sbrem Posted December 30, 2006 Share Posted December 30, 2006 I know there have been other threads on this, but I'm still a little confused. What is the best oil to use in a TRD720 Duplex? I know back when it was new Mack recommended 90 weight Mineral oil. I have heard that 50 weight engine oil is what is recommended today. What is my best bet? Also what works best in a CRD78 dual reduction rear end? Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/ Share on other sites More sharing options...
b61mack Posted December 30, 2006 Share Posted December 30, 2006 I know there have been other threads on this, but I'm still a little confused. What is the best oil to use in a TRD720 Duplex? I know back when it was new Mack recommended 90 weight Mineral oil. I have heard that 50 weight engine oil is what is recommended today. What is my best bet? Also what works best in a CRD78 dual reduction rear end? ThanksI dont know about the old tranys, but in my 63 B61 i run 85-140 gear oil, i put a gallon of 85-140 Lucas gear additve in each rearend and my 13 speed roadranger, i use Lucas hub oil in the front hubs. Ron Quote Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/#findComment-9342 Share on other sites More sharing options...
chris88 Posted December 30, 2006 Share Posted December 30, 2006 In all the transmissions that i deal with we use 50 wt synthetic and rears are either 80-140 synthetic or 85 140 dyno oil. I would NOT use an 85 140 in a trans because there are needle bearings and the 85 140 is too thick to lube them properly. Quote Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/#findComment-9343 Share on other sites More sharing options...
sbrem Posted December 31, 2006 Author Share Posted December 31, 2006 Thanks for the help guys. I think I'll use the 50 weight in the duplex and 80 -90 or 85 -140 in the rear end. If anyone thinks this is the wrong way to go, please speak up. Thanks again Quote Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/#findComment-9362 Share on other sites More sharing options...
HK Trucking Posted December 31, 2006 Share Posted December 31, 2006 Thanks for the help guys. I think I'll use the 50 weight in the duplex and 80 -90 or 85 -140 in the rear end. If anyone thinks this is the wrong way to go, please speak up. Thanks again Back in the day when I was driving & working on B models & early DM's with the TR72 or 720 series transmissions, we used 80w90 gear lube in the trans & differentials.Here is a scan of a Mack maintenance manual from that era concerning Gear lube applications & specs.So, there you have it, straight from the Bulldog's mouth.There's no way I'd use 50W engine oil in one of those older transmissions. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/#findComment-9379 Share on other sites More sharing options...
chris88 Posted December 31, 2006 Share Posted December 31, 2006 As far as I know 90 wt gear oil and 50 wt engine oil are the same visosity Quote Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/#findComment-9381 Share on other sites More sharing options...
sbrem Posted January 1, 2007 Author Share Posted January 1, 2007 As far as I know 90 wt gear oil and 50 wt engine oil are the same visosityI have heard that 90 wt mineral gear oil (which is what Mack used to recommend back when these trucks were new) and 50 wt engine oil are the same viscosity, but the newer (non mineral?) gear oils are too thick and, as you said, don't properly lubricate the needle bearings. Quote Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/#findComment-9383 Share on other sites More sharing options...
HK Trucking Posted January 1, 2007 Share Posted January 1, 2007 I have heard that 90 wt mineral gear oil (which is what Mack used to recommend back when these trucks were new) and 50 wt engine oil are the same viscosity, but the newer (non mineral?) gear oils are too thick and, as you said, don't properly lubricate the needle bearings.If your mind is already made up, then why ask the question?Use whatever you want, It ain't my transmission, so I really don't care.Maybe I should put my time to better use than trying to gather information to answer questions for people who don't want to listen. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/#findComment-9385 Share on other sites More sharing options...
sbrem Posted January 1, 2007 Author Share Posted January 1, 2007 If your mind is already made up, then why ask the question?Use whatever you want, It ain't my transmission, so I really don't care.Maybe I should put my time to better use than trying to gather information to answer questions for people who don't want to listen.I'm really sorry if I came across that way, as it wasn't my intention at all. My mind is not made up. It will be a while before I get to changing the fluid anyway and I'm hearing more then one opinion on what to use, so I'm just trying to get all the information before I go and buy the wrong thing. And I greatly appreaciate you using your time to help me out. Again, I'm sorry if I came across wrong. Quote Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/#findComment-9391 Share on other sites More sharing options...
