Warpman89 Posted March 16, 2010 Share Posted March 16, 2010 evening gentlemen,I have an '88 r688st with an E6 350 econodyne and a 12 speed mack tranny. Its the one with a direct/high/neutral/reverse all air shifted and also has a low/direct air shift on the dash for lo lo. What tranny is this, what oil do i use, and how much? also, i believe i have mack rears as well, but how can i find what model axles i have and what ratio they are? thanks Quote Link to comment https://www.bigmacktrucks.com/topic/13045-what-tranny-do-i-have/ Share on other sites More sharing options...
HK Trucking Posted March 16, 2010 Share Posted March 16, 2010 Sounds like a TRTXL1070B.Use 85W90 gear lube, and fill it until the lube is even with the filler plug hole.. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment https://www.bigmacktrucks.com/topic/13045-what-tranny-do-i-have/#findComment-51316 Share on other sites More sharing options...
Warpman89 Posted March 16, 2010 Author Share Posted March 16, 2010 (edited) Sounds like a TRTXL1070B.Use 85W90 gear lube, and fill it until the lube is even with the filler plug hole..Thanks Edited March 16, 2010 by Warpman89 Quote Link to comment https://www.bigmacktrucks.com/topic/13045-what-tranny-do-i-have/#findComment-51320 Share on other sites More sharing options...
e9500v8 Posted March 16, 2010 Share Posted March 16, 2010 evening gentlemen,I have an '88 r688st with an E6 350 econodyne and a 12 speed mack tranny. Its the one with a direct/high/neutral/reverse all air shifted and also has a low/direct air shift on the dash for lo lo. What tranny is this, what oil do i use, and how much? also, i believe i have mack rears as well, but how can i find what model axles i have and what ratio they are? thanksOn your rearend on top right on the sloped part below the breather there is a flat place clean it all off the gear ratio will be there probly 4.17 or 4.42 or 4.64 rarely could be 5.13 .For the transmission there is a flat place on one side or the other that has the numbers stamped in it also. I have the identical truck but i replace the 12 speed mack with a 13 speed fuller !! I just use gear oil the check plug is on the right side rear it is usually a square headed plug ,they hold about 4 or 5 gallon.You fill the oil up till it comes out the check plug!! Quote Link to comment https://www.bigmacktrucks.com/topic/13045-what-tranny-do-i-have/#findComment-51324 Share on other sites More sharing options...
e9500v8 Posted March 16, 2010 Share Posted March 16, 2010 evening gentlemen,I have an '88 r688st with an E6 350 econodyne and a 12 speed mack tranny. Its the one with a direct/high/neutral/reverse all air shifted and also has a low/direct air shift on the dash for lo lo. What tranny is this, what oil do i use, and how much? also, i believe i have mack rears as well, but how can i find what model axles i have and what ratio they are? thanksIn low gear your ratio is 23.08 to 1 and the over drive in the 12 speed is .78 pretty fast!! Quote Link to comment https://www.bigmacktrucks.com/topic/13045-what-tranny-do-i-have/#findComment-51326 Share on other sites More sharing options...
Warpman89 Posted March 16, 2010 Author Share Posted March 16, 2010 On your rearend on top right on the sloped part below the breather there is a flat place clean it all off the gear ratio will be there probly 4.17 or 4.42 or 4.64 rarely could be 5.13 .For the transmission there is a flat place on one side or the other that has the numbers stamped in it also. I have the identical truck but i replace the 12 speed mack with a 13 speed fuller !! I just use gear oil the check plug is on the right side rear it is usually a square headed plug ,they hold about 4 or 5 gallon.You fill the oil up till it comes out the check plug!!can i use heavy gear oil for the diffs too? like 85w-140? Quote Link to comment https://www.bigmacktrucks.com/topic/13045-what-tranny-do-i-have/#findComment-51327 Share on other sites More sharing options...
rustyparts Posted March 31, 2010 Share Posted March 31, 2010 Sounds like a TRTXL1070B.Use 85W90 gear lube, and fill it until the lube is even with the filler plug hole..I just did a ton of research on this subject from every source I could find and will never put gear oil in my trannys because it will not circulate into the small passages of the main and aux trannys. Everywhere I went from Mack to Rotella says to use either 30, 40 or 50w manual transmission or motor oil with detergent. Quote Link to comment https://www.bigmacktrucks.com/topic/13045-what-tranny-do-i-have/#findComment-52291 Share on other sites More sharing options...
HK Trucking Posted April 1, 2010 Share Posted April 1, 2010 I just did a ton of research on this subject from every source I could find and will never put gear oil in my trannys because it will not circulate into the small passages of the main and aux trannys. Everywhere I went from Mack to Rotella says to use either 30, 40 or 50w manual transmission or motor oil with detergent.Eaton Fuller transmissions should use 50w.Mack transmissions use 85 - 90 gear lube.. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment https://www.bigmacktrucks.com/topic/13045-what-tranny-do-i-have/#findComment-52364 Share on other sites More sharing options...
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