NP231 Doubler build

[Jak Flash]

Part of this years build is to make a NP231 doubler

This is how I did it.

Original plan was to get my hands on a NP231C from a GMC Jimmy but with some thought and some research it was realized that I could use some parts I had around to put this together.

I decided to blend an NP241C and a NP231J to make the doubler.

The 241





The 231



---------- Post added at 07:17 PM ---------- Previous post was at 07:14 PM ----------

Since there was a spline difference between the 23 spline input of the 231 and the 29 spline output shaft of 4L60 4 speed automatic transmission. It was necessary to replace the input of the 231 with the input of the 241.

Here are some of the pictures and comparisons of the two transfer cases.

This is the 231.



Input planetary gear.



The output shaft.



The 241





Input planetary, output shaft and case.

[Jak Flash]

Note some of the differences.

Chain and sprockets



Selection gears

Top one is from the 231.



More on the selector gear.

From the 231



And 241



And of course the input planetary gears...



For obvious reasons the planetary from the 241 as well as the selector from the 231 are going to be used in the building of the NP231 doubler box.

---------- Post added at 07:46 PM ---------- Previous post was at 07:26 PM ----------

From here it was prepping the transfer case for the doubler and building the plate as well as the clocking ring.

Vent removal





Oiling the primary bearing

In order to ensure that the Main input bearing once the t case is flipped upside down an oiling hole is drilled

The bottom hole is the stock position.



Removal of the shifter and detent ball



And since I'm going to be welding on the case the seal and bushing neeD to be removed as well

[Jak Flash]

From here it is necessary to create the clocking ring and doubler plate

I spent some time looking for cad data and with some help I was able to create these...

Doubler plate



And clocking ring



First fitting on the 231 and drawing a line for cutting.



And cut...





Now with some work the block off plate is fit.



Welding came the next day followed with a good epoxy seal to ensure the case is leak free

[Jak Flash]

Once the epoxy was set it was time to start the reassembly process.

Once all the parts were properly cleaned

I used a lithium based white grease to prepare for assembly






I ground out some material to open the second oiling hole that I drilled in for the from bearing and sealed it up with some silicone





The reinstalled shifter and new plug for the original vent tube

[Jak Flash]

From here I need to figure out the intermediate shaft

I cut the output shaft from an AX15 and the output from the 231.



And the 231







And

[Jak Flash]

Once I removed it from the shift fork I cut it to 170mm and drilled, tapped it to receive a 3/8 NC thread.





Then installed in to case again using white lithium grease.



---------- Post added at 09:52 PM ---------- Previous post was at 09:34 PM ----------

Some machining prep for the shaft.... The fear I had was that the two shafts would not go together without either being bent or not axially alined. Decision was to make a 0.500" peg and hole to align the two. When the shafts were put into the lathe they were corrected to 0.004" run out


And wow I have to say. Hard shit to cut.

23 spline shaft. The peg diameter is 1.002"



And the 34 spline. The hole diameter is 1.000"



Once this was done it was time to prep for assembly. The peg side made it's way to the freezer about an our later I began to prep the hole...



Once it seemed to have a uniform bluish I went to grab the part from the freezer and....

Voila... Note the frost line... Lol.



And after allowing some cooling time

[Jak Flash]

So it's time to finish up the shaft...

I had a conversation with the metallurgist at work and got his input....

I followed his process....

Pre heat the shaft to 680*F. For 30 min.





Bring it to welding and set it up on the rotisserie.



Put 3 quick tacks in it. And burned it in.



And voila. Two become one.



Once the welding was done. Back to the oven it goes for 30 minutes of 740*F for annealing.



Once time is up remove it for air cooling. No quenching or blankets.

And it's done... Pardon the cell pic.

[Jak Flash]

Not the final assembly but let see it all together

Shaft in the doubler box.



And assembled



Over all length of the JC441D is 20 1/2". Just 4 1/2" longer than the NP231 with a Advanced Adaptors SYE

[Jak Flash]

So there is a couple of things that still need to be figured out like venting but will look at that as I finish up the flip kit build.

I will post those pictures here and update the thread once that happens.

Vent locations have been picked and put in place. 3/8NPT for both locations. They will double as fill and drain plugs for the time being




As for conclusions. Fawk ya... Killer build. Lots more to do...

[Hotwire]

You've got some skills. Very nice build!!

[Reverage]

Well that's cool


Nice work

[BadCompany]

dude mad skills for sure....... thanks for sharing.

[Jak Flash]

Thanks guys...

[Chrisbuilt]

You were supposed to drill and tap an 1/8" npt hole for a barbed fitting before you assembled it. Good luck keeping the shift rail from spinning when you put the bolt in the end of it. It's a tricky one.

Looks the same as my $250 DD Machine Box4Rox.


Sent from my iPhone using Tapatalk. Excuse the autocorrect.

[Slag]

Awesome.

[Jak Flash]

^ thanks Slag

You were supposed to drill and tap an 1/8" npt hole for a barbed fitting before you assembled it. Good luck keeping the shift rail from spinning when you put the bolt in the end of it. It's a tricky one.

Looks the same as my $250 DD Machine Box4Rox.

Where is the 1/8 NPT supposed to go?

The shaft rail has already been bolted in place and removed with no issue but I can see how that could be a PITA.

As for cost.... 60$ for the tcase.... the rest I had as scrap material or left over parts from the various other builds

[Chrisbuilt]

Did you put fill and drain holes in the cover plate? Or sight tube holes? Or vent tube? Just razzin ya.

I didn't flip either case and use the factory vents tubes. As long as it's nice and high it don't matter if it's in the block off plate or the case. The plate would be easier to drill and tap than the case and would be easier to clean up after.

Since mine is out and on the counter I think my drain and fill plugs will become my new sight tube. Thanks for the ideas.


Sent from my iPhone, excuse the autocorrect.

[Jak Flash]

Did you put fill and drain holes in the cover plate? Or sight tube holes? Or vent tube? Just razzin ya.

I didn't flip either case and use the factory vents tubes. As long as it's nice and high it don't matter if it's in the block off plate or the case. The plate would be easier to drill and tap than the case and would be easier to clean up after.

Since mine is out and on the counter I think my drain and fill plugs will become my new sight tube. Thanks for the ideas.

well if you read instead of just looked at the pictures you would have seen that im not going to add the sight tube/vent, etc until after it ends up in the jeep....

thanks for the props...

[Chrisbuilt]

One last thing, make damn sure the D300 input seal is good or you will have ATF mixed with gear oil. When I drained my 300 it was a nice red colour.


Sent from my iPhone, excuse the autocorrect.

[Chrisbuilt]

Before and after.



Sent from my iPhone, excuse the autocorrect.