69Midd4Stang 10 Report post Posted May 8, 2014 Can anyone assist me by confirming the correct type of transmission fluid to be used in a 4 speed Toploader. Thanks Quote Share this post Link to post Share on other sites
55Mach1 10 Report post Posted May 8, 2014 GL-4 non synthetic is what it calls for approx 2-2.25 quarts. I used a standard 75-90 Lucas gear oil in mine recently and it isn't as smooth at the GL4. I ordered some Brad Pen GL-4 through Summit which showed up today so il switch back over soon. GL4 is very hard to find around my area as nobody carries anything but automatic fluid and GL5 synthetic. Quote Share this post Link to post Share on other sites
Dave R. 85 Report post Posted August 6, 2014 Motorcraft makes a GL4 that they sell in quarts at the Ford dealer or a Motorcraft distributor. I went to the shop that services my daily drivers and they were able to order 2 qts. from one of his suppliers. About $11 a qt. Everything that I read says to not use GL5 or GL4/GL5 oils. The GL5 oils have an additive that destroys the brass blocker rings in the toploader. Some guys swear that that the GL5 is fine. Google the corrosive effects of GL5 on brass. GL4 to be on the safe side for me. Dave R. Quote Share this post Link to post Share on other sites
Brian Conway 247 Report post Posted August 6, 2014 Sound like Dave has it figured out. I get mine at NAPA. My trans., RUG AE 2, is right at 2 qts. Brian Quote Share this post Link to post Share on other sites
Jefhuf 13 Report post Posted August 7, 2014 Anyone running Redline MTL? I use it in my other manual vehicles but never tried it in the Mustang Quote Share this post Link to post Share on other sites
Dave R. 85 Report post Posted August 9, 2014 Brian, I also went to NAPA but they only sold the GL4 oil in gallons. Dave R. Quote Share this post Link to post Share on other sites
Brian Conway 247 Report post Posted August 9, 2014 (edited) I bought the gallon and changed the gear oil in the 69 and the 65. Brian http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Gear-Oil-Automotive-1-QT-CRC-85W90/_/R-SLRSL24229_0006410049 Edited August 9, 2014 by Brian Conway Quote Share this post Link to post Share on other sites
Dave R. 85 Report post Posted August 9, 2014 You lucky dog. 2 Mustangs. Nice. Maybe some day. Dave. Quote Share this post Link to post Share on other sites
