Info needed: Transfer case vent

[Paul Edwards]

Hi Guys,

Does anyone know where I can get a better looking Transfer case vent from, for my Chevrolet c15a no. 12 cab.

LDW doesn't have anything.

Cheers,

Paul

[Phil Waterman]

Hi Paul


Last time I needed one (within last two years) it was an off the shelf part at my local heavy equipment and tractor dealer. Might also try some of the antique tractor online suppliers.


Cheers Phil

[wally dugan]

it looks the same as the ones fitted to the series 2A petrol land rovers engine

[Harry Moon]

Princess auto

[rob love]

Yep, princess auto, or any hydraulic shop will have them. They are on most hydraulic tanks. Not sure how common National Pipe thread is over on your side of the pond, but on this side it is still the standard.

[Paul Edwards]

Thank you for your prompt response guys.

Does anyone in the UK know a supplier?

Cheers,


Paul

[Richard Salter]

Hi Paul
Try HP Hydraulics newgate lane Fareham, Hants or Hypo hose in portsmout or Southampton

Thanks
Richard

[Paul Edwards]

Thanks Richard I'll try your source but before doing so and whilst searching the internet I came across these two photos of what appears to be images of transfer case but the vent differs, is there any reasoning behind this?

I then went on to look at my butchered vent which might suggest it was squashed to enable it to be fitted below the chassis cross member.

Any experts out there that might shed light. I'm thinking I may have the wrong vent.

Cheers,
Paul

[Grant Bowker]

A. It would be presumptuous for me to claim to be an expert
B. I suspect the simpler vent (a loose fitting cap pinned onto the vent tube) was a case of simplify to cut production time and cost while maintaining most (some?) of the dirt protection capacity of the damaged version you have
C. It is possible to use the vent caps sold for Chevrolet 235 CID valve covers to fabricate a passable replacement for the damaged transfer case vent. My process is: uncrimp the perimeter of the damaged dome to remove the perforated flat panel (and the filter medium if possible), braze/weld/solder the recovered flat panel to the recovered (or a new replacement) pipe that threads into the transfer case, reinstall the filter medium into the dome and crimp the edge onto the flat disc. If the filter medium isn't recoverable, consider usiing metal mesh from a pot scrubber (also sold as pest control https://www.leevalley.com/en-ca/shop...copper-blocker).

[Grant Bowker]

More images to show how the pipe core was facricated . Basically off the shelf black iron pipe nipple, cut in half to give two pre-threaded stubs, turned down slightly to let a drilled out nut be slid onto the pipe, brazed together then the disc drilled/cut/filed from flat sheet added.

[Grant Bowker]

more images

[Jordan Baker]

There were two different vents used.

Please see attached GM Service Information Bulletin B29, Item 64 from December 12,1942

The early one was simply a pipe with a cap on it held on by a cotter pin "Fig2". The second version was the air cleaner type "Fig2".

These were introduced into production starting at serial number 1844332070.

[Barry Churcher]

Excellent job Grant.
Barry

[Paul Edwards]

GRANT! BRILLIANT!

Took the opportunity to photograph my own tranny today, it appears to be the early version (pipe/cap/cotter pin fig2) type, the vent exits vertically, hence why the air cleaner type had been butchered to fit under the cross rail. The air cleaner one would appear to exit at 45 degree slant.

Am I reading this bulletin correct, ie: the air cleaner type superseded the simple pipe/cap/cotter pin fig 2 type?

If so and all I need is the simple version then I recall there's one of these vents on the Jeep tranny, I wonder whether this wound fit?

Cheers,


Paul

[rob love]

I sounds like the air cleaner type was a product improvement, and that is was to be retrofitted onto the earlier transfer cases to replace the simple tube and cap. But in all seriousness, for the miles any of us will put onto our vehicles, nor the dirt we will subject them to, the nipple and cap would likely be fine.

If you are talking about the little nipple and cap on the jeep transfer cases, they are normally spring loaded onto a little check valve which will build up pressure to about 3 or 4 psi before reliving the pressure. They are usually 1/8 npt thread so would be pretty small for this application. However, with some bushings, it would work fine. The same nipple was used on the M35 deuce (and a thousand other vehicles) for that large transfer case for the last 60 years.

Edited to add: I had to look up the early Jeep transfer case breather and just saw that some indeed are a nipple with small cap retained b a cotter pin. But some sources are showing the pressurized cap which is more what I am used to. Someone with a WW2 Jeep will have to confirm if the nipple and cap type is 1/8 NPT.

[Jordan Baker]

The Jeep uses a similar vent on the transfer case. It looks like one of those would work just fine.

https://forums.g503.com/viewtopic.ph...82ecd34c49e6ee

[Paul Edwards]

Thanks Rob, Jordan,

I think for the miles I'll be doing the simple early version will suffice.

The Jeep version may be small but I'll check out the Jimmy or Dodge version that may be better suited.

Cheers,


paul

[Paul Edwards]

Guys,

Would the thread be NPT or BSP?

I'm assuming 1/2BSP 14 threads/Inch 21mm-18.5mm tapering.

