Transmission fluid change

[Joseph S.]

I recently purchased a ‘89 GMC C2500. 4 speed with overdrive? (L,1,2,3,OD). Transmission has been leaking some. Looks like from the top. I am wanting to change transmission fluid. Mileage shows 184,700. Odometer works intermittent. Actual mileage unknown. My question is what type of fluid should I use and how much? I have looked everywhere on the internet that I can think of and have not been able to find any definitive answers. Looking for any and all help. Thanks.    

[LDM]

9 hours ago, Joseph S. said:

I recently purchased a ‘89 GMC C2500. 4 speed with overdrive? (L,1,2,3,OD). Transmission has been leaking some. Looks like from the top. I am wanting to change transmission fluid. Mileage shows 184,700. Odometer works intermittent. Actual mileage unknown. My question is what type of fluid should I use and how much? I have looked everywhere on the internet that I can think of and have not been able to find any definitive answers. Looking for any and all help. Thanks.    

This would have used Dexron 2 at the time but you aren't going to find that anywhere anymore.  Dexron 6 has been approved for backward compatibility for all older Dexron standard, so you could use that.  Another good options is Valvoline MaxLife, it is good Dex/Merc transmission fluid for older vehicles.  I've used it in many vehicles, including my 89 Camaro IROCZ 700R4 without issue.

[Joseph S.]

After a closer look, I believe my transmission isn’t the factor one. Would you be able to tell what you of fluid. 

[txab]

https://www.gmpartsdirect.com/oem-parts/gm-synthetic-manual-transmission-fluid-gl-4-75w-90-32-oz-19369226

 

https://www.google.com/search?hl=en&sxsrf=ALeKk01QWMv9w_3QBr5D_H8kAwKTtRCAcw%3A1588103093702&ei=tYeoXtDBKoyWtQWjsYqQCg&q=gm+p%2Fn-12346190&oq=gm+p%2Fn-12346190&gs_lcp=CgZwc3ktYWIQDFAAWABgicEIaABwAHgAgAEAiAEAkgEAmAEAqgEHZ3dzLXdpeg&sclient=psy-ab&ved=0ahUKEwiQ8JCG8YvpAhUMS60KHaOYAqIQ4dUDCAs

 

https://www.google.com/search?client=firefox-b-1-d&q=castrol+syntorq+lt+transmission+fluid

[LDM]

22 hours ago, Joseph S. said:

After a closer look, I believe my transmission isn’t the factor one. Would you be able to tell what you of fluid. 

Didn't realize you had a manual transmission.  I assumed it was an auto when you said 4 speed with Overdrive.  That's one of the New Venture manuals and takes a very specific fluid, definitely not automatic transmission fluid.  You'll need the manual transmission fluid that these take, the new GM part # should be 19369226.  I believe there are only a couple of options left for fluid on these unfortunately, the Castrol Syntorq was discontinued some years ago.