to success is to align it carefully while welding. It must be spot-on.

[primer grey]

...I wish I could figure out how to post a pic of my busted tranny here (if I even can..) but I'll refer to the thread from this forum that got me thinking about this...

 

http://community.ratsun.net/topic/42097-280zx-5-speed-rebuilt-600/

 

in the second pic, where you see the front view of the tranny, the five-bolt cover behind the throw-out & fork, (all black on this tranny), looks exactly like the one on my diesel tranny.

 

I'd use my old bellhousing and bolt this new cover on it.... Maybe?

 

 

 

[wayno]

How bad is the front lower hole in the case screwed up, as it is likely the lower bearing that went bad.

What I have done twice now is to have the lower bearing hole in the case machined out to take the later bigger bearing, and then use the later bigger bearing front cover.

An original diesel front bearing cover should be steel, this brings up questions to me, but you need to pull the front case off and inspect it.

http://community.ratsun.net/topic/28473-how-to-put-together-a-shortshaft-5-speed-for-a-l20b/

If the hole is only roughed up a little, and did not totally destroy the case, then machine it out, and then use another good gearset from a 720 with a new bigger lower bearing.

 

When your tranny starts making noise or vibrating, you need to quit using it, as this is a hard transmission to replace.

[primer grey]

it's shot. I have about a 1 1/2" piece of busted aluminum sitting on the table next to me that used to be part of the cover. Yeah, unfortunately it gave me no warning when it went out -just let out the clutch and bang, that was it. Got it home though, with a trail of gear oil now running up the driveway...

 

I can see the bearing from outside the case, & yes the lower front is missing a ball or two.

 

The rest of the case is fine. Rebuilding the guts doesn't scare me, I just need that cover.

[wayno]

What I am asking is if the case itself is missing any big chunks between or around the bearings, you can use a differant cover from another transmission, but the front case has to be savable.

 

Where are you located, if your close I can look at it.

The link I sent you about making a shortshaft was for telling you how to tear apart the tranny.

 

wayno

[ggzilla]

Correction for my earlier post.

 

the Front Cover bolts inside the front case and has the snout for the throwout bearing, and covers the input shaft bearing.

 

What many call the "bellhousing" is part of the Front Case. Most Nissan transmissions didn't have a separate bellhousing.

[primer grey]

Thanks Wayno,

yeah the case looks alright. Just fine, actually. The transmission really still functions almost perfectly. I actually even put it back in the truck (in a moment of exasperation, I planned on taking it to the scrapyard) but yeah, once I took it out & this chunk of metal is not randomly dinging off the flywheel, it acts like normal.

 

I'm relatively close to you, but not real close. Up in South King County. Probably not something you can swing past on your way home, but thanks for the offer. A little experienced insight would always be appreciated.

 

Speaking of which, yes, that's a great how-to for the tranny guts swap. I'll probably be consulting it in depth very soon. I hope.

 

Thanks.

[wayno]

Ok, if the case is all right, you can get a front cover off a 80-82ish and use it with a new small front bearing if the rest of the tranny isn't bad, or you can find another tranny from a pre 82 720 gasser, put that front cover on your diesel case with a new cluster gear bearing, or you can use a 83 and later 720 transmission and put the smaller bearing on that trans. and put it back together with your undamaged diesel front case.

If your case has damage, then it will need to be machined out to the larger 83+ bearing, buy a large bearing transmission and use that tranny and front cover on your repaired diesel case, do you understand what I am saying?

 

When it comes to the diesel transmission, if you know you lost the bearing, it is best to just not drive it at all, because these diesel cases/transmissions are hard to come by anymore, and if it gets destroyed, it's a long process to find another one.

[wayno]

...I wish I could figure out how to post a pic of my busted tranny here (if I even can..) but I'll refer to the thread from this forum that got me thinking about this...

 

http://community.ratsun.net/topic/42097-280zx-5-speed-rebuilt-600/

 

in the second pic, where you see the front view of the tranny, the five-bolt cover behind the throw-out & fork, (all black on this tranny), looks exactly like the one on my diesel tranny.

 

I'd use my old bellhousing and bolt this new cover on it.... Maybe?

 

 

_____________________________________________________________________________________________________

 

 

 

This is what I was talking about exactly, but your case bearing holes need to be checked close, and that can only be done if the case is apart with no bearings in the way.

There are two differant bearing sizes, and the stock diesel had a steel front cover, so if it had an aluminum one on it, it likely has had the same issue before.

 

wayno

[primer grey]

Thanks for the guidance Wayno,

Can I suppose that perhaps since the front cover has been replaced, this tranny might have already been fitted with the larger bearing?

I suppose in that scenario, if there's any damage to the case, I really don't have a rebuild option.

[wayno]

Thanks for the guidance Wayno,

Can I suppose that perhaps since the front cover has been replaced, this tranny might have already been fitted with the larger bearing?

I suppose in that scenario, if there's any damage to the case, I really don't have a rebuild option.

 

 

___________________________________________________________________________________________

 

You can have the bearing hole punched out to the larger sized bearing if it is buggered up, I have never heard of anyone but me doing this, but that doesn't mean it has not been done.

