The Ultimate Trans / Diff OIL Thread

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It is my intention to start the "is all, end all" thread on oils to be used in the trans and rear end. From countless hours of research I find this topic, like all other oil related topics, to be one more of religion than science with most quoting random "bob said to use" or spouting opinion based on partial observations. Well what I propose is a technical research paper based in scientific experiment and fact. 
It outlines what "GL" in GL4, GL5 stands for, and what  makes oils with these ratings different and why they should be used in some applications and not others. 

In short, if you have a syncromesh transmission with any yellow metals such as brass in it, you should NOT run a GL5 rated oil. It creates excessive wear on the brass through a chemical bonding reaction and then a mechanical stripping process. You SHOULD use the GL4 rated stuff that does not contain those additives. Preferably in a 75w90 or 80w90 weight.
The rear end however, has much higher operating pressures and temperatures with heavier grade metals that can hold up to higher levels of wear, therefore the GL5 grade SHOULD be used. A similarweight is more than adequate as well.

This means ideally we would want to run two different oils in the trans and diff.
If you're running a T-10 4 speed or other brass scynro manual trans behind a hopped up motor, this is a great solution, Amsoil Synthetic manual Transmission and Transaxle Gear Lube 75W-90 GL-4. It won't wear the yellow metals in the trans because of the grade 4 formulation, and the synthetics will help keep the oil from breaking down under high heat loads.

nicely formatted paper with charts and photos can be found here:
www.widman.biz/uploads/Transaxle_oil.pdf

I hope this helps shed some light on the issue. I am not claiming to know everything there is to know about oils. I just wanted to clearly state the difference between the grade ratings and where the newer formulations have negative effects on our classic autos.

Edited by Amurica - Feb/10/2015 at 4:27pm

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Amurica Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: Feb/05/2015 Location: United States Status: Offline Points: 13	Post Options Post Reply Quote Amurica Report Post Thanks(0) Quote Reply Topic: The Ultimate Trans / Diff OIL Thread Posted: Feb/06/2015 at 3:58pm
	It is my intention to start the "is all, end all" thread on oils to be used in the trans and rear end. From countless hours of research I find this topic, like all other oil related topics, to be one more of religion than science with most quoting random "bob said to use" or spouting opinion based on partial observations. Well what I propose is a technical research paper based in scientific experiment and fact. It outlines what "GL" in GL4, GL5 stands for, and what makes oils with these ratings different and why they should be used in some applications and not others. In short, if you have a syncromesh transmission with any yellow metals such as brass in it, you should NOT run a GL5 rated oil. It creates excessive wear on the brass through a chemical bonding reaction and then a mechanical stripping process. You SHOULD use the GL4 rated stuff that does not contain those additives. Preferably in a 75w90 or 80w90 weight. The rear end however, has much higher operating pressures and temperatures with heavier grade metals that can hold up to higher levels of wear, therefore the GL5 grade SHOULD be used. A similarweight is more than adequate as well. This means ideally we would want to run two different oils in the trans and diff. If you're running a T-10 4 speed or other brass scynro manual trans behind a hopped up motor, this is a great solution, Amsoil Synthetic manual Transmission and Transaxle Gear Lube 75W-90 GL-4. It won't wear the yellow metals in the trans because of the grade 4 formulation, and the synthetics will help keep the oil from breaking down under high heat loads. nicely formatted paper with charts and photos can be found here: www.widman.biz/uploads/Transaxle_oil.pdf I hope this helps shed some light on the issue. I am not claiming to know everything there is to know about oils. I just wanted to clearly state the difference between the grade ratings and where the newer formulations have negative effects on our classic autos. Edited by Amurica - Feb/10/2015 at 4:27pm

amxdreamer Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/30/2008 Location: Vancouver, BC Status: Offline Points: 8511	Post Options Post Reply Quote amxdreamer Report Post Thanks(0) Quote Reply Posted: Feb/06/2015 at 4:44pm
	^^^^my ADD kicked in (and I don't have ADD) and gave up...that's too hard to read!
	Tony Vancouver, BC 1970 AMX 1972 Badassador AMO#10333

