Did someone install a thread insert for my TH-400 cooling lines?

[exchaoordo]

Situation: existing line had rubber tubing in the middle. The radiator side fittings are original (middle in photo) but the transmission side was jury rigged (left in photo). As you can see, it's smaller what should be there. My best guess is that someone used an insert in the transmission side. The only solution I can see is to jury rig my own setup because I assume the thread insert is there for a reason and wouldn't come out in any event. It does seem odd though that things would rust out at a point that's filled with tranny fluid. Any thoughts?

 

[Dr. Frankenbuick]

I think someone used the smaller ST 300 fittings in your transmission. They had smaller transmission lines. I am not sure if the TH 350 also had smaller lines, There are TH 400 adapters that also fit your trans. I would try a transmission shop or parts provider.

 

[exchaoordo]

Maybe I'm reading too much into the manual page, but it looks as if the male end of the fitting at the end of the 3/8" line is smaller. In any case, I'll try to find a reducer.

 

[Dr. Frankenbuick]

GM TURBO 400...TH400...OE GM COOLER FITTINGS...ORIGINAL GM COMPONENTS CHEVY BPO | eBay

FITTINGS HAVE BEEN DE-GREASED AND TUMBLED.

www.ebay.com

There were copper washers under the earlier ST-TH 400 fittings. Don't lose the washers you have if you have them. The later ones had a pipe thread and sealant.

 

[exchaoordo]

Fantastic! After an hour of home town and online shopping, I feared I would have had to replicate what was there. I dare say, a bit of Frankenbuick.

 

[Dr. Frankenbuick]

It’s ok to Frankenbuick! Once the purists get a closer look, they put their pitchforks aside: not scary, just functional.


Sent from my iPhone using Tapatalk

 

[exchaoordo]

Sadly, the Conklin parts just arrived and they are the same thing I already had. Not really any use.

 

[Dr. Frankenbuick]

Sorry to hear that. Where did the lines come from? It those are ST400 fittings, they should work. Maybe contact the people that made your lines?

Steve

 

[exchaoordo]

Thanks again! The lines came from Inline Tube. I finally found a suitable fitting at a really good NAPA franchise in the next town over, so problem solved. I'm historian by training though and love to chase these things down. I actually bought the original parts manual (occupational hazard) and found that GM suggested Buick dealers charge $2.18 (1377941) & $2.04 (1377942) for them. Anyway, you were really helpful because the guys at Conklin, who I bought those fittings from (from your link) seem really knowledgeable so I'm glad I bought them in any case. And, I finally did find a fitting at a local auto parts store that will work. "I don't know why they made it so difficult," he said, in reference to the other parts stores. Thanks again!

 

[exchaoordo]

GM TURBO 400...TH400...OE GM COOLER FITTINGS...ORIGINAL GM COMPONENTS CHEVY BPO | eBay

FITTINGS HAVE BEEN DE-GREASED AND TUMBLED.

www.ebay.com

There were copper washers under the earlier ST-TH 400 fittings. Don't lose the washers you have if you have them. The later ones had a pipe thread and sealant.

In the end, Dave Conklin came through! He searched his warehouse and sent me the correct fittings complete with the copper washers. Apparently the Switch Pitch transmissions were just a little bit special in this regard. Boy does he know his stuff. Thanks again for your help pointing me on the right track.

 

[LARRY70GS]

As far as I know, all THM400 have conversion fittings installed in the case. They are 1/4-18 NPSM threads. The fitting converts to inverted flare. On my transmission, I used these fittings,

ATI 925137: Transmission Cooler Line Fittings 1/4-18" NPSM Threads to -6AN - JEGS

Get the Best Performance with ATI Transmission Cooler Line Fittings 1/4-18" NPSM Threads to -6AN 925137 parts at JEGS. Shop Now at the Guaranteed Lowest Price!

www.jegs.com

And used push lok -6AN hose for my transmission lines. The radiator side is 1/2-20 inverted flare.

Carb and Fuel Pump Fitting, 1/2 Inch-20, AN 6

#6 Ford, Chrysler and early Chevy fuel pumps with 1/2"-20 inverted flare thread.

www.speedwaymotors.com

 

[exchaoordo]

As far as I know, all THM400 have conversion fittings installed in the case. They are 1/4-18 NPSM threads. The fitting converts to inverted flare. On my transmission, I used these fittings,

ATI 925137: Transmission Cooler Line Fittings 1/4-18" NPSM Threads to -6AN - JEGS

Get the Best Performance with ATI Transmission Cooler Line Fittings 1/4-18" NPSM Threads to -6AN 925137 parts at JEGS. Shop Now at the Guaranteed Lowest Price!

www.jegs.com

And used push lok -6AN hose for my transmission lines. The radiator side is 1/2-20 inverted flare.

Carb and Fuel Pump Fitting, 1/2 Inch-20, AN 6

#6 Ford, Chrysler and early Chevy fuel pumps with 1/2"-20 inverted flare thread.

www.speedwaymotors.com

Thanks, Larry. Of course my TH-400 is extra special: Switch pitch apparently had a slightly different fitting, which is why when I bought the "correct fitting" it didn't fit. Conklin Automotive came through.