Cheers,

Paul

[Grant Bowker]

Based only on the part being designed/made in Canada my assumption is that it would be NPT (North American specification). This needs confirmation.


Some of my manufacture was done using reclaimed pipe and flat sheet and others were done using off the shelf NPT pipe nipples. Comparison would provide the answer but it will be a week before I have a chance to do the comparison or measurement so if others can do this sooner it would be helpful.

[Lynn Eades]

Grant, I dunno, but the influence of "mudda" England on the truck it's self was high, so I wouldn't write off BSP. As you say it needs confirmation.
I searched transmission breather (in images) There is a flat one under Midwest transmission breather at $6.00. There are options at bigger money. Back in the day, they may have been supplied by AC (GM) as in radiator caps, thermostats etc.

[Jacques Reed]

Originally Posted by Grant Bowker

Based only on the part being designed/made in Canada my assumption is that it would be NPT (North American specification). This needs confirmation.

I am with NPT also but haven't got those thread gauges to compare on my fittings. There are a few British threads on CMP vehicle so you cannot completely write off BSP- Wheel studs at 7/8" BSF are a good example.

NPT thread taper is 1:16, ¾” per foot- from Machinery’s handbook
BSPT is 1°47’ per side equals Sin 0.0311 = 1/ Sin1°47’= 1/32 each side = 1/16 (same as NPT!)

1/8 NPT 27 TPI 1/8 BSP 28 TPI
¼ NPT 18 TPI ¼ BSP 19 TPI
½ NPT 14 TPI ½ BSP 14 TPI

1/2" NPT vs 1/2" BSP: Both have 14 threads per inch, so they match up quite well. The primary difference is angle of the thread which is 60 degrees NPT to 55 degrees BSP. In low pressure applications they are ok to swap. Add PTFE tape as a bit of insurance if you feel it needs it.

In Australia NPT fittings are very hard to find. I was looking for a short 1/2" NPT nipple for the same location to swap different types of breather caps. Could get a s/s one from Canada from a home brewing company but the cost was excessive so left things as is. Shown is one available. No hexagonal area in the middle and very short like the original nipple on the transfer case.

Cheers,

[Paul Edwards]

Thank you guys for all your assistance, in the end I took the path with lest resistance.

Giving my transfer case is the early type with the vertical nipple and cap breather and whilst accepting the modification bulletin to fit the air cleaner type, it is clear why my squashed cap had been butchered to fit the tight space available. Latter breather housings were to have a new casing exiting at 45 degrees to overcome this issue.

So with the original pipe nipple and my plumbing skills I made a cap from 22mm copper pipe and a feed end cap, once painted no one will Know.

Cheers,


Paul

[rob love]

You'll just have to remember that if you drive into water that is above that level you will need to change the oil in the transfer case. Mind you, I guess the other cap doesn't prevent water from coming in either. So the only minor negative is that the normal breathing of the transfer case as it heats and cools will allow unfiltered air into the gearbox. So if you go driving through the desert,, or long gravel roads, you will want to change the transfer case oil more often.

In the real world of a restored cmp, I would say there is no negative to the modification you have done.

[Jacques Reed]

Originally Posted by Jacques Reed

I am with NPT also but haven't got those thread gauges to compare on my fittings. There are a few British threads on CMP vehicle so you cannot completely write off BSP- Wheel studs at 7/8" BSF are a good example.

NPT thread taper is 1:16, ¾” per foot- from Machinery’s handbook
BSPT is 1°47’ per side equals Sin 0.0311 = 1/ Sin1°47’= 1/32 each side = 1/16 (same as NPT!)

1/8 NPT 27 TPI 1/8 BSP 28 TPI
¼ NPT 18 TPI ¼ BSP 19 TPI
½ NPT 14 TPI ½ BSP 14 TPI

1/2" NPT vs 1/2" BSP: Both have 14 threads per inch, so they match up quite well. The primary difference is angle of the thread which is 60 degrees NPT to 55 degrees BSP. In low pressure applications they are ok to swap. Add PTFE tape as a bit of insurance if you feel it needs it.

In Australia NPT fittings are very hard to find. I was looking for a short 1/2" NPT nipple for the same location to swap different types of breather caps. Could get a s/s one from Canada from a home brewing company but the cost was excessive so left things as is. Shown is one available. No hexagonal area in the middle and very short like the original nipple on the transfer case.

Cheers,

Good Day,

Today I thought I would gamble $3.00 on a 1/2 BSP short nipple for my transfer case vent. A local home brewing supplier had these nipples. Although they told me on the phone that they had the straight ones without the hex in the middle when I got there that type was out of stock and they were not reordering them. Not an uncommon thing when chasing up parts.

I prefer the large breather cap to the smaller one so this will do in the interim. I can wait until I get the original style nipple- most likely from China on EPay. I still think the threads on the transfer case are NPT and if so, this proves that 1/2 BSP will do the job if 1/2 NPT isn't available, at least in low pressure applications.

Cheers,

[Paul Edwards]

Thanks Jacques,

The real issue becomes more apparent with the early tranny cases where the breather exits at 90 degrees (as opposed to 45 degrees), so harder to avoid hitting the chassis cross member with the replacement breather vent.

Cheers,


Paul