35 minutes ago, zKars said:

but very hard to come up with a new wear pad.

Delrin?

11 hours ago, grannyknot said:

Delrin

Probably? it's seems to be the better Nylon...  Couldn't you make just a new set on them, just a little bit bigger and secure them with rivets (like it was already) ?

15 hours ago, zKars said:

First pictures of the worn fork. Here is the "good" side of the fork so you can so the little plastic wear block with the two pins that hold it.

Wow. That's quite the failure. So on a good selector fork, the only thing that contacts the synchronizer slider sleeve is those two little plastic pads on the tips? Woof.

Is there a thinner grooved channel worn into the side of the slider where the rivet heads were located? Or are the rivets so loose that they just slide back forth inside the fork?

And on the steel forks... It looks like they don't use plastic pads at all? Seems like a much better (albeit more expensive) design. Wonder if they changed it to make it cheaper or quieter (or something else).

3 hours ago, dutchzcarguy said:

14 hours ago, grannyknot said:

Delrin

Probably? it's seems to be the better Nylon..

Here's an interesting read for anyone who wants to learn a bit about engineered thermoplastics.  It doesn't specifically mention Delrin because Delrin is the trade name for a Dupont product that falls into the category of 'Acetal POM' (acetal polyoxymethalene).  Celcon is a similar product from a different manufacturer (Celanese).  POM's, along with PA's (polyamides -- includes nylon) fall into the category of 'semi-crystalline' thermoplastics.  

From my quick read of the selection guide, Delrin and other POM's might be suspect for the task at hand, which would seem to require:

• resistance to chemicals (gearbox lube and possible additives)
• resistance to high temperatures (heat generated by sliding friction)
• good abrasion resistance

Look at the case study in Slide #50, where Nylon 66 with glass-fibre and mineral/bead additives is selected for automotive oil pan applications.  This looks like it might be a better solution for the fork friction pads.  Just source a typical 'composite' oil pan from the wreckers and then cut out a section that can be used to machine the pads. 

Thermoplastics - An Engineers Guide to Specifying - RTP Co (USA) - 2014.pdf

I love this forum!!!!

1 hour ago, Captain Obvious said:

 

And on the steel forks... It looks like they don't use plastic pads at all? Seems like a much better (albeit more expensive) design. Wonder if they changed it to make it cheaper or quieter (or something else).

 No plastic pads on the steel forks. They have 180` of contact with the synchro.

And then you find things like this:

and you begin to wonder just how similar the C type transmissions are inside. Especially since, as previously mentioned, you CAN get parts for THEM

Oh look, there's a couple of "C" cores out on the grass.... (actually a snow bank at the moment).

Guess I know what I'm doing this afternoon. Other than shoveling snow....

 

 

 

Edited December 7, 20195 yr by zKars

One of the shift rods in the C transmissions is of larger diameter than the B's.  You have to drill the hole out in the front case for the swap.  Can't remember which one but it's probably shown in one of the guides. atlanticz or zhome.

http://zhome.com/ZCMnL/tech/240SX5spd/Transmission2.htm

Sure enough, its the 1-2 rod that's larger.  16mm vs 14mm

But a little 1mm thick bushing could be used to make the C fork "fit" the B rod. Never say die!

Edited December 7, 20195 yr by zKars

You've got a lathe, right? That bushing should be easy-peasy!

More great break down pictures, this time from AutoZone.

What is unique is the text that describes every part. All of the Nissan parts catalog pages I've seen just show the reference numbers.

https://www.autozone.com/repairguides/Nissan-Pick-ups-and-Pathfinder-1970-1988/MANUAL-TRANSMISSION/Transmission/_/P-0900c1528004f739

This page also gives you C type trans pictures and STEP by STEP instructions for break down and re-assembly.

 

 

Edited December 8, 20195 yr by zKars

And is Motive Gear Products catalog pages for the kits and parts associated with the FS5W71* gear boxes

Full catalog for everything they sell.

https://www.carid.com/images/motive-gear/products/pdf/motive-gear-product-catalog.pdf

 

My reduced pdf with just the Fs5W71 pages (136-138)

motive-gear-product-Nissan.pdf

Edited December 8, 20195 yr by zKars