np 205 mods

[69LC]

i've been given the green light to build my 40. I will have to do a bunch of custom axle work, finish my custom tranny/tcase adapters and lots of other stuff, but I'm starting with the NP205.

It's a late 70's GM 8-bolt "racetrack" version. I have a complete Ford case that will be donating most of its guts. The GM case is about to have the input bearing bore opened up too.

In order to gain a couple more inches of rear driveshaft length I'm cutting off the front of the rear shift rail and running it out the back through a new seal. Shift linkage will be easy. This way I can flat mount whatever plates for the tranny/doubler adapter to the front of the 205.

$15 long 1/2" drill bit to drill one pilot hole. I ran it through a 3/4" OD SS tube in place of the rear shift rail

Double seals on rear driveshaft output cover

Machinist cut and faced the new shift rail for me

 

[69LC]

I picked up a 1 1/4" freeze plug at NAPA on my way home. That should cap the old seal bore nicely.

The drill bit guide tube

 

[74fj40]

Cool thread! Looking forward to seeing your progress

 

[69LC]

These gearboxes are heavy when fully assembled! I just hefted the Ford case to my warm basement. Wow! I'll count it as added traction for the extra power my 6.0 will have...

The Ford case is gutted. I'll take it to work for a machinist to use that case's input bore to copy to the GM case. It looked really clean inside, so even without gear oil most of the bearings are still like new.

I have to add 1 1/2-2 1/2” of 3/4” Stainless rod to the back of the rear shift rail. I haven’t decided between slotting it with a cross hole like original or to drill and tap it for a rod end.

Thoughts?

 

[69LC]

Not much to add today. I did media blast and paint a couple of the front output bearing retainers.

I dropped off the cases off at a local machinists shop. With a work trip to Ontario, CA Monday I won’t be getting any truck work done this week.

Self etching primer

NAPA Chassis Black

 

[74fj40]

What are you doing for work in Ontario? I used to get sent there for training for a previous dealership I worked at.

 

[69LC]

Annual service PMs at a juice plant.

 

[69LC]

Got back to work today and had my rear shift rail waiting for me.

 

[69LC]

Got the rail shortened and the weld cleaned up. It was a bit out of straight so I put it into the shop press and trued it up.

This is how the front and rear rails will be in relation to each other.

 

[69LC]

The rods both slide smoothly in the case. Hopefully the machinist will get the case bored soon!

 

[69LC]

I picked up the case last night from my machinist neighbor. Today after work I deburred the casting and laid a nice coat of chassis black tonight.

 

[69LC]

Progress has been a bit slow, but I found my GM shift forks all rusted in a bucket. They cleaned up well in the blaster at work though.

On my way home from work I stopped at a local old fashioned dumpy junkyard and found two old Dodge 3/4 ton trucks with front output drive flanges I can use to adapt my Toyota CVs to.

 

[69LC]

I went with my Aunt to meet other family at a restaurant in Ann Arbor today for some annual tradition meeting thing. When we got back to the farm I was in the shop checking out the work my cousin is doing on some old 820 John Deeres. I told him the work i'm trying to do on my 40 and that I'm having trouble finding junkyard 205 compatible drive flanges and he stepped outside and grabbed a tcase chunk his mom had found along a nearby road while jogging.

He pulled the flange nut off and there are 32 splines inside! Score! I don't know what truck this thing was in, but it wasn't mechanically removed. I'm pretty sure that the case it was in blew up.

A keen eye will notice that I'll have to come up with a way to add a Toyota driveshaft mating flange pilot centering bore.

 

[69LC]

The flange inside that mess turned into what will follow in pics. I had my neighbor turn the new seal surface, cut off the old slinger surface, face the GM 3R male pilot diameter off and cut an 1/8” deep x 2.75 counter bore in the center of the face. My plan is to make a washer to press in and cut the female pilot hole for Toyota driveshaft flanges. If I find the need to go to bigger domestic driveshaft Parts I can make a new stepped washer.

The Toyota cv flange sits flat against the face of the drive flange.

 

[69LC]

So the centering ring is finally done. I’ll drill and tap the flange for the Toyota cv flange and install the tcase front shaft.

 

[GLTHFJ60]

Plan to weld that centering ring in place? Nice work!

 

[69LC]

No, I want I keep it removeble so if I ever upgrade shafts all I need to do is make a new centering spud.