Transmission fluid for 1999 1500 Suburban

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Nov 25, 2003
Yesterday the vehicle showed a code that it was slipping. It still shifts well as far as I can tell. I have a feeling that I should change the atf. Can anyone tell me what type and how much? and recomended brands too. Thanks.
For your ride go with M1 ATF. It's a great oil and easy to find. Auto Zone, Advance Auto.
Get the trans flushed and replace the filter and use DexronVI. It may improve the shift quality but if it is slipping it might be too late. Any GM dealer can do the job. My dealer charged me $180 for the whole job.
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I would get several gallons of Supertech Dex III, a filter kit and perform a cooler line flush. This way you can get a good idea of what is going on inside and in the meantime, flush out that worn out ATF with some relatively inexpensive stuff. I presonally use a Dex III spec in my 90's sub but you can use the supertech Dex VI if you prefer.

After flushing you can then decide if it was the fluid or if you have a more serious issue inside the trans. If you have alot of miles it may me worn bands. I had this issue on another suburban running regular ATF and it had not been regularly maintained. If the fluid change resolves your issue thats great, and you didn't spend a fortune on synthetic ATF. I would also install a magnefine filter as well. Cheap insurance.
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I am starting to doubt that the problem is truly the fluid. It has a p1870 code. I am starting to believe that it is a valve body solenoid of some type.
It still might be worth a fluid change.
My cousin had a Pontiac, the TCC solenoid in the trans was sticking. He did a fluid change, and within 2 weeks, it was fine!
Sometimes some fresh fluid will clean some varnish from the valve body. I change my fluid every 30k and have yet to have a tranny fail, I'm at 160k on my 93 C1500!
Whatever it turns out to be you are on borrowed time. Change the fluid and then start the process of elimination. Good Luck.
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