Need Advice on Replacing NBR 70 Seals in Classic Transmission 1

[Kristoffswe]

Hi everyone,

I'm currently working on replacing an static NBR seal in an old transmission from the 40s, 50s, and 60s that uses Dexron II ATF oil.

The operating temperature for this transmission is around 170 degrees Fahrenheit, with a typical line pressure of 140 PSI and a maximum pressure of 240 PSI.

I've previously used NBR seals from well-known manufacturers without any issues, but I've noticed that many of these seals likely come from China or Taiwan.

When searching for seals from these regions, there are numerous options available at incredibly low prices. This raises my concerns about their quality.

Everyone claims to offer the best quality, but how can I trust this?

I want to ensure I'm not using or selling a seal that will harden and fail after a few years.

What should I look for in terms of specifications or certifications to determine the quality of the new seal?

Any advice on how to assess the reliability of these products would be greatly appreciated. Thank you for your help!

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[TugboatEng]

NBR, even if good quality, has a short life at the temperatures seen in automotive transmissions. Modern OEMs use ACM or acrylic rubber for transmission seals. For lip seal, FKM or Viton will likely be easier to find for low volume needs.

 

[Kristoffswe]

Thank you for your reply. I understand that AEM is commonly used for this type of sealing. I assume they opted for NBR because of the cost and the fact that these classic cars are only driven a few times a year. However, if I were to use AEM instead, my issue still remains: I have trouble determining the quality of even this material. I have what seems to be a serious and reliable contact who claims they can manufacture seals in AEM for me, but how can one determine the quality?