Amurica Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: Feb/05/2015 Location: United States Status: Offline Points: 13	Post Options Post Reply Quote Amurica Report Post Thanks(0) Quote Reply Posted: Feb/06/2015 at 4:56pm
	try not to read that. Use the link instead... muuuuuch better. http://www.widman.biz/uploads/Transaxle_oil.pdf

gtpower Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jul/20/2014 Location: South Dakota Status: Offline Points: 230	Post Options Post Reply Quote gtpower Report Post Thanks(0) Quote Reply Posted: Feb/06/2015 at 5:49pm
	Although this is a very lengthy article, I have to say it is accurate and very well written. Mr. Widman is absolutely correct in his assertion that GL5 gear oils should NOT be used in transmissions. Also "most" engine oils meet the GL4 spec. hence it is fine for you H-D riders to use motor oil in your transmissions (and actually better than a GL5 gear oil), but that is for another forum. In my T10 I use only AMSOIL Synchromesh Transmission oil.
	1968 AMX 390 4speed

dpc502 Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Jun/21/2008 Location: Georgia Status: Offline Points: 229	Post Options Post Reply Quote dpc502 Report Post Thanks(0) Quote Reply Posted: Feb/06/2015 at 7:37pm
	My personal preference is Red Line MTL synthetic 70w/80 GL-4. In a previous life (late 70's early 80's) I was a parts @ service director for a large BMW dealership. When BMW changed from 4sp. to 5sp. trans they were having lots of issues with stiff shifting and rasping between 1st and 2nd. After rebuilding several we noticed all had glazed synchronizers. I called our local lubricant distributor and ask for his input. He said he would bring a few gallons of Red Line MTL for us to try. It wasn't an instant cure , but after 500 to 1000 miles shifting was greatly improved and no more grinding. Several years ago I bought a '69 AMX that the trans was so bad I had to double clutch it to keep from grinding and shifting was very stiff. I drained the fluid and sprayed a can of aerosol brake cleaner in the drain and fill holes, let it drain overnite and refilled with MTL. It has about 4500 miles and is the best shifting car I have. So far Red Line hasn't let me down so I'll stay with them.
	'70 BBB AMX #21736 '69 BBG AMX #14222 '69 BBG 500 Special #13482 '69 BBO AMX #12938 '69 Black Mink AMX #11086

amc67rogue Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Nov/05/2008 Location: Phx. AZ. Status: Offline Points: 1578	Post Options Post Reply Quote amc67rogue Report Post Thanks(0) Quote Reply Posted: Feb/07/2015 at 12:10pm
	Sulfur corrodes copper , syncro rings are a copper alloy.
	Keith Coggins 67Rogue X code

Amurica Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: Feb/05/2015 Location: United States Status: Offline Points: 13	Post Options Post Reply Quote Amurica Report Post Thanks(0) Quote Reply Posted: Feb/10/2015 at 12:02pm
	you are correct good sir. sulfer does corrode copper. However, he does mention in the article something that addresses that concern... "Somewhere around 20 years ago a deactivated or buffered sulfur was developed that would react with the phosphorous to create the protective/sacrificial layer in the conditions created in the gear boxes (temperature and pressure) without being corrosive to the brass, copper, etc. This additive system is used in most gear oils today." The problem lies in the newer GL5 oils which have much higher levels of active sulfer than the GL4. Hence why the GL4 grade is recommended for the syncromesh trans.... "A normal GL-4 gear oil of any given viscosity has about ½ of the level of sulfur/phosphorous additive that would be in the GL-5 product, so the bond is not as strong, and therefore can be peeled off without peeling a layer of brass (or less brass). " Based on this information and theory, I am going to run one of the author recommendations. So I ordered two quarts of the Amsoil Synthetic manual Transmission and Transaxle Gear Lube 75W-90 GL-4. It should be here this week and I'll be dumping it in the trans. Lots of work going into this ol AMX, I'm sure I'll be posting more about it on the forum. Regardless, I will be sure to post any specifics I notice from running this oil in the trans for others' reference.

gtpower Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jul/20/2014 Location: South Dakota Status: Offline Points: 230	Post Options Post Reply Quote gtpower Report Post Thanks(0) Quote Reply Posted: Feb/10/2015 at 12:18pm
	Let me be perfectly clear, I use AMSOIL because it is a good product and it is readily available to me. That is not to say that Redline or any other product is not good. The point is to use a GL4 gear oil where ever it is specified (namely gearboxes with yellow metals such as sychronizers). Use what is readily available to you as long as you use the right lubricant for the application.
	1968 AMX 390 4speed

Wrambler Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/02/2007 Location: West Virginia Status: Offline Points: 4199	Post Options Post Reply Quote Wrambler Report Post Thanks(0) Quote Reply Posted: Feb/10/2015 at 1:38pm
	I use Redline MTL and our AX15 with 135k on it shifts smoother now then it did with 60K on it. The synthetics have the advantage of not stiffening up in cold weather too. I understand the intent in copying and pasting that mess, however it is impossible to read and was permission given to do the cut and paste? Just sayin YMMV.
	Wrambler 69 AMC Rambler 4.0L, 5 speed 2015 Grand Cherokee Limited 2019 Chrysler 300