You know what, I find this argument too funny. I think I've made a fool of myself. I have done some research before I made these fittings. The fitting I have pulled from my TH400 had an outside major diameter of .520"on the thread, so it was not an O-ring fitting. O-ring fittings follow the UNF thread sizes, therefor a fitting with a .520" OD diameter is not an O-ring fitting because it falls in-between 1/2"(.500") and 9/16" (.5625").
The closest size it could be is 1/4 pipe. Now I'm not going to get into the funky reasons how something measures over 1/2" is going to be a 1/4" pipe. (The size is measured on the inside but not quite exact.) Pipe thread is usually tapered because that is how it's sealed. NPT from what I have read is tapered. The fitting I've pulled does not have a taper. It's straight, and it's seal by a copper crush washer between the case and the backside of the hex. WTF is this? I asked.
So the search started, first I went to place that sold JIC fitting, hoses and XRP AN fittings. I asked the guy about the straight pipe and he told me the only thing that it could be British straight pipe. I think to myself "I believe the first TH400 was in Jaguars so it could a tooling carry over when GM finally put the TH400 in their own cars" Now don't quote me on that because I'm wrong. I took home a 1/4 British straight pipe to JIC. I screwed it into my transmission and the fitting wouldn't go in. WTF is going on here?
As it would turn out the British decided to do things different from us Yanks because British pipe thread, tapered and straight, have a 55 degree thread angle and different tread count. The TH400 fitting had a thread count of 18 TPI. The British fitting I believe was 19 TPI. WTF is going on here?
Now there is a thread on Pirate 4x4 that talks about these funky TH400 fittings, and I would bring the thread up right this minute but I not a paying member therefor I can’t do searches. WTF am I going to do now?
So at work, I started looking in the Mc Master Carr catalog and the Machinist handbook to find out what is going on, I didn’t find any fittings in the Mc Master Carr catalog but did find some information. Maybe I could find the fitting if I had more time since I was searching during lunch and I was busy eating lunch at the time. I found the specification for National Pipe Straight Thread or something similar in the hand book and made my own fittings. I got home and posted a picture on CK5 and got ridiculed. WTF have I been doing all this damn time.
I did a search on the internet and got as usual a lot of useless information but sees a lot of companies sell AN kits for the TH400. Upon closer examination, these kits come with two 6AN to 1/4 NPT. Now remember I said NPT usually means taper? So why are these companies selling kits with a taper to transmission that takes straight fittings? Well, remember I was doing research from the Machinist Handbook? Well, the handbook gets into detail what these threads are used for. The handbook basically said the straight thread is only good for low pressure application and since it is low pressure, you could thread a taper into the straight pipe, just use a sealant. NPT is the preferred way to do pipe. AAAAAARRRRRRGGGGGGGGG!!!!!!! WTF OVER!
