engine and drivetrain Long neck diff swap question

[hankapotomous]

First of all I would like to thank the community for all the great information available to use and learn. It has helped me tremendously in my project. 

My 68 2002 #1663252  has a long neck diff that sounded like a box of rocks. I have picked up a short diff with axles and I know I need a new subframe  and drive shaft, but do the axles in the rear control arms need to be changed? It looks like they will bolt up to the later half shafts.  Thanks 

 

 

 

[TobyB]

You mean the stub axles in the trailing arms?

 

They "should" work- the early ones that I have had have been drilled

for both patterns.  You "may" need different length bolts.

 

<edit- maybe not- see Armin, below>

 

t

 

Edited September 14, 2016 by TobyB
I have been wrong before, I might be wrong now, I will be wrong again in the future...

[Son of Marty]

I've been told long neck and short neck trailing arms are not interchangeable, they have a different width  between the trailing arm mounting points. 

[TobyB]

Oh, whups- I was answering for the stubs.  Hank, let us know what you find when you get in there...

 

t

 

[Preyupy]

I have never tried to swap the early "long neck" trailing arms with the ones from a "short neck" cross member.  Every time I have converted from long to short I have gotten a complete cross member with arms and made the swap (and have gotten the stub axles with the correct CV joint flange as part of the deal)  If I remember correctly the stub axles on my '68 1600 were only drilled for the early half shafts, but that was a long time ago and many of the brain cells I used back then don't work any more. 

Edited September 14, 2016 by Preyupy

[arminyack]

The trailing arm hook up points on the long neck subframe are narrower....so you'll need the short neck 02 trailing arms...and stub axles too I believe.

Edited September 14, 2016 by arminyack

[Hans]

It is my understanding that the trailing arms and the half shafts (length) are the same. This would appear to be borne out by real oem. Maybe I'm missing something, and if I am, i 'll have a problem installing CV joint half shafts on my long neck NK car as planed. 

 

The main difference, as far as I know, is the bolt hole pattern for the half shafts: the really early sliding joint shafts are drilled 3 + 3, the later CV joint shafts are 6 evenly spaced holes. You can find 3 + 3 CV joints, you can find flanges with 10 holes to take either. Or swap the whole rear cross-member if you can find one.

[arminyack]

38 minutes ago, Hans said:

It is my understanding that the trailing arms and the half shafts (length) are the same. This would appear to be borne out by real oem. Maybe I'm missing something, and if I am, i 'll have a problem installing CV joint half shafts on my long neck NK car as planed. 

 

The main difference, as far as I know, is the bolt hole pattern for the half shafts: the really early sliding joint shafts are drilled 3 + 3, the later CV joint shafts are 6 evenly spaced holes. You can find 3 + 3 CV joints, you can find flanges with 10 holes to take either. Or swap the whole rear cross-member if you can find one.

The placement of the trailing arm mounts ARE the same...the actual WIDTH of the mounting brackets/trailing arm mount point is different. The long neck ones are narrower. Ask me how I know.

Edited September 14, 2016 by arminyack

[Hans]

OK, but real Oem shows only one trailing arm for both cross-members. So what impact would the width have?

[xferboy]

The bushings are different in the long neck stuff, but the bushing housings are the same  (60mm??)  They do have an extra metal sleeve that I haven't gotten out yet, but the housings are the same (ish)

 

Since I had a set of long neck diff trailing arms kicking around, I did a quick line up with my tii stuff when I was doing camber/caster/Energy bushings and the seemed close.

 

If anyone wants any measurements done, I've got a set of trailing arms off a long neck diff setup sitting my garage.

 

<edit>  If I knew where you were, I'd offer the long neck diff I have for a song.  I'm in Canada (SK), so shipping that lump may be expensive, but may be less than buying all the other bits.  If memory serves correctly, it was pretty quiet turning it on a bench.  I never drove the car it came from.

Edited September 15, 2016 by xferboy

[Hans]

Further research on Real Oem shows that there are different bushings for long vs short neck applications - same arm, different bushings. For some reason, that is not the case on NK cars, which use the same bushing and arm for both applications. Hence my confusion.

 

So it would appear that the short neck cross member will require short neck arms - or at least change the bushings I suppose, which may be a good step anyway. Assuming the old arm flanges work with the new half shaft bolt pattern. More coffee is required.

[arminyack]

I can guarantee you the bushing for the shortneck 02 trailing arms are too long to fit in a longneck subframe. I have both a longneck and a shortneck subframe sitting in my garage...Ill take pictures tonight with calipers across the brackets that will show the differences. I think this is a case where realoem is just wrong....much like its wrong when it comes to the steering idler bushing on an early car.

[Hans]

arminyack: I think Real Oem is supporting your experience with 02- two different bushings, one 30mm and the other 50mm. Same trailing arm, longert bushing to fit wider bracket. NK is a different story. Anyway, lets see what your photos tell us.

[AceAndrew]

Hans - The fact that the trailing arms have different mounting dimensions between the different long neck and shortneck subframes is pretty common knowledge.  You will find that realOEM is far from being infallible (though still a great resource for those of us without access to ETK).

 

Hank, be aware that if you plan on changing out the stub axles, you will want to carefully follow the factory manual's guidelines on properly sizing the bearing spacer shim.  If not, you will be destroying some stuff on a regular basis.

Edited September 15, 2016 by AceAndrew

[arminyack]

Ok, below is a pic of one of the trailing arm brackets on each subframe....the top is the short neck, the bottom is the long neck

 

 

 

 

Now whether their can/should be ~0.2 of slop on each side of the trailing arm where is meets the mounting bracket if the trailing arms are indeed the same, I do not know. We need a pic of an assembled 02 shortneck subframe with a measurement!

 

 

Edited September 16, 2016 by arminyack