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1990 GMC 1500 Pickup Question: Manual Transmission Oil



, 5.0L V8, Anchorage, AK, June 26, 2009, 14:02

Hello Team,
I recently purchased a used 1990 GMC 1/2ton pickup (SL Sierra) with a 5.0L engine and 2wheel drive and am seeking to determine the proper gear oil to use in the 5 speed manual transmission, what do you recommend and why?
Alaska GMC

2 Answers
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  • Answer #1

    June 26, 2009, 16:12

    The recommended gear oil for your 5spd gear box is something called - GLS; GM part no. 12345349. I have not been able to find an specific information on GLS anywhere. I would suggest to check with your local GM dealer and see what the recommend for your area. The requirements in Alaska may be a bit different.

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  • Answer #2

    July 13, 2013, 16:37

    GM Performance 88900333 Synchromesh Transmission Fluid

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