HK Trucking Posted January 1, 2007 Share Posted January 1, 2007 50 W engine oil is OK for Eaton Fuller transmissions, past & present. Your duplex is a Mack made transmission, and to my knowledge Mack has never recommended anything other than a Mack approved gear lube for use in their transmissions.If you are concerned about using synthetic gear lube, there are still mineral based gear lubes available.Go to a reputable oil supplier and specify that you want mineral based gear lube and you'll get the proper lube for your application. Bottom line is this:Mack transmission = Gear LubeEaton Fuller = 50W engine oil (although 85W90 gear lube is listed as acceptable for these also.Here are some scans from a "modern day" Mack manual concerning trans lubes, you will note that ALL mack trans. require gear lubes of varying viscosity depending on ambient temperature.Again, I'm posting this info to show you (and anyone else who may be unsure) what Mack specified for this application.This info isn't something I just dreamed up, it's straight from the Mack technical literature, and personally, I have always used the Mack recommended types of oils & lubes for whatever truck I was working on.Best of luck. 1 Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/#findComment-9408 Share on other sites More sharing options...
sbrem Posted January 1, 2007 Author Share Posted January 1, 2007 Mack transmission = Gear LubeCool. Thanks again for the help. I guess gear lube it is. Another related question that I'm still unsure of that you probably can help with: In my 1956 owners manual it lists 3 different types of gear oil GO-A (straight-Mineral Gear oil) which is what they say to use in most transmissions, auxiliarys and some rear ends, GO-B (All-Purpose gear oil) recommended in 1 transmission, and GO-C (extreme-Pressure Gear oil) recommended in 1 transmission and some rear ends. I can try to scan the pages later if seeing it would be of help to you. So I guess my question is what gear oil today would be closest to the straight-Mineral as opposed to the all purpose gear oil.(I don't even know what the difference between the 2 is ) I don't care if it is synthetic or not as long as it lubricates properly. To be honest for the amount I'll be using they truck any type of oil probably would be fineAgain, I'm not questioning what you say at all, I'm just trying to educate myself a little better. Thanks again Quote Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/#findComment-9410 Share on other sites More sharing options...
mudslut28 Posted January 3, 2007 Share Posted January 3, 2007 As always H-K is on the mark here. My 76 dm800 gets 85w-140 in the 6 speed tranny and the 65k rears. The 92 gets 50 wt for the 14708LL tranny and 85w-140 for the 58k rears. I actually use Redline Racing Syn for the Eaton/Fuller with some RL friction modifier in it and regular Valvo for the rears. I think Mack rears would live with swampwater in them..lol. The jury is still out on this E/F 8 spd though...not sure how the reliability is gonna be. Im used to putting a clutch in front of the 6 and 7 speeds every 5 or 6 years and never touching them. Quote Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/#findComment-9451 Share on other sites More sharing options...
sbrem Posted January 3, 2007 Author Share Posted January 3, 2007 The jury is still out on this E/F 8 spd though...not sure how the reliability is gonna be. Thanks for the help. As to the 8 speed we have 4 dump trucks (not Macks) where I work with Eaton/Fuller 8LLs and they seem to be real reliable. The trucks don't have many miles on them for their age, but what miles they have are hard miles. So I think you will most likely have good luck with yours. Quote Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/#findComment-9458 Share on other sites More sharing options...
mudslut28 Posted January 4, 2007 Share Posted January 4, 2007 Thanks..I hope you ar right. Anything Non-Mack is a new experience for me. Seems to be doing well so far Quote Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/#findComment-9486 Share on other sites More sharing options...
sbrem Posted January 5, 2007 Author Share Posted January 5, 2007 I have decided to use 80-90. Thanks for the help everyone. Quote Link to comment https://www.bigmacktrucks.com/topic/1950-transmission-and-rear-end-oil/#findComment-9504 Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.