Would need a close up photo to tell if it has been machined out before, a photo of this area without the transmission hardware in it, just the case, this one is of the small bearing.

[datzenmike]

This is/was a '85 SD25 steel front cover. I don't know if the earlier SD22s were steel or aluminum. Take a good look at the counter bearing (the smaller one to the left) This is way the tranny was scrapped.

 

The later 71B tranny changed from a 56mm to a 62mm front counter drive bearing some when late in '84 but '85 for sure. Wayno, this is based on counter bearing parts numbers availability.

 

You can tell this is a 62mm bearing by how close the two bearing holes are to each other.

 

Here's a zx case shown from the inside but you can easily see the difference.

 

Primer grey you will have to remove the front cover and inspect before going further. After all these years anything could have been done. Yes an earlier aluminum cover plate, 4 or 5 speed, will work as long as it matches the counter bearing size.

 

If you find one on a transmission unbolt and remove this way...

 

... by hitting with hammer from the outside.

[wayno]

This is/was a '85 SD25 steel front cover. I don't know if the earlier SD22s were steel or aluminum. Take a good look at the counter bearing (the smaller one to the left) This is way the tranny was scrapped.

 

The later 71B tranny changed from a 56mm to a 62mm front counter drive bearing some when late in '84 but '85 for sure. Wayno, this is based on counter bearing parts numbers availability.

 

You can tell this is a 62mm bearing by how close the two bearing holes are to each other.

 

Here's a zx case shown from the inside but you can easily see the difference.

 

Primer grey you will have to remove the front cover and inspect before going further. After all these years anything could have been done. Yes an earlier aluminum cover plate, 4 or 5 speed, will work as long as it matches the counter bearing size.

 

If you find one on a transmission unbolt and remove this way...

 

... by hitting with hammer from the outside.

 

 

I don't know if the diesel transmission came with aluminum front covers or not, but the only ones I have ever seen were steel.

I held off posting bearing sizes, because I could not remember them for sure, and was to lazy to find out, thankyou for posting that info datzenmike.

Also thankyou for posting the front case photos without the gearset, as I don't seem to have a photo of one, I am still puzzled about that, as many of these that I have had apart, seems like I would have that photo, but I didn't until now.

This is a diesel case I had turned out to the larger 62mm cluster gear bearing a couple weeks ago, it will have a aluminum front cover now off a 85-86 720 napZ transmission.

 

 

 

 

 

 

 

 

 

 

[wayno]

I finally got these photos to post, what a hassle.

 

These are photos of a diesel case I had turned out to the larger 62mm bearing size.

 

 

 

It will have the aluminum front cover now.

[ggzilla]

The non-aluminum Front Cover is cast iron i think.

[Master-O-Turbonics]

The front cover on my SD22 is the iron/steel type. 

[datzenmike]

Good to know. I never checked until now but SD22 and SD25 had steel cover plates through '84. The '85 model year was also steel but had the larger counter bearing cover.

[ggzilla]

If they were steel, they wouldn't break but only deform. But cast iron will break.

[wayno]

If any of you guys that have a steel cover that you are not going to use want to trade or sell it, let me know, as the one canadian spec SD25 diesel truck I bought, the front steel cover was destroyed, so I am short a diesel steel cover now, and am going to have to use aluminum, I can use either cover(early SD22 or late SD25), as I can have the machine shop turn the early cover to to the big bearing size.

 

I really don't know if the metal is steel or cast iron ggzilla, I just know it is not aluminum.

How can you tell the differance?

[datzenmike]

Sorry, it says Fe (iron) cast iron? and not necessarily steel, I miss-spoke.

[ggzilla]

How can you tell? Hit is hard with a sledge hammer. If it breaks, it is cast iron. If it deforms it is steel.

[wayno]

How can you tell? Hit is hard with a sledge hammer. If it breaks, it is cast iron. If it deforms it is steel.

 

 

Why would I want to do that, then I would need two of them instead of just the one I need now. 

[ggzilla]

Because if you got a steel one, it would never break. Instead you have the weaker cast iron one, or even weaker yet aluminum cover. Another reason is that after breaking it with a hammer, you would really understand why they break in usage -- cast iron is brittle, and once the bearing goes bad, it starts hammering the front cover.

 

There could be a big market for Forged Billet Steel covers for SD transmissions. You could probably sell as many as six of them... but they aren't really needed, if bearings are replaced on time.

[wayno]

Because if you got a steel one, it would never break. Instead you have the weaker cast iron one, or even weaker yet aluminum cover. Another reason is that after breaking it with a hammer, you would really understand why they break in usage -- cast iron is brittle, and once the bearing goes bad, it starts hammering the front cover.

 

There could be a big market for Forged Billet Steel covers for SD transmissions. You could probably sell as many as six of them... but they aren't really needed, if bearings are replaced on time.

 

 

Yea, that is the problem, they all keep driving them till they get home, instead of stopping, that's why I can get them for cheap, the transmission is wasted, and they cannot find a replacement.

There are a lot of them out there without a good tranny, but the owners think it is still worth a lot because it is diesel, but it isn't worth anything if you can't drive it.